NA

COMMITTEE ON EPA 542-R-98-001a

O

O T

T

A N C C M S

CDSM

THE CHALLENGES OF June 1998

MODERN SOCIETY www.clu-in.com

www.nato.int/ccms

NATO/CCMS Pilot Study

Evaluation of Demonstrated and

Emerging Technologies for the

Treatment and Clean Up of

Contaminated Land and

Groundwater

PHASE II

FINAL REPORT

Number 219

NORTH ATLANTIC TREATY ORGANIZATION
NATO/CCMS Pilot Study, Phase II Final Report

CONTENTS

Chapter 1: INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.1 BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.2 STRUCTURE OF THE STUDY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

1.3 HOW THE INFORMATION IS PRESENTED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6

1.4 RELATIONSHIP TO OTHER CCMS PROGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8

1.4.1 Contributions by CCMS Fellows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8

1.4.2 CCMS Study Visit Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9

1.5 CONTRIBUTIONS BY EXPERT SPEAKERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9

1.6 CONCLUSIONS AND RECOMMENDATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9

1.7 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9

Chapter 2: TECHNICAL OVERVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.2 DEVELOPMENT STATUS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.3. IN SITU VS. EX SITU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

2.4 TECHNOLOGIES EMPLOYED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

2.5 CONTAMINANTS TREATED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

Chapter 3: PROCESS-BASED REMEDIATION METHODS . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.2 BASIC OPTIONS AND CLASSIFICATION OF METHODS . . . . . . . . . . . . . . . . . . . 3-1

3.3 CIVIL ENGINEERING-BASED METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

3.4 PROCESS-BASED METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

3.4.1 Ex Situ Methods for Solids and Liquids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

3.4.2 Ex Situ Treatment of Groundwater and Other Contaminated Liquids . . . . . . . . . . . 3-6

3.4.3 In Situ Methods for Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8

3.4.4 In Situ Treatment of Groundwater ................................. 3-12

3.5 REFERENCES ................................................... 3-15

Chapter 4: IN SITU TREATMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.2 CASE STUDIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

4.2.1 Project 1: Trial of Air-Sparging of a Petroleum-Contaminated Site . . . . . . . . . . . . 4-4

4.2.2 Project 2: Bioremediation of Petrochemicals Following a Major Fire . . . . . . . . . . 4-5

4.2.3 Project 3: Bioclogging of Aquifers for Containment and Remediation of Organic

Contaminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

4.2.4 Project 4: Remediation of Methyl Ethyl Ketone Contaminated Soil and

Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

4.2.5 Project 6: In Situ/On-Site Remediation of Wood Treatment Soils . . . . . . . . . . . . . 4-6

4.2.6 Project 9: Demonstration of an In Situ Process for Soil Remediation Using Well

Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

4.2.7 Project 12: Groundwater and Soil Remediation at a Former Manganese Sulfate

Production Plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

4.2.8 Project 15: Combined Chemical and Microbiological Treatment of Coking Sites . . 4-8

4.2.9 Project 16: Combined Vacuum Extraction and In Situ Stripping of Chlorinated

Vapors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9

4.2.10 Project 18: Biological In Situ Remediation of Contaminated Gasworks . . . . . . . . 4-9

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4.2.11 Project 23: Modeling and Optimization of In Situ Remediation ............ 4-10

4.2.12 Project 35: Combined In Situ Soil Vapor Extraction Within Containment Cells and

Subsequent Ex Situ Bioremediation .................................. 4-11

4.2.13 Project 37: Bioventing of Hydrocarbon-Contaminated Soils in the Sub-Arctic . . 4-12

4.2.14 Project 41: In situ Microbial Filters ................................ 4-13

4.2.15 Project 42: In Situ Pneumatic Fracturing and Bioremediation .............. 4-13

4.2.16 Project 43: Multi-Vendor Bioremediation Technology Demonstration ........ 4-14

4.2.17 Project 47: In Situ Electroosmosis (LasagnaTM Process) .................. 4-15

4.2.18 Project 49: Characterization of Residual Contaminants in Bioremediated Soils and

Reuse of Bioremediated Soils ...................................... 4-16

4.3 REVIEW OF CASE STUDIES AS A GROUP ............................ 4-17

4.4 ENVIRONMENTAL IMPACTS AND HEALTH AND SAFETY ............... 4-19

4.5 COSTS ........................................................ 4-20

4.6 APPLICABILITY OF IN SITU TECHNOLOGIES .......................... 4-20

Chapter 5: PHYSICAL-CHEMICAL TREATMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5.1.1 Overview of Chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5.1.2 Generic Description of Technology Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5.2 CASE STUDIES CHOSEN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

5.2.1 Group 1: Typical Soil Washing (Project 30) . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

5.2.2 Group 2: Soil Washing and Biological Treatment (Projects 24, 26, and 36) . . . . . . 5-4

5.2.3 Group 3: Soil Washing and Physical-Chemical Treatment (Projects 10, 17, 19, 27,

31, and 33) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7

5.2.4 Group 4: Physical-Chemical Treatment (No Soil Washing) (Projects 32, 44, and 47)5-15

5.2.5 Group 5: Photo-Oxidation Treatment (Projects 14, 38, and 40) ............. 5-19

5.3 BACKGROUND OF CASE STUDIES AS A GROUP ....................... 5-24

5.4 PERFORMANCE RESULTS ......................................... 5-24

5.4.1 Analytical and Assessment Procedures .............................. 5-24

5.4.1.1 Group 1: Typical Soil Washing (Project 30) ...................... 5-26

5.4.1.2 Group 2: Soil Washing and Biological Treatment (Projects 24, 26, and 36) . 5-27

5.4.1.3 Group 3: Soil Washing and Physical-Chemical Treatment (Projects 10, 17, 19,

27, and 31) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-27

5.4.1.4 Group 4: Physical-Chemical Treatment (No Soil Washing) (Projects 32, 44,

and 47) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-29

5.4.1.5 Group 5: Photo-Oxidation Treatment (Projects 14, 38, and 40) ......... 5-30

5.4.2 General Effectiveness .......................................... 5-31

5.4.3 Overall Performance ........................................... 5-35

5.4.3.1 Group 2: Soil washing and biological treatment (Projects 24, 26, and 36) . . 5-35

5.4.3.2 Group 3: Soil Washing and Physical-Chemical Treatment (Projects 10, 17, 19,

27, and 33) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-37

5.4.3.3 Group 4: Physical-Chemical Treatment (No Soil Washing) (Projects 31, 32,

44, and 47) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-37

5.4.3.4 Group 5: Photo-Oxidation Treatment (Projects 14, 38, and 40) ......... 5-40

5.5 RESIDUALS AND EMISSIONS ...................................... 5-40

5.5.1 Soil Washing ................................................ 5-40

5.5.2 Combined Treatments .......................................... 5-40

5.5.2.1 Group 2: Soil Washing and Biological Treatment (Projects 24, 26, and 36) . 5-41

5.5.2.2 Group 3: Soil Washing and Physical-Chemical Treatment (Projects 10, 17, 19,

27, 31, and 33) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-43

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5.5.2.3 Group 4: Physical-Chemical Treatment (No Soil Washing) (Projects 32, 44,

and 47) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-43

5.5.2.4 Group 5: Photo-Oxidation Treatment (Projects 14, 38, and 40) ......... 5-43

5.6 FACTORS AND LIMITATIONS TO CONSIDER FOR DETERMINING THE

APPLICABILITY OF THE TECHNOLOGY .............................. 5-44

5.6.1 Typical Soil Washing .......................................... 5-46

5.6.2 Soil Washing and Other Treatment ................................. 5-47

5.6.3 Physical-Chemical Technologies ................................... 5-48

5.6.4 Photo-Oxidation Technologies .................................... 5-49

5.7 COSTS ........................................................ 5-50

5.8 FUTURE STATUS OF THE CASE STUDY PROCESS AND THE TECHNOLOGY AS

A WHOLE ..................................................... 5-53

5.8.1 General Remarks ............................................. 5-53

5.8.2 Characterizing Contaminated Material ............................... 5-53

5.8.3 Optimizing Performance of Unit Processes ........................... 5-53

5.8.4 Investigating Cost-Effectiveness of Treatment Combinations ............... 5-53

5.8.5 Investigating Residuals ......................................... 5-54

5.9 REFERENCES ................................................... 5-54

Chapter 6: BIOLOGICAL TREATMENT PROCESSES: INTRODUCTION AND EX SITU

APPROACHES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6.2 GENERAL OVERVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6.2.1 Biological Processes, In General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6.2.2 Main Process Variations (by Biological Process) . . . . . . . . . . . . . . . . . . . . . . . . 6-3

6.2.3 Main Process Variations (by Mode of Application) . . . . . . . . . . . . . . . . . . . . . . . 6-4

6.2.4 Combinations with Abiotic Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6

6.2.5 Extensive Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7

6.2.6 Groundwater Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7

6.2.7 Indications for Using Ex Situ Treatment Technologies . . . . . . . . . . . . . . . . . . . . 6-8

6.3 CASE STUDIES CHOSEN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-9

6.4 BACKGROUND OF CASE STUDIES AS A GROUP . . . . . . . . . . . . . . . . . . . . . . . . 6-9

6.5 PERFORMANCE RESULTS ......................................... 6-14

6.5.1 Project 6: In Situ/On-Site Bioremediation of Soils Contaminated with Organic

Pollutants: Elimination of Soil Toxicity with DARAMEND® ................ 6-14

6.5.2 Project 8: Biodegradation/Bioventing of Oil-Contaminated Soils ............ 6-14

6.5.3 Project 11: On-Site Biological Degradation of PAHs in Soil at a Former Gasworks

Site ........................................................ 6-15

6.5.4 Project 15: Bioremediation of Soils from Coal and Petroleum Tar

Distillation Plants .............................................. 6-16

6.5.5 Project 24: Combined Remediation Technique for Soil Containing Organic

Contaminants: Fortec ............................................ 6-16

6.5.6 Project 25: Slurry Reactor for Soil Treatment ......................... 6-17

6.5.7 Project 26: Treatment of Creosote-Contaminated Soil (Soil Washing and Slurry

Phase Bioreactors) .............................................. 6-17

6.5.8 Project 28: Use of White-Rot Fungi for Bioremediation of Creosote-Contaminated

Soil ........................................................ 6-17

6.5.9 Project 31: Decontamination of Metalliferous Mining Spoil ................ 6-18

6.5.10 Project 35: Combined In Situ Soil Vapor Extraction within Containment Cells

Combined with Ex Situ Bioremediation and Groundwater Treatment ........... 6-18

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6.5.11 Project 36: Investigation of Enhancement Techniques for Ex Situ Separation

Processes, Particularly with Regard to Fine Particles ...................... 6-18

6.5.12 Project 43: Multi-Vendor Bioremediation Technology Demonstration Project . . . 6-19

6.5.13 Project 49: Characterization of Residual Contaminants in Bioremediated Soil and

Reuse of Bioremediated Soil ...................................... 6-19

6.5.14 Project 54: Treatment of PAH- and PCP-Contaminated Soil in Slurry Phase

Bioreactors ................................................... 6-20

6.6 GENERAL DISCUSSION OF PROJECTS ............................... 6-20

6.7 RESIDUALS AND EMISSIONS ...................................... 6-21

6.8 FACTORS AND LIMITATIONS TO CONSIDER FOR DETERMINING THE

APPLICABILITY OF THE TECHNOLOGY .............................. 6-23

6.9 COSTS ........................................................ 6-25

6.10 FUTURE STATUS OF THE CASE STUDY PROCESSES AND THE TECHNOLOGY

AS A WHOLE ................................................... 6-25

6.11 ACKNOWLEDGEMENT .......................................... 6-27

6.12 DISCLAIMER .................................................. 6-27

6.13 REFERENCES .................................................. 6-27

Chapter 7: EX SITU THERMAL METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

7.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

7.2 MAIN PROCESS VARIATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

7.3 DESCRIPTION OF MAIN PROCESS VARIATIONS . . . . . . . . . . . . . . . . . . . . . . . . 7-2

7.3.1 Thermal Desorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2

7.3.2 Incineration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-5

7.3.3 Vitrification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6

7.4 DETERMINATION OF EFFECTIVENESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6

7.5 CASE STUDIES CHOSEN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7

7.5.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process . . . . . . . . . . . 7-7

7.5.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using New

On-Site Technique ............................................. 7-11

7.5.3 Project 19: Cleaning Mercury-Contaminated Soil Using Combined Washing and

Distillation Process ............................................. 7-12

7.5.4 Project 20: Fluidized Bed soil Treatment Process—BORAN ................ 7-13

7.5.5 Project 21: Mobile Low-Temperature Thermal Treatment Process ........... 7-14

7.6 REVIEW OF CASE STUDIES AS A GROUP ............................ 7-14

7.7 PERFORMANCE RESULTS ......................................... 7-15

7.7.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process .......... 7-15

7.7.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using New

On-Site Technique ............................................. 7-17

7.7.3 Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil

Washing and Distillation Process ................................... 7-18

7.7.4 Project 20: Fluidized Bed Soil Treatment Process—BORAN ............... 7-19

7.7.5 Project 21: Mobile Low-Temperature Thermal Treatment Process ........... 7-19

7.8 ENVIRONMENTAL IMPACTS ....................................... 7-19

7.8.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process .......... 7-19

7.8.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using a New

On-Site Technique ............................................. 7-20

7.8.3 Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil

Washing and Distillation Process ................................... 7-20

7.8.4 Project 20: Fluidized Bed Soil Treatment Process—BORAN ............... 7-20

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7.8.5 Project 21: Mobile Low-Temperature Thermal Treatment Process ........... 7-20

7.9 HEALTH AND SAFETY ........................................... 7-21

7.9.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process .......... 7-21

7.9.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using a New

On-Site Technique ............................................. 7-21

7.9.3 Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil

Washing and Distillation Process ................................... 7-22

7.9.4 Project 20: Fluidized Bed Soil Treatment Process—BORAN ............... 7-22

7.9.5 Project 21: Mobile Low-Temperature Thermal Treatment Process ........... 7-22

7.10 FACTORS AND LIMITATIONS TO CONSIDER FOR DETERMINING THE

APPLICABILITY OF THE TECHNOLOGY .............................. 7-22

7.10.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process ......... 7-22

7.10.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using a New

On-Site Technique ............................................. 7-23

7.10.3 Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil

Washing and Distillation Process ................................... 7-23

7.10.4 Project 20: Fluidized Bed Soil Treatment Process—BORAN .............. 7-23

7.10.5 Project 21: Mobile Low-Temperature Thermal Treatment Process .......... 7-23

7.11 COSTS ....................................................... 7-23

7.11.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process ......... 7-24

7.11.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using a New

On-Site Technique ............................................. 7-24

7.11.3 Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil

Washing and Distillation Process ................................... 7-24

7.11.4 Project 20: Fluidized Bed Soil Treatment Process—BORAN .............. 7-24

7.11.5 Project 21: Mobile Low-Temperature Thermal Treatment Process .......... 7-25

7.12 CONCLUSIONS AND PROGNOSIS .................................. 7-25

7.13 REFERENCES .................................................. 7-25

Chapter 8: STABILIZATION/SOLIDIFICATION PROCESSES . . . . . . . . . . . . . . . . . . . . . . . 8-1

8.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

8.1.1 Main Process Variations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-2

8.1.2 Ex situ Methods of Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-3

8.1.3 In Situ Methods of Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-4

8.2 CASE STUDIES CHOSEN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-5

8.2.1 Project 34: Chemical Fixation of Soils Contaminated with Organic Chemicals

(Envirotreat Process) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-6

8.2.2 Project 29: Sorption/Solidification of Selected Heavy Metals and Radionuclides

onto Unconventional Sorbents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-8

8.4 PERFORMANCE RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-9

8.4.1 Project 34: Chemical Fixation of Soils Contaminated with Organic Chemicals

(Envirotreat Process) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-9

8.4.2 Project 29: Sorption/Solidification of Selected Heavy Metals and Radionuclides

onto Unconventional Sorbents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-9

8.5 RESIDUALS AND EMISSIONS ...................................... 8-10

8.5.1 Project 34: Chemical Fixation of Soils Contaminated with Organic Chemicals

(Envirotreat Process) ............................................ 8-10

8.5.2 Project 29: Sorption/Solidification of Selected Heavy Metals and Radionuclides

onto Unconventional Sorbents ..................................... 8-10

8.6 HEALTH AND SAFETY ........................................... 8-10

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8.6.1 Project 34: Chemical Fixation of Soils Contaminated with Organic Chemicals

(Envirotreat Process) ............................................ 8-10

8.6.2 Project 29: Sorption/Solidification of Selected Heavy Metals and Radionuclides

onto Unconventional Sorbents ..................................... 8-10

8.7 COSTS ........................................................ 8-11

8.8 FUTURE STATUS OF CASE STUDY PROCESSES AND TECHNOLOGY AS A

WHOLE ....................................................... 8-11

8.9 REFERENCES ................................................... 8-11

Chapter 9: OTHER REMEDIATION TECHNOLOGIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1

9.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1

9.2 PROJECTS IN THE SITE INVESTIGATION STAGE . . . . . . . . . . . . . . . . . . . . . . . . 9-1

9.2.1 Project 51: Sobéslav, South Bohemia Wood Treatment Plant . . . . . . . . . . . . . . . . 9-1

9.2.2 Project 56: Spolchemie a.s.—Mercury-Contaminated Site . . . . . . . . . . . . . . . . . . 9-2

9.3 PROJECTS FOR WHICH REMEDIAL OPTIONS HAVE BEEN SELECTED, BUT

NOT IMPLEMENTED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-2

9.3.1 Project 55: Czechowice Oil Refinery Project . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-2

9.4 PROJECTS FOR WHICH THE SELECTED REMEDIAL OPTION DOES NOT FIT IN

THE CATEGORIES OF TECHNOLOGIES HIGHLIGHTED IN THE OTHER

TECHNOLOGY CHAPTERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3

9.4.1 Project 22: Environmental Evaluations of Former Soviet Military Bases in Hungary 9-3

9.4.2 Project 39: Management of Soil Vapors at the Basket Creek Site . . . . . . . . . . . . . 9-4

9.4.3 Project 50: Integrated Rotary Steam Stripping and Enhanced Bioremediation for In

Situ Treatment of VOC-Contaminated Soil (Cooperative Approach to Application of

Advanced Environmental Technologies) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-5

9.4.4 Project 53: In Situ Bioremediation of Chloroethene-Contaminated Soil . . . . . . . . . 9-6

Chapter 10: INTEGRATION OF TECHNOLOGIES .............................. 10-1

10.1 INTRODUCTION ................................................ 10-1

10.2 BASIC OPTIONS AND CLASSIFICATION OF APPROACHES .............. 10-1

10.2.1 Technical Factors ............................................ 10-2

10.2.2 Organizational Factors ......................................... 10-2

10.3 CASE STUDIES CHOSEN ......................................... 10-3

10.3.1 Project 1: Field Trial of Air Sparging of a Petroleum-Contaminated Aquifer . . . 10-5

10.3.2 Project 9: Field Demonstration of an In Situ Process for Soil Remediation Using

Well Points .................................................. 10-5

10.3.3 Project 10: Recovery of Inorganic and Organic Contaminants from Soil ...... 10-5

10.3.4 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using a New

On-Site Technique ............................................. 10-6

10.3.5 Project 15: Combined Chemical and Microbiological Treatment of Coking

Sites/Bioremediation of Soils from Coal and Petroleum Tar Distillation Plants .... 10-6

10.3.6 Project 19: Cleaning Mercury-Contaminated Soil Using a Combined Washing and

Distillation Process ............................................. 10-6

10.3.7 Project 24: Combined Remediation Technique for Soil Containing Organics:

Fortec ...................................................... 10-6

10.3.8 Project 26: Treatment of Creosote-Contaminated Soil (Soil Washing and Slurry

Phase Bioreactor) .............................................. 10-7

10.3.9 Project 27: Soil Washing and Chemical Dehalogenation of PCB-contaminated

Soil ........................................................ 10-7

10.3.10 Project 31: Decontamination of Metalliferous Mining Wastes ............. 10-7

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NATO/CCMS Pilot Study, Phase II Final Report

10.3.11 Project 32: CacitoxTM Soil Treatment Process ........................ 10-7

10.3.12 Project 33: In-pulp Decontamination of Soils, Sludges, and Sediments ...... 10-7

10.3.13 Project 36: Enhancement Techniques for Ex Situ Separation Processes

Particularly with Regard to Fine Particles ............................. 10-8

10.3.14 Project 42: In Situ Pneumatic Fracturing and Biotreatment ............... 10-8

10.3.15 Project 47: In Situ Electro-Osmosis (LasagnaTM Project) ................. 10-8

10.4 REVIEW OF CASE STUDIES AS A GROUP ............................ 10-8

10.5 PERFORMANCE RESULTS ....................................... 10-10

10.5.1 Overview ................................................. 10-10

10.5.2 Separation of Fractions ....................................... 10-10

10.5.3 Mobilization of Contaminants ................................... 10-12

10.5.4 Increase of Availability ....................................... 10-13

10.5.5 Sequential Removal of Contaminants ............................. 10-14

10.6 FACTORS AND LIMITATIONS OF INTEGRATED TECHNOLOGIES ........ 10-15

10.6.1 Separation of Fractions ....................................... 10-15

10.6.2 Mobilization of Contaminants to Enhance Treatment ................... 10-15

10.6.3 Increase of Availability of Contaminants to Treatment ................. 10-16

10.6.4 Sequential Removal of Different Types of Contaminants ................ 10-16

10.7.5 General and Concluding Aspects Regarding Integration of Technologies ..... 10-16

10.7 COSTS ...................................................... 10-18

10.8 GENERAL CONCLUSIONS ....................................... 10-18

10.9 ACKNOWLEDGEMENTS ........................................ 10-18

Chapter 11: REMEDIATION TECHNOLOGY RESEARCH NEEDS .................. 11-1

11.1 INTRODUCTION ................................................ 11-1

11.2 LESSONS FROM PREVIOUS NATO/CCMS STUDIES ..................... 11-3

11.3 THE PRESENT STUDY ........................................... 11-4

11.4 REFERENCES .................................................. 11-6

Chapter 12: CONCLUSIONS AND RECOMMENDATIONS ........................ 12-1

12.1 INTRODUCTION ................................................ 12-1

12.2 GENERAL CONCLUSIONS ........................................ 12-1

12.3 GENERAL TECHNICAL CONCLUSIONS .............................. 12-2

12.4 RESEARCH NEEDS .............................................. 12-6

12.5 RECOMMENDATIONS TO CCMS ................................... 12-6

12.6 REFERENCES .................................................. 12-8

Appendix I—COUNTRY REPRESENTATIVES ................................ A-I-1

Appendix II—CCMS FELLOWS .......................................... A-II-1

Appendix III—GUEST SPEAKERS ....................................... A-III-1

Appendix IV—PROJECT SUMMARIES

Available through the Internet at http://clu-in.com or http://www.nato.int/ccms

Appendix V—FELLOW STUDIES ......................................... A-V-i

PREFACE ........................................................ A-V-i

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NATO/CCMS Pilot Study, Phase II Final Report

Quality Management Systems and the Remediation of Contaminated Land

Dr. Bob Bell and Mr. Richard Failey, SGS Environment, Colwyn Bay, U.K. ...... A-V-1

Groundwater Contamination in Portugal: Overview of the Main Problems

Maria Teresa Chambino, Instituto Nacional de Engenharia e Tecnologia Industrial (INETI),

Instituto de Tecnologias Ambientais/Dep. Tecnologias Ambientais, Portugal ....... A-V-6

Critical Review of Air Sparging and In situ Bioremediation Technologies

Domenic Grasso, The School of Engineering, University of Connecticut, Kenneth L Sperry,

Envirogen, Lawrenceville, NJ, and Susan Grasso, Environ, Princeton, NJ ........ A-V-20

The Cost of Remedial Action

Dr. Mary R. Harris, Monitor Environmental Consultants Ltd, Birmingham, U.K. . . . A-V-25

Changing Approaches to Remediation

Merten Hinsenveld, TSM Business School, University of Twente, Enschede,

The Netherlands ................................................ A-V-31

Use of Remedial Clean-Up Technology in Portugal

Maria José Macedo, Hovione - Sociedade Quimica SA, Loures, Portugal ........ A-V-32

Experiences with the Performance of In Situ Treatment Technologies

Dr. Robert L. Siegrist, Environmental Science & Engineering Division, Colorado School of

Mines ....................................................... A-V-35

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NATO/CCMS Pilot Study, Phase II Final Report

TABLES

Table 1.1: List of Projects Included in CCMS Study on Remediation Technology . . . . . . . . . . . 1-4

Table 2.1: Projects Included in NATO/CCMS Pilot Study, Classification by Technology

(February 1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

Table 2.2: Projects Included in NATO/CCMS Phase II Pilot Study, Classification by Media and

Contaminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

Table 4.1: In Situ Projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

Table 4.2. Estimated Costs of Technology Application ............................. 4-20

Table 6.1: Projects Reviewed and References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2

Table 6.2: Overview of Selected Projects ...................................... 6-10

Table 6.3: Outline of Treatment Processes By Project ............................. 6-11

Table 6.4: Biogenie Case Studies ............................................ 6-14

Table 6.5: Project 11 Treatments ............................................ 6-15

Table 6.6: Residuals and Emissions .......................................... 6-22

Table 6.7: Key Factors Limiting Performance ................................... 6-24

Table 6.8: Cost Information by Project ........................................ 6-26

Table 7.1: Projects Involving Ex Situ Thermal Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7

Table 7.2: Input Materials ................................................. 7-15

Table 7.3: Thermal Treatment Process ........................................ 7-16

Table 7.4: Performance Information .......................................... 7-17

Table 7.5: Mercury Concentrations in Waste Streams Treated in Project 19 .............. 7-18

Table 7.6: Summary Results of Pilot-Scale Trials ................................ 7-19

Table 7.7: Cost Data .................................................... 7-23

Table 10.1: Factors Limiting Effective Treatment with Only One Technology and the General

Options to Overcome the Limitations ...................................... 10-3

Table 10.2: Projects Involving Integration of Treatment Technologies .................. 10-4

Table 10.3: Goal of Combination, Input Materials in Terms of Medium Treated, Contaminants

Present, Types of Technologies Combined and Scale of Project .................... 10-9

Table 10.4: Categories of Integration of Technologies and Respective Criteria ........... 10-11

Table 10.5: Performance Data of the Separation of Fractions Category ................ 10-11

Table 10.6: Performance Data of the “Mobilization of Contaminants to Enhance Treatment”

Category ......................................................... 10-13

Table 10.7: Performance Data of the “Increase of Availability of Contaminants to Treatment”

Category ......................................................... 10-14

Table 10.8: Performance Data of the “Sequential Removal of Different Types of Contaminants”

Category ......................................................... 10-15

Table 10.9: Cost Data (to the extent available) ................................. 10-19

xi
Phase II Final Report

NATO/CCMS Pilot Study

Evaluation of Demonstrated and Emerging

Technologies for the Treatment and Clean Up

of Contaminated Land and Groundwater

June 1998
NOTICE

This Phase II Pilot Study Final Report was prepared under the auspices of the North Atlantic Treaty

Organization’s Committee on the Challenges of Modern Society (NATO/CCMS) as a service to the

technical community by the United States Environmental Protection Agency (U.S. EPA). Production of

the document was funded by U.S. EPA’s Technology Innovation Office under the direction of Michael

Kosakowski. Michael A. Smith of Berkhamsted, U.K., served as the principal editor for the report.

Final editing and formatting services were provided by Environmental Management Support, Inc., of

Silver Spring, Maryland, under U.S. EPA contract 68-W6-0014. Mention of trade names or specific

applications does not imply endorsement or acceptance by U.S. EPA.
NATO/CCMS Pilot Study, Phase II Final Report

Chapter 1: INTRODUCTION

Michael A. Smith

M.A. Smith Environmental Consultancy

1.1 BACKGROUND

Groundwater and soil contamination are among the most complex and challenging environmental

problems faced by many countries. The problems involve a number of technical issues, including the

means of identifying contamination, understanding contaminant behavior in the environment, and

mitigating the potential adverse affects to human health and the environment. There are also a number

of non-technical issues to be considered, such as the social, economic, and psychological impacts of

contamination on individuals and communities, and the need to rejuvenate old urban and industrial areas.

The NATO Committee on the Challenges to Modern Society (NATO/CCMS) has organized a number

of pilot studies on the technical aspects of contaminated land. The first pilot study (Box 1.1), which ran

from 1980-1984, included an assessment of available remediation methods and a number of other topics.

This led to the Phase I Pilot Study (Box 1.2) from 1986-1991 for the purpose of identifying and

evaluating innovative, emerging, and alternative technologies and transferring the technical performance

and economic information to potential users.

Twenty-nine demonstration projects were shared by the pilot study participants. A specific and important

objective of this study was to identify “lessons learned” from the technology demonstrations—not only

the successes but also those lessons that illustrated technology failures or limitations. Attention was paid

not only to the technologies themselves, but to the practical, operational, and organizational aspects of

implementation. Information on limitations and practical aspects of implementation is rarely presented

at conferences or discussed in the technical literature, but is very important for making informed

decisions involving critical time and monetary requirements. It is also useful for defining priorities in

research and development.

The success of the Phase I Pilot Study led to the inception of the Phase II Pilot Study in 1992. Phase

II was conducted similarly to Phase I, but was extended in scope to include technologies at an earlier

stage of development.

This report provides:

• the background and organization of the Phase II Pilot Study;

• a short description of each of the more than 50 projects included in the study;

• characterization of the projects in a variety of ways including, for example, by the technologies used,

their development status, and contaminants treated;

• a critical review of the project results in a series of technology-based chapters; and

• the conclusions and recommendations arising from the study.

The organization of the pilot study, a summary of its achievements, key conclusions, and

recommendations to the NATO/CCMS have also been published in a separate Overview Report (1).

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NATO/CCMS Pilot Study, Phase II Final Report

Technologies are frequently classified as emerging, innovative, or demonstrated. Emerging technologies

are at a stage where successful bench-scale testing has been conducted and pilot-scale evaluation is

required to determine its potential for use in remediation. Innovative technologies are at the stage where

pilot- or field-scale testing is being conducted and performance or cost information is incomplete. In

general, innovative technologies require field testing to prove their effectiveness before they can be

considered proven and available for use in remediation. Finally, demonstrated technologies have

undergone properly designed independent field evaluation to determine their performance under carefully

monitored conditions.

What is viewed as an innovative technology in one country may be regarded as established in another.

What is considered as established in one country may not be used widely in others because of doubts

about its effectiveness1

. The term “innovative” often applies to the application of a technology rather

than to the principles underlying it. While truly innovative technologies remain a goal, there is also a

need for better information and understanding of established processes or means of ensuring that their

capabilities are fully realized in practice.

Box 1.1: The First NATO/CCMS Pilot Study on Contaminated Land (1980-84)

The first NATO/CCMS Pilot Study on contaminated land was conducted from 1980 to 1984.

Seven countries participated in the study: Canada, Denmark, the Federal Republic of Germany,

France, the Netherlands, the United Kingdom (U.K.), and the United States (U.S.).

The Pilot Study culminated in publication of a report (2), which provided a state-of-the-art

review of measures available for dealing with contaminated sites and of a number of related

topics. It also provided the participating countries with a common basis for understanding the

problems posed by contaminated sites and how they might be addressed. A chapter entitled

“Long-Term Effectiveness of Remedial Measures,” provided the basis for three principal

conclusions of the Pilot Study:

• Systems based on isolation of the contamination (e.g., covering systems) are vulnerable to

loss of effectiveness with time; like many other engineered projects they have a finite life;

• The development of on-site and in situ processes resulting in the removal or destruction of

contaminants is to be encouraged as providing a one-time final solution; and

• Very few of the technologies described have been sufficiently proven in applications specific

to the treatment of contaminated land.

The initial NATO pilot study led to an extensive exchange of information between participants,

the formation of a professional and scientific network that continues to this day, and the

initiation of bilateral programs of cooperation.

1 An example is stabilization/solidification. While widely applied in the United States, it has only limited

application to date in Western Europe.

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NATO/CCMS Pilot Study, Phase II Final Report

Box 1.2: The Phase I Study (1986-1991)

The formal title of the Phase I Pilot Study was “Demonstration of Remedial Action

Technologies for Contaminated Land and Groundwater.” This Pilot Study was intended to be a

practical, rather than a desk-based exercise, although it continued to provide a forum for the

exchange of information on policy developments in the participating countries. It was co-piloted

by Germany, the Netherlands, and the United States. and ran from 1986 to 1991. Seven

countries participated formally throughout the study. A number of other countries attended at

least one meeting on a less formal basis or through the CCMS Fellowship Program.

The objectives of the Phase I Pilot Study were to:

• identify and evaluate innovative, emerging, and alternative remediation technologies and to

transfer technical performance and economic data to potential users; and

• identify “lessons learned” from the technology demonstrations, including not only the

successes, but lessons illustrating technology failures or limitations.

A total of 29 demonstration projects from several countries were included in the Phase I Pilot

Study. The results of demonstration projects were critically reviewed at the pilot study meetings

so that “lessons learned” could be distilled.

The final report (3) published by the U.S. Environmental Protection Agency (USEPA) comprises

a principal volume, which presents the lessons learned and technology classifications, and

supporting volumes, which contain the individual project reports, reports by CCMS Fellows,

papers presented by expert speakers, and other supporting material arising from the Pilot

Study.

1.2 STRUCTURE OF THE STUDY

The Phase II Pilot Study was intended to provide a means for information and technology exchange

between participating countries; information was also exchanged on regulatory and policy developments.

The primary vehicles for the exchange were the Pilot Study members' critical review of projects

submitted by the participating countries (Table 1.1), and technical presentations and themed discussions

at the meetings of the Pilot Study members. The technical work of the Pilot Study members was

enhanced by work on special topics by a number of CCMS Fellows2 (Section 1.4).

The Phase II Pilot Study was modeled on the Phase I study but included technologies that were in an

early stage of development, as well as those that were ready for full-scale demonstration.

2 The CCMS awards a number of Fellowships each year to meet travel and subsistence costs for projects related

to on-going Pilot Studies. Fellows (i.e., the recipients of fellowships) are encouraged to attend meetings of the

Study Group. Fellows have made important contributions to all three CCMS projects on contaminated land.

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NATO/CCMS Pilot Study, Phase II Final Report

Table 1.1: List of Projects Included in CCMS Study on Remediation Technology

Country Project

Number

Title

Australia 1

2

3

4

Trial of air-sparging of a petroleum-contaminated aquifer

Bioremediation of petrochemicals following a major fire

Bioclogging of aquifers for containment and remediation of organic contaminants

Remediation of methyl ethyl ketone contaminated soil and groundwater

Austria 5 In situ bioremediation, bioavailability, and process control with different soil types

Canada 6

7

8

9

10

In situ/on-site bioremediation of industrial soil contaminated with organic pollutants: elimination of soil toxicity with

DARAMEND®

Demonstration of thermal gas-phase reduction process

Biodegradation/bioventing of oil-contaminated soils

Field demonstration of an in situ process for soil remediation using well points

Integrated treatment technology for the recovery of inorganic and organic contaminants from soil

Czech Republic 51

56

Sobéslav, South Bohemia wood treatment plant

Spolchemie a.s.—mercury-contaminated site

Denmark 11

12

13

On-site biological degradation of PAHs in soil at former gasworks site

Groundwater and soil remediation at former manganese sulfate production plant

Rehabilitation of a site contaminated by tar substances using new on-site techniques

France 14

15

16

17

Ozone treatment of contaminated groundwater

Combined chemical and microbiological treatment of coking sites/bioremediation of soils from coal and petroleum tar

distillation plants

Combined vacuum extraction and in situ stripping of chlorinated vapors

Treatment of polluted soil in a mobile solvent extraction unit

45 Bioremediation of soils from coal and petroleum tar distillation plants

Germany 18

19

20

21

52

Biological in situ remediation of contaminated gasworks

Cleaning of mercury-contaminated soil using a combined washing and distillation process

Fluidized bed soil treatment process—BORAN

Mobile low-temperature thermal treatment process

Permeable treatment beds

Hungary 22 Environmental evaluations of former Soviet military bases in Hungary

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NATO/CCMS Pilot Study, Phase II Final Report

Country Project

Number

Title

Netherlands 23

24

25

53

Modeling and optimization of in situ remediation

Combined remediation technique for soil containing organic contaminants: Fortec®

Slurry reactor for soil treatment

In situ bioremediation of chloroethene-contaminated soil

Norway 26

27

28

Treatment of creosote-contaminated soil (soil washing and slurry phase bioreactor)

Soil washing and chemical dehalogenation of PCB-contaminated soil

Use of white-rot fungi for bioremediation of creosote-contaminated soil

Sweden 54 Treatment of PAH- and PCP-contaminated soil in slurry phase bioreactors

Switzerland 49 Characterization of residual contaminants in bioremediated soil and reuse of bioremediated soil

Turkey 29 Sorption/solidification of selected heavy metals and radionuclides onto unconventional sorbents

United Kingdom 30

31

32

33

34

35

36

Using separation processes from the mineral processing industry for soil treatment

Decontamination of metalliferous mining spoil

CacitoxTM soil treatment process

In-pulp decontamination of soils, sludges, and sediments

Chemical fixation of soils contaminated with organic chemicals

In situ soil vapor extraction within containment cells combined with ex situ bioremediation and groundwater treatment

Enhancement techniques for ex situ separation processes, particularly with regard to fine particles

United States 37

38

39

40

41

42

43

44

Bioventing of hydrocarbon-contaminated soils in the subarctic environment

Demonstration of Peroxidation Systems, Inc., Perox-PureTM advanced oxidation technology

Management of soil vapors at the Basket Creek site

An evaluation of the feasibility of photocatalytic oxidation and phase transfer catalysis for destruction of contaminants from

water (in situ treatment of chlorinated solvents)

In situ microbial filters

In situ pneumatic fracturing and in situ bioremediation

Multi-vendor bioremediation technology demonstration project

Enhanced in situ removal of coal tar: Brodhead Creek Superfund Site

47

50

In situ electro-osmosis (LasagnaTM project)

Integrated rotary steam stripping and enhanced bioremediation for in situ treatment of VOC-contaminated soil (cooperative

approach to application of advanced environmental technologies)

55 Czechowice oil refinery project

NOTE: There are no Project Nos. 45, 46 or 48. Project 5 from Austria was withdrawn.

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NATO/CCMS Pilot Study, Phase II Final Report

The objectives were to:

• exchange technical information on demonstrated technologies;

• exchange information on the development of emerging and innovative technologies; and

• recommend, develop, and adopt uniform data reporting methods for results of technology studies (demonstrations, bench, pilot, and other technology studies).

The third objective was intended to facilitate evaluation of the probable performance of a technology, based on a country’s environmental, health, or risk standards.

The need for better reporting standards was identified during the Phase I Pilot Study. However, the nascent stage of technical developments in many countries

did not permit this need to be fully addressed. It is anticipated that the development of better reporting standards will be addressed further during the planned Phase

III Pilot Study.

A number of the conclusions drawn from the Phase I Pilot Study report were addressed during the Phase II Pilot Study. For example, Fellowship projects addressed

the costs and the design of demonstration projects. The organization of the Phase II Pilot Study is described in Box 1.3.

1.3 HOW THE INFORMATION IS PRESENTED

Chapter 2 presents an overview of the Phase II Pilot Study. It lists the 52 projects included in the study

and classifies them in several ways, including by their development status and whether in situ or ex situ

methods were employed.

Chapter 3 provides an overview of process-based remediation methods and is intended to show how the

different technologies discussed in later chapters relate to one another. The terminology used here and

elsewhere in the report generally corresponds to with that being developed by the International

Organization for Standardization (ISO) (4).

Chapters 4 to 9, which are generally organized as shown in Box 1.4, present the results of the Pilot

Study by technology area as follows:

• Chapter 4, In Situ Treatment;

• Chapter 5, Physical-Chemical Treatment;

• Chapter 6, Ex Situ Biological Treatment;

• Chapter 7, Thermal Treatment;

• Chapter 8, Stabilization/Solidification; and

• Chapter 9, Other (includes all projects not easily dealt with in the other chapters).

The broader topic of integrated treatment systems is addressed in:

• Chapter 10: Integration of Technologies.

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NATO/CCMS Pilot Study, Phase II Final Report

Box 1.3: Organization of the Phase II Pilot Study

Formal members of the Pilot Study held either “participant” or “observer” status. Each

country nominated a representative to attend Pilot Study meetings3

, and these representatives

invited others from their countries to take part in meetings and activities. The major part of the

Phase II Pilot Study was completed during international meetings attended by:

• country representatives;

• technical experts representing Pilot Study projects;

• leading international experts invited to speak on topics of interest to the Pilot Study;

• nominated guests of the host country; and

• Pilot Study Fellows.

Individual country representatives nominated projects of potential interest to the Phase II Pilot

Study, and the representatives as a group voted whether or not to accept them. The Pilot Study

strived to maintain a balance between long-term and short-term projects4 across a range of

technologies. Projects that were accepted were expected to produce interim reports and a final

project report within the Pilot Study’s lifetime. Throughout the Pilot Study, project presentations

were open to technical scrutiny and critical review. These discussions have been used in

conjunction with each project’s interim and final presentations as the basis for information

presented in this report.

Each country was limited to a maximum of four active projects within the Pilot Study at any

one time, although during the course of the study, countries could replace completed projects

with new ones. Germany, the United Kingdom, and the United States all had more than four

projects accepted over the lifetime of this study.

The Phase II Pilot Study was at the forefront of technology development and application.

Hence, projects that might be regarded in some countries as state-of-the-art or innovative, such

as applications of thermal treatment, may not have been accepted into Phase II if they were

previously considered in Phase I. Where an established technology was accepted, it was

generally because the project focused on a novel application or involved a fundamental

investigation that offered potentially significant improvements in process optimization.

3 “Participants” are countries that had a technical project accepted within the Pilot Study while “observers” are

formal members of the Pilot Study, but did not contribute projects. Some countries have been represented by

individuals, such as the CCMS Fellows, and were not formal members of the Pilot Study.

4 Long-term projects involve technologies that are being developed in the laboratory and might not be

commercially available for another 5-10 years. Short-term projects involve technologies being evaluated in full

field-scale trials and are therefore near-market applications.

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NATO/CCMS Pilot Study, Phase II Final Report

Box 1.4: Organization of Technology Chapters

Introduction: A description of the technology including basic principles of the process and its

potential application. A fuller description is provided in Chapter 3.

Case studies included: A brief summary of the projects evaluated, including why the project

was chosen for evaluation. More detailed summaries of each project are provided in Appendix

IV (Volume 2).

Background of the case studies as a group: A synthesis of pertinent information from the

projects to help the reader understand the range of applicability of the technology. This

includes the type, concentration, and sources of contamination, as well as the type of media

that can be treated. The lessons learned in the application of the technology are also presented.

Performance results: An assessment of the results of the case studies, including whether project

objectives were met, whether the technology was effective, and lessons learned in site

preparation and operational testing.

Residuals and emissions: A discussion of the residual materials and emissions, if any,

associated with the technology that should be considered when evaluating the potential

application of these processes to contaminated sites.

Factors and limitations to consider for determining the technology's applicability: Identification

of both technical and non-technical aspects.

Costs: An overview of major capital, operating, and maintenance cost factors that need to be

considered by remediation planners. Typical costs or costs specific to case studies are provided

in some chapters.

Prognosis for technology: A summary of the state of the technology and its expected role in

future site remediation, including an identification of future research needs.

Conclusions and recommendations

1.4 RELATIONSHIP TO OTHER CCMS PROGRAMS

1.4.1 Contributions by CCMS Fellows

The CCMS Fellowship Program made an important contribution to the success of the Phase II Pilot

Study, as it did to the earlier studies on the remediation of contaminated soil and groundwater. It enabled

the participation of a number of experts from countries that would not otherwise have had a presence

in the Pilot Study. It also enabled a wider range of topics to be covered.

Ten NATO Fellows participated in the Phase II Pilot Study. Nine Fellows conducted associated studies

and submitted reports to the Pilot Study under the guidance of the Pilot Study Directors. One acted as

the editor of this report, and two others contributed to its preparation. The Fellows came from private,

university, and governmental organizations in Germany, Portugal, the Netherlands, Turkey, the United

Kingdom, and United States. Their activities examined a range of topics, including national approaches

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NATO/CCMS Pilot Study, Phase II Final Report

to environmental problems, costs and economics, quality management, innovative approaches to largescale remediation projects, and performance assessment of in situ treatment methods. The Fellows and

the subjects of their studies are listed in Appendix II. The Fellows’ summary reports are provided in

Appendix V.

1.4.2 CCMS Study Visit Program

Participation of a number of individuals, particularly expert speakers, was made possible by travel funds

provided under the CCMS Study Visit Program.

1.5 CONTRIBUTIONS BY EXPERT SPEAKERS

Invited expert speakers (see Appendix III) attended all of the meetings, which often lead to an in-depth

discussion of a particular subject area. Where relevant, these discussions have been taken into account

in the preparation of this report.

1.6 CONCLUSIONS AND RECOMMENDATIONS

One of the major achievements of the Phase II Pilot Study is that it has demonstrated the benefits of

exchanging technical and economic information on the remediation of contaminated land and

groundwater. Conclusions regarding specific technologies, remediation in general, technology transfer,

and research needs were drawn from the Pilot Study. The conclusions and recommendations are based

on an analysis of the results of Pilot Study projects, and on the contributions of expert speakers, CCMS

Fellows, and the numerous other participants in the Study Group meetings.

The conclusions and recommendations reflect both the achievements to date in devising effective

treatment technologies and the gaps in the methods available to treat some of the more difficult

problems. The conclusions are presented in Chapter 12, which also includes the recommendations made

to the CCMS/NATO Council following the Study Group’s deliberations.

1.7 REFERENCES

1. U.S. Environmental Protection Agency, Evaluation of Demonstrated and Emerging Technologies for

Treatment and Clean-up of Contaminated Land and Groundwater: Overview Report, EPA/542-R-98-

001b, 1998.

2. Smith, M. A. (editor), Contaminated Land: Reclamation and Treatment

Plenum (London) 1985.

3. U.S. Environmental Protection Agency, NATO/CCMS Pilot Study: Demonstration of Remedial Action

Technologies for Contaminated Land and Groundwater, Final Report, Volume 1, 1993, EPA/600/R93/012a.

4. International Organization for Standardization, ISO DIS 11074-4: Soil Quality - Vocabulary: Part

4: Terms and Definitions Relating to the Rehabilitation of Soils and Sites

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NATO/CCMS Pilot Study, Phase II Final Report

Chapter 2: TECHNICAL OVERVIEW

Michael A. Smith

M.A. Smith Environmental Consultancy

2.1 INTRODUCTION

While the objective of the Pilot Study was to evaluate applications of particular technologies, a large

proportion of the projects involved more than one technology. For example, some involved the use of

integrated treatment systems combining more than one technology type, and others involved the

application of different more than one technology to address different aspects of site contamination (e.g.,

more than one contaminated medium). Other projects involved:

• large-scale remediation projects for which the remediation strategy had yet to be developed (e.g.,

Projects 51 and 56);

• theoretical studies (e.g., Project 23); and

• strategic scientific studies (e.g., Project 49).

Because the projects are classified below in a variety of ways, they may be counted two or three times,

and not all projects may be included in each analysis. Furthermore, the categorization of projects is, in

part, at a matter of judgment, and alternative categorizations to those presented here are possible.

The projects have been classified as follows:

• by the development status of the technology;

• whether they are in situ, ex situ technologies, or a combination of both;

• by the type of technology used;

• by the contaminants treated; and

• whether they involve a single technology, mixed technologies, or integrated treatment systems.

Table 2.1 summarizes the 52 “active” projects in the Pilot Study. Additional information can be obtained

from the project summaries, which are provided separately (Appendix IV). The project summaries

contain a technical abstract providing a synopsis of the author’s written and oral reporting, but are not

a critical review of the material presented. The technical contact for the project is also provided in each

summary.

2.2 DEVELOPMENT STATUS

Forty-nine of the 52 pilot study projects were technology based. The Pilot Study accepted technical

projects in two stages of development: emerging and demonstration. For the purposes of this report an

emerging technology is defined (see Chapter 1) as being at bench- or pilot-scale, while a demonstrated

technology is one implemented at field- or full-scale. Demonstrated technologies are usually at or near

to commercial application. There was almost an even split of projects within the Pilot Study examining

emerging and demonstrated technologies.

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NATO/CCMS Pilot Study, Phase II Final Report

2.3. IN SITU VS. EX SITU

There were 18 projects using in situ technologies, 26 projects using ex situ technologies, six projects

using both in situ and ex situ technologies, and two projects for which the remediation strategy has yet

to be decided.

2.4 TECHNOLOGIES EMPLOYED

For the purposes of this report,the technologies described in each technical project were broadly

classified as one of five types: biological, chemical, physical-chemical, stabilization/solidification, and

thermal. The additional categories of “integrated” and “mixed” are used to describe combinations of

technologies used as part of an overall remediation strategy. Integrated refers to approaches where two

or more technologies are used simultaneously or in series to treat a specific site problem. “Mixed”

projects involved two or more technologies to treat different contaminated areas or media across a site

as part of an overall remedial strategy.

The classification of projects was as follows (Note that some projects are counted more than once.):

Technology Number of

Projects

Examples of Technologies

Biological

Physical-chemical

Chemical

Thermal

Stabilization/Solidification

Other

24

29

4

5

2

4

bioventing, biopiles, slurry reactors, white rot

fungi

soil vapor extraction, soil washing, solvent

extraction, ultraviolet treatment

photochemical oxidation, ozone treatment,

sorption, leaching

thermal desorption, incineration, thermal

vitrification

chemical fixation, grouting

site characterizations, free-product recovery

systems

There were 23 projects that relied upon a single technology, 19 that used integrated technologies, seven

mixed technologies, and three that did not involve treatment.Typical combinations were soil vapor

extraction with in situ biotreatment, soil washing followed by biotreatment, and soil washing followed

by thermal treatment.

2.5 CONTAMINANTS TREATED

Forty of the 52 projects were concerned only with the treatment of organic contaminants including

polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and BTEX compounds

(benzene, toluene, ethylbenzene, and xylenes). Six projects dealt exclusively with metals, while six dealt

with both inorganic and organic contaminants. One project focused on remediation of inorganic sulfates

and cyanides. A matrix showing the contaminants treated for each project is presented in Table 2.2.

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NATO/CCMS Pilot Study, Phase II Final Report

Table 2.1: Projects Included in NATO/CCMS Pilot Study,

Classification by Technology (February 1997)

Project Title

(Chapter in which Project is Addressed) Technology In situ/ex situ

Single/

integrated/

mixed

1 Trial of air-sparging of a petroleum-contaminated aquifer

(Chapters 4 & 10)

PhysicalchemicalIn situ Integrated

2 Bioremediation of petrochemicals following a major fire

(Chapter 4)

Biological Ex situ

In situ

Single

3 Bioclogging of aquifers for containment and remediation of

organic contaminants (Chapter 4)

Biological In situ Single

4 Remediation of methyl ethyl ketone contaminated soil and

groundwater (Chapter 4)

PhysicalchemicalIn situ Integrated

6 In situ/on-site bioremediation of industrial soils contaminated

with organic pollutants: elimination of soil toxicity with

DARAMEND® (Chapters 4 & 6)

Biological In situ

Ex situ

Single

7 Demonstration of thermal gas-phase reduction process

(Chapter 7)

Physicalchemical

Thermal

Ex situ Single

8 Biodegradation/bioventing of oil-contaminated soils (Chapter 6) Biological Ex situ Single

9 Field demonstration of an in situ process for soil remediation

using well points (Chapters 4 & 10)

PhysicalchemicalIn situ Integrated

10 Integrated treatment technology for the recovery of inorganic

and organic contaminants from soil (Chapters 5 & 10)

PhysicalchemicalIn situ Integrated

11 On-site biological degradation of PAHs in soil at a former

gasworks site (Chapter 6)

Biological Ex situ Single

12 Groundwater and soil remediation at a former manganese

sulfate production plant (Chapter 4)

PhysicalchemicalIn situ Mixed

13 Rehabilitation of a site contaminated by tar substances using a

new on-site technique (Chapters 7 & 10)

Thermal

Physicalchemical

Ex situ Integrated

14 Ozone treatment of contaminated groundwater (Chapter 5) Chemical Ex situ Single

15 Combined chemical and microbiological treatment of coking

sites/ bioremediation of soils from coal and petroleum tar

distillation plants (Chapters 4, 6, & 10)

Chemical

Biological

Ex situ Integrated

16 Combined vacuum extraction and in situ stripping of

chlorinated vapors (Chapter 4)

PhysicalchemicalIn situ Integrated

17 Treatment of polluted soil in a mobile solvent extraction unit

(Chapter 5)

PhysicalchemicalEx situ Single

18 Biological in situ remediation of contaminated gasworks

(Chapter 4)

Biological In situ Single

19 Cleaning mercury-contaminated soil using a combined

washing and distillation process (Chapters 5, 7, & 10)

Physicalchemical

Thermal

Ex situ Integrated

20 Fluidized bed soil treatment process—BORAN (Chapter 7) Thermal Ex situ Single

21 Mobile low-temperature thermal treatment process (Chapter 7) Thermal Ex situ Single

22 Environmental evaluations of former Soviet military bases in

Hungary (Chapter 9)

- - Integrated

23 Modeling and optimization of in situ remediation (Chapter 4) Physicalchemical

Biological

In situ Research

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NATO/CCMS Pilot Study, Phase II Final Report

Project Title

(Chapter in which Project is Addressed) Technology In situ/ex situ

Single/

integrated/

mixed

24 Combined remediation technique for soil containing organic

contaminants: Fortec® (Chapters 5, 6, & 10)

Physicalchemical

Biological

Ex situ Integrated

25 Slurry reactor for soil treatment (Chapter 6) Biological Ex situ Single

26 Treatment of creosote-contaminated soil (soil washing and

slurry phase bioreactor) (Chapters 5, 6, & 10)

Physicalchemical

Biological

Ex situ Integrated

27 Soil washing and chemical dehalogenation of PCBcontaminated soil (Chapters 5 & 10)Physicalchemical

Chemical

Ex situ Integrated

28 Use of white-rot fungi for bioremediation of creosotecontaminated soil (Chapter 6)Biological Ex situ Single

29 Sorption/solidification of selected heavy metals and

radionuclides onto unconventional sorbent (Chapter 8)

Stabilization/

solidification

Ex situ Single

30 Using separation processes from the mineral processing

industry for soil treatment (Chapter 5)

PhysicalchemicalEx situ Single

31 Decontamination of metalliferous mine spoil (Chapters 5, 6, &

10)

Physicalchemical

Biological

Ex situ Integrated

32 CacitoxTM soil treatment process (Chapters 5 & 10) PhysicalchemicalEx situ Integrated

33 In-pulp decontamination of soils, sludges, and sediments

(Chapters 5 & 10)

PhysicalchemicalEx situ Integrated

34 Chemical fixation of soils contaminated with organic chemicals

(Chapter 8)

Stabilization/

solidification

In situ Single

35 In situ soil vapor extraction within containment cells combined

with ex situ bioremediation and groundwater treatment

(Chapters 4 & 6)

PhysicalchemicalIn situ

Ex situ

Mixed

36 Enhancement techniques for ex situ separation processes,

particularly with regard to fine particle (Chapters 5, 6, & 10)

PhysicalchemicalEx situ Integrated

37 Bioventing of hydrocarbon-contaminated soils in the subarctic

environment (Chapter 4)

Biological In situ Single

38 Demonstration of Peroxidation Systems, Inc., Perox-PureTM

advanced oxidation technology (Chapter 5)

Physicalchemical

Chemical

Ex situ Single

39 Management of soil vapors at the Basket Creek site (Chapter

9)

PhysicalchemicalEx situ Single

40 An evaluation of the feasibility of photocatalytic oxidation and

phase transfer catalysis for destruction of contaminants from

water (in situ treatment of chlorinated solvents) (Chapter 5)

PhysicalchemicalEx situ Single

41 In situ microbial filters (Chapter 4) Biological In situ Single

42 In situ pneumatic fracturing and in situ bioremediation

(Chapters 4 & 10)

Biological

Other

In situ Integrated

43 Multi-vendor bioremediation technology demonstration project

(Chapters 4 & 6)

Biological In situ

Ex Situ

Mixed

44 Enhanced in situ removal of coal tar: Brodhead Creek

Superfund Site (Chapter 5)

PhysicalchemicalIx situ Single

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NATO/CCMS Pilot Study, Phase II Final Report

Project Title

(Chapter in which Project is Addressed) Technology In situ/ex situ

Single/

integrated/

mixed

47 In situ electro-osmosis (LasagnaTM project) (Chapters 4, 5, &

10)

Physicalchemical

Biological

In situ Integrated

49 Characterization of residual contaminants in bioremediated soil

and reuse of bioremediated soil (Chapter 6)

Biological Ex situ Research

50 Integrated rotary steam stripping and enhanced bioremediation

for in situ treatment of VOC-contaminated soil (Cooperative

approach to application of advanced environmental

technologies) (Chapter 9)

Physicalchemical

Biological

In situ Mixed

51 Sobéslav, South Bohemia wood treatment plant (Chapter 9) Biological

Containment

Ex situ

In situ

Mixed

52 Permeable treatment beds (to be addressed in the Phase III

report)

Physicalchemical

Chemical

In situ Integrated

53 In situ bioremediation of chloroethene-contaminated soil

(Chapter 9)

Biological

Physicalchemical

Ex situ Mixed

54 Treatment of PAH- and PCP-contaminated soil in slurry phase

bioreactors (Chapter 6)

Biological In situ Single

55 Czechowice oil refinery project (Chapter 9) Biological

Physicalchemical

Ex situ Mixed

56 Spolchemie a.s.— mercury-contaminated site (Chapter 9) - - Other

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NATO/CCMS Pilot Study, Phase II Final Report

Table 2.2: Projects Included in NATO/CCMS Phase II Pilot Study,

Classification by Media and Contaminants

PROJECT

NO.

MEDIUM CONTAMINANT

NOTES

SoilGroundwaterVOCsSVOCs

Pesticides/PCBs

PHCsInorganics

1 • • • benzene, xylene, petroleum hydrocarbons

2 • • • • benzene, phenol, acrylonitrile

3 • • BTEX

4 • • • • MEK, oil, gasoline, turpentine, kerosene

5 • project withdrawn

6 • • • aliphatic and aromatic hydrocarbons, phthalates, chlorophenols

7 • • • • •

TCE, 1,2-DCE, methylene chloride, toluene, ethylbenzene, PCBs, benzidine,

benzene, vinyl chloride, chlorobenzene, PAHs, lindane, dieldrin, chlordane,

DDT metabolites

8 • • • • BTEX, PAHs, mineral oil, grease, pentachlorophenols

9 • • BTEX, aliphatic hydrocarbons

10 • • • PAHs, lead, copper, zinc

11 • • PAHs

12 • • • sulfate, cyanide

13 • • • • coal tar, PAHs, BTEX, phenols, cyanides, heavy metals, ammonium compounds

14 • • • • phenols, aliphatic and aromatic hydrocarbons, BTEX, acetone, ethanol,

chlorinated solvents, petroleum hydrocarbons

15 • • • PAHs, phenols, cyanides

16 • • • PCE

17 • • • • BTEX, PAHs, PCBs

18 • • PAHs, extractable lipophilic organics

19 • • mercury

20 • • • PAHs, PCBs

21 • • • • • BTEX, PAHs, mineral oils, lignite tar oil, mercury, TNT

22 • • jet fuel, including DNAPL

23 • • • VOCs

24 • • • • mineral oils, PAHs, chlorophenol, lindane

25 • • • mineral oil, PAHs

26 • • PAHs

27 • • PCBs

28 • • PAHs

29 • • lead, cadmium, copper, cesium-137, strontium-90

30 • • • PAHs, phenols, heavy metals, cyanides

31 • • lead, zinc

32 • • heavy metals, radionuclides

33 • • copper, zinc, chromium, arsenic

34 • • • • chlorinated hydrocarbons, PAHs, benzene and benzene derivatives, phenolics,

PCBs, organophosphorus/sulphurous compounds

35 • • • • • BTEX, PAHs, phenols, heavy metals, cyanides

36 • • • PAHs, diesel fuel

37 • • • jet propellant #4

38 • • TCE, PCE, 1,1,1-TCA, 1,1-DCA

39 • • • TCE, PCE, toluene, MEK, MIBK, lead, mercury

40 • • BTEX

41 • • TCE

42 • • benzene, toluene, xylenes

43 • • TCE, PCE, DCE, acetone, MEK, toluene

44 • • • • BTEX, PAHs, coal tar

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NATO/CCMS Pilot Study, Phase II Final Report

PROJECT

NO.

MEDIUM CONTAMINANT

NOTES

SoilGroundwaterVOCsSVOCs

Pesticides/PCBs

PHCsInorganics

45 accidental replication of project #15

46 project withdrawn

47 • • • TCE

48 project withdrawn

49 • • • • • unspecified hydrocarbons

50 • • unspecified VOCs

51 • • • • PAHs, phenols, heavy metals

52 • • • • • • various contaminants

53 • • • TCE, PCE

54 • • PAHs, PCP

55 • • • oil refinery organics

56 • • • mercury

NOTES:

BTEX = benzene, toluene, ethylbenzene, and xylenes

DCE = dichloroethene

DDT = dichlorodiphenyltrichloroethane

DNAPL = dense, non-aqueous phase liquid

MEK = methyl ethyl ketone

MIBK = methyl isobutyl ketone

PAHs = polycyclic aromatic hydrocarbons

PCBs = polychlorinated biphenyls

PCE = tetrachloroethene

PCP = pentachlorophenol

PHCs = petroleum hydrocarbons

SVOCs = semivolatile organic compounds

TCE = trichloroethene

TNT = trinitrotoluene

VOCs = volatile organic compounds

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NATO/CCMS Pilot Study, Phase II Final Report

Chapter 3: PROCESS-BASED REMEDIATION METHODS

Michael A. Smith

M.A. Smith Environmental Consultancy

3.1 INTRODUCTION

A risk assessment is usually used in deciding whether or not to eliminate or reduce the risks posed by

a contaminated site. If the risks need to be reduced, a remediation strategy must be developed to address

them. For sites designated for development, the remediation strategy also must address engineering

requirements, such as minimum load-bearing capacities, and management objectives, such as making a

profit.

This chapter provides an overview of the available process-based remediation methods for controlling

risk. It draws extensively on the lessons learned from the Phase I Pilot Study (1), which also contributed

to the development of the primary reference for this chapter (2). Descriptions of specific methods are

provided in subsequent chapters.

In general, the suitability of a remediation method depends on many factors including: contaminated

media, contaminants, remediation objectives, current status of the site, location of the site, time available

to complete the treatment, and money available to pay for the treatment.

3.2 BASIC OPTIONS AND CLASSIFICATION OF METHODS

The three basic approaches to remediation are:

• risk avoidance by changing the intended use of the land, re-routing a sewer, etc.;

• elimination of the risks by removing or destroying contaminants; and

• control of risks to an acceptable level by reducing contaminant concentrations or by containing

the contaminants, such as installing barriers between the contaminants and potential receptors.

The remediation strategy developed for a particular site may combine all three approaches and several

different methods.

The methods may be classified as1 civil engineering-based methods, such as excavation, containment

using cover systems and vertical barriers, and hydrogeological controls; or process-based methods.

Process-based methods can be further classified on the basis of the underlying physical-chemical

principles involved. For the purposes of this report, they are classified according to the following generic

processes: thermal, chemical, biological, physical, and stabilization/solidification.

This allocation is a matter of judgment. For example, vitrification, considered a thermal method in this

classification scheme, may be viewed by others as a solidification process. The generic processes are

1 The terminology employed throughout this report is generally consistent with that proposed by the International

Organization for Standardization (ISO) in its draft document: CD11074-4: Soil Quality Vocabulary — Part 4

Terms and definitions relating to rehabilitation of soils and sites.

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NATO/CCMS Pilot Study, Phase II Final Report

frequently combined in treatment trains so that, for example, soil washing becomes the prelude to

chemical or biological treatment.

Process-based methods may be applied ex situ—after contaminated soil or groundwater has been

removed from the ground for treatment—or in situ—without removing the contaminated media from the

ground. Ex situ treatment may be performed onsite or offsite.

Although civil engineering approaches are discussed only briefly in this chapter, often they are used in

conjunction with process-based methods.

3.3 CIVIL ENGINEERING-BASED METHODS

Civil engineering-based methods, may be an essential precursor to the application of a process-based

method involving ex situ treatment. Furthermore, civil engineering-based methods, such as vertical

barriers and lowering the water table, can also be essential to the application of an in situ treatment, such

as soil vapor extraction. Issues to be addressed during the excavation of contaminated media for

subsequent treatment include:

• delineation of the volume of material to be removed;

• compliance with excavation specifications to ensure that all material that should be removed has

been removed;

• control of potential environmental impacts as well as other impacts, such as emissions to the

atmosphere and traffic movements;

• engineering support, such as controlling water levels, required for excavation to proceed;

• ancillary support, such as the treatment of contaminated groundwater;

• facilities required for temporary storage;

• source and specification of clean replacement material, including chemical composition; and

• planning and permissions, including permits.

Careful consideration must be given to pre-treatment requirements of civil-engineering-based methods,

such as particle size and moisture content of the contaminated media. In addition, hydraulic measures

are often essential components of remediation systems. The extraction or infiltration of groundwater may

be used to:

• control groundwater levels, enabling excavation to take place;

• control groundwater levels in conjunction with physical barriers as part of a long-term

remediation strategy;

• control groundwater levels and flow directions so that in situ treatment, such as soil flushing or

soil vapor extraction, can be applied;

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NATO/CCMS Pilot Study, Phase II Final Report

• extract groundwater for ex situ treatment (pump-and-treat) and return the treated water to the

ground; and

• infiltrate water as part of an in situ treatment process.

Extracted groundwater may be contaminated and require either disposal to the local sewer system or onsite or off-site treatment.

Vertical barriers, which can be designed in a number of ways (3, 4, 5, 6), are used to control the

migration of contaminated groundwater and soil gas. They are frequently used in conjunction with

hydraulic measures to control the groundwater plume or with an active or passive system to control gas

emissions. When used as the primary remediation method, vertical barriers must be designed to last,

sometimes for decades. When used as an adjunct to another treatment method (for example, to control

the groundwater flow rate, flow direction, and level), they usually need to last for a much shorter time.

As a permanent solution, vertical barriers have several disadvantages. No matter how well designed and

installed, barriers perform satisfactorily only for a limited time, albeit possibly several decades.

Eventually, they have to be replaced unless steps have been taken to remove the original hazard or the

potential for migration decreases with time as can occur at gas-producing sites. Because experience is

limited in the use of vertical barriers under all environmental conditions, predicting performance is

difficult.

3.4 PROCESS-BASED METHODS

3.4.1 Ex Situ Methods for Solids and Liquids

Several generic methods are available for the ex situ treatment of solids (e.g., soils, sediments, sludges,

and filter cakes) and liquids (e.g., groundwater, surface water, and wastewater). Treatment aims to

remove, destroy, or modify contaminants, rendering them unavailable to potential human and

environmental targets. Whether an ex situ method can be applied at a site is determined by the nature

and distribution of the contaminants, and by the physical, chemical, and in some cases, biological

properties of the media to be treated.

Many generic methods generate waste streams that may require further treatment or disposal. This may

take place onsite, using for example mobile or transportable treatment systems, or at off-site fixed

treatment facilities. The decision to treat contamination onsite or offsite depends on a number of factors,

including availability and cost of on- and off-site facilities; available time scales; and site-specific

factors, such as the location of the site relative to off-site treatment centers, space available for on-site

treatment and temporary storage, and availability and capacity of local services, such as power, drainage,

and water supply.

On-site treatment generally requires:

• appropriate approvals for operating the treatment equipment;

• preparation of the site to receive the treatment plant and equipment;

• appropriate site services and support facilities to protect occupational and public health and

safety and the environment;

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NATO/CCMS Pilot Study, Phase II Final Report

• installation and commissioning of the treatment plant; and

• temporary storage and materials-handling facilities for feedstocks, products, and wastes.

When the use off-site facilities is expected, it is important to:

• comply with legal requirements on the transfer of controlled wastes and the discharge of

hazardous effluents;

• make arrangements for temporary storage and pre-treatment requirements prior to transfer;

• ensure adequate protection of the workforce, public, and environment during transfer operations;

and

• agree on transport routes and permissible shipping rates.

Factors requiring special attention during the selection, design, and implementation of any remedy

include:

• properties of the material to be treated in relation to potential applicability, effectiveness, and

constraints;

• need for treatability studies;

• materials handling requirements;

• engineering aspects, such as ancillary engineering support;

• operational aspects, such as electrical and water services required;

• testing for compliance and performance to demonstrate that target concentrations and other

specifications can be achieved;

• potential for integration with other remedial measures; and

• compatibility with engineering and management objectives.

To assess the applicability and potential performance of ex situ treatment methods, information is

required on the contaminants present (e.g., types, concentrations, speciation, and distribution) and the

physical, chemical, and biological properties of the material to be treated. The data on applicability and

performance should be tailored to meet the specific requirements of the method, or methods, intended

for use. In most cases, this involves collecting supplementary data beyond that necessary for the risk

assessment and initial remedy selection. Treatability studies are likely to be required to select, design,

and implement the remedy.

Many ex situ treatment methods are specific to particular types of contaminants and are sensitive to

variations in feedstock composition. Comprehensive data on the composition of the material are needed

to ensure:

• applicability to the contaminants present;

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NATO/CCMS Pilot Study, Phase II Final Report

• applicability to the material to be treated;

• applicability to the contaminant concentration range that needs to lie within the range that can

be treated;

• absence of any interfering or inhibitory substances;

• feedstocks in the correct physical form for processing;

• maintenance of optimal processing conditions; and

• accurate predictions of the waste stream composition so that appropriate pollution control

measures can be provided and suitable disposal and discharge arrangements can be made.

Several factors determine how effective the treatment method will be in producing material that

consistently achieves pre-defined remedial objectives, such as residual contaminant concentrations. These

factors include the composition, physical condition, and homogeneity of the feedstocks; presence of

inhibitory or interfering substances; and conditions that affect the ability to maintain the process at

optimal levels. Factors that can limit the effectiveness of ex situ methods of treatment include:

• inappropriate particle size preventing effective contact between treatment reagents and

contaminants;

• heterogeneous feedstocks leading to variable performance and quality of the treated product;

• inappropriate matrix types, such as clay or humic soils in soil washing technologies or overly

coarse material in thermal treatment technologies;

• complex contaminant mixtures leading to antagonistic or unproductive reactions, or interference

in the main process reaction; and

• sub-optimal processing conditions leading to poor or variable performance.

When selecting, designing, or implementing remedial strategies that include ex situ treatment methods,

effectiveness must be defined. The potential effectiveness of the method should always be considered

in the context of its ability to meet the prescribed standard, such as allowable residual concentrations

of contaminants in treated material or compliance with leachability criteria.

Although low residual contaminant concentrations may appear to provide the most direct means of

assessing effectiveness, they may not always be a sufficient measure of the ecological quality of soil or

other treated material. A number of treatment methods, including biological and chemical methods, can

produce toxic intermediates or fail to adequately treat low concentrations of highly toxic substances.

Thus, direct measures of toxicity may be required.

All ex situ treatment operations should be subject to compliance and performance testing. Typically, such

tests include assessing the potential for exposure of personnel to hazardous materials and measuring the

composition of emissions to the atmosphere, discharges to the sewer, and any material landfilled onsite

or offsite. Performance evaluations include:

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NATO/CCMS Pilot Study, Phase II Final Report

• On-going monitoring of treatment performance, measured, for example, as interim quality

inspections on samples of processed material; and

• Final validation of the quality of the treated product to confirm that it conforms to pre-defined

remediation objectives. Validation may include a variety of measurements, such as total

concentrations of residual contamination in the treated product, concentrations of hazardous

substances in leachates prepared under standard conditions, and measurements of the physical

condition (e.g., strength development) of the treated product.

Post-treatment validation programs vary depending on the methods used, contaminants treated, volume

of material handled, and variability of the feedstocks.

Long-term testing of material processed in ex situ systems is unlikely to be required although long-term

monitoring may be necessary where stabilized/solidified material has been returned to the site. Long-term

monitoring may involve periodic removal and chemical/physical analysis of cores of treated material.

In addition, groundwater monitoring wells may have to be installed to determine long-term changes in

water quality.

3.4.2 Ex Situ Treatment of Groundwater and Other Contaminated Liquids

Where soils are treated using ex situ methods, such as soil washing, the treatment and/or disposal of

process waters and effluents usually form part of the overall treatment system. Contaminated waters

requiring ex situ treatment include:

• surface waters, such as ponds and lagoons;

• groundwater collected during pump-and-treat operations;

• groundwater removed incidentally as a result of excavation and other engineering operations;

• effluents from the pre-treatment of solids (e.g., dewatering of dredged sediments or industrial

sludges);

• aqueous liquids extracted from contaminated soil and waste;

• leachates collected from waste deposits and contaminated sites;

• contaminated water from in situ soil flushing or washing, and chemical treatment operations;

• process effluents from ex situ treatment of solids (e.g., soil washing and chemical treatment);

and

• effluents from the decontamination of plant and equipment, using, for example, high pressure

water jets.

Contaminated waters may contain only one or a small number of contaminants present over a relatively

narrow concentration range, or they may contain complex mixtures of contaminants at wide-ranging or

very high concentrations. In addition, these concentrations may fluctuate over time, and the volumes of

liquid to be treated and time scales may vary considerably. For example:

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• Process and decontamination effluents associated with the ex situ treatment of solids arise only

during the operational phase of remediation, and the total volumes of effluents to be treated may

be relatively small; and

• Treatment of large volumes of contaminated groundwater may be necessary over extended time

periods, particularly where source control measures are not possible and groundwater

remediation is the only feasible means of reducing contamination hazards.

Options other than on-site treatment of contaminated water may be available. Two examples are

discharge to an existing sewage treatment plant, possibly after some initial pre-treatment, or transfer by

tanker to a central treatment facility.

Treatment methods developed for drinking water, process water, sewage treatment, and industrial effluent

can be adapted, provided that the physical, chemical, and biological properties of the liquid to be treated

and the design and operational requirements of the treatment system have been considered. Several

methods have been specially developed for the treatment of contaminated groundwater.

Contaminated waters from land remediation projects usually require treatment in an integrated treatment

train in order to overcome variations in contaminant types and concentrations, flow rates, and physical

properties. Treatment trains usually conform to the following basic sequence: pre-treatment, primary

treatment, secondary treatment, and tertiary treatment or polishing. As liquid moves through the

treatment train, it becomes progressively cleaner. Trace levels of contamination are removed in the

tertiary treatment stage. In conventional applications, treatment trains are normally constructed as

permanent installations.

A number of treatment methods or options may be available at each stage of the treatment train. The

methods selected depend on their compatibility; the physical, chemical, and biological properties of the

liquid; and quality of the water to be achieved on completion of treatment.

The liquids must be well characterized at the outset in order to provide for appropriate treatment stages

and adequate capacity for expected variations in concentration and flow. In modern industrial plants, care

is taken to ensure that effluents from processes having different treatment requirements are not

unnecessarily mixed in, thereby adding to the technical difficulties and costs of downstream treatment.

For instance, effluents with inorganic and organic contaminants are not mixed because they have

different treatment requirements. Particular attention should be given to the potential for biological and

mineralogical fouling of treatment systems.

The information needed to design a treatment system for a contaminated land application is similar to

other systems. However, the system design must take into account the:

• variable nature of water;

• common presence of contaminant mixtures and the inability to control for them;

• range of contaminant concentrations frequently present;

• temporary status of the treatment plant (with the exception of some groundwater treatment

operations); and

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• the fact that systems often have to be installed in less than optimal physical conditions, such as

working space, services, terrain, and access.

The relatively short-term nature of many contaminated land projects, compared to conventional water

and wastewater treatment applications, presents a number of potential design problems. The conventional

treatment plant is usually designed and constructed to last for 20 years or more depending on the life

expectancy of the equipment. Contaminated land projects are typically much shorter. The shorter time

scales have implications for the commercial availability and operational efficiency of the treatment plant,

and for the cost of designing the treatment system. For instance:

• Appropriate plants may not be available “off-the-shelf;”

• Commercially available plants may not operate as effectively on a small scale due to design

constraints; and

• Cost may be very high relative to the volume of material to be treated.

During the life cycle of a groundwater treatment project, significant changes may occur in the basic

parameters that determined the selection and design of the initial treatment system. When designing

groundwater treatment systems, it must be understood that:

• Management of the hydraulic regime, including the extraction and recharge rates, should be

considered an integral part of the overall design of a pump-and-treat system;

• Flow rates may be controllable within limits (allowing for a choice of plant size) or dictated by

hydrogeological factors, such as the pumping rate required to control plume migration—all of

which may change during the lifetime of the project;

• Because contaminant concentrations decrease with time, different treatment processes may be

required at different stages of a project in order to maintain technical effectiveness and economy

of operation;

• Relatively small plant sizes may mean high operating costs compared to capital costs; and

• A point probably will be reached when ex situ treatment ceases to be more effective than natural

degradation or dispersion processes—this point may occur before target concentrations are

reached. If this occurs, a period of passive management, such as monitoring, will be required

until target concentrations are achieved.

3.4.3 In Situ Methods for Soils

In situ treatment methods avoid the above-ground environmental impacts and costs associated with

excavation and extraction. Some methods are particularly attractive for application on operating sites and

other sites where buildings and structures need to be preserved.

In situ technologies for treating soil and similar materials can be classified like their ex situ counterparts

on the basis of the underlying treatment principle, such as physical separation and biological degradation.

In addition, a distinction can be made between those methods that seek to remove, destroy, or stabilize

contaminants by introducing a treatment agent into the ground, and those that act directly on the ground,

such as electroremediation and in situ vitrification.

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Typically, the aim of in situ remediation is to treat the saturated or unsaturated zones, although some

integrated systems are capable of treating both. Methods for the treatment of soil and soil-like materials

(including soil water and gas) and methods intended to treat groundwater and associated strata may be

used separately or in an integrated system. In situ treatment methods may be combined with pump-andtreat methods to treat contaminated groundwater. Soil flushing, in situ bioremediation, and soil vapor

extraction may be combined in an integrated remediation scheme. Heat may be introduced to aid

bioremediation or vapor extraction, and electrokinetic techniques may be used to enhance penetration

of chemical or stabilization agents.

Typical in situ systems:

• deliver a treatment agent or agents in liquid, gas, or energy form;

• recover products; and

• dispose of or treat products, although the aim of many methods is to produce only non-harmful

products or safely “lock-up” contaminants in situ.

The engineering, legal, and operational issues that must be addressed in all in situ applications are

generally the same as those for ex situ treatment:

• site characterization and pilot studies to determine potential applicability, effectiveness, and

constraints;

• testing for compliance and performance; and

• compatibility with engineering objectives.

Thorough characterization of the chemical contaminants and physical properties of the contaminated

matrix is essential for a proper evaluation of the feasibility of particular in situ treatments. Also, the

mode of action, which usually involves in-ground treatment, often at significant depths, imposes unique

constraints on treatment applicability and feasibility. Site characterization should be tailored to meet the

specific requirements of the method, or combination of methods, that may be applied. This almost

certainly requires supplementary investigations beyond those that estimate risk. Bench and pilot-scale

treatability studies are frequently required.

Accurate identification of all contaminants present, combined with treatability data, is essential because

of the danger that a treatment adopted to remedy some contaminants could lead to adverse or counterproductive reactions with other contaminants. This may result in increased toxicity or mobility. An

understanding of the physical characteristics of a site is essential for all in situ techniques, especially

those requiring infiltration of treatment agents. Information on the engineering properties of the ground

is required, especially if heavy equipment is used or if the remedial action itself could lead to

unfavorable ground changes, such as increased soil density, volume, or instability.

The effectiveness of in situ treatment methods is determined by a variety of factors, including:

• nature, extent, and distribution of contaminants;

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• contact achieved between contaminants and treatment agents, and often the extent to which the

contaminants can be solubilized (Conductivity and penetration can be enhanced by a variety of

means);

• accessibility of the contaminants on a micro- and macro-scale;

• control over processing conditions in the ground which are not visible, especially when working

at considerable depth;

• extent to which treatment agents can be delivered to the site of action;

• ability to effectively remove treatment products and excess agents from the ground; and

• time available for treatment in terms of access to the site and natural factors, such as

groundwater flow rates.

Minimal information is available on the long-term effectiveness of in situ treatment methods that do not

remove or destroy contaminants. Effectiveness is limited by the actual contamination as well as the

perception of contamination. A system design based on an inadequate understanding of the contamination

and site characteristics may not be sufficient to treat the actual situation. Flexible and robust designs that

can be modified as treatment proceeds are essential.

In situ techniques are likely to be most effective when applied to specific types of contaminants in

homogeneous ground conditions or at least well defined heterogeneous ground conditions. Monitoring

undertaken during processing and for a considerable time after treatment is likely to be required to fully

demonstrate effectiveness over time.

Often engineering or hydraulic measures must be employed to contain in situ methods of treatment or

to increase the volume of soil available for treatment. For instance, if the groundwater table needs to

be lowered, consideration must be given to whether the mobility of contaminants will increase. This can

occur when a floating layer of contaminants enters the saturated zone. In addition, lowering the

groundwater table may adversely affect trees and other vegetation, and alter the level and flow of surface

water bodies. In situ treatment may have significant implications on the engineering properties of the

ground and hence on any subsequent construction works. For example:

• Infiltration/extraction operations may affect the stability of the neighboring buildings, plant, and

services;

• Density and volume increases may result from the addition of solidification/stabilization reagents

or grouts; and

• Changes in load-bearing capacity must be taken into account in designing foundations.

The delivery systems used to deliver treatment agents to the sub-surface and to recovery systems may

be propelled by gradients, such as hydraulic, pressure, chemical, temperature, and electrochemical/

electrokinetic gradients. Systems based on air or gas are driven by similar potentials.

Where aqueous fluids are to introduced into the ground, facilities for preparing, storing, and

“reconditioning” recirculated extraction solutions must be provided. Treatment agents may be hazardous

and potentially polluting and thus require appropriate storage and handling arrangements. Also, recovered

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treatment solutions or gases, and incidental emissions, such as those from heat treatment, require

appropriate treatment or disposal.

The site geology and hydrogeology may be such that treatment agents are diverted away from target

areas, thereby limiting effectiveness and possibly leading to the contamination of surrounding ground.

For water-based systems, an initial test of the delivery system using water only or water with a tracer

usually is necessary to make sure the recovery system is adequate.

Delivered materials are typically liquids but may be gases (such as those used in soil vapor extraction

and bioremediation), vapors, slurries, or solids. Recovery systems involve fluid flows (gases, liquids, and

emulsions) and may require enhancement by modifying the physical or chemical attributes of the

contaminants or pathways.

Problems associated with installing and operating delivery and recovery systems include:

• presence of structures, plant, and services;

• presence of physical obstacles, such as boulders, drums, concrete debris, and hard rock;

• depth restrictions that affect the integrity and performance of the system;

• ensuring the penetration of aqueous fluids where hydraulic conductivity is less than about 10-6

to 10-5 m/sec;

• presence of contaminants with low solubilities;

• adsorption of contaminants onto clay minerals or organic matter;

• existence of fractures or other secondary porosity that create paths of high conductivity in

bedrock of otherwise low conductivity;

• absence of an underlying low-permeability layer that precludes migration of delivered materials

and treatment products;

• whether remedial action is progressing as planned;

• whether remediation targets (standards) have been achieved;

• whether any contaminants or treatment agents have migrated beyond the operational area;

• composition of extracted fluids or emissions, which could provide information on progress and

treatment/disposal requirements;

• presence and nature of any fugitive emissions to the atmosphere;

• validating that treatment has been fully effective; and

• determining whether the engineering properties of the ground have been affected by the

treatment.

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Procedures for monitoring soil and groundwater are likely to be required in most applications of in situ

technologies. The basis for deciding compliance in terms of pre-defined remediation criteria, and the

statistical basis for accepting that compliance has been achieved, should be decided before monitoring

is carried out. Although most in situ methods affect both solid and liquid media, these media can be

affected separately when parallel treatment processes are used. Monitoring procedures vary depending

on the purpose of the testing and the methods used, but they typically include (7):

• installing monitoring wells for collecting groundwater samples as well as assessing groundwater

and contaminant movement at the site;

• monitoring recovery streams to determine the quantity of contaminants removed;

• analyzing cores of treated material to determine residual concentrations or other properties, such

as leachability of stabilized/solidified soils; and

• monitoring process streams, such as treated groundwater or air from soil vapor extraction

systems, to determine quality prior to discharge.

Monitoring data can be used in making process stream and mass balance calculations, which are used

to establish how effective in situ treatment is in removing contaminants. Such calculations are important

because demonstrating the effectiveness of in situ treatment can be difficult in the presence of

heterogeneous ground conditions, poor accessibility of contaminants, low degree of mixing, and

migration of contaminants away from the zone of treatment due to the remedial action itself. Experience

has shown that concentrations of contaminants in groundwater recovery streams may decrease initially,

but then increase after a period of inaction as contaminants move back into the groundwater system from

the fine pore structure or other locations in the ground. Similar behavior can be observed when soil

vapor extraction is applied to ground containing zones of low gas permeability within strata of higher

permeability. Long-term monitoring, well beyond the point at which remedial action appears to be

complete, is often required to confirm that remediation has been fully effective.

3.4.4 In Situ Treatment of Groundwater

In situ treatment of groundwater requires water to pass through a treatment zone where injection of

agents in solution or in gaseous form cause degradation or promote natural degradation of contaminants;

or a solid substrate exists that supports physical separation of the contaminants by adsorption, chemical

or biological degradation, or reduction in toxicity.

These two processes may be used in combination. In situ treatment of groundwater may be combined

with in situ treatment of the unsaturated zone. Soil vapor extraction coupled with microbial treatment

is an example of this type of combination. In situ groundwater treatment also may be combined with

pump-and-treat operations. The flow of groundwater through or to the treatment zone may be the result

of natural gradients; induced by pumping from vertical or horizontal wells, or by infiltration of water;

or achieved through injection of heated water or steam.

Regulatory authorities should always be consulted prior to applying such methods to obtain relevant

permissions for installing and operating injection and extraction wells, and for deliberately introducing

chemical agents into the environment.

In situ groundwater remediation requires a thorough understanding of the hydrogeology of the site and

its environs, and usually requires the prior removal or containment of the source of the contamination

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and removal of free product. As for all in situ methods, ensuring contact between contaminants and the

treatment agent is the major practical difficulty. Contaminants may be adsorbed onto mineral surfaces

and held in capillary pores. Effective long-term treatment requires that these contaminants be released

into the groundwater. A variety of means may be used to promote the movement of contaminants

through the subsurface. These include hydrofracturing, electrokinetic techniques, injection of steam or

hot water, and surfactant flushing.

Because contaminant mobility is different at each site, any in situ treatment method must take into

account the characteristics of the contaminants present. Contaminants partition between liquid, soil, and

vapor phases in amounts characteristic of the contaminants, aquifer materials, organic content, and other

geochemical factors. For many contaminants, these associations vary and may not be completely

reversible. Modeling groundwater and contaminant movement is often required to design the treatment

system.

Significant amounts of groundwater flow—both horizontally and vertically—may occur through limited

parts of the aquifer, and the direction and rate of flow may be markedly different at different depths.

This can result from spatial variability in the permeability of water, or as a result of density or other

contaminant characteristics. Thus, neither the bulk water flow nor the distribution of contaminants can

be assumed to be homogeneous.

Principal treatment methods for in situ groundwater contamination include:

• oxidation of contaminants by introducing oxidizing agents, such as oxygen, ozone, hydrogen

peroxide, and permanganate;

• enhancement of natural biological degradation processes;

• air-stripping of volatile organic compounds;

• adsorption on, or reaction with, reactive materials, such as those in a chemical barrier; and

• biological degradation within an active barrier.

Planning and management requirements typically associated with these methods include:

• obtaining appropriate approvals to install and operate extraction and infiltration wells and to

introduce treatment agents into the groundwater;

• obtaining appropriate approval to install and operate a treatment plant;

• preparing the site to receive the installation, including preparing any reagent storage or handling

facilities; and

• monitoring to measure boundary effects, check progress, and determine the completion point.

Technical specifications should ensure:

• appropriate controls over treatment agents and other materials used during treatment;

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• proper provisions for locating, installing, operating, and maintaining injection wells, barrier

systems, and associated storage facilities; and

• satisfactory monitoring arrangements, particularly to determine the end point of treatment.

Care is required in the selection and design of an in situ groundwater treatment system to ensure that:

• any chemical introduced into the ground during treatment does not itself become a pollutant;

• mobilization of contaminants other than those that are the primary object of the treatment or are

naturally present is prevented; and

• treatment end products are not more harmful than the original compound.

A full understanding of the contamination and the geological, hydrogeological, and geochemical

characteristics of the site is required to effectively design and implement the remedy. Detailed

information is necessary on a range of physical-chemical properties of the contaminants, including

sorption characteristics, volatility, partitioning, and chemical and microbial degradability.

A range of laboratory investigations, such as treatability studies, development of sorption isotherms, and

column and microcosm experiments, are necessary to determine contaminant transport and transformation

parameters, assist in developing a full understanding of site conditions, and enable evaluation of

alternative methods of treatment. When microbial treatment is used, laboratory studies usually are

required to determine if the native populations of microbes can degrade the contaminants, and if minerals

are present to promote maximum activity at ambient groundwater temperature and under aerobic

conditions. Natural conditions may be anaerobic or only slightly aerobic. Data on the quantity of

contaminants present and the porosity of the aquifer can be used to calculate theoretical oxygen

requirements for degradation and the volumes of air or water (saturated with air or oxygen) needed to

supply the oxygen. Similar calculations can be made for the unsaturated zone.

Relatively scarce information is available on the long-term effectiveness of most in situ groundwater

methods, and much of it originates only from field trials. However, the use of hydrogen peroxide as an

oxygen source at petroleum contaminated sites to enhance biological degradation rates, and sparging to

strip volatile contaminants and encourage biological degradation, are established techniques.

Effectiveness may be enhanced by using techniques, such as hydrofracturing or pneumatic fracturing,

surfactant flushing, electrokinetics, and hot water and steam flushing, to promote the movement or

penetration of treatment agents or contaminants. However, many of these systems are themselves at an

early stage of development.

Chemical and other forms of treatment requiring the introduction of agents into the ground are limited

by the fact that groundwater flows within an aquifer in a plug flow manner, providing very minimal

natural mixing. Therefore, introduced agents tend to be pushed ahead of water entering the treatment

zone. Such difficulties may be overcome by using systems designed to induce mixing, such as the UVB

system (Project 43).

Precipitation and polymerization may lower hydraulic conductivities near the injection wells making

closely spaced wells necessary for effective treatment. Microbial growth close to points of nutrient and

oxygen injection may have a similar effect.

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In general, permeable barriers can be used only in relatively shallow aquifers because the trench must

be excavated to a layer of low permeability. However, it may be possible to design fence-and-gate

systems to operate effectively where contamination is restricted to the upper portion of an aquifer. In

1992, the Technology Innovation Office (TIO) of the USEPA identified in situ groundwater treatment

as a critical area requiring research and development. TIO surveyed available technologies and ongoing

research and development on chemical, biological, and physical treatments that alter the toxicity of

contaminants, enhance their removal, or improve the mobility of non-aqueous phase liquids (8). The

report concluded that the range of techniques available was very limited; at the present rate of

development, alternative technologies may not be available for three to five years; and of the 15

technologies under development, most were at the bench- or pilot-scale stage.

3.5 REFERENCES

1. U.S. Environmental Protection Agency, NATO/CCMS Pilot Study: Demonstration of Remedial Action

Technologies for Contaminated Land and Groundwater, Final Report, Volume 1, 1993, EPA/600/R93/012a.

2. Harris, M.R., S.M. Herbert, and M.A. Smith, “Remedial Treatment for Contaminated Land, Volumes

I to XII: Selection and Classification of Available Methods,” Construction Industry Research and

Information Association, London, 1995-1997, Special Reports 101-112.

3. Harris, M.R., S.M. Herbert, and M.A. Smith, “Remedial Treatment for Contaminated Land, Volume

VI: Containment and Hydraulic Measures,” Construction Industry Research and Information

Association, London, 1996, Special Report 106.

4. Privett, K.D., S.C. Matthews, and R.A. Hodges, “Barriers, Liners and Cover Systems for

Containment and Control of Land Contamination,” Construction Industry Research and Information

Association, London, 1996, Special Report 124.

5. Building Research Establishment, “Slurry Trench Cut-off Walls to Contain Contamination,” Building

Research Establishment Digest, Garston, 1994, 395.

6. “1997 International Containment Technology Conference and Exhibition, St. Petersburg, Florida,

USA, February 9-12, 1997,” Land Contamination and Reclamation, 1997, 5(3), [Special Issue]

7. Harris, M.R., S.M. Herbert, and M.A. Smith, “Remedial Treatment for Contaminated Land, Volume

III: Site Investigation and Assessment,” Construction Industry Research and Information Association,

London, 1995, Special Report 103.

8. U.S. Environmental Protection Agency, In Situ Treatment of Contaminated Ground Water: An

Inventory of Research and Field Demonstrations and Strategies for Improving Ground Water

Remediation, 1993.

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Chapter 4: IN SITU TREATMENT

Mark Smith

European Office of Aerospace Research and Development

Cathy Vogel and Alison Thomas

Tyndall Air Force Base

4.1 INTRODUCTION

Environmental remediation technologies can be broadly divided into two categories: ex situ and in situ.

Ex situ technologies treat contaminated materials after gross removal and transport of contaminated

media to the treatment facility. Actual treatment often occurs onsite—reducing costs, risks, and

administrative burden incurred with hazardous material portage. In contrast, in situ technologies apply

the remediation process directly to the contaminants, with little or no gross movement of hazardous

material.

The cost of environmental remediation is, to a large degree, directly proportional to the amount of

material handled in the process. When large masses of earth or water are removed and cleaned, costs

are incurred for both the physical handling of the material—large fractions of which may be

uncontaminated—and for application of the treatment process in order to ensure complete

decontamination. Deep contamination can involve extensive excavation of uncontaminated overburden.

In addition to direct costs, excavation of contaminated soil is often impractical due the presence of

overlying structures.

In situ processes attempt either to destroy the contaminants where they are found or, at the very least,

to remove the contaminants from the contaminated matrix. Post-extraction physical separations are

avoided or minimized, even if destruction or recovery is necessary. The technical challenge common to

all of these processes involves moving mass to some desired area, moving reagents (oxygen, nutrients,

oxidants, etc.) to the contaminants, or moving the contamination to some subsurface treatment zone.

In general, in situ processes require less capital outlay than ex situ treatments. Material handling

requirements are lower, transportation costs are avoided, and post-process treatment (e.g., landfilling)

is avoided. In situ processes are also less invasive, which is often the reason for their use, as in the case

of treatment under a building. On the other hand, in situ treatments, especially biotreatments, are

generally slower and require longer implementation. In many circumstances, such as in the sale of

property, the need to act quickly can outweigh the lower capital costs.

In situ strategies frequently use biological processes to destroy contaminants. Bioremediation uses

microorganisms to transform the hazardous organic contaminants into harmless products, such as carbon

dioxide and water. Microorganisms require mineral nutrients and a carbon and energy source (food) to

carry out these biodegradation processes. Ideally, the target contaminant will be the food source, and

sometimes a treatment process can be designed around fortuitous incidental biochemical reactions.

Microbes also require a terminal electron acceptor to complete the circuit of reactions by which they

survive. The most familiar electron acceptor is oxygen, but certain other oxidized ionic species, such as

nitrate, sulfate, or ferrous iron, can support bacterial growth. Several other factors (e.g., temperature and

pH) affect the efficiency of these processes. Degradation capabilities of microorganisms have been used

for decades to treat municipal and industrial wastes. Recent advances in biotechnology allow these

processes to be applied to hazardous chemicals in situ.

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In general, petroleum hydrocarbons can serve as primary growth substrates for bacteria. The ease of

biodegradability of a hydrocarbon is inversely proportional to its molecular weight and complexity.

Short-chain aliphatic hydrocarbons and simple aromatic molecules are fairly readily consumed, while

large, polycyclic aromatic hydrocarbons (PAHs) are more recalcitrant. Synthetic organic compounds,

such as chlorinated solvents (tetrachloroethene [PCE], trichloroethene [TCE], carbon tetrachloride, etc.),

are much more resistant to biodegradation. Chlorinated solvents cannot serve as growth substrates for

most microorganisms, but can nonetheless be degraded or transformed by populations that grow on other

substrates. TCE, for example, can be transformed and even mineralized by a variety of microorganisms

growing on different organic compounds, including methane, phenol, toluene, propane, methanol, and

n-butane. The current challenge for bioremediation is the encouragement of microorganisms to degrade

these manufactured compounds.

Bioremediation can be very effective for removing contaminants that serve as growth substrates,

particularly if low concentrations of the contaminants are present in an appropriate environment.

Bioremediation can provide a cost-effective alternative to traditional technologies (e.g., air stripping,

carbon sorption, and excavation) for a wide range of natural organic compounds, such as motor or jet

fuel. Biological treatment offers a permanent and often less expensive solution than strictly physical

treatments, because microorganisms convert toxic organic compounds to environmentally benign

products. However, bioremediation is no panacea. In situ bioremediation systems are often integrated

with other remediation technologies to effect total cleanup.

Physical processes will also be considered as in situ for purposes of this study if the intent of the process

is to physically remove only the contaminant from the contaminated media. As an example, air sparging

is intended to remove volatile organic compounds (VOCs) from groundwater. This judgment could be

debated, as such a process still merely transfers contamination from water-saturated soil to air, which

often still requires post treatment. However, as opposed to the pumping and treating of groundwater, air

sparging promises several advantages in material handling, as well as certain challenges associated with

the physical transfer of matter at the contaminated area, and it is appropriate to discuss these processes

here.

Knowledge of contaminant location and physical state in the subsurface is critical in implementing in

situ remediation techniques. In the vadose or unsaturated zone, contamination may exist as a vapor

phase, adsorbed to particles, dissolved in the thin film of water surrounding soil particles, or as a nonaqueous phase liquid (NAPL). Contamination in the saturated zone might consist of residual saturation

or material trapped within the soil matrix, matter sorbed to solids, a pool of NAPL, or dissolved material

in the groundwater. Each situation can pose unique challenges to the remediation engineer.

Each of the technologies examined by the Phase II Pilot Study offers innovations over more traditional,

mass-intensive approaches to remediation. As they are implemented, a greater understanding of the

dynamic interaction of contamination with the subsurface is gained. Comparing and contrasting the

results of these demonstrations suggests further innovations, as well as contextual evaluation of the

technologies themselves.

4.2 CASE STUDIES

Of the 52 remediation projects examined by the pilot study, 18 were either fully in situ implementations

or involved partial in situ treatment. Of these 18, 11 provided sufficient detail by the end of the pilot

study from which to draw conclusions. These projects consisted mainly of biological treatments of

organic contaminants. Table 4.1 shows those projects considered to be totally or significantly in situ in

nature, with country of origin and a basic description. More information is provided in the sections that

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Table 4.1: In Situ Projects

Project

Number

Title Description

1 Trial of air-sparging of a

petroleum-contaminated aquifer

Field trials of air sparging combined with soil

vapor extraction (SVE) to determine the increase

of extracted VOCs.

2 Bioremediation of petrochemicals

following a major fire

In situ flushing/bioremediation process

substantially reduced the total soil contamination

burden at the site and, as a consequence, greatly

reduced the potential migration of contamination

offsite. Phenol-degrading microorganisms were

encouraged to proliferate. In situ application was

only part of overall cleanup strategy.

3 Bioclogging of aquifers for

containment and remediation of

organic contaminants

Strategy entails using biomass, polysaccharide

and gas production to decrease soil permeability.

Pilot Study report is limited to laboratory studies

and modeling.

4 Remediation of methyl ethyl

ketone contaminated soil and

groundwater

Strategy includes a combination of pump and

treat for free-phase product and SVE for volatile

and adsorbed contamination. In situ

bioremediation is planned to treat residual

contamination within the basalt aquifer after

pumping operations are complete.

6 In situ/on-site bioremediation of

wood treatment soils

Daramend® process. Land farming with

amendments. Highly effective for relatively

shallow contamination (in situ) or for excavated

soils (ex situ application)

9 Demonstration of an in situ

process for soil remediation

using well points

Field demonstration of a combined in situ soil

flushing and bioremediation technology for BTEX

and other petroleum hydrocarbons.

12 Groundwater and soil

remediation at a former

manganese sulfate production

plant

In situ treatment involving accelerating the

leaching process with an aggressive leachant, and

collecting leachate in a drainage system.

15 Combined chemical and

microbiological treatment of

coking sites

Bench-scale microbiological treatment of aromatic

hydrocarbons with and without oxidizing

pretreatments (bench-scale)

16 Combined vacuum extraction and

in situ stripping of chlorinated

vapors

NOVOCTM wells and SVE wells and blowers

remove contamination as a gas stream for

treatment above ground by carbon adsorption.

18 Biological in situ remediation of

contaminated gasworks

Large-scale injection and extraction of water

through a contaminated zone leached

contaminants. This process was later used to

introduce nutrients into the ground and to raise

soil temperature by preheating the infiltration

water.

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NATO/CCMS Pilot Study, Phase II Final Report

23 Modeling and optimization of in

situ remediation

Investigation of several aspects of remediation

models including economic and time constraints

as well as technical considerations.

35 In situ SVE within containment

cells combined with ex situ

bioremediation and groundwater

treatment

Partial in situ application for dual-phase vacuum

extraction. On-site treatment of materials in

lagoons and biopiles.

37 Bioventing of hydrocarboncontaminated soils in the subarcticStudy investigating economic viability of soil

heating to promote bioventing in cold soils.

Considerable detail is available including an

economic analysis.

41 In situ microbial filters Resting-state methanotrophic bacteria can degrade

TCE. Exploiting this capability, the bacteria are

raised in a bioreactor, and the biomass is injected

into the subsurface through a borehole where they

attach to the solid rock matrix creating an

inoculated subsurface zone. After an attachment

period to allow fixation and establishment of the

microbiological community, groundwater is

extracted from the borehole resulting in the flow

through the impregnated zone.

42 In situ pneumatic fracturing and

in situ bioremediation

Tight soils hamper in situ technologies such as

SVE, bioventing, air sparging, and other air and

nutrient injection techniques. Hydraulic and

pneumatic fracturing are enhancement

technologies to increase treatment efficiency of in

situ techniques by increasing the permeability of

the soils.

43 Multi-vendor bioremediation

technology demonstration project

Three technologies were tested, including two

aquifer stripping wells and a co-metabolic

bioventing process using added methane and

ammonia.

47 In situ electroosmosis (LasagnaTM

process)

Contaminants are directed through treatment

zones under the influence of electroosmosis.

49 Characterization of residual

contaminants in bioremediated

soil and reuse of bioremediated

soil

Bioremediated soil was chemically characterized,

and its environmental behavior was evaluated by

cultivating various plant species.

follow. The project number corresponds to extended project summaries found in Appendix IV. Note

that Project 47, which is discussed in this chapter, is also discussed in Chapter 5, Physical-Chemical

Treatment.

4.2.1 Project 1: Trial of Air-Sparging of a Petroleum-Contaminated Site

Leaking pipes beneath a gas station in Adelaide, South Australia, contaminated the soil and groundwater

with up to 2,100 mg/L petroleum hydrocarbons, up to 1.5 mg/L benzene, and up to 20 mg/L xylene.

Contamination occurred as dissolved, adsorbed, vapor, and minor free phases. The adsorbed phase

occurred as a relatively thin and widespread zone above the water table at a depth of 7.5 m. Three trials

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NATO/CCMS Pilot Study, Phase II Final Report

were conducted to determine the effectiveness of air sparging in combination with vapor extraction at

this site.

The study found that air sparging substantially increased the amount of VOCs that could be removed

by vapor extraction from soil and groundwater. The initial increase in extraction rate was short-lived,

however, and slowed dramatically after only a few days operation. The zone of influence and rate of

recovery of VOCs were highly dependent on local geology. Air sparging also produced mounding of

the water table around the sparge well, which may have forced contaminants away from the extraction

wells. Based on the results of the trials, air sparging was abandoned as a remediation strategy at this site.

4.2.2 Project 2: Bioremediation of Petrochemicals Following a Major Fire

A major fire at a petrochemical facility near Melbourne, Australia resulted in the widespread

contamination of soil and groundwater with phenol, benzene, and acrylonitrile from damaged storage

tanks. A site investigation found phenol concentrations as high as 24,000 mg/kg in near-surface soils and

700 mg/L in the groundwater, making bioremediation problematic due to the toxicity of phenol to

bacteria. Following extensive laboratory studies, a flushing-biotreatment system was investigated at field

scale.

A field study was undertaken on a 1,600-m2 area of soil. The site was prepared by plowing gypsum and

slow-release nutrients into the soil. Contaminated water was flushed through the soil, recovered, and

treated in a bioreactor. Phenol concentrations decreased rapidly in the top 0.6 m of soil after treatment

commenced. Monitoring of soil microbiology showed high concentrations of phenol-degrading bacteria

(up to 5x107

/g) were being maintained. Two months after in situ treatment began, phenol concentrations

in the groundwater rose to 1,000 mg/L, and then gradually declined to about 1 mg/L.

In situ treatment was only one aspect of this project. The overall remediation scheme for the site also

included disposal of some contaminated fire water, storm water, and groundwater to local sewage works

for aerobic lagoon biotreatment; ultraviolet (UV) peroxidation of fire water and storm water; and soil

vapor extraction (SVE) and sparging of VOCs.

4.2.3 Project 3: Bioclogging of Aquifers for Containment and Remediation of Organic

Contaminants

Recent studies have suggested a correlation between increased microbial biomass density in aquifer

materials and reduced saturated hydraulic conductivity of aquifers. This process, termed "bioclogging,"

is believed to result from several different processes, such as the production of low solubility gaseous

end products, the excretion of extra-cellular polysaccharides, and the increase in bacterial cell numbers.

The objective of this project was to investigate the potential benefits of bioclogging to provide a

temporary partial subsurface containment of contaminated areas, and to act as a site for enhanced

biodegradation of organic contaminants. Only laboratory results were reported to the Phase II Pilot

Study, and no bioclogging in the field had yet been attempted.

Test leachate containing growth medium, glucose, and sodium nitrate was passed through a 0.5-m long,

by 0.08-m diameter column at a constant volume flux density of 0.11 m3

/day. Results showed that

polysaccharide production can lead to at least one order of magnitude reduction in column hydraulic

conductivity. The study also suggested that after initial delivery of amendments (e.g., nutrients), the

reduction in hydraulic conductivity appeared to be long-lived. The most rapid change in Ksat occurred

in the first 18 hours of the experiment, with further slow reductions after 50 hours.

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4.2.4 Project 4: Remediation of Methyl Ethyl Ketone Contaminated Soil and Groundwater

This Pilot Study project reports on the development and implementation of a site remedial strategy that

incorporates in situ recovery of free product and contaminant vapors. Geology at the site consists of a

thin layer of clay and reworked soil overlying basaltic lava flows to a depth of 30 m. The basalt is an

extremely heterogeneous aquifer comprising discontinuous, very low to moderately permeable layers

with occasional interconnecting joints and fractures. There are three free product contaminant plumes

present in the aquifer: a lubrication oil plume, a methyl ethyl ketone (MEK) plume, and a mixed plume

containing benzene, toluene, ethylbenzene, and xylene (BTEX), motor fuel, turpentine, and kerosene.

The plumes cover an area of greater than 7 ha.

The initial remedial strategy consisted of a combination of pump-and-treating free phase product and

SVE for volatile and adsorbed contamination. Since contaminant distribution can be distinguished as

three separate plumes, the remediation plan addressed separate recovery and treatment systems for each

of them. Floating free product was recovered from a network of boreholes with specially designed "top

loading" pumps. These modified displacement pumps use compressed air to pump the recovered fluid

to the surface. Uncontaminated water was injected around each plume to force free product towards the

recovery wells. Vapor extraction was conducted simultaneously to take advantage of the dewatered

ground.

Recovered vapor, free product, and groundwater were treated at the surface in a treatment compound

comprising a three-stage oil/water separator, a heated air stripper for groundwater treatment, discharge

of treated wastewater to a municipal sewer, and a thermal destruction system (using a methane gas

carrier to ensure full product combustion) to treat all hydrocarbon waste streams from the air stripper

as well as the vacuum manifold system. When operated at 760°C and a retention time of 0.5 seconds,

the system ensured total destruction of hydrocarbons. Emissions met the 10 mg hydrocarbon/m3

objective.

Full-scale remediation commenced with recovery of a large volume of free product with an associated

high concentration of dissolved contamination. Two years later, remediation was on-going with an

average rate of groundwater recovery on the order of 50,000 L/day. The rate of hydrocarbon recovery

declined significantly over time. In situ bioremediation was being considered to treat the residual

contamination within the basalt aquifer after pumping operations were completed.

4.2.5 Project 6: In Situ/On-Site Remediation of Wood Treatment Soils

DARAMEND® bioremediation carefully cultivates desirable microorganisms through soil preparation

and addition of nutrients. Soil amendments are incorporated into the contaminated soil and homogenized

to supply biologically available water, nitrogen, phosphorous, micronutrients, and oxygen to support

biodegradation of the contaminants. The amendments also reduce the acute toxicity of the soil's aqueous

phase by transiently adsorbing contaminants and providing surfaces for microbial adhesion and

development of biofilms. The composition of DARAMEND® organic amendments is soil-specific and

based upon the results of a thorough physical and chemical characterization (e.g., texture, moisture

retention, carbon:nitrogen ratio, nutrient profile, and concentrations of target compounds) and treatability

studies of the soil or waste. Soil moisture content is also strictly controlled.

The process was applied ex situ to excavated, PAH-contaminated harbor dredgings; in situ to petroleum

hydrocarbon-contaminated soil in the Arctic, and in situ to soil at a wood treatment plant.

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NATO/CCMS Pilot Study, Phase II Final Report

Harbor sediments were treated for 46 days, which resulted in an 84% reduction in total PAH, from 1,146

mg/kg to 187 mg/kg. A control plot (tillage only) showed a 40% reduction. Benzo(a)anthracene

reduction for unpretreated sediment, pretreated sediment, and control sediment was 60%, 58%, and 30%,

respectively.

At the Arctic site, pilot in situ plots were covered by temporary greenhouses to control soil moisture

content and to increase soil temperatures through solar heating. Three DARAMEND® formulations were

tested, and after 10 days, 89%, 62%, and 75% reductions in total petroleum hydrocarbons (TPH) were

observed. No TPH reduction was observed in the control plot.

After 254 days in the ex situ demonstration at the wood treatment plant, PAHs were reduced 94%, from

1,710 mg/kg to 98 mg/kg; chlorophenols 96%, from 352 mg/kg to 13.6 mg/kg; and TPH by 87%. The

control area showed a reduction of 41%, but no reduction in either chlorinated phenols or TPH was

observed. Toxicity, as measured by earthworm mortality and seed germination, was eliminated or greatly

reduced only in the treated soil.

4.2.6 Project 9: Demonstration of an In Situ Process for Soil Remediation Using Well

Points

The treatment process consisted of a recirculation system with injection and extraction wells. A

surfactant/co-surfactant solution is injected into the well points to mobilize soil contaminants. The

extracted contaminated soil washings were sent to an effluent treatment plant. Biodegradation of the

remaining hydrocarbon residual located in the subsurface was stimulated by injecting nutrients and air

or hydrogen peroxide via the well points. The project scope included laboratory-scale selection of

surfactants, in situ soil washing tests using the selected surfactant, in situ biodegradation testing of

residual hydrocarbons and the contaminated washing solution, and subsequent monitoring to verify

contaminant removal. Over 50 types of surfactants and co-surfactants were tested to establish pairings

and concentrations required to extract over 95% of the hydrocarbons from the contaminated soil.

4.2.7 Project 12: Groundwater and Soil Remediation at a Former Manganese Sulfate

Production Plant

On-site disposal of about 45,000 m3 of hazardous waste at a former manganese sulfate plant in the

municipality of Tinglev, Denmark, left severe contamination of the soil and groundwater. Groundwater

was contaminated with high concentrations of manganese, sulfate, and cyanide. Solid wastes, leachate,

and contaminated groundwater all required treatment. Traditional remediation of the solid waste by offsite incineration and off-gas treatment was estimated to cost 8-13 million ECU (U.S.$9-10 million).

Paper to pilot scale studies were used to investigate alternatives.

Conceptually, the leachate and most contaminated groundwater could be collected for treatment by

constructing drains beneath the wastes. Leaching of wastes could be accelerated by installing a system

at the top of the wastes to distribute suitable treatment agents. It was estimated that leaching at a

liquid/solid ratio of 2-3 annually (40-60 times the natural rate) would leach contaminants from the solids

in 7-10 years. Between 160,000 and 240,000 m3 of leachate would have to be treated and cleaned each

year.

Ex situ batch processing of the wastes was also investigated. Sodium hydroxide was shown in pilot

studies to leach sulfate and cyanide effectively from the production waste. Another waste material, which

had been used to clean the coal gas, contained fine particles that did not allow for efficient flow of

leachant.

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NATO/CCMS Pilot Study, Phase II Final Report

Five possible methods for treating the leachate and contaminated groundwater were considered:

biodegradation, chemical precipitation, chemical oxidation, evaporation, and reverse osmosis.

Evaporation and reverse osmosis were not evaluated experimentally because economic analysis indicated

they would be too expensive. Pilot-scale tests of leachate biodegradation required continuous supervision

and were laborious, and the biomass was insensitive to fluctuations in pH. Therefore, bioremediation was

not evaluated further. Precipitation of the sulfate with barium chloride was determined to be impractical

because high residual barium levels would result in precipitation and aquifer clogging if reinjected, or

require expensive post-treatment if disposed of elsewhere. Thus, precipitation was also rejected for

technical and economic reasons. Laboratory experiments showed that UV light destroyed complex

cyanides in the range of 1-25 parts per billion (ppb) within 10 minutes.

Both ex situ batch and in situ remediation processes were proposed for the sulfate-rich solid waste. In

the ex situ batch process, solid waste would be mixed with water in an impoundment to leach the sulfate.

Effective leaching required retention times as high as 120 hours. An improved design consisted of a

fluidized bed batch treatment.

In situ treatment would involve accelerating the leaching process by using pH neutral groundwater or

an aggressive leachant containing sodium hydroxide on the waste, and collecting leachate in collection

drains. It was suggested that at a liquid/solid ratio of 20, the leachate derived from pH-neutral water

would have a concentration acceptable for being returned to the groundwater. A pilot-scale treatment

facility was constructed onsite consisting of heaped waste that was leached using a sodium hydroxide

solution. Objections to this technology are due to the use of chemicals during treatment.

It was concluded that batch treatments are unlikely to be feasible due to high treatment costs, long

treatment times, and costly effluent disposal. In situ treatment may be more viable although it will take

a long time.

Treatment of the cyanide-contaminated waste was evaluated using accelerated in situ leaching and an

ex situ batch process. In situ treatment was unsuccessful at pilot-scale because the waste heap was

clogged by fine particles. Ex situ batch processing was evaluated at bench-scale using both sodium

hydroxide solution and neutral water. Solid/liquid separation from the alkali leach proved extremely

difficult, and cyanide was incompletely leached by the neutral water. It was therefore concluded that

treatment of the cyanide wastes was not feasible due to lengthy treatment times and high costs.

In conclusion, the sulfate-contaminated wastes could be treated by an in situ method although the

treatment times could be lengthy and disposal of effluent costly. Viable options include leaving the

wastes on the site, covering it with clean soil and planting vegetation. Another option may be to cover

the wastes with a protective membrane. The cyanide-contaminated wastes are not suitable for on-site

treatment and should be excavated and removed for incineration or other treatment. Final disposition of

the site was not reported to the Pilot Study.

4.2.8 Project 15: Combined Chemical and Microbiological Treatment of Coking Sites

Disposal sites of wastes (including coal tars) from the petroleum refinery industry are often characterized

by high concentrations of total hydrocarbons (up to 2,200 mg/kg in soil and 4,800 mg/kg in settling

ponds), phenols (3-10 mg/kg), PAHs (850-1,500 mg/kg), and cyanides (10-300 mg/kg). In this project,

PAH-degrading bacteria were identified and the practical bioremediation of PAHs within the

contaminated soils was evaluated. The ability of an oxidation pretreatment to enhance subsequent

bioremediation was also assessed.

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NATO/CCMS Pilot Study, Phase II Final Report

Pilot-scale assessments were conducted with five different fungi and nine bacterial isolates in a

recirculating bioreactor. Biopiles were continuously mixed and aerated with amendments of straw, saw

dust, and uncontaminated soil. Inorganic nutrients were added to the system using a proprietary timerelease nutrient. Three oxidizing pretreatments (hydrogen peroxide, sodium hypochlorite, and ozone)

were assessed by mixing them as amendments into the biopiles during their construction.

The results after 2 months of the trial showed that only four of the bacterial isolates and none of the

fungi significantly degraded PAHs in the soil tested. The high concentrations of tar present in the soil

made it difficult to turn and mix the material which may have reduced contaminant accessibility. Despite

these difficulties, degradation rates of 75% for PAHs after 12 months, 75% for phenols after 7 weeks,

and 50% for cyanides after 2-3 months were reported. No information was provided on the relative

efficacy of each organism.

Considerable additions of oxidizing agents were required to observe any enhanced decrease in PAH

concentrations. The addition of a catalyst, such as ferrous sulfide, was found to reduce the amount of

nutrient necessary. In 19 weeks, 1,000 mg/kg PAH was reduced to 50 mg/kg with pretreatment by

hydrogen peroxide and ferrous sulfide catalyst.

4.2.9 Project 16: Combined Vacuum Extraction and In Situ Stripping of Chlorinated

Vapors

NOVOCTM, an in situ VOC removal system, is based on an air-lift pumping technology that uses air

injection. A remediation system installed at a former pigment manufacturing facility consisted of a series

of NOVOCTM wells and SVE wells and blowers. Contaminants included PCE and heavy metals. Initial

PCE concentrations ranged from 0.085-3.7 mg/L in groundwater and from 10 mg/kg to greater than

5,000 mg/kg in soil. The negotiated cleanup level for PCE was 1 mg/L in groundwater and 50 mg/kg

in soil.

The NOVOCTM system operated for a period of 22 months. System efficiency was controlled quarterly

and consisted of collecting water samples from monitoring wells adjacent to the remediation wells.

Results from the final soil and groundwater sampling showed that the target concentration of 1 mg/L

in groundwater was achieved. PCE concentrations measured in the NOVOCTM wells after the system had

been turned off for a 1-month period ranged from 200-565 mg/L.

4.2.10 Project 18: Biological In Situ Remediation of Contaminated Gasworks

This Pilot Study project followed the progress of a 3-year in situ bioremediation project of a former

gasworks site. The specific test area was located beneath a tar/ammonia separating sump, where spills

and leaks had contaminated the ground beneath. Maximum contamination was located at a depth of 5-7

m. Soil recovered from this zone contained up to 55,000 mg/kg of extractable, lipophilic organics and

14,000 mg/kg of PAHs. The intent of this project was to optimize natural degradation processes by

controlled addition of oxygen and nutrients.

The test area was sealed off from its surroundings by constructing walls into an impervious clay

aquiclude at 17 m depth, forming a test cell. The water level in the test cell was lowered below the level

of contamination to enhance air flow and promote aerobic degradation of hydrocarbons. A network of

lances was sunk into the ground to serve as injection and extraction points for oxygen, with the goal of

achieving homogeneous horizontal subsurface air flow. Above ground, an irrigation system was installed

for vertical seepage of inorganic nutrients and moisture into the soil.

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NATO/CCMS Pilot Study, Phase II Final Report

An objective of the project was to chart changing concentrations of leachable contaminants during the

course of the experiment. This was achieved by using a dedicated infiltration and extraction well to flush

the soil at long intervals during the test period. This process was later used to introduce nutrients into

the ground and to raise soil temperature by preheating the infiltration water.

Using 4-ringed PAHs as conservative tracers to compare initial to final organic contents, the researchers

reported that 54% of total PAHs present in the soil were degraded after 2.5 years of remediation.

Assuming that the hydrocarbons consumed were predominantly aromatic, the oxygen consumed and

carbon dioxide produced (which were monitored) account for 2,400 kg of organic material mineralized.

Maximum degradation rates were seen when the soil was warmed either by flushing with warm air or

water, or by natural warming during the summer months. Rapid degradation was also supported by

supplying oxygen by air flushing, rather than as dissolved oxygen in water. This latter observation

reinforced the desirability of lowering the water table below the level of contamination to facilitate

aeration of the contaminant zone.

Assessing exactly the efficiency of bioremediation in the field was difficult due to the extreme

heterogeneity of the subsoil. Analysis of contaminant composition suggested that the most available

components of the tar oil were readily biodegraded. Water was repeatedly flushed through the

contaminant zone (10-20 fold flushing of mobile soil pore water volume) approximately every three

months to extract elutable contaminants. During the 3 years of bioremediation, the chemical oxygen

demand (COD) levels thus recovered were reduced by about 83%, while dissolved organic carbon

(DOC) dropped about 76%. Over the same period, there was a parallel decrease of 97% in the

concentration of PAH.

The main limitation to biodegradation appeared to be the bioavailability of contaminants. Although in

some places the soil still contains relatively high concentrations of PAHs, the hazard potential of the

contaminated site was reduced considerably.

4.2.11 Project 23: Modeling and Optimization of In Situ Remediation

In situ remediation of contaminated soil and water is widely perceived to offer the greatest potential for

enhancing performance and reducing treatment cost. However, its commercial implementation has been

limited by the perception that current methods are unreliable and their treatment duration unpredictable.

The unpredictability of full-scale in situ treatment is not solely due to the heterogeneity of field sites,

but also due to economic and time constraints on the preliminary collection of field data. Treatment

design and predicted performance are often based on bench-scale studies used in combination with

models incorporating subjective default data values. The results are often misleading and overly

optimistic. This Pilot Study project reported on several aspects of an investigation into the modeling of

in situ treatment with an overall goal of enhancing and optimizing treatment performance.

A literature survey indicated that although several groundwater models existed, soil air models for

predicting the performance of SVE were relatively immature. A spreadsheet model to predict SVE

performance for sites contaminated with up to three VOCs linked differential equations to a mass

balance maintained on the spreadsheet. Model outputs included the cumulative amount of contaminants

extracted and soil contaminant concentration, both as a function of time. Parameters and expressions

within the model accounted for equilibrium sorption to organic matter, transfer from liquid to vapor

phase, and contaminant interactions, diffusion, biodegradation, and time dependence. The model output

was used to determine expected treatment durations. Four case studies were evaluated using the

predictive model with one laboratory-based study, two on-site studies, and another conducted in situ.

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NATO/CCMS Pilot Study, Phase II Final Report

Another model examined changes in contaminant concentration in extracted water as a function of time

to predict the treatment duration of in situ soil flushing. The model combined a simple predictive model

with statistical simulation to account for variabilities and uncertainties in the input parameters. Assuming

a homogeneous distribution of site parameters, soil flushing duration was predicted to achieve the

remedial target for groundwater contaminant concentration in three years. A more realistic scenario

accounting for site heterogeneity resulted in treatment times on the order of decades. The authors

stressed that a higher quality of soil investigation was necessary in order to generate a realistic prediction

of remediation duration and cost.

A mechanistic model of in situ bioventing, dubbed ECOSAT, was developed and calibrated with data

from laboratory batch and column bioventing tests. Mechanistic models allow for scenario calculations,

which may help to develop site-specific soil investigation strategies, to evaluate different combinations

of remediation techniques, and to design and optimize the process control of the selected techniques. The

calibrated model was used to predict bioventing performance, and the predictions were compared to ten

full-scale soil venting projects. Comparison of idealized geology with field data revealed that predictions

based on averaged properties are too optimistic—the observed duration of the remediation is longer than

predicted. The deviation between estimated and observed duration of remediation differ by up to one

order of magnitude. The stagnation of biotreatment suggests that a significant fraction of contamination

is unavailable to the treatment process.

The ECOSAT model was used to more fully investigate the “stagnation” phenomenon. The study

concluded that nonequilibrium phenomena, particularly diffusion-controlled mass transfer from areas of

the soil where convective flow was absent, were the dominant factors in treatment stagnation. The model

was also used to compare continuous vapor extraction with intermittent extraction. Results showed that

treatment times for either method were approximately the same since they were dependent upon the

slowly diffusing contaminant fraction. However, the intermittent extraction technique provided oxygen

to the bioavailable water-soluble contaminants much more efficiently, promoting biodegradation as the

dominant contaminant removal process. In contrast, the continuous extraction method rapidly reduced

the concentration of available contaminants through volatilization, not through biodegradation.

4.2.12 Project 35: Combined In Situ Soil Vapor Extraction Within Containment Cells and

Subsequent Ex Situ Bioremediation

An area of 7.9 ha was significantly contaminated with coal carbonization wastes from a cokeworks plant.

Contaminants included BTEX, PAHs, phenols, heavy metals, and cyanides. The site is underlain by

reworked soil, sand and gravel to a depth of 2-4 m, and groundwater was encountered within this

interval. The original site investigation indicated that both soil and groundwater were highly

contaminated. In particular, the groundwater was found to be contaminated across the entire site with

phenol, oil, and PAHs. NAPL was evident at certain locations, and oil was seeping into the nearby river.

Benzene and other VOCs were also detected in significant concentrations.

A deep cut-off slurry wall was installed to allow safe excavation up to 5 m and to prevent discharges

of contaminants directly into the river. Following dewatering, solid material was excavated. Solids

unsuitable for treatment were placed directly into an on-site encapsulation facility. The remaining

material was then screened and either air dried and reused or treated by ex situ bioremediation to remove

oil and PAH contamination. Treated materials were used as backfill to reinstate the excavated

contaminated area.

Dual-phase vacuum extraction (DVE) was implemented by dividing the area into a series of treatment

cells. The DVE system used an applied subsurface vacuum to draw contaminant vapors and free product

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NATO/CCMS Pilot Study, Phase II Final Report

to the surface for separation and treatment. At the surface, free product was separated from the

groundwater in a separator tank, and volatile organic vapors were adsorbed onto activated carbon filters.

In order to facilitate free product removal, dewatering trenches were dug in some areas of the site. The

DVE process was operated for 46 weeks. Severe weather conditions often caused problems during DVE

treatment because of freezing of supporting pipes and equipment. The goal of the treatment was to

remove free product and reduce VOC concentrations (particularly benzene) to safe levels for excavation,

rather than as a complete remedial treatment in itself.

Extracted groundwater was treated as follows in a succession of holding lagoons and reactors: (1)

floating product are removed by skimming reception/buffer lagoons; (2) heavy metals are removed by

hydroxide precipitation; (3) cyanide is treated by oxidation; (4) sulfide is treated by oxidation; (5) pH

is corrected; (6) filtration using sand filters and activated carbon filters; (7) ammoniacal nitrogen is

oxidized in a biological treatment plant. Inoculum from a local sewage works was found to perform far

better than commercially available inocula. Treated groundwater was discharged to a soakaway along

the river.

Treatment beds (biopiles) to treat some of the solids were constructed over a high density polyethylene

(HDPE) membrane and clay liner. Runoff was collected in an HDPE-lined ditch and was reapplied to

the treatment beds. Aeration was provided continuously via a network of air injection pipes. Effectively

treated material was re-used on site.

A reed bed has been planned to treat any residual contamination following site reinstatement. It is

envisioned that the reed bed will need to accommodate a groundwater flow of 30-50 m3

/day.

4.2.13 Project 37: Bioventing of Hydrocarbon-Contaminated Soils in the Sub-Arctic

This technology demonstration was carried out on a 0.4-ha area at an arctic air base that had been

contaminated with JP-4 jet fuel to a depth of nearly 3 m. The site is underlain by a mixture of sand and

gravel, with increasing silt content to 3 m, the depth of the water table. Total petroleum hydrocarbon

(TPH) levels ranged from 100-3,000 mg/kg. A field evaluation of bioventing was undertaken to

determine whether and to what degree soil warming can enhance the effectiveness of bioventing of JP-4

and to determine whether soil warming promoted a higher rate of biodegradation all year round.

The demonstration area was divided into four test plots, which were used to test four different soil

warming techniques:

(1) warm water system: Groundwater collected via an extraction well was pumped through an electrical

heater and warmed to around 35 ̊C before re-infiltration. Insulation was placed over the ground

surface to retain heat;

(2) heat tape system: Strips of heat tape were buried to a depth of 1 m in the test plot and warmed at

a rate of 16 W/m2

. Insulation was placed over the plot to retain heat;

(3) solar test: Insulation placed over the ground during the winter months was replaced with plastic

mulch sheeting during the spring and summer to capture solar heat and passively warm the soil;

(4) control test: Both the warm water and heat tape systems were operated for two years from summer

to summer over the demonstration period. The solar and control plots were monitored for 3 years.

No soil warming.

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NATO/CCMS Pilot Study, Phase II Final Report

Soil temperatures in the warm water and heat tape plots were consistently 10 ̊C higher than in the solarheated and control plots, resulting in average biodegradation rates three- to four-times higher in the

warmer plots than in the solar and control plots. After the heating systems were switched off,

biodegradation rates in these plots decreased below that of the control, suggesting that the

microorganisms may have adapted to the higher temperatures. TPH removal in the warmed plots was

an order of magnitude higher than in the solar heated and control plots. Warm water was most effective,

followed by heat tape. In all cases, soil TPH and BTEX levels dropped dramatically, indicating that

bioventing resulted in significant contaminant removal. In general, air emissions of benzene vapor in the

control plot were higher when the bioventing system was on than when it was off, but were still well

below regulatory limits.

From demonstration data, the estimated costs per volume of soil treated were comparable in all cases,

ranging from U.S.$31.67-$34.16 per m3 for a 5,000 m3 site with an average TPH level of 4,000 mg/kg.

Soil heating significantly decreased treatment time (from nearly 20 years to about three), however, so

that the decision to use soil heating in conjunction with bioventing becomes a choice about project

duration and budget allocation. Doubling initial TPH level increased the cost estimates by only 13-26%

4.2.14 Project 41: In situ Microbial Filters

Cultured methanotrophic bacteria injected into the subsurface through a borehole attach to the solid rock

matrix creating an inoculated subsurface zone. After an attachment period to allow fixation and

establishment of the microbiological community, groundwater is extracted from the borehole therefore

drawing the flow through the impregnated zone. It was concluded that a 100-mm thick biofilter

established at the site provided complete breakdown of TCE for a period of eight weeks, and had a

reduced degradation capacity for an additional eight weeks. The demonstration was reported to be

successful, although regulatory guidelines for TCE were not met in the treated water. The authors

concluded that this was due to a high concentration of co-contaminants, including chlorofluorocarbon

and methane, which were degraded preferentially to TCE. Remedial costs were claimed to be up to 50%

lower than pump-and-treat, with applicability problems being associated with large fast-flowing plumes

with contaminant concentrations less than 10 mg/L.

4.2.15 Project 42: In Situ Pneumatic Fracturing and Bioremediation

By increasing the permeability of the soil to liquids and vapors, removal of contaminants by SVE and

biodegradation can be accelerated. Hydraulic and pneumatic fracturing increase treatment efficiency of

in situ techniques by creating fissures in the soil, which act as conduits for air and water. Hydraulic

fracturing utilizes pressurized water while pneumatic fracturing utilizes pressurized air to create cracks

in low permeability and highly consolidated sediments. Aerobic processes dominate at the fracture

interfaces and, to a limited distance, into the soil away from the fracture.

Initial characterization of the test site revealed low permeability soils and benzene, toluene, and xylenes

(BTX) contamination. Over a one-year period, the site was pneumatically fractured, and nitrate and

ammonium salt were periodically injected to enhance aerobic and anaerobic biodegradation. Off-gasses

from monitoring wells were analyzed for BTX, carbon dioxide, methane, and oxygen to monitor the

progress of treatment. Additional soil corings were analyzed to measure the change in extent of site

contamination during remediation. Carbon mass balances were also performed to evaluate treatment

efficiency.

Fracturing increased subsurface permeability by a factor of 40 within an effective radius of

approximately 6 m. Results from soil sampling at the end of the demonstration showed a 79% reduction

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in BTX concentrations in the soil. Cores from three distinct depths taken before and after remediation

showed a 22-kg decrease in BTX. Biodegradation accounted for over 82% of total BTX mass removal

during the 12-month study period. Based on periodic soil-gas sampling, 14% of BTX was removed by

SVE. Other mechanisms accounted for 4% of the BTX loss.

4.2.16 Project 43: Multi-Vendor Bioremediation Technology Demonstration

This comparison of three treatment technologies took place at an abandoned hazardous waste disposal

site containing very high concentrations of chlorinated and non-chlorinated solvents such as TCE, PCE,

MEK, and toluene. Specific technical objectives of this study included determining whether the use of

naturally-occurring microorganisms can effectively remediate VOCs present in the unsaturated zone,

generating field data for simultaneous evaluation of different biological processes, and evaluating the

ability of the in situ and ex situ approaches to meet site specific remedial objectives.

The site consisted of a clay cap over mixed fill, which was comprised of hazardous waste and soil fill.

Beneath the mixed fill is a thin silty-clay layer with numerous fine silty-sand lenses. Beneath the fill is

sandy silt glacial till. Work during the trial revealed that a plastic liner was present between the fill

material and the natural soil creating a perched water table.

The first technology was a co-metabolic bioventing approach, consisting of extraction wells linked to

a central blower. The output of the blower was connected to the injection wells via ports to allow inputs

of ambient air, methane, and anhydrous ammonia. The methane was intended to boost co-metabolic

processes degrading chlorinated VOCs. The ammonia was intended as a bioavailable nitrogen source.

The blower operated for approximately 2 hr/day for nearly 5 months. The material treated turned out

to be relatively lightly contaminated, with many samples meeting treatment targets in advance of

treatment. The installation of the technology was complicated by the plastic liner and perched water,

which were not expected based on the available site investigation information. The system achieved the

compliance target; however, contaminant levels were already low in the test area—particularly for

methyl isobutyl ketone (MIBK) and PCE—and data for acetone and MEK could not be interpreted

because of difficulties with their detection limits. Using demonstration data, the treatment cost was

U.S.$52/m3

, and the duration of treatment was 12 months1.

The second technology consisted of biopiles constructed on twin layers of high density polyethylene

(HDPE) supported by earthen berms. The HDPE was covered by a layer of sand for protection and

drainage. The surface of the pile was covered by a similar felt, sand, and HDPE construct. Aeration was

via extraction pipes in the lower sand layer connected to a fan with passive air injection pipes in the

upper sand layer. Liquids could be percolated into the biopile via a sprinkler system. Air and liquid

movement was intended to optimize conditions for biological activity within the piles. Two piles were

set up: one with continuous aeration, and the other with discontinuous aeration to allow the development

of alternating periods of aerobic and anaerobic activity within the piles. The materials treated within the

piles were the most grossly contaminated site materials. The treatment was made more difficult by the

fine texture of the soil, which impeded aeration and water movement. The intermittent aeration pile

possibly did not achieve conditions suitable for aerobic activity. Neither the continuously nor

intermittently ventilated biopiles achieved compliance, although both substantially degraded the VOCs.

Based on demonstration data, the treatment cost was U.S.$71/m3

, and the duration was 9 months1.

1

The cost bases for each of three technologies were not the same. For instance, the co-metabolic bioventing

estimate included costs associated with permitting, while the UVB estimate did not.

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The third technology was a vacuum vaporization (UVBTM) well. The basic unit was a 400-mm diameter

steel water well with upper and lower screens inserted to a depth of 8 m below the ground surface. A

submersible pump in the bottom zone of the well pumped groundwater through an in-line bioreactor

packed with granular activated carbon. The treated water was discharged back into the soil through the

upper screen. The bioreactor unit was integrated with an air stripping function, both to remove VOCs

and to oxygenate the groundwater prior to discharge. The extraction of groundwater from the lower zone

and discharge to the upper zone was intended to circulate water around the well to create a zone of

enhanced stripping and biodegradation activity. Installation of the well was complicated by the plastic

liner and an unexpectedly shallow water table. After 5 months, when the other trials were completed,

samples from the UVB treatment area indicated little significant contaminant reduction; compliance was

achieved for PCE only. A longer treatment period was recommended for this type of technology. After

14 months, compliance was also achieved for MIBK and TCE (based on 45 usable data points). Using

demonstration data, the treatment cost was U.S.$240/m3

, and the duration was 14 months1.

4.2.17 Project 47: In Situ Electroosmosis (LasagnaTM Process)

The LasagnaTM process is intended to deliver treatment agents to contaminants in low permeability soils

and to render in situ treatments more feasible. The process depends on electroosmosis, whereby low

voltage electrical current applied to electrodes creates an electric field to mobilize contaminants through

low-permeability soil toward treatment zones. These zones, installed in close proximity through the

contaminated material, contain materials (e.g., sorbents, catalytic agents, microbes, oxidants, buffers,

etc.,) to sorb or degrade contaminants. Placing the treatment layers close to each other minimizes the

time needed for electroosmotic transport. Intermittent reversal of electrical polarity reverses liquid flow

and appears to increase the efficiency of contaminant removal as well as allowing complete

sorption/degradation by passing contaminants several times through the treatment zones. Reversed flow

minimizes the pH extremes that occur at the electrodes when the system is operated in one direction.

Various configurations of the technology are possible. The Pilot Study project used a vertical

configuration at a site contaminated with TCE. The case study was carried out in two phases: Phase I

evaluated the overall effectiveness of coupling electrokinetics and carbon adsorption treatment zones,

and Phase II examined the use of iron filings in the treatment zone to dehalogenate TCE in a

commercial-scale demonstration .

The demonstration site covers an estimated area of 557 m2 and extends to a depth of 15 m. TCE

concentrations in soil are as high as 1,523 mg/kg, but average around 84 mg/kg. Concentrations increase

with depth, and the highest concentrations are believed to occur at depths from 6-9 m. The test site was

about 4.6 m x 3 m on the surface and 4.6 m deep. A control area was built next to the test area and was

isolated from it hydraulically. The vertical configuration tested at the site consisted of steel panel

electrodes and treatment zones made of wick drains containing granular activated carbon. A direct

current of approximately 40 volt/m applied to the electrodes caused groundwater to flow from the anode

to the cathode at about 13 mm/day. The induced pH gradient caused problems such as soil drying and

cracking and the formation of metal and mineral deposits at the cathode. Pumping water from the

cathode to the anode reduced these problems.

Soil samples collected at the demonstration site before and after the test showed that the process

removed 98%-99% of the TCE from the tight clay (a reduction from 100-500 mg/kg to an average of

1 mg/kg). Carbon canisters used to collect soil vapors accounted for around 50% of the original TCE.

The remaining removal of TCE may be attributed to passive diffusion, evaporation, in situ degradation,

non-uniform distribution of the contaminant in the soil, or incomplete extraction of the compound from

the activated carbon before analysis.

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Results suggest the process is also effective for removing residual dense non-aqueous phase liquid

(DNAPL). At most soil sampling locations with TCE concentrations greater than 225 mg/kg (which is

indicative of residual DNAPL) the LasagnaTM process reduced these levels to less than 1 mg/kg.

A more extensive field investigation incorporated reactive treatment zones, such as iron filings, to

destroy TCE in situ. Preliminary results show that the iron filings can dechlorinate TCE, producing

relatively innocuous end-products such as chloride ion, ethane, and ethene. Potential intermediate

products, like dichloroethene and vinyl chloride, are associated with the surface of the filings.

An engineering evaluation and cost analysis for the vertically-configured process estimates a treatment

cost of U.S.$52-118/m3 of clay soil containing TCE at a depth of 12-15 m and over an area of 0.4-0.8

ha. With optimized electrode spacing, improved ability to install treatment zones and electrodes at closer

spacing, and mass-produced prefabricated materials resulting from wider use of the technology, costs

are expected to fall to U.S.$26-52/m3

. These costs exclude those for analyses, waste disposal, etc.

4.2.18 Project 49: Characterization of Residual Contaminants in Bioremediated Soils and

Reuse of Bioremediated Soils

The emission levels expected during the reuse of remediated soil were estimated by means of laboratory

and field tests. For all investigations, hydrocarbons were extracted by Soxhlet extraction using

tetrachloromethane, and hydrocarbon content was evaluated by infrared spectroscopy. In further

discussion, total petroleum hydrocarbon (TPH) content is defined as the total solvent extractable material

(TSEM) after removing polar compounds with alumina.

The remediated soil used for all tests contained 780 mg/dry kg TSEM and 430 mg/dry kg TPH, the

hydrocarbon originating from EL heating oil. The content of PAH was below 2.8 mg/kg and was not

subsequently measured.

Most of the residual contaminants remaining in bioremediated soil consisted of apolar, low-volatility

compounds (boiling points >280 ̊C). Small quantities of polar compounds (e.g., fatty acids and longchain alcohols) were also detected in individual fractions. On the whole, however, the compounds were

very hydrophobic, with octanol/water distribution coefficients greater than 106

.

The second phase of the project involved investigating the environmental behavior of residual

contaminants in the bioremediated soil after being applied as topsoil. The processes investigated were

biodegradation, leachability due to precipitation, and volatilization. The leachability of the residual

contaminants to percolating water was investigated in laboratory tests by means of shake and column

leachate tests and by means of a lysimeter test outdoors. The initial total hydrocarbon content was of

the order of 0.09 mg total hydrocarbons (THC) per liter, but rapidly declined thereafter. After less than

one average annual precipitation throughput, the THC content in the percolating water was already below

the drinking water limit of 0.02 mg/L. The leached quantity of contaminants corresponded to 0.1% of

the total hydrocarbon content in the soil material. Extrapolation of these measurements indicated that

only about 1% of the residual contaminants would leach out, even after 100 years’ precipitation. DOC,

which includes all the polar and apolar organic compounds dissolved in the water, ranged from 4.3-15

mg/L in the leachate from bioremediated soil, which is comparable to that of gravel. In comparison, the

DOC of garden soil is about 107 mg/L.

Further biodegradation of the residual contaminants was observed when the soil was used to cultivate

red clover or rye-grass, or left fallow or regularly plowed. Over 28 months, residual contamination

declined about 13%, with no significant differences between the cultivation types. Since only small

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quantities of residual contaminants leached out or were emitted into the air over the whole trial period,

the reduction in the TSEM/THC contents can be attributed to biodegradation.

The germination and growth of 36 plant species on both remediated soil and garden soil (control) were

investigated in greenhouse trials. The plants developed normally on both soil materials and showed no

phenotypical changes of any kind. Eight crops and eight wild herbs grown in deliberately contaminated

soil showed a slightly increased plant yield over the controls after 30 days. The effect was not

statistically significant, but these results clearly show that the contaminants added to the soil did not

inhibit growth.

DIN-S4 leachates showed no significant acute toxic effects on the water-flea (Daphnia magna). The

residual contaminants in successfully bioremediated soil are slightly soluble, difficult to volatilize, and

undergo further biodegradation only over prolonged periods. Since the anticipated emissions are very

low, no risks to humans or the environment are expected.

4.3 REVIEW OF CASE STUDIES AS A GROUP

As discussed in Chapter 2, Pilot Study projects were nominated and selected by a vote of Country

Representatives. The selections, therefore, reflect a desire of a particular panel of experts to review

representative or interesting new technologies available at that time, and should in no way be construed

as either a random sampling of available technologies or representing any relative abundance or

popularity of technologies. The in situ technologies chosen range from modeling efforts, to laboratory

studies, to field studies and full-scale remediation projects.

The period of the Pilot Study saw the rapid development and deployment of bioventing as a remediation

strategy for hydrocarbons in the vadose zone. Bioventing is similar to vacuum extraction, but whereas

vacuum extraction is used as a means to remove contaminant vapors from the soil for recovery or

disposal, bioventing is aimed at promoting microbial destruction of the contaminants before they reach

the atmosphere. Variables affecting the effectiveness of bioventing are the capacity of microorganisms

in the soil to metabolize hydrocarbons; the bioavailability of the hydrocarbons; temperature; and proper

control of air flow to supply sufficient oxygen while minimizing venting of volatilized contaminants.

While in some ways epitomizing “innovative” technology, bioventing had by 1993 become a widelyaccepted alternative to traditional excavate-and-dispose solutions. Extensions to the technology were

being sought to apply bioventing to hydrocarbon contamination in cold climates, to tight soils, and to

the cleanup of more recalcitrant contaminants, like chlorinated hydrocarbons.

The demonstration of arctic region bioventing (Project 37) and the demonstrations of co-metabolic

bioventing (Project 43) both achieved these to some degree. In Project 37, soil warming was applied to

promote biodegradation, and the economics of the use of soil warming were evaluated. It was shown

that the cost of bioventing with or without soil warming was about the same, but that soil warming

significantly accelerated cleanup. The decision to use soil heating in conjunction with bioventing then

becomes a choice about project duration and budget allocation, in the context of government imposed

or negotiated cleanup agreements. The estimated cost of less than U.S.$35/m3 is still significantly less

than typical dig-and-haul rates of U.S.$100/m3 or more.

Project 43 showed some promise as well, but the validation of co-metabolic bioventing based on the one

demonstration presented is equivocal. In situ concentrations of contaminants decreased, but some of the

target chlorinated compounds were already within regulatory limits at the demonstration site, and

degradation of other compounds, (e.g., toluene) was disappointing.

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Project 18 assessed the applicability of bioventing to the contaminated soils on a pilot scale at a former

gasworks site. Assessing exactly the efficiency of bioremediation in the field was difficult due to the

extreme heterogeneity of the subsurface. Analysis of contaminant composition suggested that the more

available tar oil components were readily biodegraded. The main limitation to biodegradation appeared

to be the bioavailability of contaminants.

Similar to bioventing are land farming and “biopile” technologies (Projects 6 and 15). These

technologies depend upon soil microbiology to perform the transformations necessary for cleanup, but

are applied to relatively shallow depths and depend upon air diffusion, natural convection, or plowing

for aeration. Several successes for the Daramend® process (Project 6) were reported to the Pilot Study,

including one at an arctic site and demonstrations involving a variety of soil types and contaminants.

The successes of this technology are attributed to the application of proprietary amendments to the soil,

which improve the bioavailability of contaminants and meet coincident microbial nutritional

requirements. A similar effort (Project 15) attempted to apply this kind of treatment on PAHs in a

biopile. Partial success was reported for PAH degradation, but significant difficulties were encountered

due to the tarry nature of the contaminated soil. A biopile was also part of the overall strategy in Project

35.

Soil flushing was attempted in two demonstrations to avoid more invasive efforts. A former manganese

sulfate plant in Denmark was severely contaminated with sulfate and cyanide (Project 12). While sodium

hydroxide solution was shown in laboratory studies to effectively leach sulfate, limited soil porosity

prevented effective in situ application, necessitating further disposal or treatment of the leachate. The

cyanide contamination was found to be unsuitable for on-site treatment. Final resolution of the treatment

plan was not reported to the Pilot Study, but the project was illustrative of practical limitations

encountered in the field. Project 9 reported attempts at flushing contaminants with surfactant and cosurfactant aqueous solutions, but final outcome of these efforts were not reported.

One of the Pilot Study projects was a hybrid between land farming and leaching. Project 2 leached water

through amended soil and recovered the leachate for treatment in a bioreactor. Successful destruction

of the contaminating phenolic compounds occurred in both the soil and the bioreactor.

The delivery of treatment to the contaminants is an alternative to remote treatment. Project 41 involved

a conceptual demonstration that created a subterranean zone of resting-stage methanotrophic bacteria

known to dechlorinate TCE. This “biofilter” provided a treatment zone capable of dechlorinating TCE

in eight weeks at a cost approximately half that for a pump and treat system. Operational limitations

include interference by other substances such as methane and chlorofluorocarbon and difficulty in

capturing a fast-moving plume, given the necessarily slow draw rate of contaminated water through the

biofilter.

Aquifer stripping and SVE are regarded in this report as in situ treatments, although the actual treatment

of the contaminants occurs ex situ. Project 4 applied SVE after dewatering, to take advantage of the

increased unsaturated volume. Project 1, applied air sparging to a petrol-contaminated site, in conjunction

with SVE. The amount of volatile hydrocarbons removed by vapor extraction when sparging commenced

initially increased, but the increase was short-lived and slowed dramatically after only a few days

operation. Two competing and patented aquifer stripping technologies were introduced during the early

1990's, and examples were included in the Pilot Study inventory. NOVOCTM (Project 16) is based on

an air-lift pumping technology using air injection. NOVOCTM was demonstrated for 22 months at a PCEcontaminated site and reduced the PCE concentration in the aquifer from up to 3.7 mg/L to less than

1 mg/L. In Project 43, a UVBTM well pumped water from the aquifer, aerated to remove VOCs, and

discharged it back to the subsurface. The system of extracting water from the lower zone and

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discharging it to the upper zone was intended to circulate water around the well and create a zone of

enhanced stripping biodegradation activity. Compliance at the site was achieved in 14 months for both

MIBK and TCE, at a cost of U.S.$240/m3

. Project 35 applied a subsurface vacuum to draw contaminant

vapors and free product to the surface for separation and treatment in a process called DVE. Applied

after dewatering, DVE in this instance was intended to reduce the benzene concentration at the site to

a level safe for excavation.

Remediation is the removal of a mass of contamination from a mass of natural materials, and the energy

and effort applied to separate these two masses are the fundamental problems requiring both

technological and economic solutions. The technology becomes more intensive and the costs increase

when the contaminated soil has low porosity, either because of inherent soil properties or due to fouling

by the contaminant. Two Pilot Study technologies addressed the subject of these “tight” soils. Bioventing

can be used in tight soils once pneumatic fracturing has been applied to increase their porosity. An

increased porosity makes contaminants more accessible and facilitates the introduction of air into the

subsurface. In Project 42, the site was pneumatically fractured, and nitrate and ammonium salt were

periodically injected to enhance aerobic and anaerobic biodegradation. Fracturing increased subsurface

permeability up to 40 fold within an effective radius of approximately 6 m. Biodegradation accounted

for over 82% of the total BTX mass removed; the remaining loss was accounted for by SVE and other

losses. Project 47, dubbed the LasagnaTM process, used electroosmotic transport to move contaminated

groundwater through treatment zones. In the Pilot Study demonstration, TCE was dehalogenated in a

treatment zone of iron filings. TCE concentrations in the soil were reduced from 100-500 mg/kg to an

average of 1 mg/kg.

An unusual application of biological processes is bioclogging. The combination of cells, polysaccharide,

and gases produced can reduce the hydraulic conductivity in an area for temporary partial subsurface

containment of contamination and to act as a site for enhanced biodegradation of organic contaminants.

In Project 3, biomass was made to grow in particular regions. However, only laboratory results were

reported to the Pilot Study, and no bioclogging in the field had yet been attempted.

Project 23 took a detailed look at technical and economic models of in situ remediation. In one of the

studies, the anticipated duration of remediation was three years, assuming homogeneous distribution of

site parameters, and several decades when accounting for site heterogeneity. Similar calculations changed

duration projections by an order of magnitude, just by accounting for heterogeneity. Modeling of

bioventing through a diffusion-controlled region suggested that intermittent convection promoted

biodegradation over vapor extraction as the dominant means of mass removal.

4.4 ENVIRONMENTAL IMPACTS AND HEALTH AND SAFETY

For the most part, those sites that selected in situ technologies are those with hydrocarbon contamination

ranging from lighter petroleum fractions to PAHs. In some cases, chlorinated hydrocarbons were present.

The typical strategy was to destroy the contaminants in the subsurface, reducing the chance for toxic

exposure to workers or the general public compared to traditional methods. Vapor extraction methods

involve plumbing that carries contaminants directly to treatment, which also reduces the risk of exposure.

Fugitive emissions are typically very low, providing for very little adverse environmental impact.

Project 49 found that the risk from the bioremediated soils was extremely low. Extensive tests of

bioremediated soils originally contaminated with EL heating oil showed very low leachability, no

toxicity to a number of different plants, and leachates non-toxic to Daphnia water fleas. These studies

strongly support the idea that residual limits should be based upon toxicological data and not upon

analytical capabilities.

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4.5 COSTS

Costs for the five Pilot Study in situ technologies that provided an economic analysis ranged from

U.S.$26-$240/m3

, and these costs were estimated based on limited field data and operating assumptions.

Actual costs of any technology at any given site are notoriously dependent on actual site parameters, but

the data in Table 4.2 indicate that the costs of in situ technologies are likely to be competitive for a

number of applications. In Project 12, the in situ technologies evaluated were deemed too expensive,

lengthy, or inadequate to apply. However, neither was an excavation-and-incinerate or landfill strategy

deemed suitable. The final disposition of the site is not known, but some type of impermeable cap was

being considered.

Table 4.2. Estimated Costs of Technology Application

Project

Number

Project Technology Costs (U.S.$)

6 In situ/on-site bioremediation of

wood treatment soils

$46/m3 (in situ) or $96/m3 (ex situ), excluding

treatability studies and disposal of hazardous

oversize screenings. $92/m3 (in situ) or $140/m3

(ex situ) including disposal.

12 Groundwater and soil remediation

at a former manganese sulfate

production plant

deemed too expensive

37 Bioventing of hydrocarboncontaminated soils in the sub-arctic$31.67-34.16/m3

See Appendix IV for assumptions and other

details.

43 Multi-vendor bioremediation

technology demonstration project

Co-metabolic in situ bioventing: $52/m3

biopiles: $71/m3

UVBTM well: $240/m3

See Appendix IV for assumptions and other

details.

47 In situ electroosmosis (LasagnaTM

process)

$26-52/m3 expected with mass-produced

prefabricated equipment. Otherwise, $52-118/m3

4.6 APPLICABILITY OF IN SITU TECHNOLOGIES

The most successful in situ technologies were those directed toward simple hydrocarbons in the vadose

zone, i.e., some form of bioventing or land farming. Complicating factors involve mass transfer and

bioavailability because tight clayey soils or tarry deposits prevent the intimate contact of microbes,

oxygen, water, contaminants, and other nutrients necessary to carry out the destruction of the

contaminant. Cold temperatures pose no great threat to implementing bioremediation—provided one is

willing to heat the soil or wait longer for success.

SVE has also come into its own during this period, with several enhancements being demonstrated.

Extension of bioventing and SVE through pneumatic fracturing of tight soils is notable.

Aquifer stripping entered the remediation scene during this Pilot Study period and met with mixed

success. These technologies appear to be most effective in relatively homogeneous aquifers contaminated

with highly volatile contaminants. Microbial filters, as demonstrated to the Pilot Study, show promise

in chlorinated hydrocarbon contamination, but still require further development. Electroosmotic transport

of contaminants through treatment zones is also promising.

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Attempts to extend bioremediation to PAHs have met with mixed success, due to the recalcitrance of

the substrate. Land farming was somewhat more successful than bioventing toward these contaminants.

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Chapter 5: PHYSICAL-CHEMICAL TREATMENT

Alex Lye and Robert Booth

Water Technology International Corporation, Burlington, Ontario, Canada

5.1 INTRODUCTION

5.1.1 Overview of Chapter

This chapter presents information for 16 projects that investigated physical-chemical techniques to treat

soils, sediments, other solid media, and groundwater containing a variety of chemicals. Most of the

chapter deals with soil washing, because it was the most frequently used technology for pretreating solid

contaminated media. Contaminated concentrates that resulted from soil washing were subsequently

treated by biological and physical-chemical technologies. Only six projects investigated physicalchemical technologies without soil washing as a pretreatment.

To make meaningful comparisons of data reported for the projects, the projects were grouped as follows:

• Group 1: Typical soil washing;

• Group 2: Soil washing and biological treatment;

• Group 3: Soil washing and physical-chemical treatment;

• Group 4: Physical-chemical treatment (no soil washing); and

• Group 5: Photo-oxidation treatment.

The project summaries presented in Section 5.2 provide an overview of the projects but do not contain

all information, such as performance data and criteria achieved. This excluded information is discussed

elsewhere in the chapter and in the project summaries (Appendix IV). However, key points of the

technologies are contained in Table 5.1.

For the purposes of this chapter, soil washing includes unit processes such as screening, attrition

scrubbing, hydrocycloning, etc., as well as enhancements such as flotation, magnetic separation, and

gravity separation.

Finally, it must be noted that the authors of this chapter summarized and compared data contained in

available reports. Data are presented as they were reported for the various projects. Final reports were

not available for some projects, while documents for others did not provide detailed information. As a

result, there are limitations to the data comparisons and observations made by the authors.

5.1.2 Generic Description of Technology Group

Typical Soil Washing

As a pretreatment for excavated material, soil washing exploits the fact that contaminants are often

preferentially adsorbed to the fine particles. This approach relies on physical processes to separate a

small volume of contaminated material from the bulk of relatively uncontaminated material. Current

commercial soil washing processes remove mainly fine fractions (<0.063 mm) containing the highest

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concentrations of contaminants. The remaining coarse fraction (>0.063 mm) is relatively clean. The clean

material is often reused as “inert” fill.

Separating the contaminated fines often results in lower costs for overall treatment, because it is only

this smaller volume of contaminated material, not all the original material, that requires further treatment

or disposal. The contaminated material is shipped to a controlled landfill or treated further by a variety

of processes that destroy, immobilize, or recycle the contaminants.

Soil washing is economically feasible only if the volume reduction is large enough to provide financial

benefits. According to a report (1) on an extensive review of commercial and pilot-scale soil washing

systems, soil washing is most effective on soils containing less than 30-35% clay and silt, i.e., particles

smaller than 0.063 mm. At higher percentages of these fines, the volume reduction is not large enough

for the process to be economical. In addition, difficulties arise in handling these materials, separating

the contaminated and uncontaminated materials, and handling the products.

Despite these problems for soils rich in fines, soil washing may be seen as a cost-effective treatment if

the technology overcomes difficulties presented by the high levels of silt and clay. Possible solutions

include enhancing soil separation techniques and developing processes to treat the fine fractions

downstream.

Soil Washing Combined with Other Technologies

With some soils, physical treatment alone will not reduce the absolute concentration of contaminants to

acceptably low levels. For soils containing more than 30% clay and silt by weight, physical pretreatment

could reduce the volume of contaminated material requiring downstream treatment. Pretreatment may

also present the separated contaminant concentrate in a form suitable for the downstream process, e.g.,

bioslurry, solvent extraction, and vacuum distillation. Case studies in this chapter illustrate soil washing

combined with biological or physical-chemical treatment such as vacuum distillation, photo-oxidation,

biodegradation, and chemical dehalogenation.

Physical-Chemical Treatment (No Soil Washing)

Some of the downstream processes mentioned above may be used directly on contaminated material that

was not previously washed. Some of the case studies in the chapter examine processes such as:

• solvent extraction and treatment of extracts by stabilization (for heavy metals);

• leaching and treatment of leachate; and

• in situ electro-osmosis and adsorption.

Like soil washing, these conventional technologies experience difficulties in treating contaminated

materials where the fines exceed 30-35%. When the levels of fines are this high, methods such as

thermal treatment and solvent extraction become more expensive, while others such as biological

treatment take a longer time.

Photo-Oxidation Treatment

This chapter restricts the discussion of photo-oxidation treatment to ultraviolet (UV) radiation and

hydrogen peroxide (H2O2) to treat groundwater.

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5.2 CASE STUDIES CHOSEN

This section summarizes each of 14 projects as a case study. The projects are discussed in groups as

follows:

• Group 1: Typical soil washing (Project 30);

• Group 2: Soil washing and biological treatment (Projects 24, 26, and 36);

• Group 3: Soil washing and physical-chemical treatment (Projects 10, 17, 19, 27, 31, and 33);

• Group 4: Physical-chemical treatment (no soil washing) (Projects 32, 44, and 47); and

• Group 5: Photo-oxidation treatment (Projects 14, 38, and 40).

Some of the projects are also discussed in other chapters: Project 47 in Chapter 4; Projects 24, 26, and

31 in Chapter 6; Project 19 in Chapter 8; and Projects 10, 24, 26, 31, 32, 33, and 47 in Chapter 11.

5.2.1 Group 1: Typical Soil Washing (Project 30)

Project 30: Using Separation Processes From The Mineral Processing Industry For Soil Treatment

Investigators evaluated the applicability of particle separation techniques from the mineral processing

industry to treat contaminated soil from sites in the U.K. This technique of soil washing by physical

separation used established and innovative mineral processing equipment to separate soil into fractions

of varying contaminant concentrations. The majority of tested soils contained clay and fines at high

levels normally considered uneconomical for soil washing. These soils contained arsenic, complexed

cyanides, and metals such as Hg, Cr, Cu, Pb, Ni, and Zn. Organics in the samples included polycyclic

aromatic hydrocarbons (PAHs) and petroleum hydrocarbons.

Laboratory studies assessed the potential of physical processes to separate the contaminated soils into

various fractions. These processes consisted of grain-size separation, attrition scrubbing, specific gravity

partitioning, froth flotation, and magnetic separation. The studies confirmed that contaminants in the

tested soils appeared to occur preferentially in particular soil fractions. Unfortunately, this preferential

distribution was not always sufficient, so that fractions with the lowest concentrations of contaminants

could be reused as inert landfill.

A pilot-scale investigation with the Warren Spring Laboratory s National Environmental Technology

Centre s (WSL/NETCEN) soil washing plant examined soils from a former metal processing works and

gasworks. Both soils were included in the laboratory studies. Material from the former gasworks

consisted of building rubble, wastes and soil. A relatively high clay content (around 30%) made handling

difficult. To exploit the physical properties of the soil and contaminants, the WSL/NETCEN soil washing

plant was designed to transfer contaminants from the soil to a water-based suspension. This plant, with

a throughput of 0.5-1.0 tonne/hr, compared froth flotation and a multi-gravity separator (MGS) for

separating fine particles. Altogether, treatment processes consisted of coarse sizing, further sizing,

attrition scrubbing and classification, and contaminant concentration.

The effectiveness of the process was measured by comparing the levels of contaminants in treated and

untreated soil. In the pilot-scale tests using froth flotation, residues with low levels of contaminants (i.e.,

treated material) made up around 48% by weight of the original feed. For similar tests with an MGS

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instead of froth flotation, the residues with low levels of contaminants totaled around 50% of the original

feed. Compared to the rest of the feed, these residues contained markedly lower levels of PAHs,

petroleum hydrocarbons, cyanide, Pb, and As. Comparing data on contaminants in the two types of

residues (i.e., froth flotation and MGS) revealed that the flotation residues contained higher levels of

PAHs and petroleum hydrocarbons, but lower levels of Pb and cyanide. Arsenic levels did not differ

much between the two residues.

Samples from the former metal reprocessing works produced a small proportion of dense material

(specific gravity >2.8) with very marked concentrations of contaminants. Despite this separation of

contaminants into the dense fraction, the remaining bulk of treated material contained unacceptable levels

of contaminants. According to a project report, researchers re-assessed results of the Toxicity

Characteristic Leaching Procedure (TCLP) of the soil and then re-considered the role of physical

treatment in a treatment train to reduce the hazard.

For the soil from the former gasworks, the researchers suggested improving separation of fractions then

destroying concentrated contaminants in the fine clay and silt fraction as a cheaper option to treating the

entire soil. The recommended approach could consist of an enhanced soil washing process to improve

separation, an in-line bioslurry reactor to destroy contaminants, or a combination of the two. The

resulting treated fines may form a sludge that could be disposed of as a contaminant-free waste.

The pilot-scale soil washing plant featured process water containment and recirculation, and carbon

filters to extract volatile contaminants from emissions. Wastes and sludges from the plant received

further treatment at downstream processes or were shipped to a licensed landfill. The reports did not

contain information on costs.

5.2.2 Group 2: Soil Washing and Biological Treatment (Projects 24, 26, and 36)

Project 24: Combined Remediation Technique for Soil Containing Organic Contaminants: FORTEC®

Developed by Heidemij Realisatie of the Netherlands, the Fortec® (Fast Organic Removal Technology)

process combines hydrocyclone separation, photo-oxidation, and bioslurry technologies to treat soils

contaminated with heavy aliphatic hydrocarbons (oils) and PAHs. A multi-staged configuration of

hydrocyclones selects specific soil fractions that contain the majority of the contaminants. A clean sand

fraction and heavily contaminated sludge result. The technology has been developed through bench- (25

m3

) and pilot- (50 m3) scale to its current demonstration-scale of 300 m3/batch.

Depending on the composition of the feed material, the sludge may be pretreated before it enters the

slurry bioreactor. Pretreatment involves photo-oxidation (using high-pressure mercury UV lamps and

H2O2) or a physical process in a batch reactor. This step transforms contaminants that are difficult to

biodegrade into readily biodegradable ones.

The batch slurry bioreactor has a retention time of 3-20 days depending on the matrix being treated.

Nutrients (nitrogen and phosphorus) are added as required. Once biotreatment is complete, the slurry is

allowed to settle. The resulting effluent is recycled, while a belt filter press dewaters the sludge.

While photo-oxidation pretreatment enhances the biodegradation of PAHs, it is not required for more

readily biodegradable contaminants. Initial studies showed that concentrations of 400-5,000 mg/kg

mineral oil in contaminated soil could be reduced to the objective of 100 mg/kg in eight days without

photo-oxidation pretreatment. In contrast, data showed that photo-oxidation helped degrade PAHs in soil

and chlorophenol in groundwater. The pretreatment reduced PAHs from 30 mg/kg to 5-10 mg/kg in 15

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NATO/CCMS Pilot Study, Phase II Final Report

days and chlorophenol from 200 μg/L to approximately 50 μg/L in 25 hours. It was suggested that the

enhanced degradation resulted from the breakdown of soil organic matter and subsequent release of

sorbed PAHs rather than to the oxidation of PAH molecules themselves. Without photo-oxidation

pretreatment, PAHs were not degraded, while chlorophenols were reduced to only 100 μg/L.

Two demonstration tests were undertaken: one on sandy soil contaminated with heavy crude oil and one

on sediment contaminated with mineral oil and PAHs. Soil washing was used as the pretreatment step

to separate the fines from the larger soil or sediment fractions. Fines rich in organics were then treated

in the 300-m3 bioslurry reactor designed to maintain a minimum dissolved oxygen concentration of 2

mg/L and a set temperature between 15-30°C.

The results of these demonstrations showed that soil contaminated with up to 14,500 mg/kg of crude oil

was treated to less than 3,000 mg/kg (in recombined fractions). Sediment contaminated with up to 2,000

mg/kg PAHs and 20,000 mg/kg mineral oil was treated to levels of 150 and 2.5 mg/kg respectively.

Project 26: Treatment of Creosote-Contaminated Soil (Soil Washing and Slurry Phase Bio-reactor)

The project investigated combining soil washing (especially using froth flotation) and slurry-phase

bioremediation to remediate soils contaminated with 3- and 4-ring PAHs. The project consisted of benchscale treatability studies and pilot-scale remediation.

The bench-scale biotreatability studies involved first isolating and screening soil microorganisms to

evaluate their tolerance to PAHs and their ability to degrade these contaminants. Subsequent experiments

with selected microorganisms provided optimum conditions for biodegradation of these compounds in

slurry reactors.

The pilot-scale plant set up at the Norwegian State railways site in Lillestrom, Norway, combined froth

flotation as a pretreatment for soil washing, a 1-tonne/hr soil washing plant, and a 454-L bioslurry

reactor. This phase of work tested four excavated soils made up of sand, silt, clay, and sawdust/sand

from the railway site, as well as two soils from another location. Investigators evaluated single and

blended commercial anionic and cationic surfactants used with a foamer at water temperatures between

10-50°C and pH of 7-11. The biotreatment phase of the study tested indigenous microorganisms as well

as patented PAH degraders. Parameters for biostimulation included nitrogen (N) and phosphorous (P),

pH, aeration, surfactant, and temperature.

Bench-scale investigations of soil washing revealed that the most effective combination of one of the

cationic collectors and a foamer removed 90-95% of PAHs from sandy soils. Increasing water

temperature or pH provided no significant benefits and was incompatible with the downstream biological

treatment. At the pilot-scale, soil washing at a loading rate of 550-859 kg/hour removed 20-90% of

PAHs from two clay soils. The cleaned soil fraction contained 15-1,500 mg/kg PAHs. Clayey soils

impaired the efficiency of soil washing and resulted in less than optimum performance.

The pilot-scale bio-reactor tested five 60 L batches of sludge resulting from soil washing two clayey

soils. During treatment of the sludges, which contained 14-20% solids, PAH concentrations fell by up

to 97% after 6 days. Oxygen uptake decreased during this time corresponding to a decrease in

bioavailable PAHs in the bioslurry. An interim report noted that the native populations of PAH degraders

“appeared to be sufficient to achieve residual PAH concentrations ranging from 55-200 mg/kg after a

6-day retention time.”

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NATO/CCMS Pilot Study, Phase II Final Report

A Microtox 15-minute bioassay revealed that the combined soil washing and biological treatment

reduced toxicity by a factor of 10. Soil washing itself reduced the relative toxicity only slightly. The

bioslurry treatment accounted for most of the reduced toxicity. Costs for various aspects of the

remediation approach for the site were estimated at U.S.$160/m3 for excavation, sorting and backfilling,

U.S.$300/m3 for washing, and U.S.$530/m3 for biological treatment.

Project 36: Enhancement Techniques for Ex Situ Soil Separation Processes, Particularly with Regard

to Fine Particles

This pilot study examined the feasibility of extending soil washing processes to soils containing a high

proportion of fine particles. The investigation focused on physical separation techniques and equipment

used to treat fine mineral ores and industrial minerals. Tested soils contained a high proportion of fines

and were contaminated with organic compounds. The studies investigated a variety of processes that

included disaggregation, sizing, and classification of particles, attrition scrubbing, dewatering, and

integration with slurry-phase biological treatment.

For the laboratory- and pilot-scale studies, two tested soils were both rich in clays. One soil from a

former industrial site contained 62% soil particles less than 0.063 mm and was contaminated with diesel

fuel. The other soil from a former gasworks facility had up to 43% soil particles less than 0.063 mm and

contained PAHs, total petroleum hydrocarbons (TPH), and complexed cyanides. Laboratory tests served

to characterize the soils and help design the pilot-scale studies. The tests evaluated disaggregation,

screening, classifying at fine sizes, attrition scrubbing, and removal of misplaced or “entrained” particles.

For the pilot plant tests, investigators used small-scale commercial separation and concentration

equipment. Tests were conducted as a number of batch processes, with material from one process being

collected and used as feed for further processes.

Contaminated fines were sometimes treated by froth flotation and specific gravity separation. The froth

flotation approach, seen as an alternative to ultrafine hydrocycloning, consisted of a coal collector and

frother. A part of the study tested 10 common organic flocculants and three inorganic coagulants to

choose a flocculant/coagulant that produced relatively large compact flocs that settled rapidly. Work

included settling tests and capillary suction tests.

Ten-liter air-sparged reactors provided a temperature-controlled environment for biological treatment.

These investigations evaluated the biodegradability of different contaminated fine fractions at different

temperatures, and with and without nutrients.

The bulk of contamination in the diesel-contaminated soil occurred in the fraction smaller than 0.002

mm. Pretreatment with a rotary ball mill partially filled with steel balls or pebbles disaggregated the soil

particles and produced a slurry amenable for separation. Up to four additional sequential stages of

hydrocycloning substantially reduced the concentration of contaminants in the coarse fraction. The

resulting contaminant-reduced fraction accounted for 68.7% of the original soil.

Froth flotation, tested on the fraction smaller than 0.01 mm, did not significantly reduce contamination

in the non-floating product. Of the 13 organic and inorganic coagulants/flocculants examined, calcium

hydroxide at a dose rate of 100 g/tonne of solids produced a floc with the lowest moisture content after

filtration.

After 28 days of treatment in the slurry reactor, fines separated from the diesel-contaminated soil

retained only 20% of their original contamination. Despite this reduction, treated fines contained

relatively high levels (2,300 mg/kg) of TPH, down by 80% from the original 12,000 mg/kg.

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Despite their success with diesel-contaminated soil, physical separation and slurry phase biological

processes experienced difficulties treating fines in the gasworks soil. Disaggregating this soil involved

a tumbling mill system, sometimes preceded by a high pressure water-sprayed screen. Laboratory studies

revealed that attrition scrubbing had little benefit because fine aggregated particles and contaminantcoated particles were minimal.

Froth flotation and specific gravity separation, unlike sizing and multi-staged classification, were able

to concentrate contaminants in specific fractions. Froth flotation proved best on the 0.01-0.063 mm

fraction, producing a non-floating fraction that accounted for 69% of the original untreated material.

Three stages of froth flotation reduced PAH contamination by 61%, petroleum hydrocarbons by 54%,

and cyanide by 39%. Specific gravity separation on the 0.01-0.063 fraction reduced PAHs, petroleum

hydrocarbons, and cyanide contamination by 68%, 76%, and 14%, respectively. Despite these reductions,

treated fractions could not be reused because they still contained unacceptable levels of contaminants.

Biological slurry treatment of the fine fractions failed to significantly reduce levels of the contaminants.

After 28 days of treatment, PAHs fell by 40-50%, and petroleum hydrocarbons by up to 20%. Cyanide

remained unchanged.

Residuals include clean treated soil materials and others that did not achieve remediation guidelines.

Clean material could be reused onsite, while partially clean materials have to be dewatered and disposed.

Water from soil washing and bioslurry treatment would also have to be treated before disposal.

For treatment to be more cost-effective than disposal of the untreated soil, the cost for transporting and

disposing of such material must exceed £40-60 (U.S.$65-100) per tonne. Total operating costs were

estimated at £23-37 (U.S.$38-60) per tonne of treated material.

The results of the study suggested that ex situ separation processes may be cost-effective for soils

containing more than 30-35% of particles smaller than 0.063 mm. However, further work should assess

the extent of application of this approach. This work may examine the mineralogy of clay particles, as

well as how the exchange capacity of these particles influences adsorption/desorption of contaminants

and subsequent dewatering.

5.2.3 Group 3: Soil Washing and Physical-Chemical Treatment (Projects 10, 17, 19, 27, 31,

and 33)

Project 10: Integrated Treatment Technology for the Recovery of Inorganic and Organic

Contaminants from Soil

This technology uses an integrated process to recover metals and organic compounds from soils and

sediments. The process combines physical and hydrometallurgical steps to recover metals, and physicalchemical methods for organics. The combination provides a technology capable of recovering organic

and inorganic contaminants simultaneously.

The first step involves separating the finer fraction of material, normally associated with contaminants,

for further treatment. Coarse screens remove the fraction greater than 75 mm, which is usually clean and

normally returned to the site. Material less than 75 mm goes through sequential soil washing separation

methods, which break down soil aggregates, separate ferrous metal, and produce fractions of different

sizes.

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The resulting slurry, free of coarse metal fractions, is then treated with proprietary reagents and

conventional flotation equipment to extract a product rich in organic contaminants. If further treatment

is required, the organic-depleted slurry passes to a hydrometallurgical circuit where fine metal

contaminants that were not recovered physically are leached into solution then extracted with VitrokeleTM

metal-selective absorbents. The resulting metal-rich filtercake is recycled, while the remaining slurry is

washed, dewatered, and disposed as a clean material.

The intended uses for treated materials govern the degree of treatment required to satisfy the relevant

criteria and the consequent overall costs. For example, sediments to be used as lake-fill may require an

extra hydrometallurgical leach and counter-current VitrokeleTM adsorption unit to achieve lake-fill

guidelines. Sediments for on-shore use as fill may not require this step.

Tallon Metal Technologies, Inc. conducted bench-scale tests with sediments from Hamilton Harbour,

Ontario, Canada. The sediments contained high concentrations of organic contaminants (PAHs, oil and

grease), metals such as Pb, Zn, Cd, Cu, and Ni, as well as a total organic carbon (TOC) load that

exceeded 10%. A 20-kg test sample was made up of approximately 92% material smaller than 100 μm

and 75% smaller than 50 μm. Metals such as Cd, Cr, Fe, Mn, Ni, Pb, and Zn exceeded the “severe

effect level” base on Ontario s sediment quality guidelines. The bench-scale treatment approach included

flotation, magnetic separation, and gravity separation techniques.

The results showed that cleaned tailings represented around 40% of the original sediment feed, but

contained only 4.1% of the total oil and grease, 4.9% of the PAHs, less than 2% of the total Pb, and

11% of the total Zn. In contrast, Cd, Ni and Fe were also reduced but remained at 24-30% of the

original load.

The organic product contained 27% of the total mass and captured 62% and 74% of the original oil and

grease and PAHs, respectively. It was also enriched in Pb, Zn, Cd, Ni, and Fe at 81%, 60%, 54%, 54%,

and 32%, respectively, of the original content.

Based on the bench-scale investigation, the treatment process for Hamilton Harbour sediments would

consist of screening, magnetic separation, concentration of organics by flotation, and a hydrometallurgical extraction if required to remove residual Zn, Cu, Ni, and Pb from feeds to the leach circuit. For this

treatment, the contractor estimated a cost of Cdn$75-100 (U.S.$52-69)/tonne, assuming at least 20,000

tonnes require treatment.

The technology was tested on soils from two industrial sites: the Ataratiri site in Toronto, Ontario,

Canada, and a site in Longue Pointe, Quebec, Canada. The soils exceeded industrial guidelines for reuse

for some heavy metals and inorganics. Ataratiri soils contained PAHs, while those from Longue Pointe

were contaminated with metals such as Pb, Cu, and Zn.

Pretreatment of Ataratiri soils resulted in a metal concentrate, suitable for recycling, containing as much

as 55% by weight iron. “Clean” fractions that made up around 95% by weight of the feed material were

within Ontario s residential criteria for some contaminants, but within industrial criteria for PAHs. The

treatment reduced benzo(b)fluoranthene from 14 mg/kg to 4 mg/kg, a value that exceeds residential

guidelines. Treatment reduced Zn from 4,026 mg/kg to 360 mg/kg, but Cu remained unchanged at 100

mg/kg. An added hydrometallurgical step proved effective for treated soils that still exceeded industrial

guidelines. When soils were treated by this extra recovery step, higher percentages of the original feed

material achieved industrial or residential guidelines.

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NATO/CCMS Pilot Study, Phase II Final Report

For Longue Pointe soils, the technology incorporated hydrometallurgical extraction and VitrokeleTM

adsorption because most of the Pb contamination occurred in fine particles in the soil. Soil treated this

way contained as little as 7% of its original Pb content (as high as 11,800 μg/g), and met regulatory

limits for industrial or residential use.

At Ataratiri and Longue Pointe, recovered contaminant metal products were of low mass, rich in metals

and suitable for recycling off-site in the steel or base metal industries. Recovered organic contaminants

were low in mass, enriched in oil and grease and PAHs, and suitable for on-site or off-site treatment by

a secondary technology.

According to the technology vendor, the integrated approach for organic and inorganic contaminants is

economically attractive over one that uses two independent treatments.

Project 17: Treatment of Polluted Soil in a Mobile Solvent Extraction Unit

The ORG-X mobile solvent extraction unit, originally designed to remove viscous non-aqueous phase

liquids (NAPLs), such as PAHs and tars, from excavated soils at manufactured gas plants, is modular

and usually mounted on five trailers. Under this NATO/CCMS Pilot Study, the ORG-X process was

combined with other technologies to treat PAHs, polychlorinated biphenyls (PCBs), petroleum

hydrocarbons, and heavy metals in different soil types.

After first screening contaminated soil to remove a coarse clean fraction (>#4 mesh), contaminated fines

are mixed with a non-chlorinated, non-toxic, biodegradable solvent at ambient temperature. An extraction

auger enhances dissolution of organics from soil in the resulting slurry and partially separates the cleaned

fines from the solvent laden with organics. The solvent then passes to a decanter where the entrained

fines settle. After settling, fines are returned to the initial mixing tank, and spent solvent is decanted and

sent to a vaporizing recovery unit. Solvent recovered from this unit is recycled to the initial mixing tank

while organics form a concentrated contaminated oil, which requires subsequent treatment.

Soil from the extraction auger goes to a dryer that evaporates residual solvent, condenses it, and sends

it to the vaporizing unit. The treated dry soil is then either stabilized if contaminants such as heavy

metals are present, or is reused. Traces of solvent in cleaned soils are claimed to be innocuous and

biodegradable.

The feed rate depends on the soil type and ranges from two to five tonnes/hour. Treatment costs vary

from U.S.$75-200/tonne depending on the volume of material to be treated.

Tests were conducted with 12-200 tonnes of media (silty sand, loamy soil, and sediment) contaminated

with PAHs, coal tar, petroleum hydrocarbons, heavy metals, and PCBs. Extraction reduced levels of

PAHs from 250-2,000 mg/kg to 6-30 mg/kg, and PCBs from 200-500 mg/kg to 1-6 mg/kg (98%

reduction). Treated materials were used as fill or treated further to stabilize metals.

The solvent formulation, protected by trade secret, which is non-specific and thus provides excellent

extraction for a wide range of organic contaminants. These include crude oil, machining oils, PCBs,

pesticides, and herbicides. A key feature of the system s design is its ability to treat finer particles with

adsorbed contaminants.

The ORG-X mobile solvent extraction unit operates best under optimum moisture content and grain size.

In one case study, the soil moisture content of 20% made the soil more difficult and costly to treat. The

process achieves higher efficiency on sandy material, but is being improved for fine-grained soils.

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NATO/CCMS Pilot Study, Phase II Final Report

The technology vendors reported that cost savings increase as the volume of material to be treated

increases, for example:

• 2,000 tonnes: approximately U.S.$200/tonne

• 20,000 tonnes: just under U.S.$100/tonne

• 100,000 tonnes: about U.S.$60/tonne

Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil Washing and Distillation

Process

The large-scale Harbauer soil washing and vacuum distillation plant was evaluated at a site in

Marktredwitz, Germany. The site contained 57,000 metric tonnes of soil and debris contaminated with

mercury, solvents, chemical waste, and treatment residuals. Mercury occurred at concentrations of 300-

5,000 mg/kg. The project s remediation goal was to clean the contaminated soil and debris to meet

criteria for landfilling.

This was reported as the first full-scale application of vacuum distillation technology. This unit is

containerized, transportable, and equipped with systems to treat process water and off-gas. During the

3-year period of operation, the unit processed 57,000 tonnes at the rate of 150 tonnes/day.

Vacuum distillation eliminates drawbacks associated with conventional thermal processes. For example,

the moderate heating does not change the mineral structure of treated soils.

In this technology, soil washing first concentrates mercury in a fine fraction (as small as 0.1 mm to as

large as 8 mm). During subsequent vacuum distillation, the fines concentrated with mercury are heated

in a rotating drum to 350-450°C under reduced pressures of 50-150 hPa. Reduced pressures (rather than

higher temperatures) lower the boiling points of contaminants and result in lower energy costs. Also,

vacuum distillation releases only 1/20 to 1/30 of emissions normally encountered with incineration.

Volatile mercury is recovered by condensation. Treated soils containing more than 50 mg/kg mercury

are passed through the process again.

In addition to soil washing and vacuum distillation, the system incorporates processes to treat water and

off-gases. Water treatment consists of thickeners, flocculants, a sand filter, and activated carbon filters.

The sand filter removes very fine particles while the carbon adsorbs organic contaminants that may be

present in the process water. An ion exchanger completes treatment before water may be discharged to

a sanitary sewer.

In the remediation project, 15,000 tonnes were treated at a rate of 150 tonnes daily during the first year

of operation. Soil containing mercury up to 1,900 mg/kg achieved levels below the target of 50 mg/kg,

and often reached 10 mg/kg. Treated off-gases and water also achieved relevant target levels.

Monitoring the plant revealed that the operation met emission standards. Under the low-oxygen

environment of vacuum distillation, secondary oxidation does not occur, so dangerous organic residues

like dioxin are not formed.

Residuals to be disposed of or recycled were condensed mercury, spent ion-exchange resin, and a finegrained precipitation sludge from the water treatment unit.

Costs for treatment, according to results from a U.S. SITE demonstration project, were estimated at

U.S.$320/tonne.

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In addition to its application for mercury in the remediation project, the combined process can be used

to treat crude oil fractions, halogenated hydrocarbons, PAHs, cyanides, and metal compounds that can

be vaporized.

Project 27: Soil Washing and Chemical Dehalogenation of PCB-Contaminated Soil

Soil washing and chemical dehalogenation were used to treat 1,288 tonnes of excavated material

contaminated with PCBs. This material came from a site in Oslo, Norway, where insulator oils

containing PCBs had leaked from transformer equipment and contaminated soil with up to 2,000 mg/kg

PCBs.

The three-year project included bench-scale studies on soil washing followed by pilot-scale and full-scale

washing. Dehalogenation investigations were conducted at bench-scale and full-scale. The Pilot Study

focused on a combined system of water-based soil washing and dehalogenation, because this

combination had not been applied before in Norway. Both processes were novel in that country, and

reductive dehalogenation was itself innovative.

Duplicate bench-scale soil washing treatability experiments with a laboratory-scale flotation cell tested

these variables: water temperature, pH, five surfactants, and a foamer (methylisobutylcarbanol). The

additives and soil were mixed for a fixed conditioning period, then aerated for a fixed period. The foam

and remaining clean soil were collected and analyzed for PCBs.

Soil washing involved first separating and sorting debris, then treating the soil in a soil washing plant.

For this treatment, the plant consisted of three processes to separate the remaining contaminated

materials into two size fractions (>0.1 mm and <0.1 mm) and to surface-wash them. The contaminated

fines (<0.1 mm), having passed through a conditioning mixing tank and a double flotation cell, were

trapped in a foam in the cell. The trapped material, laden with contaminants, was coagulated and

flocculated with an organic polymer, then thickened and dewatered.

The full-scale soil washing operation did not achieve its performance target for volume reduction

because the levels of fine particles were higher than expected. Washing reduced the volume of material

by 60%, not 70% as expected. The excess particles overloaded the system with solids, and soil that

should have been clean after one washing had to be washed again. As a result of the reduced

performance, washing produced 780 tonnes of clean soil and around 400 tonnes of sludge containing

PCBs to be destroyed.

The dehalogenation technology tested at the pilot-scale involved first drying soil to 10% moisture, then

adding a reducing agent and exposing the mixture to a reducing environment. The final report

documenting results of the pilot-scale dehalogenation investigation was not available for this review.

In terms of performance for PCBs, the duplicate bench-scale soil washing experiments on samples with

around 1,000 mg/kg PCBs achieved 80-95% removal of PCBs. The remaining soil (clean fraction)

contained residual PCBs at 40-50 mg/kg.1 The full-scale soil washing operation treated 1,400 tonnes

of soil containing 50-300 mg/kg PCBs (dry weight). All batches achieved the performance criterion of

less than 10 mg/kg PCBs.

1

Authors’ note: In the absence of mass balance data, the percent removal cannot be verified. It is possible that

the laboratory work aimed to achieve a specific concentration of PCBs in the clean fraction rather than a targeted

percent removal.

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The report did not contain information on performance in terms of discharged water. This water could

contain no more than 10 μg/L PCBs, that translates to a loading of less than 200 mg/day.

The interim report did not contain information on the full-scale dehalogenation studies, or on the ecotoxicological tests to evaluate the risk associated with clean and treated soil to be redeposited at the site.

Leachates from TCLP tests of treated material provided information on the toxicity of the biphenyl byproducts.

The soil washing operations generated residuals, but no gaseous emissions. Coarse material and treated

fines were returned to the original excavation and capped. All wash water was collected, analyzed for

PCBs, and treated if required before discharge to a sewer.

Treated soil contained residual PCBs, by-products formed during treatment, and chemicals used to

promote dehalogenation of the PCBs. All of these compounds posed possible environmental hazards.

To evaluate these hazards, a suite of eco-toxicological tests was conducted on leachate generated from

samples treated according to the TCLP.

For the full-scale soil washing operations, equipment costs were estimated at U.S.$75,000 and operations

at U.S.$380/tonne. These amounts include handling materials, and analyses (approximately U.S.$76/

tonne). Costs for dehalogenation were not available.

Project 31: Decontamination of Metalliferous Mine Spoil

The Water and Environment Division of the Welsh Office commissioned a study to evaluate methods

for decontaminating metalliferous spoil from abandoned mines in mid and north Wales. This study aimed

to determine if current metal-processing could be used to reprocess old metalliferous spoil materials to

recover metals of some value and to reduce the environmental impact of the spoil.

Laboratory-scale studies evaluated the mineral processing techniques on lead-zinc mine spoil materials

from five unreclaimed former metal mines. This evaluation, the first phase of a two-part study, set out

to identify promising treatment options for detailed examination in the second phase. Researchers first

characterized spoil material then examined techniques involving gravity separation, froth flotation,

chemical leaching and biological extraction.

Characterization of the mine spoil revealed that concentrations of Pb and Zn in the whole spoil samples

were up to 20% and 15% by mass, respectively, but Cu and Cd were in the range of parts per million.

Lead was concentrated in the finer particle sizes of the spoil. Results also showed that a fine-grained,

compact, clay-like spoil saturated with water created anaerobic conditions, which inhibited oxidation and

allowed minerals to retain their sulfide forms. In contrast, a sandy spoil allowed extensive oxidation to

occur and convert Pb and Zn minerals to their more easily leached sulfate forms.

In this study, differences in particle density and surface chemistry for the separation of spoil particles

were evaluated using dense media (so called “sink and float”) and froth flotation tests. An MGS was

further examined for density separation at pilot-scale. Laboratory-based density separation consistently

reduced metal concentrations (<2 weight %) in the lighter spoil fractions, which represented over 90%

of the total sample weight. The heavier concentrate contained up to 32% Pb and 5% Zn by weight.

Although treated material was significantly cleaner than original spoil, these levels still greatly exceeded

U.K. soil guidelines. The pilot-scale MGS treatment produced similar results on the fraction of spoil less

than 0.5 mm. Results showed that the MGS can concentrate almost 70% of the metals into a mass of

less than 10% of the original spoil. The residue has a combined metal assay of 2.5%.

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For most of the tested spoils, froth flotation performed poorly but achieved reasonable performance

where spoils remained un-oxidized. Additives showed little promise in terms of producing marketable

concentrates or significantly more acceptable (i.e., low metal) tailings. The effectiveness of this

technique depended critically upon the mineralogy of the spoil. Un-weathered material, rich in sulfides,

showed better segregation of contaminants into the concentrate.

Leaching metal contaminants from the spoil by a variety of chemical agents, such as sulfuric acid,

sodium hydroxide, diethylenetriamine, and by using ferric bacteria inoculum, was evaluated on

unprocessed spoil and treated fractions from the density and froth flotation tests. Effective chemical

leaching depended on the degree of spoil weathering. Generally, sulfuric acid and diethylenetriamine,

leached 2-33% of the Pb and 12-64% of the Zn. Sodium hydroxide leaching of weathered spoil

mobilized 25-92% of the Pb and 3-23% of the Zn in unprocessed spoil.

To evaluate the extent to which metals remaining in reprocessed (by gravity separation or froth flotation)

residues would be leached and hence be of environmental concern, the residues were subject to chemical

and biological leaching. This leaching removed 2-5% of the remaining contaminants, indicating a

resistance to leaching in residual material. Bacterial leaching proved to be ineffective for Pb but removed

significant amounts of Zn from the spoil.

Project 33: In-Pulp Decontamination of Soils, Sludges, and Sediments

This project consisted of bench-scale and demonstration-scale development of a treatment technology

by Davy International Environmental Division of the U.K. and Kommunekemi of Denmark. The process

combines conventional ex situ soil washing techniques with an innovative chemical treatment stage. A

major expected advantage is the ability of the approach to remove contaminants from fine sized soil

fractions such as silt and clay. Two measures used to extract contaminants are:

• leaching using acidic or alkaline reagents followed by adsorption to activated carbon or ion exchange

resin; and

• adsorption by activated carbon or cation exchange resins in direct contact with a soil slurry.

Contaminating substances then may be desorbed from the recovered carbon or ion exchange resin that

is then recycled.

Test materials consisted of contaminated soils and sediments. Soils came from a reclaimed site

contaminated with arsenic from a catalyst; a gasworks facility containing Zn and Pb; a wood preserving

site contaminated with Cu, Cr, and As; and chlor-alkali and gas metering sites with Hg contamination.

A sediment sample containing Zn, Pb, and Fe was collected from Hamilton Harbour in Ontario, Canada.

Zn, Pb, Fe, and Mn levels in the sediment exceeded Ontario’s “severe effect” guidelines, while Cu, Cr,

and Ni levels ranged between the “severe effect” and “limited effect” levels. This summary highlights

work done on samples from the wood preserving site, the chlor-alkali site, and the harbor. Project reports

did not contain information on the other samples.

Small pilot-scale leaching experiments examined inorganic and organic acids, alkalis, and chelating

reagents under various conditions. The results showed that mild leaching was inadequate for obtaining

target contaminant concentrations in the solid residue. The most effective leachant, sulfuric acid,

removed 90-97% of the contaminants from the soil. Cu, Zn, and Cr were removed to below target levels,

but As exceeded the target of 30 mg/kg.

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NATO/CCMS Pilot Study, Phase II Final Report

Adsorption tests on leachate from soils from the wood preserving site were carried out with ion

exchange resins, activated carbon, and magnetite to treat the leachates. Compared with the other

adsorbents, the ion exchange resins removed the most Cu, Cr, and Zn from the leachate. Acid resins

adsorbed from 75-100% of the Cu, Cr, and Zn but only 20-60% of the As.

A 10-kg sample of the soil from the wood preserving site was treated at bench-scale using the unit

operations of physical separation and chemical leaching which had been identified from the experimental

studies. The treated soil had a lower metal content than the feed material. Copper fell from 360 mg/kg

to 22 mg/kg, Cr from 621 mg/kg to 74 mg/kg, Zn 414 mg/kg to 68 mg/kg, and As from 1,204 mg/kg

to 112 mg/kg. Only As exceeded its preliminary treatment target of 30 mg/kg. Further work focusing

on protocols that take As speciation into account showed that chelating agents leached up to 52% of As.

Combining flotation, screening, and hydrocycloning achieved 60% removal in 80% of a soil but the

residual still exceeded target levels. Multiple acid leaching reduced As from 650 mg/kg to 22 mg/kg,

but at a relatively high cost.

Trials with the Hg-contaminated soil used oxidative compounds and complexing agents such as nitric

acid, hydrochloric acid, and sodium hypochlorite. To improve extraction of mercury, the approach

included size separation to remove fines and was operated at higher temperatures. Ion exchange resins

developed for mercury adsorbed the metal slowly. As a result of difficulties with this approach, a

thermal option was investigated. Preliminary tests revealed that by heating contaminated materials to

around 800°C, treated soils achieved regulatory targets for mercury.

Work with Hamilton Harbour sediment showed that the Ontario guidelines for sediment could be met.

Leaching tests were conducted with mineral and organic acids. Strong mineral acids dissolved

contaminants as well as Ca and Fe in 90 minutes. Since these two metals, as well as organic

contaminants would compete with the metal contaminants during adsorption, a two-stage leaching

approach was tested as a way to eliminate this competition. This involved a mild acid to dissolve iron

first, followed by a strong acid to attack the contaminants. The presence of organic contaminants had

little impact on the removal of metals.

Tests with several adsorbents pointed to chelating resins as the likely candidates. These resins proved

to be more selective than activated carbon or magnetite for the contaminant ions over the other metal

ions. The high level of Fe in solution inhibited the adsorption of contaminants, and thus required

pretreatment such as magnetic separation to remove iron particles from the sediment before leaching.

Precipitation to remove metals from the leachate was somewhat ineffective because some metal remained

in solution and required further processing.

The process generates a variety of residuals and emissions some of which require further treatment or

disposal. Decontaminated solids may require final treatment such as pH adjustment and dewatering

before being disposed. For most metal extractions, acid is used to remove metals from the resin,

resulting in a concentrated solution of metals which may be treated by precipitation, reduction or

electrowinning to recover metals, or may be disposed of at a secure disposal site or encapsulated. In the

case of sediments, the leach stage may produce gas emissions if anaerobic activity produces sulfides.

These emissions, noted during leach tests with sediments from Hamilton Harbour, may require gas

scrubbing in a scaled-up commercial plant. Decanted water from excavated sediment may also have to

be treated.

Treatment costs are expected to be high (no data or expected costs were provided) if the process

demands aggressive leaching with oxidative and complexing agents as well as elevated temperatures for

enhanced leaching.

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Although principally applicable to metal contamination, the technology may be adapted (by using carbon

as an additional adsorbent) to handle organic contaminants. Plans to develop the technology further

include investigating surfactants, solvents and other agents to extract organic contaminants and to

combine this with adsorption by activated carbon. The applicability of the technology would depend on

its ability to achieve regulatory requirements.

5.2.4 Group 4: Physical-Chemical Treatment (No Soil Washing) (Projects 32, 44, and 47)

Project 32: CACITOXTM Soil Treatment Process

This innovative technology aims to chemically treat soils containing significant silt and clay fractions

for which conventional soil washing techniques are not cost-effective. The technology potentially can

treat contaminated soils and sediments while not depositing unacceptable by-products into the matrix

or destroying the matrix itself.

The CACITOXTM process involves soil leaching, soil/leachate separation, and leachate treatment. The

proprietary leaching process uses a three-component mixture consisting of low concentrations of

carbonate, oxidants, and complexing agents such as carboxylic acids. This mixture, which is used at

near-neutral pH and ambient temperature, reacts with contaminated materials and converts insoluble or

absorbed contaminants into soluble complexes. The oxidant helps dissolve certain metals that occur in

their less soluble forms. As a result of its high selectivity, the leaching reagent minimizes secondary

waste.

A combination of precipitation and ion exchange removes dissolved inorganic contaminants from the

leachate. This stage of treatment may include innovative approaches such as electro-deposition/polishing

to recover valuable by-products or to minimize the volume of secondary waste. Precipitated contaminants

may be conditioned to ensure they meet requirements for disposal. This conditioning may involve

dewatering, containerization, or encapsulation. Chemical processes destroy organic contaminants in the

extract.

Treated soils can be used again because the leaching process uses low concentrations of the mild

chemicals. Hydrocyclones or mixer settlers separate the leached soil from the leachate. A filter press or

belt filter then dewaters separated soil, that was washed to remove residual reagent.

When used with a range of aqueous leaching reagents, CACITOXTM initially experienced more difficulty

decontaminating soils with high clay content than those containing sand. As a result, further work

focused on fine-grained soils to satisfy one of the aims of the project to treat soils with significant clay

and silt content.

Experiments with soils containing “high” levels of heavy metals showed that the leaching process

achieved Dutch B and Canadian Residential Values for all metals except Cd and As. A report claimed

that optimizing the formulation and process variables could enable the technology to achieve target

values for these two metals. Added organic contaminants reduced initial leaching efficiencies by 1-2%.

However, leaching removed 98% of these organics. Leaching with CACITOXTM achieved removal

efficiencies comparable to leaching with mineral acids. However, the proprietary reagent dissolved less

than 10% of the soil matrix, while the mineral acids removed 40%.

During trials to leach radionuclides from test soils, a single contact with the CACITOXTM reagent mixture

removed 52-76% of the Pu, Am, Np, Sr, and Ra, but only 2% of the Cs. Limited data for removal of

radionuclides from a contaminated site show how repeated contacts could improve removal.

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NATO/CCMS Pilot Study, Phase II Final Report

In summary, the CACITOXTM technology can process materials containing high levels of fines like silt

and clay and can selectively dissolve actinides and heavy metals from other wastes. Because the

CACITOXTM process treats inorganic contaminants, it requires other technologies for treating mixed

wastes. The final report mentioned that using low concentrations of mild chemicals resulted in low costs,

but did not provide supporting data. The pilot-scale transportable plant has a capacity of 10 kg/hour, but

can be easily scaled up to 100 kg/hr.

Project 44: Enhanced In Situ Removal of Coal Tar: Brodhead Creek Superfund Site

During the operation of a former gasworks plant from 1888 to 1944, waste coal tars were disposed onsite

in an open pit. Over time, the coal tars migrated into the subsurface, where they collected 6-9 m below

ground surface in a natural depression formed at the geological boundary between coarse gravels and

silty sands. A layer of coal tar (dense non-aqueous phase liquid—DNAPL) was shown to be polluting

0.12-ha of the underlying aquifer and a nearby river. A larger 3-acre (1.22-ha) area of residual

contamination is also present.

Remediation efforts focused on recoverable coal tar in an area with an estimated 22,700 L of DNAPL

because it was believed to represent the major source of groundwater pollutants; however, the dissolved

groundwater contaminants were not addressed. A slurry cut-off wall was constructed to protect the river

from further pollution. Excavation of the contaminated soil was not considered practical, so an

innovative in situ treatment known as Contained Removal of Oily Wastes (CROW) was selected. CROW

is a thermally enhanced in situ recovery process that uses hot water injected at the perimeter of the

contaminated area to reduce the density and viscosity of tar to a level where it can be pumped to the

surface for further treatment and disposal. The rate at which the heated water is injected into the ground

is is used to control the displacement and temperature of the tar material so that it is forced towards the

of extraction wells. Lateral containment is achieved by carefully controlling injection and extraction rates

to isolate the affected area hydraulically. A layer of cooler groundwater above the area of active recovery

prevented mobilized fluids from migrating vertically and condensed contaminants that were volatilized

by the heated water below.

Preliminary treatability studies on coal tar samples were used to determine the optimum temperature and

injection/extraction rates required for full-scale operation. These studies indicated that coal tar in soils

could be reduced to a residual saturation of 60-70%.

Full-scale operation was based on a pattern of six injection wells surrounding two extraction wells in

the center of the contaminated area. Well screens focused injection and extraction flows at the depth of

contamination. A greater amount of water was extracted than injected to hydraulically isolate the

contaminated area. The design flow for injection of heated water was 378 L/min and 435 L/min for

recovery of the water and coal tar mixture. However, much lower injection rates were actually attained

because iron precipitate that formed around the injection well screens significantly reduced operational

performance. This problem was partially solved by installing agitators in the injection wells, but flow

rates remained low (114-132 L/min). The system operated at 71°C instead of the expected 93°C because

the water heater was designed for high flows and could not heat the water to the required temperatures

at the lower flows. The reduced flow rate and lower operating temperature extended the treatment time

to 10 months, approximately twice the expected treatment time. A higher injection temperature of 96°C

was achieved in January 1996 with the installation of the new heater.

At the ground surface, the initial treatment step was to separate the coal tar from the water. The coal

tar was incinerated, and the water was treated by removing the dissolved inorganics (primarily iron and

manganese) through oxygenation and pH adjustment of the water. The precipitated inorganics were

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NATO/CCMS Pilot Study, Phase II Final Report

removed by gravity separation. (The inorganics required removal because they were found to inhibit the

coal tar separation process and foul the system.) The treated water was reheated and reinjected into the

subsurface. A lesser amount was injected than was extracted to maintain hydraulic isolation. The

overdraw of water was treated in a fluidized bed reactor followed by granular activated carbon units and

then discharged into Brodhead Creek.

The performance standard for the CROW process was to continue operating the system until the

cumulative recovery of coal tar dropped to 0.5% or less per pore volume of water flushed through the

contaminated zone. This was based on previous operational experiences at a similar site where achieving

this specification meant that 98.5% recovery of recoverable tar had been attained. Planned groundwater

sampling will assess the overall effectiveness of the treatment. During December 1995, a cumulative

flow of 3.1 pore volumes resulted in recovery of 602 L of tar. Over a 10-month period of operation, 29

pore volumes of hot water were flushed through the formation, and a total of 5,400 L of coal tar was

recovered as pure tar.

Groundwater contaminants and residual coal tar remain at the site. A "No-Further Action" record of

decision was issued for groundwater and residual coal tar contamination because of technical

impractibility considerations.

Project 47: In Situ Electro-Osmosis (LasagnaTM Project)

In the LasagnaTM in situ treatment process, electro-osmosis moves dissolved contaminants to treatment

zones, where they are degraded or adsorbed. This process can be operated in a horizontal or vertical

configuration. The vertical configuration consists of outer layers that act as either positively or negatively

charged electrodes and promote electro-osmosis. Sheet piling, trenching, and slurry walls can be used

to create vertical treatment zones, in between the outer electrodes. In the horizontal configuration, which

is installed by hydraulic fracturing or related methods, treatment layers occur between the upper and

lower layers that make up the electrodes. These electrodes may contain graphite or other granular,

electrically conductive materials.

Site characteristics and contaminants determine the configuration to use. In general, the vertical

configuration is more applicable to contamination occurring within about 15 m (50 ft) of the surface.

The horizontal configuration works best for deeper contamination.

The NATO/CCMS case study was limited to the field demonstration of electro-osmosis, using the

vertical configuration to transport and adsorb trichloroethene (TCE) at the U.S. Department of Energy’s

Paducah Gaseous Diffusion Plant in Kentucky. The case study was carried out in three phases. Phase

I, conducted January-May 1995, evaluated the overall effectiveness of coupling electrokinetics and

carbon adsorption treatment zones. In 1996, the Phase IIa commercial-scale demonstration examined iron

filings in the treatment zone to dehalogenate TCE. This work was conducted to depths of about 14 m

(45 ft) and with a wider spacing between the treatment zones. The full-scale Phase II cleanup will take

place if the Phase IIa tests successfully reduce TCE levels in soil to 5.6 mg/kg.

The field study lasted for 120 days. A key objective was to successfully demonstrate coupling electroosmosis to flush TCE from the clay soil (hydraulic conductivity <10-9 m/sec) and adsorption to remove

the contaminant from the pore water. The test site was about 4.6 m x 3 m (15 ft x 10 ft) on the surface

and 4.6 m (15 ft) deep. A control area was built next to the test area and isolated from it hydraulically.

The vertical configuration tested at the site consisted of steel panel electrodes and treatment zones made

of wickdrains containing granular activated carbon.

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NATO/CCMS Pilot Study, Phase II Final Report

A direct current of around 40 volt/m applied to the electrodes caused groundwater to flow from the

anode to the cathode at about 13 mm/day. The induced pH gradient caused problems such as soil drying

and cracking, and metal and mineral deposits at the cathode. Pumping water from the cathode to the

anode reduced these problems. Operating parameters during this period were:

• Power requirements: 105 volts and 40 amperes

• Electro-osmotic flow rate: 4-5 L/hr

• Average soil temperature: 25-30°C

Soil samples collected throughout the demonstration site before and after the test showed that the process

removed 98-99% of the TCE from the tight clay. TCE levels in the soil were reduced from 100-500

mg/kg to an average of 1 mg/kg. Sampling and analyzing the carbon revealed how much dissolved TCE

was adsorbed in the treatment zones and provided mass balance data. These carbon samples accounted

for around 50% of the original TCE. The remaining TCE reduction may be attributed to passive

diffusion (5%), evaporation (5%), in situ degradation of TCE, non-uniform distribution of the

contaminant in the soil, or incomplete extraction of the compound from the activated carbon before

analysis.

The results suggest the process is effective for removing residual DNAPL as well. At most soil sampling

locations with TCE concentrations of more than 225 mg/kg—indicative of residual DNAPL in soil pores

—the process reduced these levels to less than 1 mg/kg.

A more extensive field investigation incorporated material such as iron filings in reactive treatment zones

to destroy TCE in situ. The first part (Phase IIa) of this two-stage investigation, to be conducted on 20

times more soil than was treated in the preliminary field investigation, will try to resolve scale-up

questions, verify cost estimates for treatment, and evaluate how the zero-valent iron performs.

Preliminary results of the Phase IIa demonstration at the site in Kentucky show that treatment zones with

iron filings can dechlorinate TCE, producing relatively innocuous end products such as chloride ion,

ethane, and ethene. Other potential intermediate products like dichloroethene and vinyl chloride are

associated with the surface of the filings.

Residuals and emissions include off-gases resulting from evaporation, and the treatment layers. At the

test site in Kentucky, TCE losses by evaporation accounted for 5% of the mass balance. These off-gases

did not require treatment. If treatment zones are determined to be a hazardous waste, removing and

disposing them may be an issue.

An engineering evaluation and cost analysis for the vertically configured process estimates a treatment

cost of U.S.$52-118/m3 of clay soil containing TCE at a depth of 12-15 m and over an area of 0.4-0.8

ha. With optimized electrode spacing, improved ability to install treatment zones and electrodes at closer

spacing, and mass-produced prefabricated materials resulting from wider use of the technology, costs

are expected to fall to U.S.$26-52/m3

. These costs exclude those for analyses, waste disposal, etc.

The LasagnaTM process reportedly offers promise for treating water-soluble organic and inorganic

contaminants, and mixed wastes in low-permeability soils as well as in groundwater. For highly nonpolar contaminants, surfactants introduced into groundwater or incorporated into treatment zones will

solubilize the organics. The process has been shown to be effective in treating residual DNAPL as well.

Larger scale demonstrations need to be conducted to confirm the effectiveness of using zero-valent iron

to degrade contaminants. The horizontal configuration using biological treatment zones also needs to be

evaluated.

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NATO/CCMS Pilot Study, Phase II Final Report

5.2.5 Group 5: Photo-Oxidation Treatment (Projects 14, 38, and 40)

Project 14: Ozone Treatment of Contaminated Groundwater

This project examined biological and advanced oxidation treatment of groundwater contaminated by

leachate from an abandoned quarry located at Vaucelles, France. Between 1963 and 1972, this quarry

served as a site for disposal of various chemical wastes.

After an initial site investigation to confirm the source and extent of contamination, the project focused

on examining optional treatments for contaminated groundwater to achieve acceptable drinking water

limits. The water contained a wide variety of organic compounds such as chlorinated and non-chlorinated

solvents at concentrations of 0.8-360 mg/L.

The selected approach combined biological pre-treatment and a UV/ozone oxidation system. The

biological process is seen as a way to degrade chlorinated contaminants into a form more amenable for

photo-oxidation. A membrane filter that separates activated sludge from purified water was claimed to

be better than the conventional process by producing five times less sludge. In the second treatment step,

photo-oxidation degrades compounds remaining in the biologically purified water. Tested treatment

combinations were:

• ozone, and ozone/UV without biological treatment; and

• ozone, ozone/UV, and ozone/H2O2 after biological treatment.

Pilot testing showed that the combined biological/photo-oxidation treatment was more effective than

photo-oxidation alone. The combination reduced chemical oxygen demand (COD) by 90-95%, TOC by

80%, and volatile organic compounds (VOCs) by 100%. The report did not mention investigations to

identify by-products.

In terms of costs, achieving the goal that treated water should achieve drinking water guidelines for

VOCs was estimated to cost FF15 million (U.S.$2.5 million) in capital cost and FF23.7 million (U.S.$4

million) annually. Alternatively, discharge to a surface water body would cost FF10 million (U.S.$1.7

million) at first, and only FF1.7 million (U.S.$280,000) annually.

Project 38: Demonstration of Peroxidation Systems, Inc., Perox-PureTM Advanced Oxidation

Technology

The Perox-PureTM UV/oxidation technology combines UV radiation and hydrogen peroxide to treat

groundwater contaminated with a variety of organic compounds. Other components such as acid and base

feed systems may be added to the treatment train to ensure successful treatment of the contaminants.

Adding acid to the water feed reduces the pH (<5.5) to minimize interferences by bicarbonates and

carbonates. Following treatment, adding a base increases the pH to normal levels (6.5-7.5) so that

discharged water meets designated criteria.

The Perox-PureTM UV/Oxidation treatment technology was evaluated under the USEPA Superfund

Innovative Technology Evaluation (SITE) program at a site at the Lawrence Livermore National

Laboratory in California. Evaluation of the technology s performance at three other sites was used to

support findings for the SITE demonstration.

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NATO/CCMS Pilot Study, Phase II Final Report

At the Lawrence Livermore National Laboratory site, shallow groundwater was contaminated with TCE

and tetrachloroethene (PCE) at concentrations around 1,000 μg/L and 100 μg/L, respectively. The SITE

technology demonstration intended to:

• determine the ability of the technology to remove VOCs from groundwater under different operating

conditions;

• find out if treated water achieved applicable disposal requirements at the 95% confidence level; and

• estimate treatment costs.

A secondary objective was to identify by-products formed during treatment.

The Perox-PureTM system effectively achieved the California drinking water action levels and U.S. federal

drinking water maximum contaminant levels for the five compounds studied. Quartz tube wipers kept

the quartz tubes clean and prevented scaling, which is detrimental to contaminant removal efficiencies.

Bioassay tests results demonstrated that the effluent was acutely toxic to freshwater test organisms. This

toxicity may have been caused by the residual hydrogen peroxide rather than by treatment by-products.

The following three case studies summarize work and findings to demonstrate the technology for:

• wastewater containing acetone and isopropanol (IPA);

• groundwater contaminated with TCE; and

• groundwater contaminated with pentachlorophenol (PCP).

The first study, at the Kennedy Space Center in Florida, tested the photo-oxidation system as a

replacement for the existing carbon adsorption treatment for wastewater. The replaced system could not

achieve the required discharge level of 0.5 mg/L. In contrast, effluent from the new oxidation system

met all of the discharge criteria, including the demineralization discharge standards, in less than the

specified 24-hour maximum treatment time. The system was efficient enough to allow treatment of the

wastewater in a flow-through mode rather than a batch mode at a flow rate of 18.9 L/min (5 U.S.

gal/min), a hydrogen peroxide dosage of 100 mg/L, and 10 kilowatts of power for a period of 20 hours

per day.

For the second study, the Perox-PureTM technology was used to treat well water containing 50-400 mg/L

of TCE. Because the well was located in the middle of a large residential area in Arizona, the treatment

was chosen because of its low-visibility and quiet operation. When treatment was conducted at a flow

rate of 510 L/min (135 U.S. gal/min) and 15 kW of power, TCE was consistently treated to a level

below the analytical detection limit of 0.5 μg/L.

A full-scale Perox-PureTM system treated groundwater contaminated with PCP at levels up to 15 mg/L

for the third study conducted on the property of a chemical manufacturing company in Washington in

1988. Continued operation confirmed that the Perox-PureTM system could destroy the PCP to below the

target level of 0.1 mg/L. To obtain this result, the system operated at a flow rate of approximately 265

L/min (70 gal/min), a hydrogen peroxide concentration of 150 mg/L, and a power requirement of 180

kW. A pretreatment system oxidized and removed high levels of iron. To reduce the scaling tendency,

acid was added to decrease the pH of water to about 5.0. The photo-oxidation system featured automatic

devices to keep the reactors clear.

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NATO/CCMS Pilot Study, Phase II Final Report

Treatment costs for three of the four tests were U.S.$0.95-1.3/m3 (U.S.$3.60-5.00 per 1,000 U.S.

gallons). Treating well water in the second case study cost only U.S.$0.07/m3 (U.S.$0.28 per 1,000 U.S.

gallons). These costs exclude those for capital.

Project 40: An Evaluation of the Feasibility of Photocatalytic Oxidation and Phase Transfer Catalysis

for Destruction of Contaminants from Water (In Situ Treatment of Chlorinated Solvents)

Photocatalysis is an emerging treatment technology that uses an advanced oxidation process based on

generating hydroxyl radicals using UV light in the presence of a semi-conductor catalyst, such as

platinum-coated titanium oxide. The Hand D process uses a fixed-bed catalyst with the semi-conductor

fixed to a silica gel support. Pretreatment of groundwater by removing suspended matter and inorganic

ions is conducted by a series of filters and ion-exchange columns. Dissolved oxygen levels are increased,

as necessary, to supply oxidants for the destructive oxidation process. The UV light is provided by

natural sunlight.

The project researched development of highly photoactive catalysts and a fixed-bed photocatalytic

process to destroy toxics in air and water. It also researched development of a treatment process using

adsorption to remove contaminants and advanced oxidation processes (AOPs) to regenerate spent

adsorbents. The developed technologies were field tested at Tyndall Air Force Base (AFB), K.I. Sawyer

AFB, and the Wausau Water Treatment Plant.

Some of the photocatalysts used in the laboratory studies were modified on their surfaces with noble

metals, or changed by doping with transition metals to extend the photocatalyst’s response to visible

light. Artificial light and UV sources and solar radiation were used to evaluate the photoactivities of

these catalysts for destroying model compounds. Results showed that platinum-coated Aldrich titanium

oxide (Pt-Aldrich-TiO2)—a surface-modified catalyst—performed best for destroying hydrophobic

compounds. The laboratory-developed, platinum-coated Michigan Technology University TiO2 catalyst

performed best for hydrophilic compounds.

The supports tested for fixed-bed photocatalysts consisted of random packing and structured materials.

These supports were chosen for their adsorption capacity, UV transmission, and mass transfer properties.

Silica-based materials were included to test how they performed at destroying organic compounds, and

some of them were surface-modified to increase their adsorption capacity. Investigations excluded

electron-rich materials that could scavenge reactive radicals and diminish the efficiency of photocatalysis.

Researchers developed a unique procedure involving heating and annealing to prepare supported catalysts

for fixed-bed reactors. During solar experiments, the fixed-bed processes were optimized with respect

to the type of catalyst and dosage, support type and size, and preparation methods. Destruction of a

model compound was tested under various UV irradiance, influent concentration, pH, and hydraulic

loading. Tanning lamps tested on the same fixed-bed process tested the destruction of several other

compounds in air and water. Two reactor designs consisted of a catalyst added as a slurry and passed

through a lighted reactor, and a catalyst attached to a support in a lighted fixed-bed reactor.

Tests with the fixed-bed photocatalysts revealed that Pt-Aldrich-TiO2 supported on silica gel completely

mineralized TCE in water (8 mg/L) in one contact time of 1.3 minutes. This destruction rate was 16

times better than observed for an optimized slurry of a commercially-available photocatalyst (Degussa

P25).

Increasing the adsorption capacity of a silica-based support improved the overall destruction kinetics.

Silica gel modified to increase surface hydrophobicity and the adsorption capacity for non-polar organic

water pollutants increased the adsorption capacity for trichloroethene (TCE) in water by more than a

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NATO/CCMS Pilot Study, Phase II Final Report

factor of five. When used as a support for Pt-TiO2, the modified silica gel showed faster overall

degradation kinetics for TCE than did the unmodified silica gel.

For experiments with contaminants in the gas-phase, results showed faster destruction kinetics than in

the aqueous phase. This suggests the option to strip volatile compounds followed by gas-phase

destruction by photocatalysis. For trichloroethane (TCA), a relative humidity of 25% yielded the best

destruction rate. On the other hand, toluene destruction increased with increasing vapor content. The

fixed-bed approach provided high light efficiency. The reported ratio of organic molecules destroyed to

UV photons required was 40%—much higher than the 5% value commonly reported. Phosgene and

carbon monoxide, two major toxic by-products in air-phase photocatalysis, were not found above

regulated levels.

Developing the combined processes of adsorption followed by regeneration consisted of using a fixedbed system adsorber to remove and accumulate organic compounds, and regenerate the spent adsorbent

using homogeneous AOP, photocatalysis, or a combination of steam and photocatalysis. For

homogeneous AOP, hydrogen peroxide/ozone and UV light/hydrogen peroxide were used for destructive

adsorbent regeneration. Both of these options consumed three to six times more oxidants in the

regeneration process than would be needed to destroy the contaminants in water directly by conventional

AOP. Regeneration appeared to be limited by adsorbate desorption from the interior to the exterior

adsorbent surface. Neither option is feasible because the desorption rate is too slow, and therefore too

much oxidant is required to regenerate the adsorbents.

In testing photocatalysis for destruction of adsorbed contaminants and regeneration of adsorbents

simultaneously, the catalysts were impregnated onto the adsorbent before being used to adsorb organics.

The first test consisted of using UV illumination to test photocatalysis alone for regenerating the spent

adsorbents and destroying the contaminants. Results showed that desorption of adsorbates from the

interior to the exterior of an adsorbent limited the regeneration process. Thus, temperature played a

leading role in photocatalytic regeneration, and increasing temperature enhanced regeneration rate much

more effectively than increasing light intensity. Using heat to increase the desorption rate and match the

photocatalytic oxidation rate is one way to maximize the photolytic regeneration efficiency.

Saturated steam was used to overcome this problem of slow desorption rates. Heating promoted the

kinetics of photocatalysis and AOP processes by desorbing organic contaminants on the interior of the

adsorbents and moving them to the exterior for oxidation. Thus, steam followed by photocatalysis was

found to be an effective way to regenerate spent adsorbents and to clean up the regeneration fluid (offsteam or steam condensate).

At Tyndall AFB, a solar photocatalytic process was used to remediate fuel-contaminated groundwater

containing BTEX compounds (benzene, toluene, ethylbenzene, and xylenes) at greater than 2 mg/L. Two

options were tested: (1) a solar photocatalytic fixed-bed process using Pt-TiO2 supported on silica; and

(2) fixed-bed process with Pt-TiO2 impregnated adsorbents alone or combined with Pt-TiO2 supported

on silica gel. During option 1, ionic species fouled the catalysts and inhibited destruction, so the water

was pretreated to remove suspended particulates and ionic species and to increase dissolved oxygen.

Following pretreatment, catalyst photo-activity continued undiminished after 25 days of operation. The

BTEX compounds were destroyed with 6.5 minutes of empty bed contact time on rainy days. Test

results with various flow rates, reactor diameters, influent concentrations, solar irradiances and weather

conditions confirmed the potential application of the process. Treatment cost was estimated at

U.S.$5.52/1,000 U.S. gallons (U.S.$1.46/m3

).

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NATO/CCMS Pilot Study, Phase II Final Report

During option 2, two different reactor design configurations were tested. The first design was a

continuous flow configuration with three fixed-bed reactors in series. The first and third reactors were

packed with platinum-coated TiO2 supported on silica gel supports. The second reactor was packed with

a photocatalyst-impregnated adsorbent. In daylight, the incoming organic compounds were destroyed in

the first reactor. At night, the organics were adsorbed onto photocatalyst-impregnated adsorbent in the

second reactor; the adsorbed organics were either mineralized or partially mineralized in the second

reactor during daylight. The remaining organics or destruction by-products were destroyed in the third

reactor. Because organic compounds can be adsorbed during periods of insufficient sunlight, the process

can treat water continuously. Like option 1, option 2 was also affected by catalyst fouling. After four

days of operation, the process was apparently unable to destroy any more BTEX compounds. An ion

exchange unit was added to the system and satisfactory BTEX destruction was resumed; however, the

third reactor still did not perform well, presumably due to fouling species desorbed from the second

reactor.

In the second design, a reactor packed with photocatalyst-impregnated adsorbents was used to remove

the organics during darkness. During daylight, the adsorbent was taken off-line and regenerated by

passing heated water through the reactor. The hot water was then passed through a fixed-bed reactor

packed with platinum-coated TiO2 supported on silica gel supports to destroy any residual desorbed

organics or by-products. The strategy behind this design was to have an 18-hour adsorption period

followed by a 6-hour regeneration period during which the solar irradiance is strong enough to destroy

most contaminants.

The spent adsorbents were regenerated in the presence of sunlight while passing hot water (90°C)

counter-current to the flow direction during the adsorption process. The desorbed organics from the

regeneration process were destroyed in the subsequent fixed-bed photoreactor. The process was examined

for 10 adsorption and regeneration cycles. The efficiency (ratio of organics removed and destroyed to

organics adsorbed) of the process to regenerate the adsorbents was examined for each cycle. Overall,

21% of the total influent BTEX was destroyed, and 98% of the BTEX was removed from the waste

stream. The detention times required for 99.9% destruction of TCE (5 mg/L), TCA (5 mg/L), and

toluene (115 mg/L) were 2.15 seconds, 11.2 seconds, and 40 seconds, respectively. While the process

appears to be effective for 10 cycles, more cycles are required to determine whether steady-state is

achieved.

At K.I. Sawyer AFB, the unit used a fixed-bed photocatalyst and a solar panel made up of 80 tubular

reactors to treat chlorinated compounds in groundwater. The design included a water pretreatment unit,

which included a turbidity filter, a bubble-less oxygen contactor, and ion-exchange columns. The reactor

was a modified solar thermal reactor panel with 80 plastic tubes mounted in parallel. The capacity for

each reactor panel was designed as 0.25 U.S. gallons per minute. On a sunny afternoon, the panel

destroyed 95% TCE, which was present in groundwater at 100 μg/L, within a two-minute contact time.

At the Wausau Water Treatment Plant, fixed-bed adsorption removed and accumulated organic

compounds. The spent adsorbents were regenerated off-line with steam followed by photocatalysis. The

groundwater contained chlorinated compounds and BTEX. Direct photocatalytic oxidation was not

effective for regenerating spent adsorbent loaded with contaminated groundwater because nuisance

substances in the water fouled the catalyst. Tests combining steam regeneration followed by

photocatalysis of steam condensate showed that carbon adsorbent was not effectively regenerated and

lost a significant amount of capacity. Background organic matter in the water may have caused this loss

of efficiency. Based on the results of chloride yield with all the tested adsorbents, steam regeneration

did not appear to destroy significant amounts of the sorbed chlorinated compounds.

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NATO/CCMS Pilot Study, Phase II Final Report

5.3 BACKGROUND OF CASE STUDIES AS A GROUP

Table 5.1 presents key information on the projects. In terms of media treated, Projects in Groups 1-4

dealt with contaminated solids, while Group 5 projects addresses groundwater contamination. Project

44, which is in Group 4, addressed DNAPL contamination in a gravel layer, but not the dissolved

groundwater contaminants. In general, the contaminated solids consisted of soils and sediments

containing a high content of fines. The fines made up 12.5-63% of the parent material. Metalliferous

spoil examined for Project 31 also had a high proportion of fines.

Organic and inorganic compounds were present in some of the contaminated solid media. Typical

concentrations of organic contaminants were 200–5,000 mg/kg petroleum hydrocarbons, 30–2,000 mg/kg

PAHs, and around 120–1,000 mg/kg PCBs. One site contained a concentration of 100–500 ppm TCE,

while another reported chlorophenols at 200 μg/L. Heavy metal contamination attributed to individual

species included Pb (up to 12%), Zn (up to 5%), Cu (360 mg/kg), Cr (621 mg/kg), Hg (300–5,000

mg/kg), and As (1,204 mg/kg). At one site, total metals were detected at 32-650 mg/kg, while cyanides

were detected at 2,000–3,000 mg/kg.

Treatment technologies generally consisted of soil washing and groups of other treatments that included

biological or physical-chemical treatment. Soil washing usually involved screening, scrubbing and

particle size separation. Specialized techniques such as flotation and density and gravity separation were

sometimes used to obtain better separation of clean fractions and contaminated concentrates. Other

groups of treatments that did not include soil washing relied upon physical-chemical or photo-oxidation

technologies.

5.4 PERFORMANCE RESULTS

5.4.1 Analytical and Assessment Procedures

Common analytical and assessment approaches were adopted for all the projects regardless of the

contaminants or media to be treated, the technology being used, or the targeted criteria.

For projects with a soil washing component, the contaminated soil or sediment was first characterized

with respect to particle size distribution and the concentration of organic and inorganic contaminants in

the various particle fractions. Soil washing products were also checked for distributions of mass and

contaminants.

For all projects, the effectiveness of the processes was determined by comparing the levels of

contaminants in treated and untreated materials. All streams were reportedly sampled to measure flows

in the slurry, solids, and water. These data were sometimes used to provide a mass balance. Contaminant

concentrates and products low in contamination were analyzed to determine the degree of contaminant

reduction.

Agency-approved procedures were used to determine characteristics such as pH, moisture content, and

organic and inorganic constituents. For example, analytical approaches included USEPA procedures for

digesting samples, atomic absorption spectrophotometry (AAS) for metal content of aqueous samples,

gas chromatography (GC) for mineral oil, and x-ray fluorescence (XRF) to determine the mineralogy

of the soil and sediment. Specialized methods (e.g., DEXSIL L2000 PCB/chloride analyzer) were

sometimes required.

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NATO/CCMS Pilot Study, Phase II Final Report

Table 5.1: Classification of the 14 Case Studies by Technology Used

Project

Number

Media

Treated

Contaminants

Treated

Contaminant

Concentrations

Technology

Used

Treatment

Process

Group 1: Soil Washing Only

30 Soil (mainly

clayey)

Heavy metals,

inorganic cyanides,

PAHs, petroleum

hydrocarbons

Heavy metals (32-

650 mg/kg); PAHs

(184 mg/kg);

petroleum hydrocarbons (200 mg/kg)

Soil washing Particle size

separation

Group 2: Soil Washing and Biological Treatment

24 Soil,

sediment

PAHs, heavy

aliphatic

hydrocarbons (oils),

chlorophenols

400-5,000 mg/kg

mineral oil; 30 mg/kg

PAHs; 200 μg/L

chlorophenol

Soil washing,

bioslurry reactor,

photo-oxidation

Particle size

separation,

biodegradation

26 Soil (sandy

and clayey)

PAHs (3- and 4-ring)

from creosote

180-3,500 mg/kg

PAHs

Soil washing,

bioslurry

Flotation,

biodegradation

36 Soils with

high fines

content

Diesel, PAHs, TPH,

complexed cyanides

2,000-4,000 mg/kg;

TPH; 200-300 mg/kg

PAHs; 2,000-3,000

mg/kg cyanides

Soil washing,

bioslurry

treatment

physical

separation,

bioremediation

Group 3: Soil Washing and Physical-Chemical Treatment

10 Soil,

sediment

Heavy metals (Pb,

Zn, etc.), PAHs

11,800 μg/g Pb;

7,400 μg/g Zn; 12.15

μg/g pyrene

Soil washing,

hydrometallurgy

Particle size

separation, metal

recovery, chemical destruction

of organics

17 Soil,

sediment

PAHs, PCBs,

petroleum

hydrocarbons, metals

250-2,000 ppm

PAHs; 200-500 ppm

PCBs

Soil washing,

solvent extraction

Particle size

separation,

extraction (for

organics),

stabilization

19 Soil, debris Solvents, chemical

waste, Hg

300-5,000 mg/kg Hg Soil washing,

vacuum

distillation

Particle size

separation,

distillation,

condensation

27 Soil, other

solids

PCBs 120-1,000 mg/kg

PCBs

Soil washing,

chemical

dehalogenation

Particle size

separation,

dehalogenation

31 Metalliferous

spoil

Pb, Zn, Cu, Cd up to 12% Pb; up to

5% Zn; Cu and Cd in

ppm range

Gravity separation, flotation,

chemical leaching, biological

extraction

Particle size

separation,

leaching and

extraction

33 Soil with

high fines,

sediment

Heavy metals (Cu,

Cr, Zn, As), Hg

360 mg/kg Cu;

621 mg/kg Cr;

414 mg/kg Zn;

1,204 mg/kg As

Combined soil

washing and

chemical

treatment

Leaching and

adsorption

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NATO/CCMS Pilot Study, Phase II Final Report

Project

Number

Media

Treated

Contaminants

Treated

Contaminant

Concentrations

Technology

Used

Treatment

Process

Group 4: Physical-Chemical Treatment

32 Soil with

high clay and

silt content

Heavy metals,

radionuclides,

organics

Leaching Oxidation,

complexing,

precipitation, ion

exchange

44 Gravelly soil

and groundwater

Coal tar DNAPL DNAPL over 0.12 ha Thermally

enhanced

recovery of coal

tar

Coal tar: ex situ

incineration.

Water: ex situ

precipitation,

fluidized bed

reactor, and

filtration

47 Soil (clay) TCE 100-500 ppm TCE Electro-osmosis,

in situ treatment

Electro-osmosis,

adsorption

Group 5: Photo-Oxidation Treatment

14 Groundwater Chlorinated solvents,

esters, phenols,

BTEX, etc.

0.8-360 mg/L Combined

biological and

photo-oxidation

Activated

sludge, ozone,

UV/ozone,

ozone/H2O2

38 Groundwater,

wastewater

TCE, PCE, acetone,

IPA, PCP

1,000 μg/L TCE;

100 μg/L PCE; 15

mg/L PCP

Advanced

oxidation and

chemical

oxidation

UV radiation

and O3/H2O2 or

H2O2

40 Groundwater BTEX, TCE, other

chlorinated solvents

100 μg/L TCE,

others not given

Adsorption and

advanced

oxidation

Highly photoactive catalysts

and fixed-bed

photocatalysis

Treatability studies were often conducted on various contaminants and matrices. During these studies,

measurements of the initial and final concentrations of the contaminants provided information to assess

the probable performance of planned full-scale operations.

Full-scale treatment plants were monitored to ensure they met operational requirements. In some cases,

concentrations of contaminants in emissions and discharges were measured and compared to specified

target levels. For technology evaluations conducted under the SITE program, routine operation of a

treatment plant followed SITE protocols.

Finally, treatments were assessed in terms of their ability to achieve regulatory targets and criteria or

the hazards posed by treated materials. Microtox or a suite of ecological tests were sometimes used to

assess hazards associated with contaminants, residual process additives, and by-products in treated

materials.

5.4.1.1 Group 1: Typical Soil Washing (Project 30)

Comparing the levels of contaminants in treated and untreated soil showed the effectiveness of the

process. All streams were sampled to measure flows in the slurry, solids, and water, and data were

compiled to provide a mass balance. Contaminant concentrates and products low in contamination were

analyzed to determine the degree of contaminant reduction.

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NATO/CCMS Pilot Study, Phase II Final Report

Batch processes (for jigging coarse material and the MGS for separating sand and silt) were incorporated

into the overall materials balance to determine how the entire circuit performed.

5.4.1.2 Group 2: Soil Washing and Biological Treatment (Projects 24, 26, and 36)

Soil Washing

Test materials were first characterized according to the approaches summarized above. Preliminary

experiments first determined the percentages of sand, fines, and coarse material in soil and sediment test

samples. Soil washing was evaluated with bench-scale and small-scale commercial equipment and a pilot

plant. Following soil washing, test material and the resulting wash fractions were analyzed to determine

initial and final concentrations, respectively, of contaminants. This information was used to determine

if contaminants in these fractions were significantly reduced so that the fractions could be reused or

discharged, or required further treatment.

Biological Treatment

To assess the biological phase of the treatment, researchers measured initial concentrations of

contaminants in the soil wash concentrates and compared them with final concentrations of contaminants

after a known treatment period. The final concentrations of contaminants in the recombined treated

fractions (from soil washing and biological treatment) were also measured.

To assess the impact of biological activity, experiments focused on measuring contaminant degradation

over time, comparing the carbon dioxide concentration in the headspace to the concentration in the

atmosphere, and monitoring biological activity expressed as the respiration rate (mg O2/g-hr).

Microtox was used in Project 26 to measure the acute toxicity of water-extractable components of the

soils. Test results assessed hazards associated with the soils that could not be quantified by chemical

analyses, and also the formation of possible toxic intermediates from the biological process.

5.4.1.3 Group 3: Soil Washing and Physical-Chemical Treatment (Projects 10, 17, 19, 27,

and 31)

Characterization

Where mentioned in project reports, characterization of contaminated material involved determining

particle size distribution and analyzing sub-samples of the separated fractions for organics and

inorganics. Preparing materials consisted of screening soil samples at various sizes (e.g., 20 mm, 6 mm,

and 2 mm and with a standard set of screens) sometimes down to 45 μm. Yields at each screen size

were calculated as dry weights and used to prepare particle size distribution curves.

Each major fraction was digested using standard USEPA procedures and analyzed for contaminants and

other soluble species. For the content of inorganics, digested samples were analyzed by methods such

as AAS. In the project on metalliferous spoil (Project 31), the mineralogy of the separated fractions was

examined by XRF. For XRF, samples were subjected to a 0-100° scan against standard results for lead

sulfide, lead sulfate, and lead carbonate. Analytical procedures for Project 33 consisted of USEPA

Method 3010 for acid digestion of aqueous samples and extracts for total metals for analysis by FLAA

or ICP spectroscopy, and Method 3050 for acid digestion of sediments, sludges, and soils. The

investigators modified recommended procedures by using hydrochloric and nitric acids in the USEPA

protocols, since the use of hydrofluoric acid in U.K. laboratories is restricted.

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NATO/CCMS Pilot Study, Phase II Final Report

Soil Washing

Soil washing was conducted at bench-, pilot-, and full-scale. To assess this technology, feed material

as well as contaminant concentrates and various separated fractions were weighed and analyzed for

contaminants such as oil and grease, and metals. Samples were sometimes analyzed in duplicate or

triplicate.

Physical-Chemical Treatment

In general, performance was assessed by checking mass and contaminant distributions in feed and

recovered products. This approach was taken for investigations from bench-scale treatability to full-scale

application. Analyses were usually conducted in a laboratory, but for Project 27, PCB analyses were

done in the field with a DEXSIL L2000 PCB/chloride analyzer.

At full-scale, plants were sometimes monitored to ensure that they met operational requirements. For

a technology evaluation conducted under the USEPA SITE program, routine operation of the plant work

followed SITE protocols. As an example, instruments at the field site for Project 27 monitored air for

particle-bound and free PCBs.

Because different technologies were used to treat soil wash fractions, different assessment procedures

were applied during subsequent work with these wash fractions. In froth flotation tests (Project 31), for

example, the technology was initially assessed in a 2.5-L Denver flotation cell under conventional

conditions practiced widely in the base metal industry to recover sulfide minerals. Similarly, a

preliminary leach program with several types of soils (Project 33) tested various inorganic and organic

acids, as well as alkaline and chelating reagents under various conditions. Samples of the soil wash

mixture, which were withdrawn and analyzed periodically, revealed concentrations of metals in both the

solid and liquid fractions. Adsorption tests with the leachates involved first screening a variety of

adsorbents then obtaining adsorption isotherms for candidate adsorbents.

Only one report documented quality assurance and quality control (QA/QC) procedures. For Project 33,

where work was conducted on Hamilton Harbour sediment, Davy International Environmental Division

and the Wastewater Technology Center (WTC) in Burlington, Ontario, agreed on a program of

laboratory work and a QA program. As agreed with the WTC, a full USEPA quality assurance project

plan was inappropriate for the laboratory work. However, to obtain quality data and have confidence in

the pilot plant design, control actions included performing analyses in duplicate, testing blanks and

spiked samples (approximately 10% of samples over the whole program), performing elemental mass

balances for each test, and completing an independent audit.

Overall Assessment

This overall assessment concerns criteria/targets used to assess the performance of the technologies in

this group.

In terms of targets, mercury emissions from vacuum distillation used for Project 19 were measured, and

concentrations were compared to a specified level of 50 μg/dscm. Mercury was measured in the feed

and treated stream to evaluate the performance of the technology and to determine if the residual had

achieved the target of 50 mg/kg. Mercury in cleaned water for discharge to a sewer had to achieve a

target level of 10 μg/L. For Project 27, the Norwegian Pollution Control Authority proposed the test

methods and acceptance criteria for PCB reduction and eco-toxicological tests. A 70% guideline was set

for volume reduction. This agency also recommended a suite of ecological tests (biodegradation, acute

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NATO/CCMS Pilot Study, Phase II Final Report

toxicity, and bioaccumulation) to evaluate risk associated with the clean soil and dehalogenated sludge

that would remain onsite. These tests were conducted on leachate generated from samples treated

according to the TCLP. The potential risks included residual PCBs as well as residual process additives

and by-products of the chemical dehalogenation process. To assess performance, criteria for PCBs were

less than 10 mg/kg for soils; less than 10 μg/L for water to be discharged; and less than 100 μg/100 cm2

for non-porous scrap for landfilling.

Other regulatory agencies also established criteria or targets to assess performance. This applied to

Project 31, which investigated reprocessing techniques such as gravity separation, froth flotation,

chemical leaching, and biological extraction for metalliferous mine spoil. To determine the effectiveness

of the treatments on various types of spoil, residual levels of metals in treated spoil were compared with

U.K. soil guidelines for corresponding metals. To determine the extent to which metals in original spoil

and reprocessed residues could be leached and hence be of environmental concern, both materials were

subjected to chemical and biological leaching. The procedure for chemical leaching tests was a modified

version of the shake-flask test described in the Acid Rock Drainage Prediction Manual published by the

Canadian Center for Mineral and Energy Research (CANMET). Laboratory microcosms were set up to

investigate how oxidative microbial activity affected metal leachability. These studies simulated natural

biological processes that occur when the residues are exposed to air and water, and quantified losses of

metals from such a weathered deposit.

Finally, for Project 33, the technology on in-pulp decontamination of soils, sludges and sediments was

assessed in terms of its ability to achieve low absolute regulatory levels (e.g., Danish, U.K., and Dutch)

and leachability criteria recommended by the U.S.

5.4.1.4 Group 4: Physical-Chemical Treatment (No Soil Washing) (Projects 32, 44, and 47)

Characterization

For Projects 32 and 47, characterization of test material comprised determination of particle size

distribution, mass distribution, and distribution of heavy metals (Project 32 only) across the size

fractions. Project 44 involved initial laboratory studies on the coal tar and soil to obtain data for system

design. The specific gravity of the coal tar was determined, and the optimum temperature for the injected

water was determined to be 68°C. It was estimated that 60% of the coal tar in the soil could be removed

with 98% of the removable tar being recovered after 19 pore volumes were flushed through the surface.

Piezometers were installed to define the areal extent of the coal tar.

Treatment Assessment

For Project 32 (CACITOXTM treatment), differences in contaminant removal effectiveness for varying

levels of heavy metal contaminants were determined using a range of tests, including tests on soils

spiked at “high” (1,000-22,500 mg/kg) and “low” (10-450 mg/kg) concentrations of these metals. To

assess the decontamination efficiency of the treatment for radionuclides, researchers spiked USEPA

simulated soil matrices with individual radioisotopes of Pu, Am, Np, Sr, Cs, and Ra.

In Project 44, the recovery of coal tar was measured and compared to performance specifications.

Performance specifications required treatment to continue until results showed that there was less than

0.5% additional recovery of coal tar per pore volume of water flushed through the contaminated zone.

To evaluate the performance of the in situ LasagnaTM technology (Project 47), soil samples and sampling

cassettes were analyzed to assess the TCE removal efficiency. Twelve soil borings were completed

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NATO/CCMS Pilot Study, Phase II Final Report

before and after the demonstration. The soil samples collected from each boring were analyzed to assess

how TCE concentration changed at each location. Also, cassettes from 12 treatment zones and from the

control zone were analyzed to determine the amount of TCE they collected. The data were used to

perform a mass balance.

Overall Assessment

To evaluate the success of a given formulation or process change in the leaching process (Project 32)

for heavy metals, concentrations of these metals in the feed and product were compared against Dutch

B values and Canadian Residential values for heavy metals in soil. The CROW process used in Project

44 was considered successful although it did not achieve expected operating conditions and recovery of

contaminants. Groundwater sampling was planned to assess the overall effectiveness of the treatment.

No overall assessment criteria were reported for the in situ demonstration of the LasagnaTM technology.

5.4.1.5 Group 5: Photo-Oxidation Treatment (Projects 14, 38, and 40)

Unlike the projects in the other groups, Group 5 projects solely involved technologies for treating

groundwater. Biological treatment (Project 14), chemical treatment (Project 38), and adsorption (Project

40) accompanied photo-oxidation, the main technology for each project.

Characterization

Investigators characterized groundwater by analyzing samples for contaminants of concern and other

parameters. For Project 14, concentrations of organic contaminants as well as COD, TOC and adsorbed

organic halogens (AOX) were determined first for untreated groundwater. In addition to conducting gas

chromatography/mass spectrometry (GC-MS) analysis of influent samples for VOCs, investigators

working on Project 38 determined toxicity of influents by subjecting them to bioassay tests with

waterfleas and minnows. As discussed in Section 5.2.5, a number of laboratory tests were conducted

during Project 40 to optimize the photoactivities of photocatalysts and to optimize the supports for fixedbed photocatalysts.

Treatment Assessment

To assess the biological pretreatment coupled with an ozone/UV combination process, researchers

measured COD, TOC, VOC, and AOX levels as a function of ozone concentrations. For Project 38,

samples were taken at several locations to evaluate the treatment system s efficiency. GC-MS analysis

of influent and effluent samples for VOCs were used to indicate levels of intermediate organic

compounds created during treatment. Other analyses included parameters such as total organic halogens

(TOX), AOX, TOC, total carbon, and purgeable organic carbon. To obtain reliable data, USEPAapproved sampling, analytical, and QA/QC procedures were followed. For toxicity assessment, influents

and effluents were subjected to bioassay tests with waterfleas and minnows.

Overall Assessment

Projects 14 and 38 were assessed in terms of their ability to achieve target levels of contaminants or

toxicity limits. The combined biological and photo-oxidation treatment was required to achieve

acceptable drinking water limits. The effectiveness of the Perox-PureTM system was measured in terms

of its ability to achieve the California drinking water action levels and U.S. federal drinking water

maximum contaminant levels for the five compounds studied. However, neither project report listed the

numerical values for the target limits. However, for a separate study involving treatment of groundwater

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NATO/CCMS Pilot Study, Phase II Final Report

containing TCE, the discharge level for the treatment was set at 0.5 mg/L. Bioassay tests also

demonstrated whether the effluent was toxic to freshwater organisms.

The effectiveness of the systems tested at Tydall AFB and K.I. Sawyer AFB for Project 40 were

assessed in terms the destruction rates of contaminants. The effectiveness of the system tested at the

Wausau Water Treatment Plant was not measured because fouling of the catalyst inhibited destruction

of the adsorbates.

5.4.2 General Effectiveness

This section of the chapter examines the performance of soil washing when it was used alone or in

combination with other technologies. In the latter cases where soil washing was used as a pretreatment

to provide a contaminant concentrate for further treatment, this review considers the performance of the

pretreatment step only.

Unfortunately, some data on soil washing are not available for reporting or comparison here. Instead of

documenting the effectiveness of soil washing and the add-on treatments separately, some investigators

provided information on the overall performance for pretreating the feed and treating the concentrate.

Another part of this chapter focuses on this overall performance.

It is somewhat difficult to compare reported performance of soil washing because the projects did not

use the same unit processes. For example, one project examined hydrocycloning only, while others

incorporated sizing, scrubbing, froth flotation, magnetic and gravity separation, etc. Thus, effectiveness

will be measured in terms of targets and criteria mentioned in Section 5.4.1.

Table 5.2 provides data on contaminated material before and after soil washing and on the treatment

processes used. Where results were not provided, a notation has been made. Performance data in Table

5.2 also identify if treated materials achieved their target criteria.

Data for these projects confirm reported observations that washing efficiency was dependent on the

composition of the soil, and specifically that particle size distribution plays an important role in washing

effectiveness. In general, the process is very efficient on sandy material, but fine-grained materials

containing relatively high percentages of silt and clay were more difficult to treat. As reported in the

Introduction, soil washing is most effective on soils containing less than 30-35% clay and silt.

As demonstrated in Project 36, additional treatments or several passes of the same unit process overcame

treatment difficulties presented by materials high in fines. Investigators deliberately tested material

containing up to 62% of particles less than 0.063 mm to test the feasibility of extending soil-washing

processes to such materials. The results confirmed that three stages of froth flotation or gravity

separation succeeded in significantly reducing levels of contaminants in the clean fraction. Despite these

reductions, contaminants in the treated fraction were still significant making it unsuitable for reuse.

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Table 5.2: Performance of Soil Washing Only

Project Contaminant Levels1 Media Treatment Processes Performa

10 (B) TOC, >10%; high concentrations of

PAHs and O&G; 92% metals in<100 μm fraction; 75% metals in<50 μm fraction

Sediment Flotation, magnetic and gravity

separation

Tailings: 40%; O&G, 4.1%; PZn, 11%; Cd, Ni, and Fe, 24-3Organic concentrate: 27%; O&Pb, 81%; Zn, 68%; Cd, 54%; 

10 (P) 4,026 mg/kg Zn; 100 mg/kg Cu Soil Clean: 95%: 360 mg/kg Zn; C

industrial guidelines for PAHs guidelines for some contaminaMetal concentrate: Fe, 55%

17 (F) Not provided Soil, sediment Screening, solvent extraction No data on screening.19 (P) Not provided Soil, debris Soil washing, vacuum

distillation

No data on soil washing.

24 (F) Crude oil up to 14,500 mg/kg Sandy soil (77%

sand, 12.5%fines, 10.5%coarse)

Multi-step hydrocyclone Sand fraction: 87.5%; 130 mg/

Coarse fraction, 10.5%Fine fraction: 12.5%; 110,000 

24 (F) High levels of mineral oil and

PAHs (no data given)

Sediment (40%sand, 55% fines,5% coarse)

Multi-step hydrocyclone Sand fraction: no data; hydroc

Fine fraction: no data; 20,000 1,000-2,000 mg/kg PAHs

26 (B) 180-3,500 mg/kg PAHs Sandy soils Screening, flotation Washed fraction: 20-185 mg/k

Concentrate: no data

26 (P) 100-11,000 mg/kg PAHs Clayey soils Screening, flotation Washed fraction: 24-1,250 mg

Concentrate: 480-6,000 mg/kg 

27 (B) up to 1,000 mg/kg PCBs Soil Screening; flotation Clean fraction: 40-500 mg/kg 27 (P) 10-100 mg/kg PCBs Soil Screening, flotation Clean fraction: 0.7-5.0 mg/kg 

5-32
NATO/CCMS Pilot Study, Phase II 

Project Contaminant Levels1 Media Treatment Processes Performa

27 (F) 50-300 mg/kg PCBs 1,288 tonnes

soil; Fines, 63%(30% notexpected)

Screening, flotation 780 tonnes clean fraction (60%

400 tonnes PCB-enriched slud

30 (P) 184 mg/kg PAHs; 937 mg/kg TPH;

2,332 mg/kg CN; 650 mg/kg Pb;32 mg/kg As

Clayey soil Sizing, scrubbing, flotation Clean: 48%; 48 mg/kg PAHs; 

mg/kg CN; 540 mg/kg Pb; 18 Fines: 29%; 170 mg/kg PAHs3,423 mg/kg CN; 1,000 mg/kg Concentrate: 24%; 476 mg/kg TPH; 3,191 mg/kg CN; 441 m

30 (P) 163 mg/kg PAHs; 939 mg/kg TPH;

2,340 mg/kg CN; 733 mg/kg Pb;32 mg/kg As

Clayey soil Sizing, scrubbing, multigravity separation Clean: 50%; 39 mg/kg PAHs; 

mg/kg CN; 577 mg/kg Pb; 18 Fines: 29%; 170 mg/kg PAHs3,422 mg/kg; 1,001 mg/kg Pb; Concentrate: 21%; 450 mg/kg TPH; 2,494 mg/kg CN; 735 m

31 (B) Pb, 20%; Zn, 15% Pb in fines; finegrained material,

anaerobic; coarsematerial, aerobic

Gravity separation Light fraction: >90%; <2% me

guidelinesConcentrate: <10%; Pb, 32%; 

31 (P) Not provided <0.5 mm

fraction of spoil

Multi-gravity separation Light: 90%: metals, 2.5%

Concentrate: 10%; metals, 70%

31 (B) Pb, 9.8%; Zn, 2.3% <180 μm

fraction unoxidized spoil

Froth flotation Tailings: Pb, 3.0-3.5%; Zn, 0.1

33 360 mg/kg Cu; 621 mg/kg Cr; 414

mg/kg Zn; 1,204 mg/kg As

Soil, sediment Screening, hydrocycloning,

flotation

No information on performanc

36 (P) 3,000-4,000 mg/kg TPH Soil, 62%

<0.063 mm

Sizing Clean fraction: 68.7%; 200-21

Fines: 26-31%; 12,000 mg/kg 

5-33
NATO/CCMS Pilot Study, Phase II 

Project Contaminant Levels1 Media Treatment Processes Performa

36 (P) 200-300 mg/kg PAHs; 2,000-3,000

mg/kg TPH; 2,000-3,000 mg/kgCN

Gasworks soil,43% <0.063 mm

3 stages of froth flotation;gravity flotation. Applied toseparate 0.01-0.63 mmfraction.

Clean fraction from froth flotareduced by 61%, TPH by 54%Clean fraction from gravity seby 68%; TPH reduced by 76%14%.

Notes:1 Data are presented in the units that appeared in the various project reports.2 Washed media and concentrate provided as percentage of feed.(B)= bench-scale (F)= full-scale(P)= pilot-scale O&G= oil and grease

5-34
NATO/CCMS Pilot Study, Phase II t r o

Project 27 demonstrates how an unanticipated high quantity of fines impaired soil-washing performance

and required changes to the treatment. The higher than anticipated fines (63% rather than 30%)

overloaded the system with solids and reduced performance. A volume reduction of 60%—not the

targeted 70%—was achieved. Treated material often did not achieve target levels for PCBs and had to

be washed again.

In summary, the projects demonstrated that soil washing may require several unit processes before

treated materials can achieve target criteria. While this goal is desirable, it must be pointed out that

performance should take into account the ability of the processes to produce a concentrate suitable for

downstream treatment.

5.4.3 Overall Performance

To complement the discussion above on the performance of soil washing alone, this section of the report

presents overall performance for the treatments, which may or may not have included soil washing. Data

are presented for Group 2 on soil washing and biological treatment, Group 3 on soil washing and

physical-chemical treatment, Group 4 on physical-chemical treatment, and Group 5 on photo-oxidation

treatment.

5.4.3.1 Group 2: Soil washing and biological treatment (Projects 24, 26, and 36)

Table 5.3 summarizes data for projects conducted at the bench-scale to full-scale. Demonstration projects

used soil washing as a pretreatment followed by bioslurry treatment of contaminant concentrates. To

achieve better degradation rates, photo-oxidation was used as an added pretreatment in Project 24 to

convert contaminants such as PAHs to readily biodegradable forms.

Materials tested in Project 24 consisted of a sandy soil contaminated with crude oil and a sediment

contaminated with mineral oil and PAHs. In experiments conducted at the pilot scale, soil washing and

biodegradation reduced mineral oil in soil from 400-5,000 mg/kg in the original feed to less than 100

mg/kg in the biologically-treated material. Biological treatment lasted 3-8 days. For treating soil

contaminated with PAHs, pilot-scale investigations supplemented biological treatment with UV/H2O2

pretreatment. This combined photo-oxidation and biological treatment reduced PAH levels in soil wash

concentrates from 30 mg/kg to 2-4 mg/kg in recombined soil in 15 days. PAH availability to UV/H2O2

pretreatment appears to be a rate-limiting factor. For soil washing and biological treatment at the full

scale, crude oil levels in a soil fell from 14,500 mg/kg to less than 3,000 mg/kg (in recombined

fractions). Similarly, soil washing a contaminated sediment resulted in a sludge with up to 2,000 mg/kg

PAHs and 20,000 mg/kg hydrocarbons. After 30-32 days of treating the sludge biologically, residuals

contained 2,000 mg/kg hydrocarbons and 200 mg/kg PAHs.

When the froth flotation fraction of a diesel-contaminated soil (Project 36) containing 12,000 mg/kg TPH

was treated in a bioslurry reactor, the TPH concentration fell by 81%. However, treated solids still

contained relatively high TPH (2,300 mg/kg). Similarly, biological treatment of fines generated by froth

flotation and specific gravity separation of a gasworks soil failed to significantly reduce levels of

contaminants. After 28 days of treatment, PAHs fell by 40-50%, and petroleum hydrocarbons by up to

20%. Cyanide remained unchanged.

Photo-oxidation pretreatment of soil-washed residues enhanced the subsequent biodegradation of PAHs,

but was not required for more readily biodegradable contaminants such as mineral oil. As demonstrated

in Project 24, pretreatment enhanced subsequent biological treatment which reduced PAHs from 30

mg/kg to 5-10 mg/kg in 15 days. PAHs were not biodegraded without this pretreatment. In contrast, the

pilot-scale bioreactor tested batches of sludge resulting from soil washing two clayey soils in Project 26.

5-35
NATO/CCMS Pilot Study, Phase II 

Table 5.3: Overall Performance of Soil Washing and Biological Treatment

Project Treated Media and

Contaminants Soil Washing Performance

Biological Treatment

(Before) (After)

24 (P) 400-5,000 mg/kg mineral oil in

soil

Not provided Not provided <100 mg/kg mineral oil 

24 (P) 30 mg/kg PAHs in soil Not provided Not provided 2-4 mg/kg PAHs in recom

soil

24 (F) 14,500 mg/kg mineral oil in

sandy soil (77% sand, 12.5%fines, 10.5% coarse)

Fines: 110,000 mg/kg mineral oil;Clean: 130 mg/kg mineral oil

110,000 mg/kgmineral oil

22,000 mg/kg mineral oil treated sludge; <3,000 mgrecombined soil

24 (F) Mineral oil and PAHs

(concentrations not provided) insediment (40% sand, 55% fines,5% coarse)

Sand fraction: 100 mg/kghydrocarbons;Sludge: 20,000 mg/kg hydrocarbons;1,000-2,000 mg/kg PAHs

Sludge (seeprevious cell)

2,000 mg/kg hydrocarbonmg/kg PAHs

26 (B) 180-3,500 mg/kg PAHs in sandy

soil

Clean fraction: 17-185 mg/kg PAHs 180-52,000

mg/kg PAHs

55-4,800 mg/kg PAHs

26 (P) 41-12,000 mg/kg PAHs in clay

soils

Clean fraction: 30-1,500 mg/kgPAHs;sludge: 2,400-3,750 mg/kg PAHs

2,400-3,750mg/kg PAHs

55-200 mg/kg PAHs 

36 (P) Diesel fuel (3,000-4,000 mg/kg

TPH) in fine-grained soil (62%<0.063 mm)

Clean fraction: 200-210 mg/kg TPH;fines: 120,000 mg/kg TPH

120,000 mg/kgTPH

2,300 mg/kg TPH 

36 (P) 200-300 mg/kg PAHs; 2,000-

3,000 mg/kg petroleumhydrocarbons; 2,000-3,000 mg/kg cyanide in fine-grained soil

Flotation clean fraction: 80-117mg/kg PAHs; 920-1170 mg/kg TPH;1,220-1,830 mg/kg CN

Not provided Slurry reduced PAHs by 

hydrocarbons by 20%; CNunaffected

36 (P) 200-300 mg/kg PAHs; 2,000-

3,000 mg/kg petroleumhydrocarbons; 2,000-3,000 mg/kg cyanide in fine soil

Gravity clean fraction: 62-93 mg/kgPAHs; 460-690 mg/kg TPH; 1,680-2,520 mg/kg CN

Not provided Slurry reduced PAHs by 

and hydrocarbons by 20%unaffected.

Notes:(P)= pilot-scale(F)= full-scale

5-36
NATO/CCMS Pilot Study, Phase II Final Report

After 6 days of treatment, PAH concentrations fell by up to 97% (from 2,400-3,750 mg/kg to 55-200

mg/kg). A project report claimed that indigenous PAH degraders could achieve residual PAH

concentrations ranging from 55-200 mg/kg after a 6-day retention time.

According to data collected during the biological treatment for Project 24, toxicity was reduced

significantly. Since soil washing itself accounted for little of the reduced toxicity, it was concluded that

bioslurry treatment accounted for most of the reduced toxicity.

5.4.3.2 Group 3: Soil Washing and Physical-Chemical Treatment (Projects 10, 17, 19, 27,

and 33)

Table 5.4 summarizes data for projects conducted at the bench-scale to full-scale. Physical-chemical

treatments applied to the soil wash concentrates were leaching and adsorption (Projects 10 and 33),

solvent extraction (Project 17), vacuum distillation (Project 19) and chemical dehalogenation (Project

27). Because little similarity exists among these treatments, their performances will be assessed

individually.

When used on concentrates containing heavy metals, leaching and adsorption reduced metal

concentrations in treated materials by between 60-95%. In both cases, metal residuals fell within

regulatory industrial and residential limits. However, the in-pulp leaching and adsorption method used

in Project 33 appeared to be better than the approach used for Project 10. The metal content in the first

case was lower, but the relative removal was higher than observed in the second case.

Materials treated by solvent extraction, vacuum distillation, and chemical dehalogenation reportedly

achieved their regulatory targets. Solvent extraction removed almost 98% of PAHs and PCBs from soil

that originally contained between 250-2,000 mg/kg PCBs and 200-500 mg/kg PCBs. Chemical

dehalogenation achieved a similar level of success on soil wash concentrates with PCBs in the same

concentration range. However, data suggest that when compared with these technologies, vacuum

distillation achieved the highest removal. Treated soil contained less than 1% of the original organic

contaminants and only around 3% of the mercury. Altogether, vacuum distillation will likely perform

better than the others because it can remove volatile organic and inorganic contaminants from

contaminated materials.

5.4.3.3 Group 4: Physical-Chemical Treatment (No Soil Washing) (Projects 31, 32, 44, and

47)

Table 5.5 summarizes data for projects conducted at the bench-scale to full-scale. The table identifies

the NATO project number and the scale of the investigation, characteristics of the tested material, and

overall performance of the treatment.

Physical-chemical treatments applied to unwashed contaminated material were leaching and adsorption

(Project 31), leaching and extraction (Project 32), in situ thermally enhanced recovery (Project 40), and

in situ electro-osmosis and adsorption (Project 47). Because little similarity exists among these

treatments, their performances is assessed individually.

Of all the reprocessing techniques tested (others discussed for Project 31 under Group 3), leaching of

oxidized Pb minerals with alkalis like sodium hydroxide displayed the highest potential for removing

metals from spoil thereby resulting in the lowest concentrations of metals in the residue. Sodium

hydroxide released 25-92% of the Pb and 3-23% of the Zn in un-reprocessed spoil containing 7.5% Pb

and 0.1% Zn. These releases correspond to 1.5-5 tonnes Pb and 0.1-1.2 tonnes Zn per 100 tonnes spoil.

5-37
NATO/CCMS Pilot Study, Phase II 

Table 5.4: Overall Performance of Soil Washing and Physical-Chemical Treatment

Project

Number Contaminants in Feed Contaminants in Concentrate Overall Performance 

10 (P) 2,112 mg/kg Pb; 950 mg/kg Cu; 4

mg/kg Cd; 2,535 mg/kg Zn

Not applicable Soil solids after leaching: 1,070 mg/kg Pb; 480 mg/

mg/kg Cd; 1,050 mg/kg ZnSoil solids after metal adsorption: 898 mg/kg Pb; 28Cu; <1 mg/kg Cd; 286 mg/kg Zn;Recovery= Pb, 57%; Cu, 70%; Cd, >90%; Zn, 67%residuals within regulatory industrial (1,000 mg/kg) residential (500 mg/kg) limits

10 (P) Pb as high as 11,800 μg/g Not applicable Clean material (7% original Pb) met regulatory indu

and residential criteria

17 (F) Silty sand, loamy soil, and

sediment (250-2,000 mg/kg PAHs;200-500 mg/kg PCBs; 2,000 mg/kgheavy organics

Not provided Treated material (6-30 mg/kg PAHs; 1-6 mg/kg PC

mg/kg heavy organics

19 (P) 32,000 mg/kg PAHs; 102,000 mg/

kg TPH; 1,728 mg/kg CN; 8,000mg/kg HG; 100,000 mg/kg TNT;3,400 mg/kg lindane

Not provided Treated soil: <1 mg/kg PAHs; <10 mg/kg TPH; <10 

CN; 0.5-4.0 mg/kg Hg; 0.4 mg/kg TNT; 0.0002 mglindane

19 (F) Hg up to 1,900 mg/kg 100 μm - 8 mm;

contaminantconcentrations not given

Treated material (Hg 10-50 mg/kg); below target of kg.

27 (B) PCBs at unknown levels 250 mg/kg PCBs Treated concentrate (PCBs <1 mg/kg); below target 

mg/kg.

33 (B) 1,204 mg/kg As; 360 mg/kg Cu;

621 mg/kg Cr; 414 mg/kg Zn

Information not provided Treated product: 112 mg/kg As; 22 mg/kg Cu; 74 m

68 mg/kg Zn. Corresponding targets are 30, 100, 16100 mg/kg, respectively.

Notes:(B)= bench-scale(F)= full-scale(P)= pilot-scale

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NATO/CCMS Pilot Study, Phase II Final Report

Table 5.5: Overall Performance of Physical-Chemical Treatment Without Soil Washing

Project

Number

Characteristics of

Contaminated Media Overall Performance TreatmentProcesses

31 (P) Un-reprocessed metalliferous

spoil: Pb, 7%; Zn, 0.1%

Sodium hydroxide leached 25-92% Pb

and 3-23% Zn.

Sulfuric acid leached 2-33% Pb and 12-

64% Zn.

Aggressive leaching

32 (F) Soil with 46% silt/clay: total

heavy metals 1,000- 22,500

mg/kg;

Treated material achieved Dutch B values

and Canadian residential values for Cr,

Ni, Cu, Zn, and PB, but not for As or Cd.

Mild leaching and

extraction

32 (F) Soil spiked with radionuclides Treated material contained 24-48% of Pu,

U, Ru, Am, Np, and Sr.

Leaching and

extraction

44 (F) Gravelly soil with coal tar

DNAPL

5,400 L of pure coal tar was removed DNAPL: thermally

enhanced recovery,

incineration

Water: precipitation,

fluidized bed

reactor, filtration

47 (P) Soil with TCE averaging 72.6

mg/kg

Treated soil contained 1.1 mg/kg TCE;

removal efficiency 98%;

Electro-osmosis and

adsorption

Notes:

(F)= full-scale (P)= pilot-scale

Other leach tests showed that sulfuric acid was more effective at leaching Pb from un-oxidized spoil than

from oxidized material. The acid leached 2-33% Pb and 12-64% Zn. By comparison, tests with

reprocessed spoil showed that the acid leached only 2-5% of the original Pb, suggesting that the residual

Pb is resistant to acid leaching.

As demonstrated for Project 32, using the CACITOXTM reagent to leach a 46% silty clay soil containing

a variety of heavy metals at concentrations in the range of 1,000-22,500 mg/kg resulted in simultaneous

removal of metals. The treated material achieved Dutch B values and Canadian Residential values for

Cr, Ni, Cu, Zn, and Pb, but not for As and Cd. The researchers reported that if the conditions were

optimized, all metals would have met the criteria. In tests of soil spiked with radionuclides, a single

leach removed between 52 and 76% of Pu, U, Ru, Am, Np, and Sr. Multiple contacts could have

resulted in better removal of these radionuclides.

When the LasagnaTM technology was applied to a contaminated site (Project 47), TCE concentrations

were reduced on average from 72.6 mg/kg to 1.1 mg/kg, which translates to an average removal

efficiency of 98%. At sampling locations where the initial concentrations were as high as 225 mg/kg,

indicative of residual DNAPL in soil pores, the process reduced these concentrations to less than 1

mg/kg in all but one sample. Upward diffusion of TCE from untreated soil may explain the single

discrepancy of 17.4 mg/kg TCE. TCE reduction in a control area averaged at around 45%, falling from

89.9 m/kg to 49.5 mg/kg. These data, when compared to those from the demonstration area, confirm the

effectiveness of the LasagnaTM process for removing TCE from soil.

Mass balance accounted for 50% of the pre-demonstration TCE. The remaining 50% may be attributed

to passive diffusion (5%), evaporation (5%), in situ degradation of TCE, non-uniform distribution of

TCE in the soil, or incomplete extraction of TCE from the activated carbon (taken from the treatment

layer) before analysis.

5-39
NATO/CCMS Pilot Study, Phase II Final Report

5.4.3.4 Group 5: Photo-Oxidation Treatment (Projects 14, 38, and 40)

Table 5.6 summarizes the performance data for the Group 5 projects. The table identifies the scale of

the investigation, characteristics of the tested groundwater and wastewater, and overall performance of

the photo-oxidation treatment.

While all three projects used photo-oxidation, Project 14 included biological treatment with activated

sludge to improve performance. The project report did not explain how the biological step improved

performance, or why it was necessary. However, the combined approach reduced dissolved constituents

by 80-85%, eliminated VOCs, and lowered COD from 239 ppm to undetectable levels.

For the three tests conducted under Project 38, the photo-oxidation technology generally achieved

regulatory targets and reduced contaminants to below detection levels. For a technology demonstration

conducted at the Lawrence Livermore National Laboratory facility, groundwater contained TCE and PCE

at 1 mg/L and 0.1 mg/L, respectively. Treated water contained TCE and PCE at levels below detection

limits, while TCA and chloroform occurred at levels slightly above detection limits. In another study

where the technology was used to treat well water containing 50 to 400 mg/L TCE, effluents consistently

achieved levels below the analytical detection limit of 0.5 μg/L. Also, at a full-scale treatment for

groundwater containing PCPs as high as 15 mg/L, the system destroyed the contaminants to below the

target level of 0.1 mg/L.

5.5 RESIDUALS AND EMISSIONS

5.5.1 Soil Washing

Table 5.7 identifies residuals (i.e., soil/sediment, water, and concentrates) and emissions (air) from soil

washing only. For projects that used soil washing as a pretreatment to provide a concentrate for further

treatment, residuals and emissions for the subsequent treatments are covered under the project groups

to follow.

As seen in the examples in Table 5.7, soil washing residuals usually include the following:

• Wastewater from sizing and classifying material. This water is usually recycled, but may eventually

require treatment before disposal.

• Concentrates that may be treated further to destroy or stabilize contaminants, or to extract useable

products.

• Treated material that may be reused or recycled if it meets regulatory criteria, or disposed of at a

landfill, incinerated, etc., if it does not.

• Off-gases that may contain volatile contaminants, which may be removed by techniques such as

adsorption by activated carbon.

5.5.2 Combined Treatments

Residuals from combined treatments consist of those identified for soil washing in Table 5.7, as well

as others unique to the treatments used on contaminant concentrates. Residuals discussed below pertain

mainly to treatment of the concentrates.

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NATO/CCMS Pilot Study, Phase II Final Report

Table 5.6: Overall Performance of Photo-Oxidation Treatment of Contaminated Water and

Wastewater

Project

Number

Characteristics of contaminated

water/wastewater Overall Performance

14 (F) 239 ppm COD; chlorinated

solvents, esters, phenols, BTEX,

etc., at 0.8–360 mg/L

COD undetected; dissolved organic constituents reduced by

80%-85%; VOCs eliminated.

38 (F) Groundwater: TCE 1 mg/L; PCE

0.1 mg/L

TCE (99.9% removal) and PCE (98.7% removal) below

detection limits in treated water; TCA and chloroform slightly

above detection limits.

38 (F) Drinking water: TCE 50–400 mg/L Effluents below analytical detection of 0.5 μg/L.

38 (F) Groundwater: PCPs up to 15 mg/L PCPs in treated water below target level of 0.1 mg/L.

40 (F) Groundwater: contained total BTEX

compounds greater than 2 mg/L

Ionic species initially fouled the catalysts and inhibited

destruction. Following treatment to remove suspended

particulates and ionic species, catalyst photo-activity did not

decrease after 25 days of operation. BTEX compounds were

destroyed within 6.5 minutes of empty bed contact time on

rainy days.

40 (F) Groundwater: 100 μg/L TCE >21% of total influent BTEX destroyed; 98% of BTEX

removed from waste stream.

40 (F) Groundwater: 100 μg/L TCE >95% of TCE was destroyed within a 2-minute contact time.

40 (F) Groundwater: contained chlorinated

solvents and BTEX compounds at

unspecified concentrations

Direct photocatalytic oxidation did not effectively regenerate

spent adsorbent because nuisance substances in the groundwater fouled the catalyst. Tests combining steam regeneration

followed by photocatalysis of steam condensate showed that

carbon adsorbent was not effectively regenerated an lost a

significant amount of capacity. Background organic matter in

the water may have caused this loss of efficiency. Also,

steam regeneration did not appear to destroy significant

amounts of the sorbed chlorinated compounds.

Notes:

(F)= full-scale BTEX= benzene, toluene, ethylbenzene, and xylenes

5.5.2.1 Group 2: Soil Washing and Biological Treatment (Projects 24, 26, and 36)

The main residuals from biological treatment are process water and sludge. Table 5.8 identifies residuals

(soil/sediment, water, and concentrate/other) associated with biological treatment of soil wash

concentrates for the three Group 2 projects.

Only one of the three projects reported recycling of the process water, and it is not clear what was done

for the other projects. Contaminants in treated concentrate achieved regulatory guidelines or remained

at unacceptable levels. Clean material derived from Project 24 was described as having no residuals,

while Microtox analysis of treated material from Project 26 revealed that toxicity had been reduced

significantly. In contrast, unacceptable levels of contaminants remained in fines treated in Project 36.

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NATO/CCMS Pilot Study, Phase II Final Report

Table 5.7: Residuals and Emissions Associated with Soil Washing

Project

Number Soil/Sediment Water Air Concentrate/Other

10 Treated sediment material

achieved industrial limits

for Pb, Cd, and organics.

Not suitable as off-shore

fill.

Wastewater from sizing and

classifying material

Not reported Inorganic concentrates

for disposal or recovery

of metals; organic

concentrate for

secondary treatment

17 Treated material used as

fill, or treated further to

stabilize metals.

Not reported Not reported Concentrate treated by

solvent extraction.

19 Not reported Wastewater treated

chemically to form a

precipitation sludge.

Disposed in a hazardous

waste facility. Water

polished with activated

carbon.

Off-gases

treated with

activated

carbon.

Light-weight particles

and spent activated

carbon treated by

vacuum distillation.

24 Not provided Not provided Not provided Concentrate treated

biologically.

26 Not provided Not provided Not provided Concentrate treated

biologically.

27 Non-porous debris disposed

in a landfill; porous debris

registered as hazardous

waste for incineration;

coarse fraction (>0.1 mm)

returned to excavation and

capped

Wash water treated if it

contained PCBs, then

recirculated or discharged

to a sewer.

No off-gases

generated

Concentrate treated by

chemical

dehalogenation.

30 Not provided Process water was

contained and recirculated.

Carbon

filters, which

extracted

volatile

contaminants,

created

emissions.

Wastes and sludges

received further

treatment or shipped to

a licensed landfill.

31 Residue contained total

metals exceeding U.K.

guidelines for soils. Metals

are leachable.

Not provided Not provided Not provided

33 Provided for overall

treatment, not for soil

washing only.

Decanted water Off-gases

may be

produced

Concentrate leached and

metals adsorbed.

36 Residue contaminantreduced, but unsuitable for

reuse. Contamination levels

still significant.

Not provided Not provided Concentrate treated

biologically.

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NATO/CCMS Pilot Study, Phase II Final Report

Table 5.8: Residuals Associated with Biological Treatment of Soil Wash Concentrates

Project

Number Soil/Sediment Water Concentrate/Other

24 Clean soil with no residuals;

treated fractions recombined.

Effluent from

biodegradation

was recycled.

Not clear what was done with sludge treated

biologically.

26 Not applicable Not provided Microtox analysis of water-extractable

components of treated concentrate showed

significantly reduced toxicity.

36 Not applicable Not provided Treated fines contained unacceptable levels of

contaminants.

5.5.2.2 Group 3: Soil Washing and Physical-Chemical Treatment (Projects 10, 17, 19, 27,

31, and 33)

The type of physical-chemical treatment used on soil wash concentrates determined the nature and

quality of residuals. Table 5.9 identifies residuals (soil/sediment, off-gases, and concentrate/other)

associated with physical-chemical treatment of soil wash concentrates for five of the six Group 3

projects. For four of these projects in this group, treatment consisted of further concentrating the

contaminants to provide a recoverable product or a smaller volume of contaminated material for disposal.

These treatments resulted in products such as a metal-rich filter cake, oil, and mercury. The treated

materials were usually suitable for reuse or disposal. If carbon filters were used in the treatment, they

contained captured volatile contaminants.

Only Project 27 examined chemical destruction of PCBs in the concentrate. Based on bench-scale studies

only, the treated material contained acceptable residual PCBs.

5.5.2.3 Group 4: Physical-Chemical Treatment (No Soil Washing) (Projects 32, 44, and 47)

Like the Group 3 projects already discussed, the type of physical-chemical treatment used on

contaminated materials treated by Group 4 projects determined the nature and quality of residuals. Table

5.10 identifies residuals (soil, sediment, water, off-gases, and concentrate/other) associated with physicalchemical treatment (no soil washing) for three projects.

In Projects 31 and 32, treated materials were reused or disposed. One of these materials had to be

washed before disposal to remove residual leachant. In the case of Project 47 (in situ treatment of TCE

contaminated soil), soil retained around 1 mg/kg TCE after treatment. The physical treatments concentrated the contaminants further rather than destroying them. Because of this, contaminant-rich products

resulted. These consisted of metal-rich concentrates as well as treatment cartridges that captured TCE.

Only Project 47 reported residuals in off-gases and water.

5.5.2.4 Group 5: Photo-Oxidation Treatment (Projects 14, 38, and 40)

When used to treat contaminated groundwater, photo-oxidation—with or without biological treatment—

resulted in few residuals (water, off-gases, and concentrate/other) as noted in Table 5.11. Treated

groundwater contained low levels of contaminants that could be discharged directly or treated further

before being sent to a municipal treatment facility.

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Table 5.9: Residuals Associated with Physical-Chemical Treatment of Soil Wash Concentrates

Project

Number Treatment Process Soil/Sediment Off-Gases Concentrate/Other

10 Metal recovery,

chemical destruction

of organics

Treated sediment material

achieved industrial limits

for Pb, Cd, and organics.

Could be used as fill onshore or offshore.

Not

applicable

Metal-rich filter cake for offsite recycling

17 Solvent extraction,

stabilization

Traces of solvent in cleaned

soils. Claimed to be

innocuous and biodegradable

Carbon filters

with

recovered

vapors

Oil concentrate requires

treatment, recycling, or

disposal.

19 Distillation Not provided Not provided Spent ion-exchange resins for

recycling; condensed mercury.

27 Chemical

dehalogenation

Not applicable Not provided Treated concentrate contained

<1 mg/kg PCBs.

33 Leaching, adsorption Treated material was

disposed.

Gaseous

emissions

may require

scrubbing

Acid used to remove metals

was recycled. Concentrated

solution of metals may be

treated by precipitation,

reduction, or electrowinning

to recover metals, or

encapsulated or disposed.

Precipitated residues may

require fixation before

disposal.

Photo-oxidation treatments normally do not result in sludge or spent media requiring further processing,

handling, or disposal. Ideally, end-products include water, carbon dioxide, halides, and in some cases

organic acids. However, although Project 14 included a biological step, the reports did not mention how

a biological sludge was treated or the levels of residual contaminants.

GC/MS analysis of influent and effluent samples examined for Project 38 revealed no new target

compounds or other tentatively identified compounds being formed during treatment. The report for

Project 14 did not mention work to identify possible by-products resulting from the ozonation treatment.

Finally, treated water may have retained unused hydrogen peroxide: investigators for the study at the

Lawrence Livermore Laboratory (Project 38) reported residual hydrogen peroxide in the effluent.

5.6 FACTORS AND LIMITATIONS TO CONSIDER FOR DETERMINING THE APPLICABILITY

OF THE TECHNOLOGY

Several factors determine the success of physical-chemical technologies. As most of the case studies

dealt with in this chapter involved soil washing as a pretreatment stage, consideration is given below

to this technology both when used alone and in combination with other technologies. The final part of

this section examines the factors governing the applicability of physical-chemical treatment not involving

soil washing.

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Table 5.10: Residuals Associated with Physical-Chemical Treatment of Contaminated Materials (No

Soil Washing)

Project

Number

Treatment

Process Soil/Sediment Water Off-gases Concentrate/Other

31 Froth flotation,

gravity

separation,

density

separation

Treated spoil was

disposed or reused.

The effluent has

to be addressed.

Options include

conventional

metal adsorption

filters.

Not reported Compared to other

treatments, alkali

leaching provides the

residue with the

lowest concentration

of metals.

32 Leaching,

complexation,

precipitation, ion

exchange

Treated soil was

washed to remove

residual leaching

agent, dewatered,

then reused

Not reported Not reported Precipitated

contaminants may be

reconditioned

(contained or

encapsulated).

Electro-deposition/

polishing the leachate

may recover valuable

products or minimize

secondary waste.

44 Thermally

enhanced

recovery

Soil and groundwater concentrations

were not provided.

Recovered coal tar

DNAPL was

incinerated.

Groundwater was

treated and was

either reinjected

or discharged to

Brodhead Creek

Not reported Sludge and spent

carbon from treatment

of groundwater and

the recovered DNAPL

must be disposed.

47 Electro-osmosis,

adsorption

Soil treated in situ

contained <1 ppm

TCE.

Recycling water

from the cathode

to the anode

eliminates

effluent.

Evaporation

produces

contaminant

vapors

Treatment layers with

captured TCE may

require disposal as a

hazardous waste.

Table 5.11: Residuals Associated with Photo-Oxidation Treatment of Groundwater

Project

Number Water Off-Gases Concentrate/Other

14 Dissolved contaminants were reduced by 80-85%. Water

was treated again before being sent to treatment plant or

discharged to a stream.

Not

provided

Sludge. No mention of

the levels of residual

contaminants.

38 Treated water has TCE and PCE below the detection limit

of 0.5 μg/L. Chloroform slightly exceeds detection limits.

Effluent may contain residual H2O2;

None

generated

Not applicable

38 For a full-scale treatment, treated water contained 0.1

mg/L PCP.

None

generated

Not applicable

40 Concentrations of residual contaminants varied, depending

on the system tested.

Not

provided

Not provided, but

presumably sludge from

water pretreatment and

spent catalyst and

support materials.

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NATO/CCMS Pilot Study, Phase II Final Report

5.6.1 Typical Soil Washing

General Issues

This ex situ separation process could potentially be applied cost-effectively to materials with less than

30-35% of particles less than 0.063 mm. When the concentration of fines exceeds this range,

conventional soil washing may have to include other treatments (e.g., flotation, density and gravity

separation), washed material will have to be reprocessed, or several cycles of the same treatment (e.g.,

hydrocycloning) may have to be implemented. Another option includes using the CACITOXTM technology

(Project 19) which is claimed to be effective for soils containing a high content of silt and clay, a

characteristic that presents difficulties to other treatment technologies—including soil washing.

If low absolute standards cannot be achieved with a single technology, pretreatment by flotation or size

separation may be used to complement a treatment process. Pretreatment may reduce the volume

requiring downstream treatment and may also present the separated contaminant concentrate in a form

suitable for the downstream process (e.g., bioslurry).

For soil washing pretreatment and companion treatment technologies to be viable, the treatment process

on the separated contaminated fines has to be rapid. Otherwise, long treatment periods will cause

problems when matching commercially viable throughput of physical processes with relatively slow

treatments such as biological processes.

Coarse-grained soils would not benefit much from soil washing and accompanying treatments. As

explained for Project 33 which used soil washing and in-pulp extraction, coarse-grained soils containing

metals can be easily leached, filtered and washed. Extracted metals can then be precipitated or adsorbed

from the resulting wash and leachate. In contrast, the washing step becomes more difficult for soils high

in fines.

Material Characteristics

When soil washing is used as a pretreatment for other technologies, accurate determination of feed

material characteristics is a crucial step. These characteristics have a key influence on the choice of the

most efficient technologies to treat soil wash concentrates, and on how the selected technology performs.

Single unit operations can then be combined to provide tailor-made solutions to deal with the

contamination. However, it is important to note that for complex sites with many sources of

contamination, the contaminated material may not behave consistently during the separation process.

Thus, the chosen technology should be able to cope with variations in the chemical and physical

composition of the feed.

For example, the ORG-X solvent extraction unit (Project 17) operates best under optimum moisture

content and grain size. Soil moisture content of 20% in one case made the soil difficult and more costly

to treat. The process achieves higher efficiency on sandy material, but is being improved for fine-grained

soils. Similarly, the mineralogy of clay particles in a soil matrix may influence the overall treatment

process. The exchange capacity of different clay minerals affects the degree to which contaminants can

be adsorbed or desorbed, and strongly influences the characteristics of subsequent dewatering.

In contrast, some treatment technologies are insensitive to variations in soil types. Vacuum distillation

(Project 19), for example, can effectively treat materials such as gravel, sandy soils, fine-grained soils

(up to 90% silt and clay although at a reduced throughput); slags, concrete and brick debris, etc.

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Contaminant Characteristics

Physical and chemical properties of contaminants to be treated influence the applicability of

technologies. For example, vacuum distillation (Project 19) is suitable for volatile contaminants with

boiling points of 350-400°C at pressures of 50-150 hPa. In terms of biological treatment, candidate

contaminants must be amenable to biological degradation. Other factors influencing the applicability of

a technology are operating parameters and maintenance requirements of equipment used in the treatment

processes.

Treatment Criteria and Characteristics of Residuals

With some soils, physical pretreatment alone will not reduce the absolute concentration of contaminants

to acceptably low levels. However, by combining this pretreatment with other approaches such as

biodegradation and chemical treatment, treated material may achieve the regulatory criteria. Thus, the

applicability of a treatment system would depend on its overall ability to achieve regulatory

requirements.

A technology that may not achieve absolute regulatory criteria should not necessarily be discounted as

a treatment option. As shown in Project 33, in-pulp extraction provides an attractive option for removing

metals from pulp generated by leaching a contaminated soil high in fines. The project s report notes that

achieving low absolute levels can be difficult and costly. On the other hand, leachability criteria could

be achieved easily.

Before using soil washing pretreatment and companion treatments, property owners should clarify the

intended use or disposal of treated materials and soil wash concentrates. This is a key point because it

determines which soil washing processes should be used to achieve this goal. For example, if treated

material is to be disposed of at a secure landfill, the feed will require less rigorous treatment than a

material for reuse on an industrial or residential property.

If destruction of a soil matrix is not desirable, strong acids should not be used for treatment because they

can significantly impair the integrity of a soil matrix. In contrast, weak extractants such as those used

in the CACITOXTM technology (Project 32) do not destroy the matrix and thus be potentially be used

treat contaminated soils and sediments when this is an important consideration.

5.6.2 Soil Washing and Other Treatment

With some soils, soil washing alone will not reduce the absolute concentration of contaminants to

acceptably low levels. Combining this treatment with other proven extraction, destruction, or

concentration approaches may reduce contaminants in treated media to meet acceptable criteria. The

proven technologies must be combined in such a way that each technique is properly integrated and the

overall performance better than could be achieved with a single unit application alone.

An alternative approach, claimed to be more economically attractive than one using two independent

treatments in sequence, is one that combines treatment of inorganic and organic contaminants in a single

unit operation.

In a combined treatment approach that includes soil washing, the selectivity of the companion

technology for contaminants determines its applicability to soil wash concentrates. Biological treatments,

for example, can be applied only to contaminants that are biodegradable. Similarly, the CACITOXTM

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NATO/CCMS Pilot Study, Phase II Final Report

technology is claimed to selectively dissolve and extract heavy metals and transuranic elements from

other wastes.

Soil Washing and Biological Technologies

This combination of technologies is restricted to soil and sediment with a low content of organic matter

and contaminated with high concentrations of biodegradable organic compounds, such as mineral oil and

PAHs. High molecular weight PAHs biodegrade slowly, and the limited bioavailability of these

compounds restricts degradation to even lower rates. Limited bioavailability of PAHs results from

adsorption of these compounds to the organic soil matrix. As seen in Project 24, using a UV/H2O2

pretreatment to break down the organic matrix and release the PAHs can increase this bioavailability.

The combination of soil washing and slurry-phase treatment provides a viable option for treating

contaminated soil. The washing step reduces the volume of material requiring treatment by up to 80-90%

and can function as the prerequisite mixing operation for microorganisms, nutrients, and contaminants.

Under optimal conditions (e.g., pH, temperature, and nutrients) during the bioslurry phase, indigenous

degraders in the contaminated material may significantly increase removal of contaminants.

For the overall treatment to be viable, the degradation process on separated contaminated fines has to

be rapid. Otherwise, long degradation periods will cause problems when coupling commercially viable

throughput of physical processes with relatively slow biological processes.

Soil Washing and Physical-Chemical Technologies

Soil washing pretreatment should reduce the volume of material requiring downstream treatment and also

present the separated contaminant concentrate in a form suitable for the downstream physical treatment.

If the feed to soil washing contains organic and inorganic contaminants, the organic and inorganic

concentrates should be separated for subsequent treatment.

To be applied successfully for treating a contaminant concentrate, physical-chemical technologies have

to complement each other. For example, if a treatment involves leaching contaminated materials and

subsequently adsorbing metals, the leached metals have to be in a form suitable for adsorption. As

demonstrated in Project 33, ion exchange resins work well for Cu, Cr, and Zn. However, these resins

experienced difficulties removing As because the metal forms un-dissociated arsenic acid, which is

unavailable for ion exchange, at the low pHs needed to dissolve arsenates. At high pHs, the ion exists

in solution but preferentially adsorbs onto iron precipitates formed under these conditions.

The degree to which physical-chemical treatments destroy a soil matrix may be significant. When this

is a concern, other technologies may have to be considered. The CACITOXTM technology, for example,

which employs “weak extractants,” potentially can treat contaminated soils and sediments without

destroying the matrix.

5.6.3 Physical-Chemical Technologies

Like biological treatments, physical-chemical technologies treat specific contaminants and media. The

LasagnaTM process (Project 47) demonstrates this selectivity, because it offers promise for treating watersoluble organic and inorganic contaminants and mixed wastes in groundwater and low-permeability soils.

For highly non-polar contaminants, surfactants introduced into groundwater or incorporated into

treatment zones will solubilize the organics. The process has been shown also to be effective in treating

residual DNAPLs. If contaminated soil has a relatively high permeability, other treatment processes may

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NATO/CCMS Pilot Study, Phase II Final Report

be more effective or more economical than the LasagnaTM process. The CACITOXTM process also

demonstrates this selectivity by dissolving and extracting heavy metals and transuranic elements from

other wastes.

For in situ treatment, the spatial distribution of contamination may influence how a technology is

applied. Contaminated material within 10 m of the surface may be easily excavated for treatment on the

surface. However, when contamination occurs at depths greater than 10 m, it is usually treated in situ.

A similar rationale applies to using the LasagnaTM technology. The vertical configuration of the

technology is more appropriate for contamination near the ground surface. For deeper contamination,

installing horizontal treatment zones provides a better option. Finally, if contaminant concentrates are

determined to be hazardous wastes, treating, removing and disposing of them may be an issue and may

prove costly.

5.6.4 Photo-Oxidation Technologies

Photo-oxidation treatment does not transfer or concentrate contaminants that may require further

treatment or costly disposal. Treated water can be disposed onsite or offsite. Options for on-site disposal

include groundwater recharge or temporary on-site storage for sanitary use. Off-site disposal options

include discharge into surface water bodies, storm sewers, and sanitary sewers. Depending on permit

requirements, discharged water may have to be adjusted for pH. Factors influencing the applicability of

photo-oxidation can be grouped into four categories: site characteristics, influent characteristics, operating

parameters, and maintenance requirements.

Site Characteristics

Site characteristics can influence the application of the technology. Site-specific factors include support

systems (e.g., extraction wells, facility for treatment, and equalization tanks), site area and preparation,

climate, utilities, and services and supplies.

Influent Characteristics

In general, minimal pretreatment is required. If needed, it usually consists of oil and grease removal,

suspended solids removal, metals removal, or pH adjustment to reduce carbonate and bicarbonate levels.

Under a given set of operating conditions, contaminant removal efficiencies depend on the chemical

structure of the contaminants. Removal efficiencies are high for organic compounds with double bonds

(e.g., TCE, PCE, and vinyl chloride) and aromatic compounds (e.g., benzene, toluene, xylene, and

phenol) because these compounds are easily oxidized. Organic compounds without double bonds (e.g.,

TCA and chloroform) are not easily oxidized and are more difficult to remove.

Contaminant concentration also influences the technology s effectiveness. The system is most effective

for contaminant concentrations lower than 500 mg/L. At higher concentrations, the technology can be

combined with others such as air stripping. For highly contaminated water, the system can be operated

in a “flow-through with recycle” mode. In this arrangement, part of the effluent is recycled through the

oxidation unit to improve overall removal efficiency.

Other chemical species in influents may consume oxidants and place an additional load on the system.

These species, known as scavengers, include anions such as bicarbonate, carbonate, sulfide, nitrite,

bromide and cyanide. Metals in reduced states (e.g., trivalent chromium, ferrous iron, manganesian ion)

are also likely to be oxidized. Under alkaline conditions, these reduced metal species can cause other

concerns. For example, trivalent chromium can be converted to the more toxic hexavalent form, while

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NATO/CCMS Pilot Study, Phase II Final Report

ferrous and manganous ions can be converted to insoluble forms which precipitate to create suspended

solids that can build up on the quartz tubes housing the UV lamps. Natural organic compounds such as

humic acids (often measured as TOC) are also potential scavengers.

Suspended solids, oil, and grease pose potential problems because they can build up on the quartz

sleeves, reduce UV transmission and so decrease treatment efficiency.

Operating Parameters

The main operating parameters are hydrogen peroxide dose, influent pH, and flow rate. Treatment unit

configuration, contaminated water chemistry, and contaminant oxidation rates determine the hydrogen

peroxide dose. A hydrogen peroxide splitter allows the operator to inject hydrogen peroxide to the

oxidation unit influent and directly to any of the individual oxidation reactors. Influent pH controls the

equilibrium among carbonate, bicarbonate, and carbonic acid. When carbonate and bicarbonate

concentrations exceed 400 mg/L, lowering the influent pH to between 4 and 6 improves the efficiency

by shifting the carbonate equilibrium to carbonic acid that is not a scavenger. In general, increasing the

hydraulic retention time improves treatment effectiveness by increasing the time available for

contaminant destruction.

Maintenance Requirements

Regular maintenance by trained personnel is essential for the successful operation of photo-oxidation

systems. The lamp assembly is the only major system component requiring regular maintenance. Other

components of the system can be checked monthly.

5.7 COSTS

Table 5.12 summarizes information on contaminants and media treated, pretreatment and other treatments

used, reported treatment costs, and qualifiers regarding the costs. Some of these costs are based on actual

remediation projects, while others are estimated from results of bench- and pilot-scale investigations. In

another approach (Project 47), a cost model examined a contamination scenario and predicted treatment

costs. The currencies used for costs are those used in project reports.

The costs in Table 5.12 should be treated with caution. The reports for some of the projects did not

differentiate between capital and operating costs; and generally did not clearly state if the costs were for

treatment only, exclusive of excavation, handling and disposal. However, for Project 26 the cost of

excavation, sorting and backfilling was reported as U.S.$160/m3 and the cost of washing as U.S.$300/m3

.

Cost-effectiveness and costs will be highly site-specific and will depend on factors that influence

treatment. For example, the nature of the material determines the need for various types of specialized

pretreatment processes such as magnetic separation, flotation, and density separation. If material

contaminated with organic and inorganic compounds contains relatively high concentrations of fines,

specialized treatments will require additional handling of material and result in higher costs. As

demonstrated in Project 19, the rate of utilization of a soil washing plant influences treatment costs. Cost

decreases as the rate of utilization increases. The size of a treatment plant also has an impact on cost.

For example, for the groundwater treatment conducted during Project 38, a larger plant, if required,

could offer lower treatment costs.

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Table 5.12: Reported Costs for Different Options Used to Treat Contaminated Media

Project

Number

Contaminants and

Media Treated

Treatment

Processes

Overall Cost

(per m3 unless other

units given)

Comments

Group 1: Typical Soil Washing

30 32-650 mg/kg metals;

184 mg/kg PAHs; 200

mg/kg TPH

Particle size

separation, froth

flotation, gravity

separation

Not provided.

Group 2: Soil Washing and Biological Treatment

24 14,500 mg/kg crude

oil in soil; PAHs in

sediment

Hydrocycloning

photo-oxidation,

bioslurry

Not provided Pretreatment by photooxidation and hydrocycloning can be expensive,

depending on the ratio of

sand to fines and the

organic matter content

26 180-3,500 mg/kg

PAHs in sandy and

clayey soil

Flotation, bioslurry Excavation, sorting,

backfilling (U.S.$160/

m3); washing

(U.S.$300/m3);

biological (U.S.$530/

m3)

36 2,000-4,000 mg/kg

TPH; 200-300 mg/kg

PAHs; 2,000-3,000

mg/kg CN in soils

high in fines

Size separation,

bioslurry

£23-£37 (U.S.$38-

61)/tonne of treated

material

Treatment is more costeffective only if

transporting and disposing

of untreated Mattel exceeds

£40-60 (U.S.$65-

100)/tonne.

Group 3: Soil Washing and Physical-chemical Treatment

10 4,026 mg/kg Zn; 100

mg/kg Cu in soil

Flotation, magnetic

separation, leaching

of metals and

adsorption

U.S.$75/tonne Estimated cost for treating

500,000 tonnes of soil

containing PAHs and

metals.

17 250-2,000 mg/kg

PAHs; 200-500 mg/kg

PCBs in soil and

sediment

Size separation,

solvent extraction,

oil recovery

U.S.$200/tonne for

2,000 tonnes;

U.S.$100/tonne for

20,000 tonnes;

U.S.$60/tonne for

100,000 tonnes

19 875 mg/kg Hg in

sandy loam and loam

soils

size separation,

scrubbing, vacuum

distillation

U.S.$320/tonne Rate of utilization of the

soil washing plant

influences treatment costs.

Soil wash treatment costs

U.S.$221/tonne if utilization is 25%, but drops to

$70/ tonne if utilization is

100%.

27 50-300 mg/kg PCBs

in soil and other solids

Particle size

separation, chemical

dehalogenation

Soil washing alone

cost U.S.$380/tonne

Costs for dehalogenation

were not provided.

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Project

Number

Contaminants and

Media Treated

Treatment

Processes

Overall Cost

(per m3 unless other

units given)

Comments

31 Metals in mine spoil Particle size

separation, flotation

Not available. The project was not at the

stage where meaningful

costs could be calculated.

33 360 mg/kg Cu; 621

mg/kg Cr; 414 mg/kg

Zn; 1,204 mg/kg As

Particle size

separation, leaching,

adsorption

For proposed scale-up

plant, cost estimated

at £70-£80 (U.S.$115-

130)/tonne.

Treating Hg-contaminated

soil by aggressive leaching

and complexing agents

requires costly unique

construction materials for a

treatment plant.

Group 4: Physical-Chemical Treatment (no soil washing)

31 Metals in mine spoil Leaching,

adsorption

Not available. The project was not at the

stage where meaningful

costs could be calculated.

32 Heavy metals and

radionuclides in

clay/silt soil

Oxidation,

complexation,

precipitation, ion

exchange

Not provided. Report noted that using low

concentrations of mild

chemicals for leaching

yielded low costs, but did

not provide supporting data.

44 Coal tar DNAPL in

gravelly soil

Thermally enhanced

recovery

Total cost:

approx. U.S.$1.8M

Cost for removing 5,400 L

of recoverable coal tar and

treating groundwater before

reinjection or discharge.

47 TCE in clay Electro-osmosis U.S.$52-118/m3; Costs obtained from a costoptimization model; 1-2

acre site with TCE at depth

of 12-15 m (40-50 ft)

electrode installation

accounts for 20-40% of the

overall cost.

Group 5: Photo-Oxidation Treatment (no soil washing)

14 0.8-360 mg/L

chlorinated

compounds in

groundwater

Biodegradation,

photo-oxidation

15 million FF

(U.S.$2.5 million)

capital costs; 23

million FF (U.S.$3.9

million) annual costs

Costs for achieving

acceptable drinking water

limits. To achieve surface

water discharge, costs

would be U.S.$1.7 million

for capital, and U.S.12.9

million annually.

38 1,000 μg/L TCE; 100

μg/L PCE; 15 mg/L

PCP in groundwater

and wastewater

Chemical oxidation,

photo-oxidation

U.S.$2-3/m3 for a 190

L/min unit

Unit costs increase as the

size of the treatment unit

gets smaller and

contaminants become more

difficult to oxidize.

40 BTEX and chlorinated

solvents (Tyndall

AFB)

Adsorption and

photocatalysis

U.S.$1.46/m3 The unit cost is for treating

BTEX-contaminated water

using a solar photocatalytic

fixed-bed process (Pt-TiO2

supported on silica gel).

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In summary, unit costs will vary from site to site. However, these costs may sometimes be offset by the

sale of concentrate produced by treatments although none of the project reports provided evidence that

recovered concentrates were actually sold for profit.

5.8 FUTURE STATUS OF THE CASE STUDY PROCESS AND THE TECHNOLOGY AS A

WHOLE

5.8.1 General Remarks

Physical-chemical methods, used alone or in combination with other technologies in a treatment train,

have proved capable of treating mainly fine-grained materials contaminated with organic and inorganic

contaminants. Despite their successes, these technologies have limitations that restrict their ability to treat

certain types of media and contaminants effectively. If planned investigations reveal ways to overcome

these limitations, the future of physical-chemical technologies will lie in their ability to cost-effectively

treat a wide range of contaminants in a wide variety of media. This section of the chapter presents some

of the issues that could have an impact on the future of the technologies.

5.8.2 Characterizing Contaminated Material

Soil washing provides a reliable way to treat contaminated solids, and specialized treatments like

flotation enhance the overall physical separation of clean and contaminated materials. For the approach

to be most effective, material to be treated must be properly characterized. When feed material is

properly characterized, unit processes can be tailored to site-specific contamination situations.

5.8.3 Optimizing Performance of Unit Processes

Unit processes have proven excellent for media such as sand and gravel, but need to be improved for

fine-grained soils where more than 30-35% of particles are less than 0.063 mm. In terms of other

physical characteristics of contaminated materials, future investigations should investigate the feasibility

of treating sediments and sludges with high water content.

Improved performance in the separation methods is required to increase the weight of the clean fraction

and reduce the volume of contaminated concentrate. Obtaining better effectiveness at this separation

stage of treatment could improve the performance of downstream treatments.

Optimizing plant operation may lead to lower levels of contaminants, a key requirement if reuse of

treated material is required, and residual contaminants are otherwise unacceptably high. For example,

the pilot-scale MGS described in Project 31 achieved a combined metal assay of 2.5% in the residue.

Optimizing the MGS could result in higher separation efficiencies. Similarly, for soil washing and

bioslurry treatment demonstrated in Project 26, using longer retention times or adding special microbial

cultures were proposed as ways to achieve further reductions in contaminant concentrations in treated

materials.

5.8.4 Investigating Cost-Effectiveness of Treatment Combinations

Preliminary investigations conducted for some of the case studies identified specific treatments that may

perform better if combined with others. This observation confirms that the future of physical-chemical

technologies lies in their ability to be used both alone and in existing and new combinations for treating

contaminated materials. For example, a proposed new combination consists of MGS physical separation

and chemical leaching as a potentially effective two-stage process for decontaminating metalliferous

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mine spoil. This combination needs further investigation with larger volumes and varieties of spoil

samples before being used in the field.

Some existing combinations have proved to be cost-effective in some situations, but investigations

should confirm their full range of application. For example, further investigations should assess the

extent of application of the combined soil washing/slurry biodegradation processes which can likely be

applied cost-effectively. Long degradation periods will cause problems when combining commercially

viable throughput of physical processes with relatively slow biological processes. To enhance the

viability of the treatment, further work should investigate ways to achieve rapid biodegradation to a

reusable product. As an example, further work for Project 36 could investigate if continuous biological

treatment can reduce the contaminant levels in fewer than the reported 28 days.

Similarly, many water treatment systems combine the Perox-PureTM technology with carbon adsorption,

air stripping, and biological treatment. Depending on the influent water quality and treatment objectives,

the technology can be paired with others to produce a more cost-effective solution than any single

process.

5.8.5 Investigating Residuals

The physical and chemical characteristics of residuals from physical-chemical treatments are key

attributes when considering the applicability and acceptability of the treatments for any particular

application. For example, two key factors will be their ability to achieve regulatory requirements for the

reuse and recycling of treatment chemicals, and the use or disposal of treated materials and concentrates.

Projects 31 and 47 illustrate considerations of regulatory requirements for residuals.

Further investigations should focus on the feasibility of reprocessing metalliferous mine spoil (Project

31) by single-stage physical separation or two-stage physical-chemical treatment to achieve regulatory

criteria for treated material to be redeposited onsite. Tests of treated material should examine the

susceptibility of residual tailings to biological leaching. If this leaching does occur, leached metals may

contaminate surface water and groundwater.

The formation of potentially harmful intermediates may limit the applicability of emerging technologies.

In the LasagnaTM technology (Project 47), for example, result show that iron filings in treatment zones

can decontaminate TCE resulting in innocuous end products such as chloride ion, ethane, and ethene.

While the technology satisfies regulatory criteria for these compounds, more attention has to be paid to

potential intermediate products such as dichloroethene (DCE) and vinyl chloride. These products tend

to be associated with the iron surface.

5.9 REFERENCES

1. Pearl, Mike and Peter Wood (1994). Review of Pilot and Full Scale Soil Washing Plants. AEA

Technology, National Environmental Technology Centre, Oxford, 113p.

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Chapter 6: BIOLOGICAL TREATMENT PROCESSES: INTRODUCTION AND EX

SITU APPROACHES

R. Paul Bardos

r

3 Environmental Technology Ltd.

6.1 INTRODUCTION

This chapter reviews the projects presented at the Pilot Study that focused on, or included in a

significant way, ex situ biological treatments. These are listed in Table 6.1. All of these projects

investigated the treatment of solid materials rather than groundwater. This chapter also provides a brief

overview of biological treatment with particular regard to ex situ approaches and appropriate situations

for their use. It summarizes the case studies and then discusses them with regard to:

• performance;

• residuals and emissions;

• applicability;

• costs; and

• prognosis for the future.

Where possible, project references that are in the public domain have been provided. Some of the

projects dealt with in this chapter are also dealt with in other chapters: Projects 24, 26, 31 and 36 are

dealt with in Chapter 5, and Projects 15, 24, 26, 31, and 36 are dealt with in Chapter 11.

6.2 GENERAL OVERVIEW

6.2.1 Biological Processes, In General

Innovative treatments are often described as ex situ or in situ. Ex situ refers to processes applied to

excavated soil either onsite or offsite. In situ refers to processes occurring in unexcavated soil, which

remains relatively undisturbed. Treatment processes can also be categorized according to their general

operating principles (5, 32), for instance: biological, chemical, physical, solidification or thermal.

For ease of discussion, materials are considered in this chapter as three basic types in the context of

materials handling: groundwater, soil, and slurry, where slurry is some mixture of soil and groundwater

or added water from another source. “Soil” is used to describe the solid phase material. However, in

reality, the solid phase materials encountered and treated encompass a far broader range of materials,

including, but not limited to topsoil, subsoil, and other natural regolith, fill, waste deposits and industrial

process residues, sediment, demolition debris, vegetation, and refuse. In many cases, remediation of

bedrock is required. Typically, treatment of bedrock—if it is attempted at all—is approached in situ, so

it is not considered in this chapter. Some materials onsite are liquid or semisolid in nature, such as

sludges and coal tars. So far as ex situ biological approaches are concerned, these are treated either by

mixing with a solid material or by treatment in a bioreactor in some form of suspension or slurry

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treatment (25). In some cases, the semi-solid material to be treated is a process residue from an earlier

non-biological treatment process such as soil washing.

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Table 6.1: Projects Reviewed and References

Project

Number

Project Title

6 In situ/on-site bioremediation of industrial soils contaminated with organic pollutants:

elimination of soil toxicity with DARAMEND® (55, 57)

8 Biodegradation/bioventing of oil-contaminated soils (35, 45)

11 On-site biological degradation of PAHs in soil at a former gasworks site (33)

15 Combined chemical and microbiological treatment of coking sites/bioremediation of

soils from coal and petroleum tar distillation plants

24 Combined remediation technique for soil containing organic contaminants: Fortec

25 Slurry reactor for soil treatment (30, 39)

26 Treatment of creosote-contaminated soil (soil washing and slurry phase bioreactors)

(16, 17)

28 Use of white-rot fungi for bioremediation of creosote-contaminated soil

31 Decontamination of metalliferous mining spoil (59)

35 In situ soil vapor extraction within containment cells and combined with ex situ

bioremediation and groundwater treatment (47)

36 Enhancement techniques for ex situ separation processes, particularly with regard to

fine particles (43, 60)

43 Multi-vendor bioremediation technology demonstration project (24, 31)

49 Characterization of residual contaminants in bioremediated soil and reuse of

bioremediated soil

54 Treatment of PAH- and PCP-contaminated soil in slurry phase bioreactors

Biological processes for the remediation of contaminated land depend on one or more of four basic

processes: (1) biodegradation; (2) biological transformation to a less toxic form (e.g., for metals); (3)

biological accumulation into biomass; or, conversely, (4) mobilization of contaminants for downstream

recovery. In general, established commercial processes are limited to those based on biodegradation.

The vast majority of practical biological treatments exploit degradation (5, 8, 13, 38, 56) and are

variously described as bioremediation, bioreclamation, biotreatment or biorestoration. Contaminated sites

are also commonly revegetated to improve their stability and aesthetic appeal and to reduce windblow

of contaminated dust (18).

Concerns about current biological processes include:

• Their susceptibility to inhibition by toxic contaminants (13) (e.g., for example heavy metals)

although some biodegradation processes appear quite robust (26);

• The low biodegradability and or bioavailability of some common organic pollutants, found with other

more degradable contaminants (34). (Current research includes the use of chemical pre-treatments

to enhance biodegradability (1) and treatment of an increasing number of compounds is found to be

feasible, for example chlorinated solvents (11));

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• Residual concentrations of contaminants after treatment, whose environmental significance is not

known (34, 44); and

• The mobilization and release of potentially toxic, partially degraded contaminants from in situ

treatments (12, 27, 40).

6.2.2 Main Process Variations (by Biological Process)

Degradation and Transformation

Biodegradation describes the decomposition of an organic compound into smaller chemical subunits

through the action of organisms. Both aerobic and anaerobic degradation pathways exist, although there

are some differences in the types of compound that will degrade under aerobic and anaerobic conditions

(3). Principally, soil microorganisms (bacteria, fungi, and actinomycetes) are responsible for bioremediation processes, but some researchers are interested in prospects for plants and algae (13, 53). As

summarized below, plants may be of more immediate use in the accumulation of contaminants or as a

means of stimulating soil microbial activity. These approaches are known collectively as

“phytoremediation” and are regarded as an important emerging technology for future research(4, 34, 49).

Completely degraded compounds are said to be “mineralized,” and the end products of the aerobic

degradation of chlorinated hydrocarbon might be carbon dioxide, water, and chloride ions. Guthrie (23)

describes this as “ultimate biodegradation.” He defines “acceptable biodegradation” as breakdown to

below toxic levels, and “primary biodegradation as a structural change in the parent molecule. Primary

biodegradation is more commonly referred to as “biotransformation.”

Biotransformation may be of use in biological treatment of contaminated soil, but has not been exploited.

It has the drawback that further transformations could regenerate toxic forms. In addition, biotransformation can be accompanied by an enhancement in toxicity.

Biodegradation may proceed via enzymic activity on compounds adsorbed into cells or through the

activity of extracelluar enzymes active outside the confines of the cell. Cells also use enzymes to

generate free radicals or peroxide ions that attack organic compounds, particularly insoluble compounds

(2, 5, 13). In many cases, organic compounds do not readily enter microbial cells since the compounds

are either sorbed to soil surfaces, are too large, or are physically incapable of being sorbed into cells.

Bioavailability is regarded as one of the key limiting factors for bioremediation (34).

More complex compounds may not be completely degradable by single organisms, but are degraded by

consortia of organisms, or in some cases may not be completely degradable in any circumstance. Some

organic compounds may be coincidentally degraded as a result of microbial activity against other

substrates, a process called “cometabolism.” An example of this is the use of methane oxidation to

degrade some chlorinated solvents (14). There are a number of organic compounds, such as

tetrachloroethene (PCE), whose degradation is not energetically favorable to microorganisms. However,

in some cases, under anaerobic conditions, these compounds may be biodegraded. The compound does

not serve as an energy source or carbon source, but is used as an electron acceptor, i.e., it is reduced

during the conversion of other organic materials (40).

It is likely that several of these processes may occur simultaneously in practical bioremediation

treatments; however, some techniques are designed to capitalize on particular microbial processes, such

as the use of fungal lignase systems to degrade recalcitrant organic contaminants like pentachlorophenol

(PCP) and polycyclic aromatic hydrocarbons (PAHs) (26).

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Inorganic compounds may also be changed by microorganisms, either by direct metabolism (as in the

oxidation of sulfur or the methylation of mercury) or indirectly through the release of ligands or acids

(6). These processes may mobilize inorganic contaminants such as heavy metals. There may be potential

applications for mobilization as a means of stripping inorganic contaminants from soils, and several laboratoryand pilot-scale initiatives based on microbial mobilization are underway (5). Arsenic and some heavy

metals may be converted into volatile methylated forms by microbial activity (also referred to as

“biotransformation”). However, the toxicity of the methylated compounds may raise serious issues of

operational safety and environmental emissions from such an approach.

Other Processes

Biological immobilization of contaminants is common, for example, the sorption of metals or organic

compounds to plant roots. The bioavailability of sorbed compounds may be reduced by this process, but

the effect is temporary, depending on the lifetime of the root. Contaminants would be mobilized as the

supporting plant matter was degraded. There is some evidence that PAHs may be irreversibly adsorbed

into soil humus (51); however, the usefulness of this in land remediation may be limited by current

approaches to hazard assessment based on total soil concentrations of contaminants.

Biological accumulation of contaminants by plants and fungi is a well-known phenomenon. The potential

use of plants that accumulate metals in their leaves and shoots is being investigated as a possible means

of removing metals from contaminated soils (7). The approach seems particularly suited to shallow

contamination arising, for example, from sewage sludge disposal or atmospheric deposition of metal-rich

dusts. More recently, interest has emerged in combining accumulation of contaminants with energy

forestry to achieve use of the land during the remediation process.

Commercially Available Processes

At present, the great majority of commercially available bio-remediation techniques assist the

biodegradation of fairly readily degradable contaminants: mononuclear aromatics (e.g., benzene toluene,

ethylbenzene, and xylenes); simple aliphatic hydrocarbons (e.g., mineral oils and diesel fuel) and lower

PAHs (2-, 3- and 4-ringed) (8). However, full-scale applications of bio-remediation to treat more

complex contaminants (such as pentachlorophenol, chlorinated solvents and possible more difficult

PAHs) are taking place, and some successes are being reported (11). Recently, the use of metal

accumulation by plants has also begun to be exploited in full-scale practical applications (58).

6.2.3 Main Process Variations (by Mode of Application)

Ex situ application of biological processes allows better process control—in particular, the breaking

down of soil material into small particles (e.g., by cultivation, grading, or conversion into a slurry). This

overcomes one of the major limitations of in situ processes, which is ensuring the accessibility of the

contaminant to the treatment (9). Ex situ processes can be divided into four basic groups (8):

(1) Shallow cultivation, where contaminated soil is cultivated in a treatment bed or in situ by cultivating

the surface layers of a specially prepared area of a contaminated site (e.g., Project 6);

(2) Windrow turning, where piles of contaminated soil often mixed with organic materials such as bark

are turned on a regular basis using processes akin to green waste composting (e.g., Project 11);

(3) Biopiles, where static piles of contaminated soil are vented and irrigated using processes akin to

static pile waste composting (e.g., Project 8); and

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(4) Bioreactors where groundwater or a soil slurry is treated in a reaction vessel (e.g., Project 25).

Cultivation

The term “landfarming” has been used to

50 cm

(Till Depth) <10 mm soil for treatment and amendments

Cultivation

Irrigation

(2X Per Week)

Sand (10 cm)

Sand (10 cm)

HDPE Geotextile

Underlying site material

Figure 6.1: Section Through a Treatment Bed

(based on Project 6)

describe cultivation processes, but is avoided here

to avoid confusion with the treatment of oily

sludges by cultivation on land, which is also

known as landfarming. Methods vary from simple

to advanced techniques—which are all largely

based on agricultural practice. Contaminated soil

is spread over a surface, typically to a thickness

of about 0.5 m. The soil is regularly mixed and

tilled to improve soil structure and oxygen

supply. Water can be supplied to adjust the

moisture content and supply inorganic nutrients to

the system. In many applications the treatment

bed is placed over an impermeable membrane to

ensure complete collection of leachate. Spray

irrigation/recirculation of leachate is also common

practice. An example configuration is provided in Figure 6.1.

Windrows

Treatment techniques using windrows are similar



yyyyyyyy







y

y

y

2m

Screened Soil and 

amendments turned weekly

Hard Stand Leachate drain

Figure 6.2: Windrow Treatment (schematic)

to approaches used for waste composting, for

example, of urban and agricultural wastes. Soil is

placed in thick layers or heaps (see Figure 6.2).

Materials such as wood chips, bark, or compost

are often mixed in to improve the soil structure

and increase aeration. Regular turning and tilling

is often carried out to further improve aeration.

Specialized equipment using technology borrowed

from the waste composting industry is typically

used for this purpose. In most cases, true

composting (i.e., a controlled aerobic, solid-phase

thermophilic process) does not take place.

Furthermore, amendments tend to be added to condition the soil, rather than as part of an integrated

waste management approach, which perhaps remains an under-exploited opportunity.

Biopiles

Excavated soil is placed in a static heap (i.e., no mechanical turning or tilling is conducted). Nutrients

and water are added to the contaminated soil by percolation or along a network of internal galleries. The

conditions in the piles are monitored and optimized through aeration and water supply. An example

schematic (based on Project 35) is provided in Figure 6.3. The principal distinction between biopiles and

windrow-based systems is the use of active aeration and irrigation. Biopiles are closely allied to the

aerated static pile technique for waste composting (52), although refinements such as feedback control

based on temperature, moisture, and partial pressure of oxygen (pO2) are less frequent in soil treatment

than aerated static pile composting. The technology has a longer history for waste composting, and there

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would appear to be still some capacity for technology transfer to soil treatment (e.g., combined aeration

Haul Road

Monitoring Probe

Graded

material for

treatment

Aeration Pipe

Basal layer (e.g., gravel, clay)

Prepared surface

Impermeable 

Membrane

Collection

System

Leachate

Aeration

supply

main

Bed height

2.5 m

Figure 6.3: Example Biopile Configuration (based on Project 35)

and turning technologies).

Bioreactors

Pre-treated soil (e.g., soil with particles >4-5 mm removed) are slurried with water and treated in a

purpose built reactor system with a mechanical agitation device. Within the reactor, controls on

temperature, pH, nutrients, and oxygen supply can be amended to gain the maximum contaminant

degradation rates using either microorganisms indigenous to the soil or specially added cultures.

Bioreactors can range from treatment lagoons Soil +

sediment inflow

Sand fractions

Fine fractions

Outflow fines

Outflow sand

Slurry Air

Slury

recycle

Bed volume

Bulk volume

Figure 6.4: Principle of the DITS Reactor with

the Dual Injection Manifold at the Bottom of the

Reactor (based on Project 25)

(38) to contained in-vessel systems (19), and the

sophistication of engineering approach can vary

accordingly. Bioreactors can also operate in the

solid phase. Although infrequent for soil remediation, this is a common approach for waste treatment. Waste compost bioreactors often incorporate an ability to turn and mix materials, as well

as to simply aerate. The technology is robust, and

again there may be opportunities for technology

transfer to soil remediation (20, 48). An example

slurry-phase bioreactor (based on Project 25) is

illustrated in Figure 6.4.

6.2.4 Combinations with Abiotic Processes

The difficulties of remediating complex

contamination problems with individual process

technologies has led to the development of

process integration, which combines unit process treatments to provide an effective overall treatment (43,

54). Two examples follow:

• Bioventing, which can be applied in situ or ex situ in treatment beds, is an integrated technology that

combines biodegradation and volatilization. A significant problem for biological treatment has been

to supply the active microbial population with sufficient nutrients and oxygen to ensure rapid

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biodegradation. In bioventing, soil vapor extraction (SVE) is used to supply oxygen as well as a

means of removing volatile organic compounds (VOCs) from soil. Bioventing is far more efficient

at delivering oxygen to soil microorganisms than systems that use recirculated groundwater. Project

8 used bioventing to treat soil ex situ.

• Project 24 is a pilot-scale investigation that combined hydrocyclone treatment with separate

“cleaned” sandy fractions from a process residue, which was then sequentially treated by photooxidation and biodegradation.

Treatment integration in general within the Pilot study projects is discussed in Chapter 11.

6.2.5 Extensive Approaches

Intensive treatments, such as soil washing or incineration, use relatively complex equipment and plants,

and require a lot of resources for initiation, running, and support. Therefore, they tend to be costly.

Extensive technologies operate over a longer period with low maintenance, cost, and energy requirements. Approaches being considered include reducing contaminant concentrations, environmental

mobility, and availability and toxicity, or enhancing natural attenuation processes. Techniques include

hyper-accumulator plants and enhanced rhizosphere-mediated biodegradation, and fixation by minerals.

In addition to cost savings, they tend to have less impact on soil quality than their intensive counterparts.

Indeed, biologically based extensive methods such as the promotion of in situ biological activity by plant

roots actually may enhance soil structure and fertility. The development of extensive treatments is of

particular interest to industrial holders of contaminated land as potential low cost treatments over the

lifetime of existing industrial plant operation (12, 44).

Extensive approaches considered to date are mostly in situ techniques (11). However, ex situ approaches

include techniques based on waste composting, and are particularly appropriate where there is a -

possibility of synergy between the treatment of hazardous wastes and other organic wastes such as

sewage sludge or green wastes.

6.2.6 Groundwater Treatment

Contaminated groundwater is treated in three main contexts:

(1) As part of a system where it acts as carrier to transport contamination from soil to the treatment

process(es), for example, in pump-and-treat systems (32);

(2) When it is removed to lower the water table for treatment of contaminated ground; and

(3) As effluent treatment prior to re-infiltration or discharge to surface water.

A permanent solution to groundwater contamination will always require the reduction of contamination

in the aquifer and the source of contamination.

Where groundwater is treated above ground, biological approaches include:

• a variety of bioreactors (5, 46);

• treatment within a soil mass (e.g., through the irrigation of a biopile, windrow, or treatment bed);

and

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• combined treatment with solids in slurry bioreactors.

The majority viewpoint is that simple approaches to pump-and-treat, using groundwater as a carrier to

effect an in situ treatment, are rarely effective; this has led to the emergence of more elegant approaches

(37). These can be divided into two broad and overlapping categories: treatment zones and active

containment.

Treatment zones improve in situ remediation by treating contamination in a smaller, more clearly defined

and better optimized subsurface volume to address typical limitations of in situ remediation, such as

process and emissions control, and to ensure contaminant availability and accessibility. Treatment zones

employ groundwater as a “carrier” for the contamination.

Contamination may be directed or mobilized to the in situ treatment technology by processes such as

the natural groundwater flow, managed groundwater flow (e.g., funnel and gate systems (50)), or by

manipulation such as by using electroosmosis. This approach has a cross-over with ex situ techniques

in several ways:

• The operating principle of the in situ treatment zone may be contained in some form of removable

cartridge or cassette, in which case, it may be considered as a buried ex situ system;

• The treatment system may be entirely or partially above ground; and

• More complex permutations are possible, for example, where a fairly dispersed in situ technique is

used to mobilize contaminants, which are then contained and collected for further treatment above

ground.

Active containment, or use of treatment walls, is a special case of an in situ treatment zone that treats

migrating contaminants, usually dissolved in groundwater or in the vapor phase, where the source cannot

be treated. Active containment targets treatment of the pathway rather than the source. It aims to

overcome the perceived limitations of passive containment measures (which physically restrict migration

of contaminants) such as doubts over long-term barrier integrity and treatment of contaminants.

The control of the contaminant plume can be visualized in terms of a control surface or boundary

beyond which contaminant levels are “acceptable.” The treatment system may or may not act at this

surface. For example, a treatment process may be remote from the boundary where subsequent natural

degradation and attenuation also plays a part in contaminant destruction. Active containment deals with

migrating contaminants. At its most elegant, active containment does not contain groundwater, but

contains the contaminants by destroying them or removing them from the groundwater (28).

6.2.7 Indications for Using Ex Situ Treatment Technologies

Within the process industries sector and among much of the research community, there is great interest

in developing in situ treatment technologies because of their perceived advantages in terms of cost and

environmental impact. These advantages are clearest when remediation can proceed over significant

periods of time, and perhaps when in situ treatments are compared with excavation and transportation

to the intensive ex situ treatment plants.

However, the availability of time is a critical limitation to the use of in situ treatments for many

situations, for example, where an acute risk exists or a redevelopment is planned. Furthermore, in situ

applications are limited by subsurface conditions. Even where in situ techniques are applied, many in

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situ treatment approaches still require the removal of concentrated hot spots. In addition, practical site

reclamation for redevelopment often requires removal of debris and site materials. In such cases, ex situ

treatment may be performed to reduce the volume of material requiring disposal offsite through materials

recovery, or to render the materials more environmentally benign.

Ex situ treatment may take place onsite (e.g., for minimization of material taken off site) or at a remote

site (e.g., to recycle re-usable components and render contamination “safe”). The costs of mobilizing a

treatment plant usually means that on-site treatment is only cost effective above some threshold of

volume of material to be treated. Many countries, including Canada, Denmark, Germany, and the

Netherlands, have off-site biological treatment plants for contaminated site materials. However, an

opportunity that has yet to be broadly exploited is synergy with recycling and reuse of contaminated site

materials and other wastes, for example, construction wastes, civic amenity wastes, or compostable

wastes. Indeed, the longer-term goals of sustainable waste management and sustainable approaches to

dealing with contaminated land are seen not only as an opportunity for synergy, but requiring an

integrated approach if the best opportunities for either are to be realized. An interesting illustration of

this is where an old landfill must be excavated and removed for redevelopment. A particular interest may

be the stationing of an off-site treatment plant at landfills where the opportunities for co-treatment with

materials from different sites and waste streams is greatest (21).

There also may be opportunities for synergy among the needs of sustainable waste management,

recovery of materials from land remediation, and the improvement of marginal land. In this context,

marginal land refers to land that could be remediated, but whose remediation is not possible from a

strictly commercial viewpoint. An example is the possibility of linkage among land remediation, waste

management, and sustainable energy forestry. The opportunity is the long-term reuse of waste (e.g., as

compost or site engineering materials such as gravel substitutes) in ongoing productive use of marginal

land for non-food uses. This may be particularly appropriate for former coal fields, providing new jobs

as well as environmental improvement and sustainable waste management into the long term. However,

it could be appropriate for a wide range of marginal land types.

6.3 CASE STUDIES CHOSEN

The Pilot Study projects chosen as case studies for this chapter are listed in Table 6.1.

6.4 BACKGROUND OF CASE STUDIES AS A GROUP

Table 6.2 describes the Pilot Study projects involving ex situ treatment in terms of the type of

technology configuration (as described in Section 6.2). Projects in the Pilot Study cover the four modes

of treatment application described in Section 6.2.3. The majority of these projects examine exploiting

biodegradation. However, one project examines bioleaching (mobilization of metals by reducing pH

through the action sulfur-oxidizing bacteria). Another is an investigation of the risks posed by a variety

of inorganic and organic contaminants. Table 6.3 outlines the process investigated for each project.

Detailed project summaries are provided in Appendix IV.

Although site details are lacking for some projects, those sites for which details are reported are mainly

wood preservation plants or other sites with PAH contamination, including gasworks and coking works.

PAH and oil degradation are the main processes reported, although some projects also considered PCP

degradation. One project considered treatment of chlorinated and non-chlorinated solvents.

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Table 6.2: Overview of Selected Projects

Project Technology Type Input Material for Treatment S

6 In situ/on-site bioremediation of industrial soil

contaminated with organic pollutants:elimination of soil toxicity withDARAMEND®

Cultivation (full-scale) Screened soil (<100 mm) + proprietary

amendment(a screen size of 250 mm was alsomentioned)

Main results froCanada. Former that used PCP, sediments from 

8 Biodegradation/bioventing of oil-contaminated

soils

Biopile + monthlyturning (full scale)

Screened soil + organic amendments Boucerville (con

transformer oilsstation) Canada other sites

11 On-site biological degradation of PAHs in soil

at former gasworks site

Windrow (+ “passive”aeration) (full-scale)

Screened soil (<80 mm) + organicamendments

Frederiksberg G

15 Combined chemical and microbiological

treatment of coking sites/bioremediation ofsoils from coal and petroleum tar distillationplants

Biopile (“pilot”-scale) Soil + organic amendments / untreated

soil

Not specified, F

24 Combined remediation technique for soil

containing organic contaminants: Fortec

Bioreactor (part of atreatment train)(pilot-scale)

Soil slurry and sediment slurrycontaminated with PAHs orhydrocarbons

Various, not spe

25 Slurry reactor for soil treatment Bioreactor (pilot-scale) Clay-rich soil and harbor sediment

contaminated with PAHs

Mijdrecht and PNetherlands

26 Treatment of creosote-contaminated soil (soil

washing and slurry phase bioreactor)

Bioreactor (part of apilot-scale treatmenttrain)

Soil slurry (PAHs) Former wood p

(creosote contamNorway

28 Use of white-rot fungi for bioremediation of

creosote-contaminated soil

Laboratory-scale R&D Soil, examined degradation of higher

PAHs

Former wood p(creosote contamNorway

31 Decontamination of metalliferous mining spoil Laboratory-scale R&D

on “bioleaching” ofheavy metals

Mine spoil (metals) Former metallif

U.K.

35 In situ soil vapor extraction within

containment cells combined with ex situbioremediation and groundwater treatment

Biopile (part of a fullscale integratedapproach)

Screened and “vented” soil (variousorganinc and inorganic contaminants)

Derwenthaugh Ccontamination, metals)

36 Enhancement techniques for ex situ separation

processes, particularly with regard to fineparticles

Laboratory-scalebioreactors (part of apilot-scale treatmenttrain)

Soil slurries from a dieselcontaminated soil, and a gasworks soil

Unspecified U.K

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Project Technology Type Input Material for Treatment S

43 Multi-vendor bioremediation technology

demonstration project

Biopile (full-scale) Soil contaminated with chlorinated and

non-chlorinated solvents

Sweden 3-ChapYork, USA, an waste disposal a

49 Characterization of residual contaminants in

bioremediated soil and reuse of bioremediatedsoil

Laboratory-scale R&D Soils treated at a full-scale ex situ

biological treatment plant, variousresidual contaminants tested for.

Unspecified loc

54 Treatment of PAH- and PCP-contaminated soil

in slurry phase bioreactors

Bioreactor (pilot-scale) Soil (PAHs, PCP) A closed wood 

contaminated), contaminated), 

Table 6.3: Outline of Treatment Processes By Project

Project Process Outline (see Project Summary for further Information)

6 In situ/on-site bioremediation

of industrial soilcontaminated with organicpollutants: elimination of soiltoxicity with DARAMEND®

The technology is a proprietary system: DARAMEND® bioremediation. It is targeted at a range 

including aliphatic and aromatic hydrocarbons, chlorinated phenols, and phthalates. The test results rfocused on PAH and PCP in the range of 1,000s and 100s of mg/kg. The treatment is based amendment. Its composition varies from site to site depending on soil analyses. The amendments arand increase the water holding capacity of the soil. They include slow-release nutrients and surfacwith the claimed effects of reducing their toxicity to microbial activity and also increasing their Soil amendments are introduced at 1-5% by weight using conventional agricultural equipment followFor “ex situ” application, soil or sediment to be treated is transported to the treatment area and hom

power take-off driven rotary tiller. During the remediation process, soil moisture content is maintainwith drip irrigation. The DARAMEND® amendment is also cultivated directly into to the surface 

which is termed an “in situ” application. Pilot Study reports also suggest its use in biopile applicati

the amendments could also be applied in windrow and solid-phase bioreactor systems.

8 Biodegradation/bioventing of

oil-contaminated soils

Biogénie has developed a biopile-based, ex situ bioremediation technique whereby soil is heaped in 

on an asphalt pad with drainage collection, and supplied with oxygen, moisture, and nutrients to enprocesses. The test results center on soils contaminated with oil and grease in the range of 104 

discussed the use of biofilters for emissions control from the process (see project summary). Since Study the company has also carried out a large number of commercial remediation projects. Results were presented in 1996, total tonnage nearly 400,000 tonnes. On the basis of these projects, the codegradations of 75% for mineral oil and grease; 99% for BTEX; 95% for PCP; 90% for total naphthalene.

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Project Process Outline (see Project Summary for further Information)

11 On-site biological degradation

of PAHs in soil at formergasworks site

Windrow-based treatments were tested for their ability to reduce PAH concentrations at pilot-scale (

and microcosm studies on <4-mm fraction. The soil was screened at 80 mm. The tests were containing total PAH at about 400 mg-kg-1. After mixing soil was spilt into test windrows. W

amendments (wood chips, compost, none) and the impact of adding nutrients (N, P, K) and Ca examined.

15 Combined chemical and

microbiological treatment ofcoking sites/bioremediation ofsoils from coal and petroleumtar distillation plants

Investigations encompassed the use of bioreactors and biopiles at pilot-scale to treat PAH & hydro(103 mg/kg. Biopiles were made of contaminated soil/wastes mixed with organic amendments (stra

ted soil). The effect of adding oxidizing agents (hydrogen peroxide, sodium hypochlorite, anconstruction was also evaluated.

24 Combined remediation

technique for soil containingorganic contaminants: Fortec

Fortec® consists of three unit operations combined in series: multi-step hydrocyclone separation

photochemical pretreatment, and slurry-phase bioremediation. It deals with more recalcitrant contamcommon soil washing residual). The photo-chemical oxidation is designed to transform recalcitranmore readily biodegradable compounds. The bioreactor is slurry based and operates at mesophilic Mixing is achieved by slurry recirculation and reactor operates on a batch-wise process, residereactor has been tested at up to 300 m3 as part of an integrated soil washing process. Testing has 

contaminated with diesel oil and PAH.

25 Slurry reactor for soil

treatment

This project treats excavated clay soils and sediments contaminated with organic compounds, such The treatment technology described is the Slurry Decontamination Process (SDP), which combines a microbiological slurry reactor. The bioreactor is used to treat a <4 mm fraction produced by remgrinding, and sieving. The basic bioreactor configuration has been tested up to 4 m3. The pr

bioreactors. A key aspect of the configuration is the triangular base and the turbulent flow producmaintain the soil particles in suspension, mix and grade them by particle size. Coarse particlbioreactor. Subsequent bioreactors treat the finer fractions and the more recalcitrant contaminaremaining in solution or suspension. Testing has focused on mineral oils and PAHs.

26 Treatment of creosotecontaminated soil (soil

washing and slurry phasebioreactor)

This project is an investigation into the remediation of three and four ring PAHs contaminated combines soil washing (especially froth flotation) with slurry-phase bioremediation. The project treatability studies and pilot-scale remediation trials. Bioslurry testing was carried out initially at 454 L, using fines slurry from froth flotation in a tonne/hour soil washing plant. PAH degradation w

28 Use of white-rot fungi for

bioremediation of creosotecontaminated soil

Laboratory-scale testing was carried out to determine the potential of white and brown rot fungi from an abandoned wood preservation site contaminated with creosote. Testing consisted of screefungal types for their capacity to degrade PAH and determine their requirements for optimal demesophilic temperatures (20°C), such ase lignin-rich substrates. Subsequently, 60-L batches were due in 1995/96 has been delayed.

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Project Process Outline (see Project Summary for further Information)

31 Decontamination of

metalliferous mining spoil

This project investigated a variety of treatments for dealing with metalliferous mining wastes. centered on ferric bacterial leaching (Thiobacillus spp) of metals from metalliferous mine tailings residue from MGS (a particle separation process exploiting density—see Chapter 5). The investigaboth the potential of “bioleaching” as a treatment, and as a factor causing the release of metals frothe environment. Investigations were carried out at bench-scale.

35 In situ soil vapor extraction

within containment cellscombined with ex situbioremediation andgroundwater treatment

Investigation of the former Derwenthaugh Cokeworks site identified an area of 7.9 ha that was swith coal carbonization wastes from the original plant including BTEX, PAHs, phenols, heavy mremedial scheme involved four stages: (1) Installation of a cut-off wall to protect the adjacent river to allow safe excavation (to a depth of 5 m) of the contaminated ground; (2) Installation of weExtraction (DVE) to remove VOCs and free phase product; (3) Use of wells to abstract contaminatetreatment; and (4) Excavation and biological treatment of contaminated ground. A biopile technique m3 of material in four batches using continuous forced aeration over 2-3 months. All material was 

oversize being crushed and then re-used on site if found acceptable.

36 Enhancement techniques for

ex situ separation processes,particularly with regard tofine particles

Laboratory-scale, slurry-phase bioreactors (10-L) were used to test the potential for biodegradfractions of soil from a gasworks site and from a site contaminated by diesel (locations not reveproduced from a pilot-scale soil washing plant and had been stored briefly prior to testing. contaminated soil were tested: 0.002-0.01 mm and <0.002 mm. One fraction of gasworks soil was periods were 10-14 days, and the bioreactor operated at mesophilic temperatures (15°C or 25°Camendments was also evaluated.

43 Multi-vendor bioremediation

technology demonstrationproject

The biopile treatment investigated was one of three technologies investigated at field-scale at the The other two were in situ approaches and are discussed in Chapter 4. The site is an abandoned 

area containing very high concentrations of chlorinated and non-chlorinated solvents sutetrachloroethene, 2-butanone (MEK) and toluene. Materials were tested at pilot-scale (76 m3 bio

continuous forced aeration was tested. Irrigation was via a sprinkler system.

49 Characterization of residual

contaminants inbioremediated soil and reuseof bioremediated soil

Mineral oil products are major pollutants found at contaminated sites in Switzerland. Certain residusoils contaminated with oil products have been bioremediated. The emission levels to be experemediated soil were estimated in laboratory and field tests. The remediated soil material used for aminor oil spills (primarily involving EL heating oil) and was combined before being sent as a singtion plant. The contaminant content in the fine material (<2 mm) was 780 mg (TSEM) and 430 mrelated to the dry content of the sample. The PAH content (according to EPA) was below 2.8 mg/subsequently. The project was subdivided into the following operational stages: (1) physical and chthe residual contaminants; (2) environmental behavior of the residual contaminants; (3) effects of on the environment; and (4) evaluation of the environmental acceptability by means of a risk assess

54 Treatment of PAH- and PCPcontaminated soil in slurry

phase bioreactors

Eko Tec has carried out several full-scale remedial actions at contaminated sites across Sweden. Tintended use of these reactors to treat 3,000 metric tons of creosote-contaminated soil containing 1and 100 metric tons soil contaminated with 500-1,000 mg/kg PCP. Small-scale bioreactors were usem3 of each contaminated soil. Pilot-scale testing was scheduled for 1996/97 but results have not yet 

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6.5 PERFORMANCE RESULTS

6.5.1 Project 6: In Situ/On-Site Bioremediation of Soils Contaminated with Organic

Pollutants: Elimination of Soil Toxicity with DARAMEND®

A 216-m2 test plot and a 12-m2 control plot were compared using ex situ treatment beds (Table 6.3).

Total PAH removal was in excess of 90%, and total chlorophenol removal was just below 90% using

the DARAMEND® technology (55). These removals were about double the removals found for the

control plot, which was left unattended over the treatment period (254 days). Removals for individual

PAH and chlorophenol compounds showed some variation, (from 41% to 98%). Higher-ring PAH

compounds were more recalcitrant. Tests of toxicity to earthworms and seeding emergence also indicated

amelioration through treatment. Total petroleum hydrocarbon (TPH) removal in the test plot was 87%.

Interestingly, a zero value for the TPH removal was recorded for the control plot, despite the reported

removals of PAHs and chlorophenols. The fate of compounds was not reported (e.g., disappearance into

humic materials versus degradation). The vendor has provided further case study information where

similar treatment performances were achieved.

6.5.2 Project 8: Biodegradation/Bioventing of Oil-Contaminated Soils

Field tests at Boucherville and Jonquiere reported total hydrocarbon removals of around 70%. The

contractor, Biogenie, also presented summary data from 25 practical remediation projects. The

cumulative amount of material treated was around 400,000 “tons.” (Note the exact unit of measurement

was not specified). These case studies are listed in Table 6.4. Biogenie reports average removal

efficiency for a variety of contaminant classes: mineral oil and grease, 75%; benzene, toluene,

ethylbenzene, and xylenes (BTEX), 99%; PCP, 95%; and total PAHs, 90%, with 99% removal for

naphthalene.

Table 6.4: Biogenie Case Studies

Type of Site Number of Sites Amount of Material

Treated (tons1

)

Gas station (decommissioning and underground

storage tank replacement)

8 174,800

Former diesel power station 5 78,200

Manufactured gas plant 1 75,000

Refinery 2 40,500

Former petroleum depot 3 10,000

Industrial yard and waste lagoon 2 7,000

Others (railroad yard, electrical substation, etc.) 4 4,700

TOTAL: 25 390,200

1 The original reports do not specify whether “tons” refers to metric tons (tonnes), U.S. short tons

(2,000 lbs), or Imperial long tons (2,240 lbs).

Aging has been suggested as a major factor in reducing the degradability of mineral oil and grease.

Some projects were halted as soon as regulatory criteria were met. Pile temperatures may be on the order

of 50°C, so some loss of organics through volatilization will take place. However, based on the tests at

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Jonquiere, Biogenie believes that more than 99% of contaminant removal is due to degradation. No other

information on fate of compounds was reported. Field-scale performance tends to be less than the

potential treatment performance based on bench-scale test work. This indicates some potential for further

optimization of the full scale treatment. The trade-off is whether such optimization is achievable at a

reasonable cost and within a reasonable treatment duration.

6.5.3 Project 11: On-Site Biological Degradation of PAHs in Soil at a Former Gasworks

Site

Ten turned-windrow configurations were tested (Table 6.5), and the authors compared: “ordinary”

sampling with analysis shortly after sampling; freeze drying for sample preservation; and freezing of

samples for sample preservation.

Table 6.5: Project 11 Treatments

Windrow 1 Amount of soil

(m3

)

Aeration2 Treatment at

initiation of test

Treatment in the test

period

IG Control 33 - -

Addition, as required,

of:

- NPK fertilizer

- calcium nitrate

- water

IB Control 21 - -

2G 19 Turning + 11 m3 wood chips

2B 19 Aeration + 11 m3 wood chips

3G 20 Turning + 10 m3 compost

3B 20 Aeration + 10 m3 compost

4G 32 Turning + detergent solution

Addition of detergent

solution to windrows

4G and 4B

4B 32 Turning + detergent solution

5G 33 Turning -

5B 36 Turning -

Notes:

1 (1G-5G): Windrows located outside.

(1B-5B): Windrows located inside. 2 Aeration by turning of soil with excavator (a total of 10 times during the test period).

Aeration via air drains in the bottom of the windrow from where air is drawn (around 50 m3/hour). 3 A 5% detergent solution was added three times during the test period. A total of 1.6 g of detergent/kg of

soil was added to test windrow 4G, and 2.6 g of detergent/kg of soil was added to test windrow 4B.

The sample preservation route had a strong impact on reported findings. For freeze-dried samples no

significant differences between PAH removal for the different treatments were found. However, some

differences were found for analyses of ordinary samples. Significant degradation (at the 5% level)

compared with the starting concentration was found for both indoor and outdoor control batches, and

for batches that had detergent addition and were turned. In addition, the indoor batch with turning but

not detergent addition also showed significant total PAH removal. The remaining piles, including piles

with compost addition (turned or otherwise), showed no significant decrease in total PAH concentration.

It appears that turning is beneficial except that the control batches that were not turned also showed

significant decreases in total PAH concentration. This study shows the difficulties in interpreting

biodegradation data. The data are strongly affected by the sample preservation and subsequent analytical

approach. Furthermore, results vary greatly for individual PAHs. The authors suggest that bioavailability

was a limiting factor for PAH removal and was affected by aging and sorption of the PAH to soil

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surfaces. It may also be that the relatively low initial levels of PAH in the soil (400 mg/kg in total)

affected treatment performance, although this is not suggested by the authors. The low initial

concentration may have meant a much smaller pool of available degradable PAHs, and hence a much

slower initiation of biological action.

6.5.4 Project 15: Bioremediation of Soils from Coal and Petroleum Tar Distillation Plants

Biopiles and recirculating bioreactors were used to screen 14 fungal and biological isolates. However,

no detailed results were provided for this project.

6.5.5 Project 24: Combined Remediation Technique for Soil Containing Organic

Contaminants: Fortec

The process concept uses a hydrocyclone treatment to separate the sandy fraction from finer soil grains.

The fines are then treated biologically in a batch mode slurry reactor (3% solids) with a retention time

of 3-20 days. The test work investigated whether a photochemical treatment of the hydrocyclone-treated

soil before biological treatment led to further reductions in residual contaminant concentrations in the

treated residues. The photochemical pretreatment consisted of ultraviolet (UV) irradiation and addition

of hydrogen peroxide.

The pilot-scale reactor had a capacity of 25 m3

, and its contents were mixed by air sparging and slurry

pumping. The initial charge of biomass was 1 m3 of activated sludge from sewage treatment. Subsequent

batches were seeded with recycled biomass from earlier runs. Reactor effluent was recycled to a process

water “buffer.” Nitrogen and phosphorus amendments were made during processing, based on initial

contaminant loadings. Processes were carried out at ambient temperatures (10-16°C).

Tests on mineral oil contaminated soil (input loadings 400-5,000 mg/kg) set a target residual concentration of 100 mg/kg. Treatment times to reach this target were found to be in the range 3-8 days. The

sandy fractions separated by hydrocyclone treatment generally contained less than 50 mg/kg mineral oil.

No detectable benefit of photochemical pretreatment was found.

Tests on PAH-contaminated soil (input loading 30 mg/kg) used target residual concentrations of 1 mg/kg

and 20 mg/kg. Only slight PAH removal from the fines fraction took place in the absence of photochemical pretreatment. With pretreatment, PAH levels decreased to around 5-10 mg/kg after 15 days

treatment in the bioslurry reactor. If the fines fraction and sandy fraction were recombined, final residual

PAH concentrations would be in the order of 2-4 mg/kg, which is lower than 20 mg/kg and close to 1

mg/kg. The accumulation of organic effluents in the process effluent was not severe.

Further studies on high molecular weight PAH compounds concluded that degradation rates were limited

by contaminant bioavailability, which decreased due to strong adsorption of these compounds to organic

matter in the soil. The photochemical pretreatment appeared to act as a mechanism for destroying the

soil organic matter and increasing contaminant bioavailability. Comparative results showed that

pretreatment significantly increased slurry phase biological degradation of PAH compounds. Sixty-nine

percent of the PAH compounds were degraded after 12 days for the pretreated sample compared with

26% for the sample without photochemical pretreatment. It was concluded by the authors that

photochemical destruction of soil organic matter enhances subsequent degradation but the technique

would be limited to soils with a naturally low soil organic matter content (tests of the 300-m3 reactor

were not reported in detail).

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Tests on β-HCH (lindane), including chemical pretreatment, resulted in no biological degradation of the

contaminant. It was concluded that the chemical stability of β-HCH was too high for this combined

process.

6.5.6 Project 25: Slurry Reactor for Soil Treatment

Pilot-scale tests (1 m3

) were conducted, and removal rates of 95% for oil contamination (Petroleumhaven

clay soil) and 90% for total PAH (Mijdrecht sediment) were achieved in under two weeks. Starting

concentrations were 800 mg/kg and 300-400 mg/kg respectively. A lower removal of oil contamination

was found for the Mijdrecht sediment (80%). Process losses to volatilization were checked using capture

of VOCs in filters and found to account for 1% or less of contaminant removals.

6.5.7 Project 26: Treatment of Creosote-Contaminated Soil (Soil Washing and Slurry

Phase Bioreactors)

Bench-scale tests indicated that:

• PAH degrading organisms could be isolated from the creosote contaminated soil, and under optimal

culture conditions, 94% of PAHs was degraded in 7 days (after acclimation); and

• PAHs could be concentrated by froth flotation.

Pilot-scale test work using a 454-L bioslurry reactor examined the treatment of PAH concentrates from

froth flotation. Process optimization was carried out for biostimulation using nutrient (nitrogen and

phosphorous) addition, pH amendment, aeration, addition of surfactants and temperature control. Tests

were carried out on five 600-L batches from two clay-rich soils of solids content 14-20%. These initial

tests resulted in 97% PAH removal—better than the bench-scale finding. Residual PAH concentrations

were 71-200 mg/kg, from starting concentrations of 480-6,000 mg/kg. The removal of PAHs was found

to correspond with oxygen uptake indicating that aerobic biodegradation had taken place. Addition of

commercially available inocula was not found to be necessary at pilot-scale.

6.5.8 Project 28: Use of White-Rot Fungi for Bioremediation of Creosote-Contaminated

Soil

Screening tests were conducted using the white-rot fungi Pleurotus ostreatus and Trametes versicolor

and the brown-rot fungus Lentinus leptinus. The tests were used to evaluate different lignin substrates,

such as wheat straw, wood chips (birch or pine), and newspaper, and to determine the influence of pH,

aeration, and addition of compost. Tests were carried out either on petri dishes or in 1-L Erlenmeyer

flasks. Following these tests, Pleurotus ostreatus was investigated further using wheat straw as the lignin

substrate.

Contaminated soils were incubated with straw and fungus for 8 weeks at 20o

C. A range of supplements

was added (peat, compost, potato pulp). Degradation performance was dependent upon the number of

aromatic rings in each PAH compound ranging from up to 70% degradation for 3-ring PAHs to less than

35% for 5-ringed PAHs.

Further bench studies (using 60-L batches) investigated the impact on degradation of indigenous

microbial populations as a pretreatment, followed by fungal inoculation. The pre-inoculation incubation

period was two months. After inoculation, samples were incubated for a further three months. Samples

incubated with bark prior to fungal inoculation were found to show the greatest PAH degradation. This

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benefit was reduced if fertilizer was also added during the pre-inoculation incubation period. Degradation

of PAH was greater at 20°C than at 8°C; however, the benefit of preliminary incubation with bark was

greater for the lower temperature. Compared with controls, degradation of PAHs, but not heterocyclic

compounds, was enhanced by the fungal inoculation.

Radiolabelling of the PAH compounds was used to enable tracing of treatment metabolites to be

conducted. These produced the contradictory findings that no accumulation of intermediate metabolites

was detected, yet mineralization rates were low.

6.5.9 Project 31: Decontamination of Metalliferous Mining Spoil

Biological leaching due to microbial generation of sulfuric acid from sulfide was investigated for a

highly oxidized sandy spoil (Frongoch); fine particle size sulfitic material (Y Fan); and high metals

content tailings (Cwmerfyn). Ten-gram samples were subjected to a standard bioleaching test (from the

Canadian Centre for Mineral and Energy Research) which was not described. Aliquots were tested of

untreated material (“head”); residues remaining after soil washing (as described in Chapter 4); and a

heat-treated aliquot (500°C for 18 hours) intended to simulate oxidation through weathering in the long

term. The residues remaining after soil washing tended to have a lowered content of lead, zinc,

cadmium, and sulfur.

Heat-treated samples showed higher zinc leaching than untreated samples. In all cases, the initial rate

of bioleaching of zinc was high but then declined. The authors concluded that bioleaching can lead to

significant movement of zinc from the solid to the aqueous phase. In regards to using bioleaching as a

treatment, the authors concluded that it would be ineffective for lead. Lead would be rapidly precipitated

as sulfate and hence remain in the solid phase. It was also regarded as less suitable than chemical

leaching for zinc removal. However, bioleaching may have a significant environmental impact for zinc

spoils, even if reprocessed, in cases where iron sulfide is also present and conditions are aerobic.

6.5.10 Project 35: Combined In Situ Soil Vapor Extraction within Containment Cells

Combined with Ex Situ Bioremediation and Groundwater Treatment

Initial laboratory-scale studies discounted the need for using inocula in the proposed biopile system.

Nutrient addition and aeration were found to enhance biodegradation at this scale. However, at full-scale,

attempts to reproduce optimization through nutrient addition were not found to be cost effective.

Following the main works, it was noted that the main factors affecting the degradation process were

aeration and ambient temperature. Attempts to replicate the laboratory conditions indicated as beneficial

showed no cost benefits at full-scale. Significant reductions in the contaminant levels were achieved

through redistribution and volatilization. Often these processes alone were enough to achieve the

specified criteria, with no further action required. A key contribution to success is careful management

of material batches and the screening of materials before placement in the biopiles. Treatment targets

were set by the local regulatory authorities to allow reuse of the treated material onsite. No additional

information on removal rates was reported.

6.5.11 Project 36: Investigation of Enhancement Techniques for Ex Situ Separation

Processes, Particularly with Regard to Fine Particles

Bench-scale (10 L) bioreactor degradation of organic contaminants produced from a pilot-scale soil

washing plant was investigated. Soil washing treatment residues for a gasworks soil and a diesel

contaminated soil were tested.

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For the gasworks soil, the <0.063 mm fraction was tested. Management of pH was difficult, with large

decreases in the first 4 days of operation requiring correction. In addition, CO2 was consumed by the

process over this period of time. The authors believe this was due to the stimulation of chemolithotropic

organisms, such as Thiobacillus, metabolizing sulfide compounds in the gasworks material. Three

bioreactor tests were carried out: one at 12°C, one at 12°C with added nitrogen (N) and phosphorous

(P), 25°C operation with added N and P. The best performance came from the 25°C treatment, but still

only 40-50% of PAHs and 20% of TPH were removed after 28 days. There was no indication of cyanide

degradation. It was suggested that the initial problems with acidification reduced the potential for PAH

degradation.

Greater success was achieved for the diesel-contaminated soil. The size fractions 0.002-0.01 mm and

<0.002 mm were treated. (Note that the performance of the soil washing stages is discussed in Chapter

4). A single test of degradation in a bioreactor at 15°C with no additives was carried out for the 0.002-

0.01 mm fraction. Three tests were carried out for the <0.002 mm fraction: 15°C no additions; 15°C plus

N and P, 25°C plus N and P. Two flushes of activity were noted for the <0.002 fractions tested, the first

over the initial three days of treatment, and a second less intense flush some 8 to 10 days later. The

authors postulated that during the first flush microorganisms degraded readily available substrates, and

then a period of acclimation took place to deal with more complex substrates, resulting in the second

flush of activity (as measured by CO2 release). The size of the flush was enhanced by both temperature

and nutrient addition. Similar removal rates for TPH (80%) were observed for both the 15°C and 25°C

treatments with N and P addition. The removal rate for the 15°C treatment was around 20% without

nutrient addition, similar to the removal rate found for the <0.002 to 0.01 mm fraction, which was also

tested at 15°C without nutrient addition. The duration of all four tests was 28 days.

6.5.12 Project 43: Multi-Vendor Bioremediation Technology Demonstration Project

Aeration of two 76-m3 test piles (Table 6.3) was found to be difficult because of the fine texture of the

soil being treated. Average removal percentages of VOCs by the biopile technologies ranged from 43-

99%, depending on the compound.

Soil clean-up goals were set by the New York State Department of Environmental Conservation for six

VOCs: acetone, 200; methyl ethyl ketone (MEK), 600; methyl isobutyl ketone (MIBK), 2,000; PCE,

2,500; trichloroethene (TCE), 1,500; and dichloroethene (DCE), 600 μg/kg. Ninety percent of the tested

samples were to meet these targets to achieve compliance (success) in the test.

Only 79% of the samples from the biopile treatment met these limits, so on these grounds it was deemed

unsuccessful. Stripping and volatilization accounted for some of the VOC removal. The treatment

duration was nine months. The aeration used was negative forced aeration (i.e., air was sucked through

the piles). Evidence from conventional composting technology is that negative aeration tends to be less

effective for process optimization, especially for finely-textured materials such as sewage sludges (52).

However, positive aeration would require containment of the process to prevent the release of VOCs.

6.5.13 Project 49: Characterization of Residual Contaminants in Bioremediated Soil and

Reuse of Bioremediated Soil

The availability of residual contaminants remaining after biological treatment was tested by leaching

tests. Biodegradability studies and bioassays of the residues’ toxicity were also performed. The nature

of the treatment process was not specified, only that it was a commercial treatment plant, presumably

ex situ and offsite. Dissolved organic carbon levels in the leachate of the treated soil were comparable

to those from gravel. The residual organic contaminant levels, while detectable, were found to be only

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slowly leachable and only slowly biodegradable. Only around 10% degradation was observed over a twoyear period. No negative impact was found on the growth yield for a number of plant species compared

with controls in growth trials. Indeed, a significant enhancement was reported. Patterns of plant growth

were normal. Ecotoxicity tests (using Daphnia and Vibrio ficheri) did not detect significant toxicity from

soil leachates. A qualitative risk assessment based on the experimental findings concluded only a low

possibility of adverse effects on human health and the environment from residual contaminants in the

treated soil.

6.5.14 Project 54: Treatment of PAH- and PCP-Contaminated Soil in Slurry Phase

Bioreactors

A trial using a 1-m3 Eko Tec bioreactor over 28 days was carried out at 24-28°C. Biostimulation and

bioaugmentation were conducted. Input material was screened at 2-3 mm, and the total PAH concentration was 859 mg/kg. The residual concentration after treatment was 75 mg/kg. In a second trial, the Eko

Tec bioreactor was evaluated in parallel with a 450-L EIMCO reactor. In this case, concentrations of

total PAHs were 313 mg/kg and 164 mg/kg, respectively. Both bioreactors yielded total PAH levels of

48 mg/kg after 28 days. Emissions of VOCs were found to be negligible. Eko Tec also reported a PCP

treatment trial, using soil with an initial PCP level of 630 mg/kg. Redox conditions were varied from

anaerobic to aerobic over a 6-week period. The exact nature of the process was not described. The PCP

level after treatment was reported to be 80 mg/kg. An unspecified composting treatment was also found

to reduce PCP levels over a 4-month period, with initial and treated concentrations of 126 mg/kg and

75 mg/kg, respectively. The full-scale process will be included in the Phase III Pilot Study.

6.6 GENERAL DISCUSSION OF PROJECTS

The general level and quality of information provided in a number of projects is inadequate to support

a detailed discussion. However, the following points were worthy of note.

Ex situ biological treatments, with the possible exception of bioslurry reactors, are rapidly becoming

established technologies for contaminated solids. The number of full-scale demonstrations and commercial projects has increased for several of the treatment approaches included in the Pilot Study, in

particular for biopile and cultivation-based approaches. These approaches appear to be robust and

relatively simple treatments for organic contaminants including simple alkanes and aromatics, as well

as for more recalcitrant compounds such as 3- and 4-ringed PAHs and PCP. However, this is not a uniform picture. Biological treatments may fail to reach desired targets, even where there are good

experimental reasons to believe that they should succeed. The reasons for this often appear to be

associated with the texture of the contaminated medium, its organic matter content, and its age (Section

6.8).

While it is hard to make a generalization, it does appear that the technical “know-how” of the

remediation contractor is also a key factor to success. The likelihood of success for solid phase

treatments appears to be related to the “ingredients” in the mix of materials used, and to relatively

simple process changes. Examples of these simple changes include how to improve porosity for finegrained soils, how to improve activity for low initial concentration or for aged contaminants, and how

best to optimize the flow of air and water.

One issue that is well-known in waste composting but has been little reported in biopile projects is that

of “edge effects.” Materials at the edge of a static pile or treatment bed may be affected by greater

variations in process conditions such as temperature, moisture, or nutrient supply, but conversely have

better access to oxygen. The significance of edge effects is that treatment effectiveness depends on

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where the contaminated material is in the pile, bed or windrow. The idea of zones of activity is

recognized in composting (22, 52) as a particular problem for static systems. As a result, turning is

commonly employed for windrows, for actively aerated “piles,” and in-vessel to ensure that edge effects

have no lasting impact on overall treatment effectiveness and to reduce heterogeneity of the treated

product through mixing.

Bioslurry reactors have not seen widespread adoption at a practical scale. However, treatment in

bioslurry reactors, as indicated by some of the Pilot Study projects, may extend the range of biologically

treatable contaminants, for example to include higher PAHs. However, this technology is also more

expensive and creates a need for dewatering of the treated product and, as a result, process water

handling. One application where bioslurry reactors may have a competitive edge is in situations where

a material is already in a liquid or semi-liquid form. Examples examined by Pilot Study projects are

treatment concentrates from soil washing.

The majority, if not all of practical ex situ biological treatments, rely on biodegradation processes

mediated by bacteria—mostly as a direct carbon source for microbial growth. Fungal lignolytic activity

has long been recognized as a possible means of extending the range of biologically treatable contaminants, to more insoluble and recalcitrant compounds (Section 6.2.2). Of course, many such contaminants

may be biodegradable ultimately by bacteria, but the lignolytic attack mediated by nonspecific enzymes

and free radicals may be faster. It may be conjectured that fungi may offer the opportunity to extend the

range of contaminants treatable in simple solid phase systems, to include those currently regarded as

being practically biodegradable only in bioslurry reactors.

As a final comment, there appear to be two sets of competing factors that fundamentally determine the

effectiveness of an ex situ biological treatment:

• The competing needs to use pore space for air and water movement, discussed below in the context

of forward and reversed aeration, but also evident in trying to supply solutions (e.g., of nutrients or

detergents) at the same time as supplying air; and

• The need to mobilize and render contamination available to facilitate biodegradation (which typically

means moving it to gaseous or liquid phase), versus the need to limit process emissions of

contaminants in vented air or in leachate.

6.7 RESIDUALS AND EMISSIONS

Residuals and emissions generated from the projects are summarized by project in Table 6.6. Whether

collected or left to disperse, gaseous and aqueous phase emissions are likely for any biological treatment

(ex situ or in situ) based on biodegradation. Gaseous emissions in process air or that leave the surface

of treatment beds or windrows comprise VOCs that are stripped and not biodegraded. Forced aeration

tends to increase the amount of VOCs stripped and volatilized. The amount of VOCs lost to volatilization is dependent on the nature of the contamination. Amounts recorded for semivolatiles such as PAHs

were low, but were high for solvents.

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NATO/CCMS Phase II Pilot Study Final Report Final Report

Table 6.6: Residuals and Emissions

Project Comments on Residuals and Emissions

6 In situ/on-site bioremediation of industrial soil

contaminated with organic pollutants

No leachate generation was recorded. Oversize

screenings were the main process residue.

8 Biodegradation/bioventing of oil-contaminated

soils

Leachate is reportedly recirculated to irrigate the

biopile, but no information on generation rates was

provided. Vented air is treated by a biofilter card,

which apparently removes 85% of the VOC’s passing

through it. Oversize rejects may also be a significant

process residual.

11 On-site biological degradation of PAHs in soil

at a former gasworks site

Pilot trial. No practical information reported.

15 Combined chemical and micro-biological

treatment of coking sites

Not reported.

24 Combined remediation technique for soil

containing organic contaminants: Fortec

Process and dewatering effluent not recycled elsewhere

in the soil washing plant may be a significant

emission. (For residues from the washing stage see

Chapter 4.)

25 Slurry reactor for soil treatment Process effluent and water from solids removal that are

not recycled, oversize reject material, and process air

emissions.

26 Treatment of creosote-contaminated soil (soil

washing and slurry phase bioreactor)

Process effluent and water from solids removal that are

not recycled, process air emissions. (For residues from

the washing stage see Chapter 4.)

28 Use of white-rot fungi for bioremediation of

creosote-contaminated soil

Not applicable.

31 Decontamination of metalliferous mining spoil See comments in text.

35 in situ SVE within containment cells combined

with ex situ bioremediation and groundwater

treatment

For the biopile process, vented air (significant VOC

removals due to volatilization were reported) and

leachate.

36 Enhancement techniques for ex situ separation

processes, particularly with regard to fine

particles

Presumably bioreactor and dewatering effluent.

Presumably bioreactor process air.

43 Multi-vendor bioremediation technology

demonstration project

VOCs in process air emissions.

49 Characterization of residual contaminants in

bioremediated soil and reuse of bioremediated

soil

Not applicable.

54 Treatment of PAH- and PCP-contaminated soil

in slurry phase bioreactors

Screened oversize (>2-3 mm) and presumably excess

water from bioreactor and dewatering operations.

Not all of the biopile or bioreactor studies reported here record the steps being taken to treat process air.

Reversed aeration (suction) is a common approach to ensuring that process air from aeration of biopiles

can be collected; for example for subsequent treatment in a biofilter (e.g., a peat bed). Reversed aeration

is not, however, optimal for enhancing the degradation process, particularly as particle size decreases.

A recognized effect of reversed aeration in waste composting (22) is that the pile retains a higher

moisture content and that moisture is drawn to the center of the pile to points of suction. This effectively

clogs the system’s air supply, reducing the amount of air that can be delivered to the system.

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NATO/CCMS Phase II Pilot Study Final Report Final Report

Steps to contain process water and leachate containment were reported for many trials. However,

treatment of the process water was not typically described, but presumably relied on capture and

recirculation.

Most biological processes are intended to destroy contaminants rather than collect them in a solid waste

residual. Nonetheless, residual contaminants are commonly detected in treated soils after processing. It

appears from Project 49, which deals with residuals from biological treatment, that such residuals can

be effectively inert, at least in terms of risk management. However, that should not be taken as a blanket

assumption.

The most common solid process residue is over-size material after screening prior to biological

treatment. While this may not be important for an approach integrated with, for example, a soil washing

plant, it could lead to large volumes of solid residues for approaches centered on a biological treatment

such as a biopile. One possibility is to crush such materials and incorporate them in the biopile if testing

indicates they require treatment.

6.8 FACTORS AND LIMITATIONS TO CONSIDER FOR DETERMINING THE APPLICABILITY

OF THE TECHNOLOGY

The majority of ex situ treatment technologies with established track records are relatively simple to

apply and relatively robust in the hands of an experienced operator. Table 6.7 lists key factors and

limitations found for the various projects discussed in this chapter including:

• Biodegradability and bioavailability (which may be linked to the age and initial concentrations of

the contaminants as well as the sorptive capacities of the solid matrix);

• Dewatering and water handling for slurry-based processes;

• Dealing with edge effects and heterogeneity and ensuring adequate process control (e.g., air and

water supply) for solid-phase technologies;

• The texture of the treated material (content of fine particles); and

• The distribution of contaminants by particle size for slurry-based systems.

Two other interesting observations were made:

(1) Project 36 postulated that interactions between different biological processes could limit the success

of slurry-phase treatment of soil at gasworks sites. It was also suggested that sulfide oxidation

leading to changes in slurry pH might have limited subsequent biodegradation of PAHs.

(2) Based on the results of several of the Pilot Study projects, laboratory-, bench-, and pilot-scale tests

do not always predict the performance of full-scale treatment.

In the absence of an adequate fundamental understanding, know-how appears to be a key factor in

process prediction: both in interpreting test data, and in knowing which tests to carry out. This comment

links back to the earlier comment that in general treatment performance may be linked to empirical

operational expertise of the practitioner.

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NATO/CCMS Phase II Pilot Study Final Report Final Report

Table 6.7: Key Factors Limiting Performance

Project Comments on Factors Limiting Performance

6 In situ/on-site bioremediation of

industrial soil contaminated with

organic pollutants: elimination of

soil toxicity with DARAMEND®

• Proportion of more recalcitrant organics (e.g., higher PAHs).

• Ambient conditions and their impact on possible leachate generation.

• Maximum treatment depth (in situ application) of 0.6 m.

• Proportion of oversize material.

8 Biodegradation/bioventing of oilcontaminated soils• Biodegradability/availability.

• Proportion of oversize material.

• Temperature, although piles can be air heated.

• Soil texture. Heavier soils are harder to treat, which increases costs

because of their more difficult materials handling properties and

often extended treatment time.

11 On-site biological degradation of

PAHs in soil at a former

gasworks site

• Aging, which was thought to have reduced the biological treatability

of the PAHs, along with sorption to soil particles.

• Turning the windrows?

• Initial concentration of PAHs? (related to aging factor).

15 Combined chemical and

microbiological treatment of

coking sites

No relevant information provided.

24 Combined remediation technique

for soil containing organic

contaminants: Fortec

• Contaminant distribution by particle size.

• Biodegradability/treatability by photooxidation.

• Soil composition (texture and organic matter content).

25 Slurry reactor for soil treatment • Contaminant distribution by particle size.

• Contaminant bioavailability and biodegradability.

26 Treatment of creosotecontaminated soil (soil washing

and slurry phase bioreactor)

• Presumably contaminant distribution by particle size.

• Contaminant bioavailability and biodegradability.

• Optimization of the biodegradation process in the reactor.

28 Use of white-rot fungi for

bioremediation of creosotecontaminated soil

No relevant information provided.

31 Decontamination of metalliferous

mining spoil

Bioleaching was not recommended as a treatment option.

35 In situ soil vapor extraction

within containment cells

combined with ex situ

bioremediation and groundwater

treatment

• Treatment is more difficult for heavier, less porous fractions.

• The main process factors affecting the degradation process at full

scale were aeration and temperature.

• Process optimization through nutrient addition was not found to be

cost effective at full-scale.

36 Enhancement techniques for ex

situ separation processes,

particularly with regard to fine

particles

• Dewatering the treated slurry. Up to 57% solids could be achieved

after 10 minutes of filtration at 1,600 Kpa with calcium hydroxide

as a coagulant.

• Temperature and nutrient addition strongly affect bioreactor

performance.

• The nature of the contaminated matrix (e.g., sulfide content. See

text).

• Bioavailability and biodegradability of contaminants.

43 Multi-vendor bioremediation

technology demonstration project

• Soil texture affects aeration.

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NATO/CCMS Phase II Pilot Study Final Report Final Report

Project Comments on Factors Limiting Performance

49 Characterization of residual

contaminants in bioremediated

soil and reuse of bioremediated

soil

Not applicable (see text).

54 Treatment of PAH- and PCPcontaminated soil in slurry phase

bioreactors

No relevant information provided. Limitations are presumably similar

to bioreactors in general.

6.9 COSTS

Scant cost data could be compiled for most projects. What could be gleaned is summarized in Table 6.8.

However, it would be wise to treat the data in Table 6.8 with a great deal of caution. Costs are strongly

dependent on site specific factors, and cost data were reported in different years.

6.10 FUTURE STATUS OF THE CASE STUDY PROCESSES AND THE TECHNOLOGY AS

A WHOLE

The pilot study projects discussed here as case studies are an interesting cross-section of the biological

treatments applied to solid materials and slurries. Dealing with the technology overall first, it is clear

that ex situ biological treatments are an effective means of dealing with many contamination problems

and offer great advantages over in situ approaches in terms of process control, monitoring and

assessment, and treatment duration. These advantages come at a premium. This premium encompasses

the possibility of higher costs, a more intrusive response, and greater visible generation of process

residuals and emissions. In some situations, the specific circumstances of a site’s redevelopment make

this premium worth paying for the ex situ treatment advantages.

Across Europe, great attention is being paid to the treatment of wastes in general, with a desire to reduce

the volumes of material being landfilled, more specifically the disposal of biodegradable or chemically

active wastes. These desires are manifest in the latest Landfill Directive draft and the intention for a

Directive on composting. It would therefore seem likely that possibilities for synergy in the co-treatment

of different waste types will be of increasing interest. It also seems likely that landfill operators and

waste management companies will become more open to treatment-based waste management solutions.

It may be that these two factors will extend to wastes arising from contaminated sites and offer new

opportunities for offsite and integrated treatment plant. Ex situ treatment also offers the opportunity for

on-site recycling, and it does seem likely that future redevelopment projects will take a more strategic

and integrated view of risk reduction, waste minimization, and construction requirements.

Biopile, windrow, and treatment bed approaches are now well established approaches and because of

their track record and the know-how acquired for them, these approaches seem set to be used more

widely. So far as fundamental advances are concerned, the best place to look for these might be around

the resolution of the two process conflicts outlined in Section 5: air versus water movement; and

mobilization versus containment.

Bioslurry bioreactor technologies are under active development, but at present are not easily costcompetitive. However, bioreactors for slurries are likely to continue to be a useful approach for specific

circumstances, such as the treatment of sludges from soil washing.

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NATO/CCMS Phase II Pilot Study Final Report Final Report

Table 6.8: Cost Information by Project

Project Comment

6 In situ/on-site bioremediation of industrial soil

contaminated with organic pollutants: elimination of soil

toxicity with DARAMEND®

In situ unit costs are estimated to be U.S.$46-

92/m3

, and ex situ process costs are estimated

to be U.S.$96-140/m3 (1995).

8 Biodegradation/bioventing of oil-contaminated soils Based on the 24 case studies reported,

0-5,000 tons, $45-90/ton;

5,000-25,000 tons, $30-45/ton; and

>25,000 tons, $15-30/ton.

The type of “ton” is not specified, nor is it stated whether

Canadian or U.S. dollars are used.

11 On-site biological degradation of PAHs in soil at a

former gasworks site

Not applicable.

15 Combined chemical and microbiological treatment of

coking sites

Not applicable.

24 Combined remediation technique for soil containing

organic contaminants: Fortec

Cost data not provided.

25 Slurry reactor for soil treatment Cost data not provided.

26 Treatment of creosote-contaminated soil (soil washing

and slurry phase bioreactor)

Estimated to be U.S.$530/m3 of froth flotation

sludge (1993).

28 Use of white-rot fungi for bioremediation of creosotecontaminated soilNot applicable.

31 Decontamination of metalliferous mining spoil Not applicable.

35 In situ soil vapor extraction within containment cells

combined with ex situ bioremediation and groundwater

treatment

The biological treatment costs were not

separately reported.

36 Enhancement techniques for ex situ separation processes,

particularly with regard to fine particles

The authors felt that reporting treatment costs

would be misleading as they depend on too

many site-specific factors.

43 Multi-vendor bioremediation technology demonstration

project

Estimated to be U.S.$71/m3 (1996).

49 Characterization of residual contaminants in

bioremediated soil and reuse of bioremediated soil

Not applicable.

54 Treatment of PAH- and PCP-contaminated soil in slurry

phase bioreactors

Not reported.

Bioreactor technologies for the solid phase may be a suggestion for useful future development, taking

advantage of existing waste composting technology and know-how. In-vessel treatments, particularly

those involving mixing, offer advantages over cultivation, biopile, and windrow systems including better

containment, process control and monitoring, as well as improved product homogeneity and elimination

of edge effects. An opportunity for such enhanced process control is to make better use of fungal

processes, which tend to be inhibited above 50°C, or to achieve sequential aerobic and anaerobic effects.

More complex ex situ biological treatments may tend to be most easily installed as fixed plant, perhaps

as part of an integrated wastemanagement system.

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NATO/CCMS Phase II Pilot Study Final Report Final Report

6.11 ACKNOWLEDGEMENT

Note the author acknowledges the support of the Environment Agency for England and Wales and the

U.K. Department of the Environment Transport and the Regions (DETR) which supported his attendance

of the Pilot Study. However, the views expressed in this paper are those of the authors only and do not

necessarily reflect the views of the Department of the Environment. The work of Ian Martin (now with

the Environment Agency) is also acknowledged. Mr. Martin is a co-author of several of the papers that

this summary chapter draws upon.

6.12 DISCLAIMER

Reference to any individual or organization or mention of any proprietary name or product in this report

does not confer any endorsement by the author, nor the Environment Agency, nor DETR.

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55. USEPA (1996) GRACE Bioremediation Technologies Daremend® Bioremediation Technology. EPA

Report: EPA/540/R-95/536.

56. USEPA (1997) Cleaning Up the Nation’s Waste Sites: Markets and Technology Trends. 1996 Edition.

EPA Report: EPA/542/R-96/005.

57. Wastewater Technology Centre (1995) Performance Evaluation Of The Daremendtm Bioremediation

Process At The Domtar Wood Preserving Site In Trenton, Ontario. And Independent Evaluation Under

The Auspices Of The DESRT Program, September 1995. Available On The DESRT Programme.

Available from he, Environmental Technology Advancement, Environmental Protection Service,

Environment Canada, Ottawa Ontariok1a 0H3, Canada.

58. Watanabe, M.E. (1997) Phytoremediation on the brink of commercialisation. Environ. Sci. Technol.

31 (4) 182A-186A.

59. Welsh Office (1993) Decontamination of metalliferous Spoil. Report Reference PB/GR/1261(6.93).

Available from: Environment Division, Welsh Office, Cathays Park, Cardiff CF1 3NQ.

60. Wood, P., Pearl, M., West, D. and Dunn, R. (1994) laboratory and pilot scale investigations into the

integrated treatment of contaminated soil.Warren Spring Laboratory Report. LR 1018. Available from

Waste Management Information Bureau, National Environmental Technology Centre, AEA

Technology, Abingdon, Oxon OX14 3DB.

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Chapter 7: EX SITU THERMAL METHODS

Michael A. Smith

M.A. Smith Environmental Consultancy, U.K.

7.1 INTRODUCTION

Thermal treatment methods use heat to remove or destroy contaminants (1). Some methods also

encapsulate contaminants that cannot be volatilized or burned. Processes vary with respect to:

• the heat source (e.g., heated air or another gas, open flame, or liquid heat-transfer medium) and

method of application (direct or indirect contact);

• operating temperature;

• phasing of the process (i.e., one or more stages);

• the equipment used to contain the thermal process and provide heat and mass transfer (e.g., a rotary

kiln or fluidized bed reactor);

• the materials handling methods used both before and after treatment; and

• methods used to collect and contain and treat air and other emissions from the process.

7.2 MAIN PROCESS VARIATIONS

Three main types of thermal treatment can be identified for contaminated soils, sediments, sludges, filter

cakes (e.g., from soil washing) and similar materials:

(1) Thermal desorption in which contaminants are removed from the feedstocks at relatively low

temperatures and then destroyed or collected from the gas stream in a subsequent stage;

(2) Incineration (thermal destruction) in which contaminants are destroyed at high temperature; and

(3) Vitrification in which very high operating temperatures destroy some contaminants and trap others

in a glassy product.

The thermal process projects reviewed in this chapter involved either thermal desorption or incineration,

and the introductory sections that follow concentrate on these forms of treatment. In practice, there is

no clear technical distinction between thermal desorption and incineration, since thermal desorption of

contaminants occurs during incineration of soils or other solids, and partial combustion of desorbed

organic compounds often occurs within a desorber unit or downstream in a fume incinerator, depending

on the design.

Existing industrial thermal processors, such as cement kilns and coal-fired boilers, are also sometimes

used for organic-rich residues. Other thermal processes can be used for specific contaminants; for

example, retorts have been specified by the USEPA for the treatment of mercury-contaminated soil.

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7.3 DESCRIPTION OF MAIN PROCESS VARIATIONS

7.3.1 Thermal Desorption

Thermal desorption methods physically separate volatile and semivolatile1 contaminants from soils,

sludges, and sediments. They do not generally result in a high degree of thermal decomposition of

contaminants, although temperature variations between different systems may allow for some localized

oxidation or pyrolysis. The thermal desorption unit is only one part of a treatment train; some

pretreatment of feedstocks and post-treatment of treated soil or separated contaminants is usually

required.

Efficient separation can occur at temperatures of up to 600°C, although temperatures may reach 900°C

during the primary stage in some specialized systems. In practice, many systems operate at relatively

low solids temperatures; even polychlorinated biphenyls (PCBs) can be removed at 450-500°C. An

important design parameter is the length of time that soils remain at the target temperature.

Separated contaminants, water vapor, and particulates must be collected and treated. Typically, this is

done using conventional methods of condensation, adsorption, incineration, filtration, etc. The methods

are selected according to the nature and concentration of contaminants, regulatory regime, and economics

of the system employed. It may be possible to recover separated contaminants for reuse. Thermal

desorption systems that employ combustion or other oxidation processes for treating the off-gas can

accomplish the same goal as incineration—i.e., destruction of contaminants.

Two basic configurations are available:

(1) Direct systems, in which heat is transferred by convection, radiation from heated air (or another gas),

or an open flame to the contaminated feedstock; and

(2) Indirect systems, in which heat is transferred by conduction from the heat source to the contaminated

feedstock.

Project 7, in which soil was floated on molten metal, can be regarded as a directly heated system, while

Project 13 involved two indirectly heated stages. A classification of thermal desorption systems is shown

in Figure 7.1. In practice some commercial types occupy a hybrid position and are capable of operating

in different modes. Most systems of both types employ rotary kilns, although more innovative systems

use various types of conveyors (e.g., screw, paddle, mixing, or belt). Fluidized beds are also under

development (see Project 20).

The achievable solids-treatment temperature is a function of the temperature of the heating medium as

well as the heat transfer area and the heat burden posed by the feedstock. Both directly and indirectly

heated desorbers can be classified as low- or high-temperature systems. High-temperature desorbers can

achieve solids temperatures comparable to some incinerators, depending on the design, operating

conditions, and the volatility and thermal characteristics of the contaminants. In the U.S., many thermal

desorption units are regarded as low-temperature systems and are employed for soils contaminated with

hydrocarbon fuel. Evolved water and volatile compounds may be swept from the processor using an inert

gas such as nitrogen or oxygen-deficient (<4 % by volume) combustion off-gas (see Project 13).

1 What matters is whether the contaminants of concern are volatile under the conditions of temperature, etc.,

in the desorber. The terms “volatile” and “semivolatile” are here used as in much USEPA literature.

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Depending on the pretreatment handling processes used and the temperatures applied during treatment,

Figure 7.1: A Classification of Thermal Desorption Systems

thermal desorption may not significantly alter the physical properties of the soil or its ability to support

vegetation, although resident microbial populations will have been affected. Provided the material

conforms to all site-specific remediation standards, it may be returned for reuse onsite. At high operating

temperatures, however, the natural organic constituents of the soil (e.g., humic acids) are broken down.

This reduces the utility of the treated product for landscaping. Furthermore, changes in mineral properties

may lead to a loss of cohesiveness, and the loss of water from clay matrices may render them potentially

reactive (pozzolanic).

Directly Heated Processes

Direct processes usually take place in a rotary kiln into which externally heated air or gas is introduced

or an open flame provided. Energy requirements vary according to the moisture content of the

contaminated feedstocks, the maximum bed temperature required, ambient temperatures, maximum gas

combustion temperatures, and the extent to which heat is transferred and recovered from the kiln exhaust

gases.

Indirectly Heated Processes

Indirect methods operate by transferring heat across a metal surface, either from a fired or electrical

furnace adjacent to the desorber or from a heated fluid, such as steam, flue gas, air, heat transfer liquid

or molten salt. Indirect heating can be carried out in a rotary unit (similar to a rotary calciner) with a

furnace shell surrounding the rotating desorber, or in conveyor systems equipped with a travelling belt

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or pipes or hollow augers through which a heat transfer medium (such as steam, oil, or molten salts) is

fed.

In the conveyor systems, screw conveyors or hollow augers are used to transport the soil or other

feedstock, continuously through an enclosed trough. Hot oil or steam circulates through the conveyor

or auger to heat the soil. Molten salts have seen limited use. A heat transfer fluid is commonly pumped

through the walls of the trough for additional heat transfer. One, two, or four augers may be arranged

in a trough to provide mixing during the heating and conveying process. More than one trough system

can be run in series to achieve the bed temperature and residence time required. A clean sweep gas, such

as nitrogen or steam, typically is used to convey the vaporized contaminants and water from the troughs.

The sweep gas also may be used to minimize oxidation of the contaminants by reducing the availability

of oxygen. The maximum bed temperature is limited by the properties of the heat transfer fluid and the

materials used to construct the equipment. It also depends on the speed at which soils are conveyed

through the trough(s) and the operating temperature of the heat transfer fluid. Advantages of this type

of desorption unit include simplicity of operation and temperature control, as well as reduced generation

of fines or dust.

A typical indirectly fired rotary unit consists of an outer furnace that is heated and a rotary inner drum

that contains the contaminated soil. The soil is primarily heated by direct contact with the drum and by

radiation from the drum walls. The efficiency of indirect systems relies on the provision of a large heat

exchange area. Compared to directly heated rotary kiln systems, a much smaller volume of gas (approximately 300 m3

/tonne of treated soil) is discharged from the desorber. As a result, secondary combustion

and gas cleaning systems are smaller and more economical to construct compared to those of direct

systems. However, construction costs for indirect systems may be high due to the complexity of the heat

exchanger.

Gas Collection and Treatment

Gas collection and treatment arrangements vary according to the design of the plant, whether it is

directly or indirectly heated, its capacity and the type of contaminants being treated. Regulatory

requirements on acceptable emissions are also important, as is the availability of a water supply and

discharge facility. Gas collection and treatment systems in common use include:

• combustion of volatile contaminants at high temperatures (up to 1,400°C) in an afterburner followed

by gas cleaning and discharge through a stack;

• thermal treatment at moderate temperatures (200-400°C) using catalysts (e.g., nickel or zinc/ copper)

to assist oxidation, followed by gas cleaning and discharge through a stack;

• for indirect heating systems, conventional low-temperature scrubbers using water or organic solvents,

and activated carbon absorption; and

• for indirect systems, condensation of volatile compounds with possible recovery.

A combination of systems may be necessary to comprehensively treat all the constituents present in the

gas phase exiting the primary desorber.

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7.3.2 Incineration

Incineration (thermal destruction) destroys contaminants at high temperature (800-1,200°C). Specifically,

incineration is a high-temperature oxidation reaction between combustible substances and oxygen under

controlled conditions of retention time, temperature, and turbulence within a single- or multiple-stage

combustion chamber2

. Although organic contaminants are destroyed in the process, air pollution control

equipment must be provided to collect and treat combustion products, particulates, and volatile metals

present in exhaust gases. Incineration of soils and sediments involves volatilization and desorption of

water and organic contaminants (and some inorganic contaminants), as in thermal desorption. A

secondary combustion chamber to complete oxidation of the volatilized materials is generally required.

The high temperatures used during incineration have implications for the reuse of the treated soil due

to changes to the physical, chemical, and biological properties of the material. Changes in soil texture

together with the loss of natural organic constituents, reduce the ability of treated material to support

vegetation and may affect engineering properties. The loss of soil structure and organic content also may

increase the leachability of any heavy metals remaining in the treated product. Further treatment, e.g.,

stabilization/solidification (Chapter 8), may therefore be required before the material is acceptable for

reuse.

A wide range of incineration techniques have been developed for the treatment of contaminated soils,

sediments, and sludges, including direct-fired rotary kilns, fluidized beds, and infrared belt conveyor

systems.

Direct Fired Rotary Kiln Incinerators

Direct fired rotary kiln incinerators typically contain a primary and a secondary combustion chamber.

The primary chamber is a cylindrical, sloping, rotating, refractory-lined shell in which the soil is dried

and heated by firing fuel or liquid wastes with a high calorific value. The secondary combustion chamber

provides additional capacity for any contaminants not destroyed at the primary stage. Soil may move

with, or counter to, the direction of gas flow. The kiln can be designed to operate in an oxidation mode

or pyrolysis (anoxic) mode, with the latter generating smaller volumes of flue gas. Rotation and

inclination provide the necessary mixing and heat transfer functions. Gases exiting the secondary

combustion chamber pass through a multi-stage gas cleaning plant.

Fluidized Beds

Fluidized beds have been used for the treatment of waste liquids and sludges and, on a more limited

scale, of contaminated soils and sediments. In these systems, air or combustion gases are used to develop

and maintain a fluidized bed of solid particles derived from sand or the inorganic residue from the soil

or waste being treated. The continuous movement of the solids in the bed promotes rapid heat and mass

transfer, and hence destruction of the contaminants. Continuous removal of bed solids is required for the

treatment of soil or sediments. Additional fuel is added as necessary to maintain a bed temperature of

between 700-1,200°C, although temperatures must be limited to prevent sintering. Particulates escaping

the bed are generally recovered in a cyclone and returned to the combustion chamber if treatment is

incomplete.

2 Thermal processors also can be operated at high temperatures under anoxic conditions, so that pyrolysis

(reductive degradation) of organic substances occurs.

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Infrared Incinerator Systems

Infrared systems use infrared radiant heat (generated by electrically powered silicon carbide elements)

to heat organic wastes to combustion temperatures. A typical configuration comprises an infrared

primary chamber, a gas-fired secondary combustion chamber, an emissions control system, and a control

center. Mobile infrared incineration systems have been developed for use in the United States.

7.3.3 Vitrification

Vitrification destroys contaminants by oxidation and thermal decomposition and immobilizes residual

contaminants in a vitreous product. The advantages of vitrification over other thermal treatment

processes are that it produces fewer air emissions and a solid residue with favorable leaching

characteristics.

Vitrification systems consist of a melter, heat recovery system, air pollution control system, and storage

and handling for feedstock and raw materials. There are various configurations for melters, some of

which are multi-chamber and others which use mechanical agitation. Energy requirements are significant

where feedstocks have a high mineral content. The most common melters are heated by electrical

currents passed through the melt mixture from electrodes. Variations between melters include the method

of introducing feed, the degree and type of mixing, electrode design, and the means of achieving

complete combustion of organic compounds. More recent melter designs utilize alternative methods of

introducing heat and have different heat and mass transfer characteristics.

Typical melt temperatures are about 1,500°C. Sufficient glass-forming material (silicate) must be present

to produce a proper melt that will result in a durable vitrified product. This may require the addition of

fluxing agents. Molten product is continuously drawn off the melter either into containers for cooling,

solidification, and handling, or through some type of cooling process to produce granular solids.

Emissions of the more volatile metals is a potential concern, and air pollution control systems must be

highly efficient. Process residues include glass/vitrified waste, molten metal (not produced as a separate

phase in most processes), scrubbing and cooling liquors, and off-gases.

Commercial vitrification systems have been developed for the treatment of contaminated soils and

sediments in the U.S. where a number of vendors have field-, bench- and pilot-tested the technology.

Most of these systems were modifications of different types of glass-making furnaces, and development

was directed initially towards radioactive or other highly hazardous solid wastes. One commercial facility

in the United States was used to treat organic wastes for several years.

7.4 DETERMINATION OF EFFECTIVENESS

The effectiveness of both thermal desorption and incineration (thermal destruction) systems should be

judged on the basis of their ability to achieve target residual concentrations while complying with

emission limits to air, etc.

The primary technical factors governing the performance of thermal desorption processes are the

maximum bed temperature achieved; the total residence time; the content of organic contaminants and

water; contaminant characteristics; and medium (e.g., soil) properties.

Since the basis of the processes is the physical removal of contaminants from the medium by

volatilization, bed temperature directly determines end point concentrations. The degree of mixing and,

where applicable, sweep gas rate will also affect the effectiveness of the process.

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The primary technical factor affecting performance of thermal destruction (incineration) systems is also

the maximum bed temperature of the solids. Overly large particle sizes lead to poor performance. A high

proportion of fines leads to high dust loading in the downstream air pollution control system.

7.5 CASE STUDIES CHOSEN

The projects reviewed for this chapter are listed and described in Table 7.1. Brief descriptions of the

projects are provided in Sections 7.5.2 to 7.5.6. Project summaries can be found in Appendix IV.

Table 7.1: Projects Involving Ex Situ Thermal Treatment

Project Description

7 Demonstration of thermal gas-phase

reduction process

Key feature is the high temperature (850°C) thermal reduction

unit. Contaminants in soils are volatilized in a specially

designed thermal desorber and then injected into the unit.

Contaminated aqueous phases are vaporized before injection.

Successfully demonstrated by USEPA’s SITE Program in 1992.

13 Rehabilitation of a site contaminated

by tar substances using a new on-site

technique

Integrated soil washing and two-stage thermal treatment

employing ventilated tent to reduce atmospheric emissions.

19 Cleaning mercury-contaminated soil

using a combined washing and

distillation process

Integrated soil washing and vacuum distillation plant used to

treat mercury-contaminated soil and debris. Started operation in

1993.

20 Fluidized bed soil treatment process—

BORAN

Fluidized bed thermal desorption plant with high-temperature

afterburner intended to treat soils and residues from soil

washing plants. Full-scale, but regarded as test plant by the

design/operating company. In September 1996, the plant was

undergoing modifications to overcome feed problems.

21 Mobile low-temperature thermal

treatment process

Low-temperature (<300°C) sealed processor employs steam

injection. Pilot plant successfully operated in 1994 and 1995.

Three projects (Projects 7, 20 and 21) involved the use of ex situ thermal treatment as the main

treatment element, and two (Projects 13 and 19) used ex situ thermal treatment as the second element

of a treatment train. In both cases, the first element was a soil washing process.

7.5.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process

The ECO LOGIC thermo-chemical process employs hydrogen to chemically reduce organic compounds

to mineral components at temperatures of about 900°C. Soils are treated with the aid of a novel thermal

desorber involving use of a molten metal bath. A technology demonstration at the Middleground Landfill, Bay City, Michigan, U.S., was conducted in 1992 under the USEPA’s Superfund Innovative

Technology Evaluation (SITE) Program with partial funding from the Canadian and Ontario governments. The wastes processed were oily PCB contaminated water, high-strength PCB oils, and PCBcontaminated soil.

Background

The Middleground Landfill accepted municipal wastes for approximately 40 years. A 1991 investigation

indicated elevated levels in groundwater of trichloroethene (TCE), PCBs, 1,2-dichloroethene, methylene

chloride, toluene, and ethylbenzene. The groundwater contained lesser concentrations of benzidine,

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benzene, vinyl chloride, chlorobenzene, polycyclic aromatic hydrocarbons (PAHs), lindane, dieldrin,

chlordane, and DDT metabolites.

Technical Concept

The ECO LOGIC thermo-chemical process employs hydrogen to chemically reduce organic compounds

to mineral components at temperatures of about 900°C. Chlorinated hydrocarbons, such as PCBs and

polychlorinated dibenzo-p-dioxins, are converted to methane and hydrogen chloride, while nonchlorinated organic compounds, such as PAHs, are reduced to methane and ethene. Incomplete

reduction/combustion in the system may result in benzene formation (as noted below, residual benzene

was a problem in the demonstration project. Ethene produced by contaminant breakdown may undergo

additional conversion to methane. Methane reacts with water vapor to form hydrogen and carbon

monoxide. The hydrogen chloride is removed in a caustic soda scrubber downstream of the processor.

The reformed process gas can then be recirculated in the system or used as fuel in various stages of the

process. The absence of free oxygen in the reactor inhibits dioxin and furan formation. The process

employs automatic monitoring to maintain optimum operating conditions.

The reactor feed is dependent upon the soil or waste being treated. Aqueous streams, such as

groundwater, are preheated in a vaporizer using steam from a boiler that is fired by propane or process

gas, before injection. When soils or sediments are to be processed, they are first pretreated in a linked

thermal desorption unit (TDU), in which the soil or sediment is floated on a bath of molten tin.

Volatilized contaminants are sent to the reactor through a separate port. Contaminated solids, such as

transformer parts, can be handled in sequencing batch vaporizer chambers. The process is shown

schematically in Figure 7.2.

Figure 7.2: Reactor and Thermal Desorption Unit Schematic Diagram

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The Demonstration Reactor

The demonstration-scale reactor (Figure 7.3) was 2 m in diameter and 3 m tall, mounted on a 15-m

drop-deck trailer. This trailer carried a scrubber system, a recirculation gas system, and an electrical

control center. A second trailer held a propane boiler, a waste preheating vessel, and a waste storage

tank.

In the demonstration, a heat exchanger evaporated contaminated aqueous feedstock to form steam and

Figure 7.3: The ECO LOGIC Reactor

a concentrated liquor. Atomizing nozzles sprayed the heated liquor and associated particulates into the

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reactor; a separate set of atomizing nozzles injected the PCB-rich oil directly into the reactor.

Compressed hydrogen-rich recirculation gas passed through a gas-fired heat exchanger and entered the

top of the reactor tangentially. The tangential entry swirled the fluids to provide effective mixing. As

indicated in Figure 7.3, the swirling mixture travelled downwards in the annulus formed by the reactor

wall and the central ceramic-coated steel tube, past electrically heated silicon carbide elements. These

elements heated the mixture to 900°C. At the bottom of the reactor, the mixture entered the central tube

and flowed upwards to the outlet of the reactor. The reduction reactions occurred as the gases travelled

from the reactor inlets to the scrubber inlet.

Heavy particulates dropped out of the gas stream and collected at the base of the reactor in a grit box.

The gas leaving the reactor was scrubbed using a caustic alkaline (pH 9) wet scrubber, which removes

steam, particulates, and gases such as hydrogen chloride. Ninety-five per cent of the exhaust gases

(reheated to 500°C) were recycled, and 5% were used as a supplementary fuel for the propane-fired

boiler. The boiler produced steam, which was used in the heat exchanger and burned the reformed gas.

The exhaust from this boiler was the only source of emissions to air from the process.

Thermal Desorption Unit

The TDU desorbs organic compounds at 500-600°C into a hydrogen-rich carrier gas from soil supported

on a molten tin bath. Hydrogen and tin are used because they do not react. Tin offers favorable

properties: high density, low vapor pressure, high surface tension (which means it does not “wet” the

soil and enter the pores), high thermal conductivity, and good solvent properties for heavy metals such

as lead, cadmium, and arsenic.

Some of each volatile metal present passes to the reactor, some dissolves in the molten tin bath, and the

remainder stays in the soil. Non-volatile metals remain in the treated soil. Quench water cools the soil

before disposal.

During the demonstration, a hopper with a screw feed dropped waste soil onto the tin bath. The screw

feeder provided a gas seal between the hydrogen and the outside air. Once inside the TDU, the soil

floated on the molten tin. A paddle wheel removed treated soil from the end of the tin bath and fed it

to the quench tank.

Materials Processed

The wastes processed were oily PCB contaminated water, high-strength PCB oils, and PCB-contaminated

soil extracted directly from the landfill. The tests on the two liquid wastes yielded information on reactor

performance; the tests on the soil yielded information on the functioning of the complementary thermal

desorption unit.

A liquid pool of waste within the landfill provided feedstock for the tests. Tetrachloroethene (PCE) was

added to the feedstocks to serve as a tracer to determine destruction efficiencies (DEs)3

. The reactor

program treated approximately 2.6 tonnes of wastewater contaminated with 3,757 mg/L PCBs and 3,209

mg/L PCE at a rate of 1.73 kg/min, and 0.2 tonnes of waste oil containing 25.4% PCBs and 6,203

mg/kg PCE at a rate of 0.385 kg/min. Additional feedstock contaminants included fluoranthene,

3 DE is a measure of the system’s ability to destroy organic compounds, as measured around the system and all output

streams. DE(%) = {(1-Massoutput)/Massinput}*100.

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naphthalene, phenanthrene, other PAHs, chlorobenzene, chlorophenol, methyl chloride, toluene, and

various metals.

Two runs were conducted with the TDU on PCB-contaminated soil. The two runs treated 1 tonne of soil

contaminated with 627 mg/kg PCB and 14,693 mg/kg hexachlorobenzene (HCB).

7.5.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using New OnSite Technique

This on-site remedial demonstration project combining excavation of tar-contaminated soil followed by

on-site ex situ thermal desorption was carried out at an old gasworks site in a densely populated area

of Copenhagen. The excavation was performed inside a ventilated tent. The project was regarded as a

demonstration of a new on-site technique.

Background

The Valby Gasworks was one of the largest in Copenhagen with an operating capacity of up to 300,000

m3 coal gas/day. Site investigation results showed a wide distribution of contaminants in the soil and

groundwater including coal tars, phenols, ammonium compounds, cyanides, and heavy metals. One area

of the site contained two tar reservoirs that had been partially filled with demolition debris after site

closure. A large amount of tar was left at the base of the reservoirs. The upper part was filled with

rainwater mixed with tar substances. The total amount of contaminated material in the two reservoirs

was about 12,000 tonnes.

The objective of the demonstration project was to remediate the heavily contaminated soil and debris

within and around the pits using an approach that minimized off-site migration (for example as air

emissions) since the site was located in an urban area.

Technical Concept

Free-phase tar and heavily contaminated materials were excavated within the tent, which covered an area

of 40 m by 50 m (with a height of up to 10 m). The air within the tent was cleaned using three powerful

extraction ventilators connected to a two-stage filter system consisting of particle and active carbon

filters. About 60% of ventilation air was blown in actively as fresh air at the end of the tent away from

the extraction fans; the remaining 40% came from general leakages.

Although on-site thermal desorption is claimed to be suitable for treating tar contaminants, it was

considered uneconomical to treat all of the excavated material in this manner. Therefore, a soil washing

system was used to provide a volume reduction step by producing clean fractions in the particle size

ranges of greater than 50 mm and 2-50 mm through screening and high pressure spray washing. All solid

fractions were dewatered before further treatment or reuse, and the contaminated process effluent was

recycled and treated before discharge. It was observed that tar removal efficiencies were increased

through using recycled water. Elevated levels of ammonia in the recycled water (up to 20,000 mg/L)

were believed to have assisted tar solvation. The contaminated fraction (<2 mm) was treated using the

thermal desorption process.

The thermal treatment plant consisted of two separate indirect heat treatment units: the first operating

at 250-300°C, while the second operated at 800-900°C. In the first stage water and volatile substances

were evaporated from the contaminated materials The off-gas was treated using a particulate dust trap

and an air/oil/water separator and condenser. The second stage was used to volatilize the heavier tar

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substances, which were then recovered in an air/tar condenser. Each treatment unit was transported in

a standard 12 m x 9 m container and had a maximum operating capacity of 2.5 tonnes/hr. However,

during operation, its practical operating capacity was only 1 tonne/hr—the limiting factor being the rate

at which energy could be transferred from the reactor walls to the material. Treated material had a

residence time of approximately 3 hours inside the reactors. After treatment, the decontaminated soil was

cooled using a closed single axle screw conveyor with a box cover to prevent dust emissions.

The first stage desorber was a specially designed, indirectly heated rotary unit operated in a strictly

controlled atmosphere, which was slightly over-pressurized and secured by inert gas. The processor was

heated by a closed-loop thermal fluid (boiler). The slight excess pressure led the gaseous hydrocarbons

and steam to the controlled condensation stage. Non-condensable gases (nitrogen, argon, methane,

hydrogen, etc.) were removed from the condenser and fed to the oil-fired burner of the Stage-2

processor. Stage 2 employed an indirect rotary heat exchanger with an external shell temperature of

1,100°C produced by oil burners.

7.5.3 Project 19: Cleaning Mercury-Contaminated Soil Using Combined Washing and

Distillation Process

The Marktredwitz Chemical factory in Germany, which was established in 1786, manufactured various

mercury compounds (including agrochemicals) and mineral acids. Site investigations in the early 1980s

found that the buildings, soil, and groundwater were heavily contaminated with mercury and other

contaminants. Mercury concentrations ranged from 400-3,300 mg/kg on the surfaces of brickwork, from

1,000-4,000 mg/kg in the soil, and up to 200 mg/L in the wastewater. This led to closure of the factory

in 1985. The Pilot Study project reported on the remedial operations employed including:

• Dismantling of the production plant, which involved removal of highly contaminated wall plastering

and supporting pipework for disposal in a secure on-site facility (approximately 5,000 tonnes);

• Protection of the River Kösseine, which flows adjacent to the site, using a sheet piling wall and a

pump-and-treat system;

• Demolition of the old factory building;

• Excavation of soil and debris to an average depth of 5 m across the entire site followed by refilling

to prepare the entire site for further urban redevelopment. Contaminated material was transported

offsite for treatment and disposal. A large off-site monofill waste disposal area was prepared where

treated material and slightly contaminated material (<50 mg/kg mercury) was disposed.

• Treatment of excavated soil and debris at an off-site treatment plant, which was constructed as a

semi-mobile (i.e., transportable) operation consisting of several modularized containers. This project

is the first full-scale application of vacuum distillation technology applied to debris and soil

contaminated by volatile and semivolatile substances like oil, mercury, and the lighter fractions of

tar.

The distillation unit is used in combination with a soil washing plant that separates out the highly

contaminated silt and clay soil fractions to form a pretreatment concentrate for thermal treatment. The

soil washing plant includes the following processes: crushing of material and screening at 0.05 m; wet

screening and density separation of slurried contaminated material; attrition scrubbing to remove fine

particles from coarser material; and dewatering and waste stream categorization. The sand and rubble

7-12
NATO/CCMS Pilot Study, Phase II Final Report

fraction is discharged as clean fill. The fine fraction (<0.008 mm) is concentrated in thickeners,

dewatered in a chamber filter press, and then transferred to the vacuum distillation unit.

The thermal treatment process is a two-stage system involving thermal desorption at 100°C to reduce

material moisture content followed by vacuum distillation at the higher temperature. Treated material

exiting Stage 1 has a reported moisture content of about 1%. Volatilized contaminants and steam are

recovered from the off-gas using condensers. In the vacuum distillation reactor contaminated waste is

heated to temperatures between 350-450°C at a pressure of 50-150 hPa and the volatilized contaminants

recovered from the off-gas. By using reduced pressures rather than higher temperatures it is claimed that

overall energy consumption is significantly reduced and that off-gas volume is less than 1/30th of that

produced by an incineration plant. After treatment, the treated soil is water cooled in a rotating drum

to an average temperature less than 50°C and is recombined with the coarse-grained material from the

soil washing plant. Treated soil with residual concentrations greater than 50 mg/kg are treated again.

The Harbauer soil treatment plant is a full-scale, commercial, transportable plant. The plant is a modular

system, and the process units are preassembled in about 60 containers (3-m wide, 3-m high, 10-14 m

long). The plant is gas-sealed; internal air is kept and treated; noise-reduced equipment is used; and soil

underlying the site is protected by a bottom-sealing system.

About 57,000 tonnes of soil were treated between 1993 and 1996, with an average daily throughput of

150 tonnes. Besides routine monitoring during operation, the technology demonstration was conducted

according to the USEPA’s SITE Program protocols.

7.5.4 Project 20: Fluidized Bed soil Treatment Process—BORAN

The BORAN thermal fluidized bed soil treatment process plant has been designed primarily to treat slurry

residues from soil washing plants. It is designed to treat contaminants such as PAHs and PCBs. The

plant is operated by its designers and manufacturers, and while intended to be a commercial operation,

is also intended to be used as a full-scale test bed for design modifications. The basic technology is in

use for waste treatment and a number of other applications.

Before the contaminated soil is fed into the furnace, it is screened in a vibrating bar sizer with a cutpoint at 20 mm. Material greater than 20 mm is transferred elsewhere for alternative treatment and safe

disposal. Material less than 20 mm is fed into the furnace.

The furnace is fitted with two over-bed screw feeders for soils and four in-bed feed points for fine

residues. A bed temperature of 900°C is maintained to ensure that the organic content of the soil is fully

oxidized and destroyed. The combustion chamber is rectangular with one side wall being inwardly

inclined to act as a deflector plate and a limit to bed expansion. Preheated air is injected into the

chamber to ensure that feedstock (contaminated soil), combustion gases, and the bed materials are

circulated rapidly in an elliptical path within the combustion chamber. The controlled circulation

produces lateral mixing and turbulence, which reportedly enhances combustion efficiency.

Immediately downstream of the reactor is a hot gas cyclone, which is capable of removing up to 85%

of the soil and fines expected to be carried by the fast moving off-gas stream. The cyclone is designed

to remove up to 7.5 tonnes of particles per hour. This material is cooled from approximately 900°C to

180°C using water-cooled screw feeders before it is transferred to three storage silos as a clean product.

The majority of the treated soil is collected at this stage, although some of the coarser particles sink to

the base of the fluid bed within the furnace and are collected as a heavy ash product.

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NATO/CCMS Pilot Study, Phase II Final Report

After the hot gas cyclone the off-gas stream passes to an afterburner where it is heated to 1,200°C by

an oil-fired heater. The flue gas enters the treatment chamber at the top, passes down the center of the

chamber, and exits at the base. The afterburner gases are directed at high velocity and tangentially to

the flue gas stream to mix turbulently with the flue gas at the top of the chamber. At the base of the

chamber, a water bath with an immersed screw feeder extracts any soft entrained material. When the

afterburner is in use the following quench chamber reduces the temperature of the flue gas back to

900°C. A heat exchanger system uses the flue gases to preheat air about to be injected into the main

furnace. The flue gas cleaning plant consists of a primary and a secondary system. Primary absorption

of inorganic gases, such as hydrogen chloride and sulfur dioxide, is achieved by mixing finely powdered

limestone into the flue gas stream. The limestone is subsequently collected in a baghouse. In the

secondary absorption system any residual organic compounds, including dioxins and furans, are collected

by activated brown coal coke filters. Fouled coke is incinerated in the furnace.

No performance data for this technology were available.

7.5.5 Project 21: Mobile Low-Temperature Thermal Treatment Process

Many commercially available thermal treatment plants for contaminated soil are based on rotary kilns

operating at temperatures above 500°C, although some hydrocarbons are volatile at temperatures below

300°C. Use of lower operating temperatures, where appropriate, would reduce the environmental and

economic cost of treatment significantly.

Ruhrkohle Umwelttechnik GmbH have been operating thermal treatment facilities for contaminated soil

since 1986. In 1990, they began developing a mobile low-temperature treatment system for a range of

soil contaminants (such as volatile hydrocarbons, chlorinated solvents, and various forms of mercury)

with the following objectives: to reduce overall treatment costs compared with high temperature

treatment; to reduce plant transport costs in order to increase applicability of on-site treatment to smaller

remediation projects; to improve performance and cost effectiveness of thermal treatments for finegrained (especially clay-rich) soils; and to shorten project initiation times by developing a process that

did not require regulatory permitting for any off-gas or effluent emissions.

The process involves heating soil of less than 15 mm grain size in a gas-tight evaporator to 290°C under

continuous agitation for 30-45 minutes. Direct heating is achieved by mixing the soil with a hot medium

such as steam. Volatilized contaminants are collected from the off-gases by a multi-step condensation

system. Contaminants such as chlorinated solvents and mercury are separated from the condensed steam

which is cleaned and reused. Further contaminant separation may be carried out to produce low boiling

point and high boiling point products to increase their recycling value. The cooled off-gas (at about 5°C)

is cleaned further using an activated carbon filter for organic contaminants and an unspecified chemical

adsorption unit for inorganics (such as mercury) before discharging to the atmosphere. The treated soil

is cooled to about 60°C and water added to raise soil moisture content to 7-10%.

7.6 REVIEW OF CASE STUDIES AS A GROUP

Projects 7, 20 and 21 used ex situ thermal methods as the main element of treatment, while Projects 13

and 19 used ex situ thermal methods as the second element of a treatment train (the first element of

which was a soil washing process). Project 20 (fluidized bed treatment) assumed that some enrichment

of organic contaminants in the feedstock would take place elsewhere, for example, in a soil washing

plant. Tables 7.2 and 7.3 describe the input materials and thermal treatment processes of the projects,

respectively.

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NATO/CCMS Pilot Study, Phase II Final Report

Table 7.2: Input Materials

Project Medium Contaminants Pretreatment/

Fraction treated

7 Demonstration of

thermal gas-phase

reduction process

Soil, groundwater,

and oily waste.

Chlorinated hydrocarbons, including PCBs

and HCB, PAHs,

chlorobenzene,

chlorophenol, methyl

chloride, PCE, toluene,

metals.

Soil homogenized to provide

uniform feed. Volatile compounds

in soil desorbed and subjected to

gas-phase reduction.

Oil injected directly into gasphase reduction unit.

Concentrate from pre-treatment of

aqueous phases injected directly

into reduction unit.

13 Rehabilitation of a site

contaminated by tar

substances using a new

on-site technique

Soil and

demolition debris.

Coal tars. First stage soil washing. The

fraction <2 mm was subjected to

thermal desorption.

19 Cleaning mercurycontaminated soil using

a combined washing

and distillation process

Soil and debris. Mercury. First stage soil washing. The

fraction 0.1-8 mm was subjected

to thermal desorption under

vacuum.

20 Fluidized bed soil

treatment process—

BORAN

Designed for soil

and slurry residues

from soil washing

plants.

Designed for PAHs,

PCBs, etc.

Simple screening to remove >20

mm material for treatment

elsewhere (plant does not have

crushing equipment).

21 Mobile low-temperature

thermal treatment

process

Soil. Volatile hydrocarbons

and 5- and 6-ringed

PAHs.

Fraction <15 mm subjected to

steam injection.

7.7 PERFORMANCE RESULTS

Performance results of each project are summarized in Table 7.4 and discussed in more detail in the

paragraphs that follow. There are no results for Project 20 as this plant had not become operational by

the time the study ended.

7.7.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process

The runs employing liquid feeds confirmed the feasibility of the gas-phase reduction process for treating

PCBs and other chlorinated organic compounds, producing a fuel gas from contaminated liquids that

yielded environmentally acceptable air emissions. In general, the reactor system destroyed PCBs

effectively, reducing them to lighter hydrocarbons.

Theoretically, the overall effectiveness of the destruction process could depend on the functioning of

both the reactor system’s gas phase reduction process (which produced the reformed gas), and the

propane and reformed-gas fired boiler. Destruction and removal efficiencies (DREs)4 for PCBs in the

4 DREs compare the mass flow rate of selected feedstock compounds, in this case PCBs, to their mass flow

rate in the boiler stack gas. DRE(%)= {(1-Massstack)/Massinput)}*100.

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NATO/CCMS Pilot Study, Phase II Final Report

scrubbed reformed gas essentially were equal to the DREs at the boiler stack. This shows that

combustion of the reformed gas in the boiler is not required to complete PCB destruction.

Stack emissions generally met stringent regulatory standards. However, average benzene concentrations

in the stack gas (corrected to 7% oxygen) and scrubber liquor required close monitoring. Benzene

emissions (73-113 μg per dry standard cubic meter [dscm]) exceeded the regulatory limit. The scrubber

liquor required either disposal as a Resource Conservation and Recovery Act (RCRA) waste or recycling

through the system for additional treatment.

Demonstrated DREs for PCBs ranged from 99.9999 to 99.99999%. Demonstrated DEs for PCE was

99.99%. There was no net formation of dioxin or furan.

The TDU did not operate to specification. The most important finding was inefficient desorption from

soil during one of the runs. The DE for HCB ranged from 72.13 to 99.99%.

Table 7.3: Thermal Treatment Process

Project Process Temperature

(°C) Fate of contaminants

Fate of

treated

material

7 Demonstration of

thermal gas-phase

reduction process

Thermal desorber

using molten metal

bath for soil, etc.

Gas-phase reduction

500-600

850

Degraded to hydrogen

chloride, hydrogen,

methane, ethene, etc.,

depending on feedstock. Recirculated or

removed by wet

scrubbing.

Fate of

treated water

and soil not

indicated in

reports.

13 Rehabilitation of a site

contaminated by tar

substances using a

new on-site technique

Two-stage thermal

desorption. Both

stages employed

indirect heating.

Stage 1: 250-300

Stage 2: 800-900

Condensed. Coarse (>2

mm) washed

material

backfilled

onsite.

Fate of

thermally

treated

material not

clear.

19 Cleaning mercurycontaminated soil

using a combined

washing and

distillation process

Two-stage thermal

desorption: (1) to

remove water; and

(2) vacuum distillation at 50-150 hPa.

Stage 1: 100

Stage 2: 350-400

Condensed Landfilled

with

untreated

materials

containing

<50 mg/kg

mercury.

20 Fluidized bed soil

treatment process—

BORAN

Fluidized bed

Afterburner

900

1,200

Condensed, if not

thermally degraded.

No operating

results

available.

21 Mobile low-temperature thermal treatment

process

Sealed thermal

desorption with

steam injection.

270-290 Condensed. No information

available.

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NATO/CCMS Pilot Study, Phase II Final Report

Table 7.4: Performance Information

Project

Contaminant Concentrations

Removal Efficiency Input Output

7 Demonstration of thermal

gas-phase reduction

process

Soil: 1,000 mg/kg PCBs

Oil: 25.4% PCBs, 0.6% PCE

Water: 3,757 mg/kg, PCB

3,209 mg/kg, PCE

(tracer)

0.6 mg/kg in soil

from desorber

PCB DE1 for soil up

to 99.9%

PCB DRE2

99.9999%+

PCB DE1

13 Rehabilitation of a site

contaminated by tar

substances using a new

on-site technique

1,500-80,000 mg/kg total tars.

Median value is 11,000 mg/kg.

22 mg/kg total tars 99.8%

19 Cleaning mercurycontaminated soil using a

combined washing and

distillation process

400-3,000 mg/kg Hg on

surface of brickwork

1,000-4,000 mg/kg Hg in soil

Average from

January 1995:

20 mg/kg Hg

No overall figures.

20 Fluidized bed soil

treatment process—

BORAN

No information No information No information.

21 Mobile low-temperature

thermal treatment process

Mineral oil, 3.8%

Heavy mineral oil, 2.2%

Light tar oil (PAH C2-6), 0.45%

Tar oil (C2-6), 0.5%

TNT, 180 mg/kg

Mercury, 11,000 mg/kg

900 mg/kg

300 mg/kg

60 mg/kg

1,000 mg/kg

2 mg/kg

20 mg/kg

4.5 mg/kg

85 mg/kg

25 mg/kg

5 mg/kg

No information.

Notes: 1 Destruction efficiency (DE) is a measure of the system’s ability to destroy organic compounds as

measured around the system and all output streams. DE(%)= (1-Massoutput/Massinput) x 100 2 Destruction and removal efficiencies (DREs) compare the mass flow rate of selected feedstock

compounds to their mass flow rate in the boiler stack gas. DRE(%)= {(1-Massstack)/Massinput)} x

100

7.7.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using New OnSite Technique

Analysis of the “clean” products of the soil washing process proved difficult due to the heterogeneity

of the coarse material, which comprised pieces of brick, concrete, and stones. Only limited chemical

analysis of the coarse washed fraction (2-50 mm) was conducted. Reliance was largely placed on visual

inspection. Ammonia in the recycled wash water enhanced washing efficiency. However, as tar

concentrations in the recycled wash water built up, washing efficiency decreased because at high tar

concentrations, the water lost its ability to emulsify the tar.

Concentrations of total tars in the fine concentrate (<2 mm) treated at the thermal treatment plant were

found to range between 1,500 mg/kg and 83,000 mg/kg. The fine concentrate was regarded as of optimal

grain size and homogeneity for the thermal treatment. Because of the variable nature of the feed material

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NATO/CCMS Pilot Study, Phase II Final Report

and the 3-hour plug-flow operation, it was difficult to match input and output samples. The characteristics were therefore expressed statistically; the distribution of values for both was approximately log

normal.

Treatment efficiency was reported to be in the order of 99.8% with total tar concentrations reduced to

22 mg/kg from a median input of 11,000 mg/kg. Comparable performance was achieved for individual

PAHs including benzo(a)pyrene, which was reduced from a median value of 100 mg/kg to less than 0.1

mg/kg.

7.7.3 Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil Washing

and Distillation Process

Results of Routine Plant Monitoring

About 57,000 metric tons of soil were successfully treated between 1993 and 1996; the daily average

throughput was about 150 metric tons. Thorough monitoring of the plant showed that all requirements

were met during operation of the system. Emissions were found to be well below the specified criteria.

Long-term plant monitoring has shown that residual concentrations are well below 50 mg/kg, even if

peaks of very high input concentrations amount to more than 5,000 mg/kg mercury (Table 7.5). Trial

runs done with mercury-contaminated soil from another site showed that a clean-up criterion of 2 mg/kg

can be reliably met using an appropriate plant configuration.

Table 7.5: Mercury Concentrations in Waste Streams Treated in Project 19

Unit Period

Average Concentration of Mercury

Treatment

Criteria

Feed Stream

(mg/kg)

Treated Stream

(mg/kg)

soil washing plus

vacuum distillation

Sept. 93-Oct. 94

average= 500

peaks up to 5,000

23 50 mg/kg

Nov. 94-Oct. 95 19

Nov. 95-Feb. 96 7.9

vacuum distillation Oct. 95-Apr. 96 - 3.6 -

water treatment 1993-96 - (see Section 3.2) 10 μg/L

stack gas 1993-96 - (see Section 3.2) 50 μg/dscm

Results of a Technology Demonstration Under USEPA’s SITE Program

The Harbauer Treatment System was the subject of a technology demonstration in a joint project of the

German Federal Ministry of Science, Education, Research and Technology and the USEPA. The

technology demonstration was done according to the SITE protocols during routine operation of the

plant. Based on the SITE demonstration results, the following conclusions were drawn about the

Harbauer soil washing and vacuum distillation soil treatment technology:

• Average total mercury concentrations in the treated sandy loam and loam soils were reduced from

875 mg/kg to less than 18 mg/kg (95% confidence level).

• Average total mercury removal efficiencies for the soils ranged from 98-99%.

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NATO/CCMS Pilot Study, Phase II Final Report

• Average Toxicity Characteristic Leaching Procedure (TCLP) mercury concentrations in the soil

leachates were reduced from 82 μg/L to less than 6 μg/L.

• The average mercury concentration in treated process water discharged to the municipal sewer was

5 μg/L.

• The average mercury concentration in the treated stack gas discharged to the atmosphere was 2.92

μg per normal cubic meter (However, these measurements were not made during the same test runs

as the demonstration soil samples that were collected.).

7.7.4 Project 20: Fluidized Bed Soil Treatment Process—BORAN

There are no results for Project 20 because the plant was not operational by the time the Phase II Pilot

Study ended.

7.7.5 Project 21: Mobile Low-Temperature Thermal Treatment Process

Pilot-scale trials (Table 7.6) were carried out during 1994 and 1995 to evaluate process performance and

to aid design of a commercial scale plant. In many cases, the observed concentration of contaminants

in the process water was low or below detection limits. Steam injection enhanced volatilization of certain

contaminants at a particular temperature. The results showed that at 270°C, and at low steam injection

rates, a treated soil sample still contained up to 35 mg/kg of 5- and 6-ringed PAHs. At higher injection

rates but at the same temperature this residual concentration dropped to about 10 mg/kg.

Table 7.6: Summary Results of Pilot-Scale Trials

Contaminant Temperature

(°C)

Stripping

Steam

(kg/hr)

Input

Concentration

(mg/kg)

Output

Concentration

(mg/kg)

Mineral oil in clay soil 240 6 38,000 60

Heavy mineral oil 270 5 22,000 1,000

Light tar oil (PAH C2-C4) 270 6 4,500 2

Tar oil (PAH C2-C6) 240 6 5,000 50

Mercury in sandy soil

in clay soil

in clay soil

280

330

320

4

6

6

300

900

11,000

5

25

85

Trinitrotoluene (TNT) 210 8 180 4.5

7.8 ENVIRONMENTAL IMPACTS

7.8.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process

During the tests, continuous emission monitors measured the concentrations of the criteria air pollutants

at the stack: nitrogen oxides (NOx), sulfur dioxide (SO2), total hydrocarbons (THC), and carbon

monoxide (CO). Each of these pollutant concentrations were well under the level established in the

Michigan Department of Natural Resources (MDNR) permit.

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NATO/CCMS Pilot Study, Phase II Final Report

The demonstration boiler operated between high and low fire, depending on the system’s steam

requirements. The test analyses showed out-of-range spike concentrations of THC and CO, which are

indicators of combustion efficiency, during low-fire operation, most notably during treatment of the

wastewater when cycling between high- and low-fire conditions.

Hydrogen chloride emissions were well below the MDNR permitted level of 4 lbs/hr (1.81 kg/hr or 99%

removal); average stack concentrations ranged from 0.66 mg/dscm at 109 mg/hr to 0.81 mg/dscm at 198

mg/hr. Removal efficiencies reached 99.98%.

Process residuals comprised reactor grit, scrubber sludge, scrubber decant, scrubber liquor, compressed

tank condensate and stack gas—and when the TDU was used, treated soil. The reactor grit contained

PCBs, PAHs, and other organic compounds. However, ECO LOGIC intend to recirculate the grit through

the reactor in a full-scale plant. Scrubber residuals also contained metals and a variety of organic

compounds, but again recycling through the plant should be possible.

7.8.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using a New

On-Site Technique

Washed coarse material (>2 mm) was returned to the excavation. The disposal route for thermally treated

fine materials is not clear from the report.

One of the key elements of the project was to avoid emissions to atmosphere by the use of a ventilated

tent. Air emissions from the thermal treatment process were destroyed by feeding them to the Stage-2

oil burner.

One of the projects key conclusions concerned the noise associated with the remedial process. It was

found that with a measured level of about 60 dB(A) at the working site it was difficult but practical to

meet the maximum permitted noise level of 50 dB(A) at the site boundary.

Water from the tar reservoirs was used in the soil washing process and treated in a plant (1 m3

/hr

capacity) comprised of an oil skimmer, cellulose filter for particulates and an active carbon filter.

7.8.3 Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil Washing

and Distillation Process

Precipitation sludge from the water treatment system was disposed in subsurface hazardous waste storage

facilities. Spent ion exchange resin was reactivated off-site for recycling. Condensed mercury was

disposed off-site for reuse or proper disposal. During plant operation, nearly 30 tonnes of mercury were

recovered. Treated wastewater and treated off-gas were subject to constant on-line monitoring. Treatment

criteria of 10 μg/L and 50 μg/dscm, respectively, were achieved.

7.8.4 Project 20: Fluidized Bed Soil Treatment Process—BORAN

No performance data available because the plant was not operational by the end of the Phase II Pilot

Study.

7.8.5 Project 21: Mobile Low-Temperature Thermal Treatment Process

No information on emissions was provided.

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NATO/CCMS Pilot Study, Phase II Final Report

7.9 HEALTH AND SAFETY

7.9.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process

The principal health and safety concerns were the physical hazards common on construction and

remediation sites, chemical use, equipment integrity, and process control.

The chemical hazards arise from the use of propane, liquified nitrogen and oxygen, hydrogen, industrial

chemicals, and hazardous feed materials. In addition, the process generates methane. Standardized

industrial procedures provided adequate guidance for storing, transporting and handling these materials.

There should be no undue concern associated with hydrogen usage in the process. Well-established and

proven procedures are available for safe hydrogen storage and use. Hydrogen is no more or less

dangerous than gasoline or methane, but it must be handled with regard to its unique properties.

Verification of system integrity is essential for process safety. Hydrogen is more difficult to contain

because of its small molecular size. Therefore, interfaces of equipment, instruments, and piping must

be leak-free. To provide additional safeguards, the process is operated at a slight positive pressure to

prevent oxygen ingress, internal oxygen concentrations are monitored, and gas feeds (propane and

hydrogen) maintained at low pressure to minimize the likelihood of pipeline breaks. The plant is fitted

with an automatic safety system which initiates plant shutdown in the event of a number of hazardous

situations occurring.

7.9.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using a New

On-Site Technique

During excavation, the release of volatile substances was very high. Although a ventilation rate of three

air exchanges per hour was maintained, it was still necessary for workers within the tent to use personal

protection. Two principal levels of protection were provided:

• chemically resistant suits with fresh-air supply through an air tube for manual work involving direct

contact with heavily contaminated material; and

• fabric coveralls combined with a fresh-air mask with multi-filter in all other work operations.

Excavator operators either used a fresh-air mask with multi-filter or were supplied with a pressurized

cabin with filtered air supply.

The effectiveness of the chemically resistant suits was checked. Volatile tar substances such as BTEX

compounds (benzene, toluene, ethylbenzene, and xylenes), phenols and naphthalene, could not be

detected inside the suits.

Both of the desorber units were protected by two independent systems:

(1) Jets spraying water on the hot internal surface thereby producing steam. This steam has three

functions: (a) as a start up procedure to remove air/oxygen from internal hot parts before feeding

materials; (b) to keep the system over-pressurized relative to atmospheric pressure during operation;

and (c) back-up in shutdown situations, when steam production from wet material decreased.

(2) Nitrogen was added automatically to the processor if the internal pressure dropped below

atmospheric pressure.

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NATO/CCMS Pilot Study, Phase II Final Report

7.9.3 Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil Washing

and Distillation Process

No information was provided.

7.9.4 Project 20: Fluidized Bed Soil Treatment Process—BORAN

No information was provided.

7.9.5 Project 21: Mobile Low-Temperature Thermal Treatment Process

No information was provided.

7.10 FACTORS AND LIMITATIONS TO CONSIDER FOR DETERMINING THE

APPLICABILITY OF THE TECHNOLOGY

7.10.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process

The SITE Program concluded that the ECO LOGIC process efficiently treated liquid wastes containing

oily PCBs and other organic compounds, and water containing PCBs, other organic compounds, and

metals. Stack emissions met stringent regulatory levels. The principal residual stream—the scrubber

effluent—concentrated metals and some organic compounds (benzene, PCBs, PAHs), indicating that

additional treatment, such as recycling through the process, might be required prior to disposal. However,

throughput reliability was only 20-55% of design and system availability was 24% indicating that system

reliability needs improvement. A number of technical problems were encountered during operation of

the plant and are recorded in the SITE program report. The boiler should be operated at firing rates and

air/fuel ratios that prevent the spikes of THC and CO observed during the trial.

The reactor system is best suited for processing liquids and TDU off-gases and water vapor. The waste’s

organic content limits the demonstration-scale system’s feed rate because of the reformed gas generation.

ECO LOGIC plans to improve throughput by storing excess reformed gas after compressing it. Future

users should consider the implications, logistics, and costs of this approach.

The TDU did not perform to design specifications. The USEPA categorized the TDU test data as a

system proof-of-concept rather than as a comprehensive evaluation of a fully developed unit. The TDU

only achieved acceptable desorption efficiencies at the expense of throughput. In addition, ECO LOGIC

experienced material handling problems with the TDU feed. The combination of feed problems and

inadequate organics desorption showed a need for further development. Nevertheless, the demonstration

did show that the TDU can desorb PCBs and that satisfactory treatment in the reactor system was

possible.

Cold-weather operations may inhibit efficient destruction because of the incremental amount of energy

required to heat the reactor. In addition, frozen feedstock liquids would require melting prior to

treatment, and liquid residuals could freeze in the unheated storage tanks. Winterization, including heat

tracing, is necessary to provide adequate feedstock and to ensure uninterrupted processing.

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NATO/CCMS Pilot Study, Phase II Final Report

7.10.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using a New

On-Site Technique

The only specific difficulty noted in the report was the reduction in effectiveness of the soil washing

plant as the concentration of tarry substances built up in the recycled wash water. This could presumably

be overcome by introducing a greater proportion of fresh water. This has also been noted as a limitation

in other soil washing operations.

Operation within a tent successfully limited emissions to the atmosphere from soil handling although

noise remained a potential problem. However, containment in this way, does increase the potential risks

to workers compared to working in the open when emissions can rapidly disperse into the air. However,

avoidance of weather extremes may help to reduce the potential for accidents due to difficult working

conditions.

7.10.3 Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil

Washing and Distillation Process

No specific limitation regarding the technology were noted in the report. However, it emerged during

analysis of the results of the USEPA-German Bilateral project that the analytical method used to

determine PAH concentrations in the untreated and treated soils is important. In particular, the extraction

method used as some methods will tend to underestimate the proportion of the more volatile PAHs

present, and other methods will tend to underestimate the less volatile fraction. Reliable assessment of

effectiveness may, therefore, require use of more than one analytical method in parallel.

7.10.4 Project 20: Fluidized Bed Soil Treatment Process—BORAN

No performance data available because the plant was not operational by the end of the Phase II Pilot

Study.

7.10.5 Project 21: Mobile Low-Temperature Thermal Treatment Process

No specific limitations were noted in the project reports.

7.11 COSTS

Cost data are summarized in Table 7.7.

Table 7.7: Cost Data

Project Cost information

7 Demonstration of thermal gas-phase

reduction process

Liquids: U.S.$1,840-2,205/ton

Soil: U.S.$550-695/ton

13 Rehabilitation of a site contaminated by tar

substances using a new on-site technique

Total cost U.S.$2.6M, of which 70% is directly attributable

to soil and ground water treatment.

19 Cleaning mercury-contaminated soil using a

combined washing and distillation process

Total cost estimated to be DM 150M.

20 Fluidized bed soil treatment process—

BORAN

Plant not operated.

21 Mobile low-temperature thermal treatment

process

Costs of a full-scale plant are estimated to be about DM

150-250 (U.S.$90-160), depending on the contaminants

(1996 prices). The report suggested the process would not

be economical for remedial actions of less than 100 tonnes.

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7.11.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process

The 12 categories established for the SITE Program5 formed the basis for the cost analysis of the

treatment of liquid wastes. Costs relate to the reactor system, processing an average 2.2 kg/min, as

operated at the Middleground Landfill site. For this estimate it was assumed that 378 m3 (100,000 U.S.

gallons) of wastewater and 114 m3 (30,000 U.S. gallons) of waste oil were stockpiled for treatment.

Based on the economic analysis, the estimated cost (1994 U.S. dollars) for treating liquid wastes similar

to those at the Bay City site ranged from U.S.$2,205/tonne (60% utilization factor) to U.S.$1,840 (80%

utilization factor). The most important element affecting cost is labor (52%), followed by site preparation

(15%), supplies (12%), and start up/mobilization (12%).

Demonstration site preparation costs were U.S.$127,400. Capital costs (for the reactor and immediately

associated equipment, but excluding the TDU) for a commercial operation are estimated to be

U.S.$585,000.

Similarly, the costs of treating contaminated soils were estimated. These were estimated at

U.S.$695/tonne (at a 60% utilization factor) and U.S.$550/tonne (80% utilization factor). Important

elements affecting cost are fuel (67%), equipment (11%), and labor (9%).

7.11.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using a New

On-Site Technique

The total project cost was about 18M DKK (about U.S.$2.6M) of which 15M DKK (about 70%) was

for contracted clean up costs. The total cost included:

Personnel costs (consultant and contractor) 13%

Operation and maintenance 7%

Establishment and rental of the tent 7%

Soil. air and water cleaning costs 70%

Analytical costs 1%

Miscellaneous 2%

7.11.3 Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil

Washing and Distillation Process

The estimated treatment cost was 480 Deutsche Marks (DM) per tonne, which is approximately

U.S.$320/tonne (assuming 1.5 DM= U.S.$1).

7.11.4 Project 20: Fluidized Bed Soil Treatment Process—BORAN

No projected costs for an operational process were provided.

5

Site preparation, permitting and regulatory, capital equipment, mobilization and start-up, operations labor, supplies, utilities, effluents,

residuals, analytical, repair and maintenance, demobilization.

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7.11.5 Project 21: Mobile Low-Temperature Thermal Treatment Process

According to Ruhrkohle, the costs of cleaning soil using a full-scale plant based on this process would

be about 150-250 DM/tonne (U.S.$90-160), depending on the contaminant(s). The cost depends on the

plant equipment required and waste disposal costs.

An important factor influencing costs is the quantity of soil to be treated at a particular site. Ruhrkohle

accepts that a mobile plant cannot compete with stationary plants when only a small amount of soil is

to be treated (for example, mobilization costs would be disproportionally high). However, for larger

quantities of soil, treatment of the contaminants such as mineral oils and PAHs in the mobile plant

should be less expensive, because on-site cleaning does not involve transport costs for the soil and does

not require any expenditure for obtaining permits. It can be installed rapidly and operated under German

law without the need for time-consuming applications for approvals to set up and operate.

7.12 CONCLUSIONS AND PROGNOSIS

As a group, the projects showed that thermal treatment plants can provide a technically satisfactory

means of dealing with a wide range of organic contaminants and with mercury. They also showed that

thermal treatment can be integrated well with pretreatment processes such as soil washing that are

intended to reduce the volume of material to be treated. Unfortunately, the promising fluidized bed

technology described under Project 20 did not become operational during the study.

Project 13 illustrated the benefits and practicality of operating even complex on-site operations under

cover thereby limiting possible impacts from emissions within an urban area; however, noise may still

remain a problem. Containing the operations under a tent may increase risks to workers from emissions

that might otherwise rapidly disperse into the air.

The thermal processor employed in Project 11 appears to be uniquely versatile in being able to handle

contaminated soils, waste waters and non-aqueous phase liquids (NAPLs).

Costs will remain a limiting factor for the technologies described here, hence pretreatment to reduce the

amount of contaminated material to be treated is important. The cost of U.S.$550-695/tonne of soil

quoted for the Eco Logic process (Project 7) is only likely to be justified for treatment of difficult

contaminants such as PCBs. Costs for processing of less difficult materials such as PAHs and hydrocarbon oils are most likely to come from measures to reduce energy requirements, which are much more

expensive in Europe than in the United States, and to increase throughput of mobile plants of a given

size.

7.13 REFERENCES

1. Harris, M.R., S.M. Herbert, and M.A. Smith. Remedial treatment for contaminated land: Ex-situ

remedial methods for soils, sludges and sediments, Construction Industry Research and Information

Association, London, Special Publication 108, 1995.

2. Anderson W.C. (editor). Monograph on innovative remediation technology: thermal desorption

American Academy of Environmental Engineers (Annapolis, MA) 1994.

3. Anderson W.C. (editor). Monograph on innovative remediation technology: thermal destruction

American Academy of Environmental Engineers (Annapolis, MA) 1994.

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Chapter 8: STABILIZATION/SOLIDIFICATION PROCESSES

Michael A. Smith

M.A. Smith Environmental Consultancy

8.1 INTRODUCTION

Stabilization/solidification methods (sometimes called immobilization methods) change the physical state

of a contaminated material, such as solidifying a contaminated sludge. In addition, chemical stabilization

can reduce the “availability” of contaminants to potential targets, usually by containment within a solid

product of low permeability. Harris (1) and the American Academy of Environmental Engineers (2) have

recently reviewed stabilization/solidification methods.

Stabilization involves adding chemicals to the contaminated material to produce more chemically stable

constituents, for example, is the formation of virtually insoluble metal hydroxides. Stabilization may not

result in an improvement in the physical characteristics of the material. For instance, the material may

remain as a relatively mobile sludge, but the stabilization process will have reduced the toxicity or

mobility of the hazardous constituents within it.

Solidification involves adding reagents to the contaminated material to reduce the material’s fluidity or

friability and to prevent access by external mobilizing agents, such as wind or water, to the contaminants

contained in the solid product. Solidification does not necessarily require that chemical reactions occur

between contaminants and the solidification agent, although such reactions may take place depending

on the nature of the reagent.

In practice, many commercial systems and applications involve a combination of stabilization and

solidification processes. Solidification follows stabilization to reduce exposure of the stabilized material

to the environment through, for example, formation of a monolithic mass of low permeability.

Although volatile constituents may be driven off (because heat is often generated) and some hydrolysis

of chlorinated organic compounds may occur during the application of some processes, the destruction

or removal of contaminants is not the objective of stabilization/solidification.

Contaminants may become available once again if the physical or chemical nature of the treated product

alters in response to changes in the external environment, such as exposure to an acidic discharge or

leachate or physical breakdown of a compacted soil mass due to freezing and thawing. Solidified

products also may be subject to internal degradation reactions over time (e.g., the oxidation of sulfides

to form expansive sulfates). Key points for selecting a stabilization/solidification method are therefore:

• its ability to achieve and retain the desired physical properties, chemically stabilize or permanently

bind contaminants, and contain (physically entrap) contaminants over the long-term; and

• the methods to be used to determine treatability and short- and long-term performance.

The effectiveness of stabilization/solidification methods depends on:

• proper characterization of the material to be treated so that the most appropriate formulation can be

selected;

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• effective contact between the contaminants and treatment reagents—for many systems this can be

achieved by ensuring a high degree of chemical and physical consistency of the feedstock, and the

use of appropriate mixing equipment;

• control over external factors, such as temperature, humidity, and amount of mixing after gel formation, since these affect the setting and strength development processes and the long-term durability

of the product; and

• absence of substances that inhibit the stabilization/solidification process and development of the

required physical characteristics, or pretreatment to render such substances harmless, such as by

sorbent addition.

Treatability studies are always required to establish anticipated effectiveness and materials handling

requirements.

Because most stabilization/solidification methods involve the addition of solid reagents to the

contaminated material, some increase in the final volume of the treated product can be expected.

Increases in the range 30-130% are typical (4). A major advantage of most stabilization/solidification

methods is that they improve the handling characteristics of sludges and other high-water content

materials, and may confer additional structural strength on contaminated material. Sometimes these are

the primary reasons for their use, and they may be an important consideration for contaminated sites

undergoing redevelopment. Stabilization/solidification methods are readily applied onsite using mobile

mixing and blending equipment.

Most commercial stabilization/solidification systems are derived from established hazardous waste

treatment techniques and use relatively simple equipment and conventional reagents (binders) to

immobilize the contaminants. Systems may be classified according to the primary stabilization agent

used: cement-based, pozzolan-based, silicate-based, thermoplastic-based, or polymer-based systems. In

practice, a combination of these reagents may be employed. The formulations actually used on a

commercial basis are often proprietary in nature.

In the U.S., stabilization/solidification is considered an established technology for the treatment of certain

inorganic forms of contamination, and long-term monitoring data are available on the performance of

solidified wastes in the field (4, 5, 6). Stabilization/solidification techniques have also been used in

Europe for the treatment of hazardous waste. However, doubts remain over their long-term performance.

These doubts arise from the chemical and physical nature of the processes themselves and from observed

deficiencies in the quality of application in the field (and in fixed plant). In addition, methods of testing

and predicting performance are not well developed and are the subject of continuing debate (7).

Proprietary formulations for the treatment of organic contaminants prior to the use of conventional

binders are available in the U.S., but practical experience in their application is limited.

8.1.1 Main Process Variations

Processes can be grouped according to the reagents used to achieve stabilization/solidification and

conveniently categorized into three main groups:

(1) Those based on inorganic cementitious systems including Portland cement, pozzolans, hydraulic

slags, and lime.

(2) Those using organic binders, including asphalt emulsions, bitumen, and other thermoplastics.

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(3) Other systems, such as those using sulfur as a binder (2).

Other materials used in cementitious systems include cement kiln dust, lime kiln dust, and steel slag

fines. Depending on the source, cement kiln dust may contain variable proportions of reactive calcium

silicates, free lime, partially reacted and possibly pozzolanic clay minerals, and alkali sulfates.

With the exception of proprietary lime and thermoplastic-based methods, which can be applied to solids

contaminated with organic residues, one of the principal limiting factors associated with conventional

stabilization/solidification systems is that even very low concentrations of organic contaminants may

interfere with setting and hardening processes. Thus, recent research has addressed the development of

methods that can treat materials contaminated with both organic and inorganic contaminants. One

approach involves the use of organophilic clays to preferentially absorb organic contaminants (see

discussion of Project 34 below). Treated material then undergoes conventional stabilization/solidification

to immobilize the inorganic constituents and provide a secondary layer of protection around the claybound organics. Other potentially useful adsorbents include ion exchange resins, activated carbon, and

zeolites.

8.1.2 Ex situ Methods of Application

Ex situ stabilization/solidification methods can be applied in three main ways:

(1) Plant processing, in which contaminated material is excavated and then mixed with stabilization/

solidification reagents in a plant specifically designed for the purpose or adapted from other

applications, such as concrete batching and mixing plants.

(2) Direct mixing, in which contaminated material is excavated and transported to a designated area

of the site. The material is then spread out in layers, and the reactive ingredients are added and

mixed in using a mechanical plant. Direct addition and mixing may be used to treat contaminated sludges and sediments present in lagoon areas and ponds.

(3) In-drum processing, in which binders are added to contaminated material contained in a drum

or other container. After mixing and setting, the product is disposed in the drum.

Plant processing has considerable advantages: it ensures adequate mixing and reduces unacceptable

environmental impacts due to the release of particulates and vapors. Three principal steps are employed

in the application of plant processing:

• pretreatment, for example to dewater, grade, or homogenize the material to be treated, or to

concentrate the contaminants (e.g., by soil washing);

• mixing of waste with active ingredients either to form a pumpable slurry or a material that can be

placed using standard earth moving/engineering equipment; and

• placement and curing.

Curing of pumpable material requires maintenance of appropriate temperature and humidity to promote

stabilizing reactions and proper development of physical properties. Curing may take place in molds or

in disposal lagoons. With low-moisture content material, curing occurs at the final disposal site. When

treated material is placed in lagoons, care should be taken to prevent the formation of “cold joints,”

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which would allow water easy access and allow excessive accumulation of contaminated free water

(bleeding).

Effective treatment usually requires a relatively high ratio of treatment agent to feedstock. The amounts

used affect chemical stabilization capacity, permeability, and the long-term strength and durability of

the product.

The required amount of water varies with the system and can be very important. For instance, in cementbased systems, the water:cement ratio is an important factor in the development of early and long-term

properties of the system. Water is a reactive component of the system. Lower water contents are

generally preferred.

The options for final disposal should be taken into account when deciding on the acceptability of a

particular application. What is permitted depends on the nature of the product and may vary among

countries. In some cases, a full containment landfill may be required. In contrast, there are reported cases

(8, 9) where treated material has been used successfully as a construction base. In these cases, the

material is placed and compacted in thin layers to agreed specifications using standard engineering

procedures.

8.1.3 In Situ Methods of Application

Stabilization/solidification reagents may be introduced into the ground using soil mixing equipment (e.g.,

contra-rotating hollow stem augers through which treatment agents are injected) or by pressure injection

using techniques analogous to conventional grouting.

Only the former method has been developed on a commercial scale, and the discussion that follows is

restricted to such systems. The latter concept was examined in a report for the U.K. Department of the

Environment in 1982 (10), and two principal disadvantages were identified:

• difficulty in ensuring even permeation of the treatment agent in the ground; and

• treatment depth limitations (in excess of about 2 m) because of a need for sufficient overburden

pressure to withstand the injection pressures required (the report indicated that this might be

overcome by temporary surcharging).

Stabilization/solidification, when applied to material in lagoons, is typically performed using

conventional construction equipment, such as backhoe excavators and draglines. Effective mixing is very

difficult to achieve. The primary purpose of these operations is usually to improve the physical

characteristics of the material (11).

The in-ground mixing process developed in the U.S. by International Waste Technologies and Geo Con,

Inc., was evaluated under the USEPA Superfund Innovative Technology Evaluation (SITE) Program in

1988 (12). Other in situ stabilization/solidification processes are under development and scheduled for

demonstration under the SITE program (13, 14). An established ground improvement (solidification)

technique, using jet grouting, also has potential for application (see Box 8.1).

As with ex situ stabilization/solidification processes, the product obtained after treatment typically should

comprise a dense, homogeneous material with favorable leaching and weathering characteristics, low

permeability (<10-5m/s), and good (>0.34 MPa) unconfined compressive strength. Unlike ex situ systems,

where the physical properties of the excavated material can be determined in advance of processing and

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some pretreatment preparation is possible, the effectiveness of in situ applications relies on adequate

characterization of the ground at the treatment location to optimize the mixing conditions.

Box 8.1: Soilcrete® Jet Grouting

In this process, soil is loosened by the high pressure action of water, often sheafed in a cone

of air (jet-cutting). The loosened soil is partially removed to the surface via air-lift pressure as

the remaining soil is simultaneously mixed with cementitious or cement/bentonite grout.

Columns can be made to overlap, thus treating all of the soil. The columns have diameters of

0.5-1.8 m, depending on soil type. Compressive strengths of up to 10 MPa can be achieved in

granular soils and 5 MPa can be achieved in cohesive soils. Some binding of inorganic

contaminants can be expected. Permeabilities in the range 10-6-10-9 m/s can be achieved.

A variation of the jet-cutting process, in which the soil is displaced by clean material

introduced at the base of the hole, has been applied to permit ex situ treatment of the

displaced soil.

8.2 CASE STUDIES CHOSEN

Only two stabilization projects were included in the pilot study:

• Project 34 Chemical fixation of soils contaminated with organic chemicals (Envirotreat); and

• Project 29 Sorption/solidification of selected heavy metals and radionuclides on to unconventional

sorbents.

Conventional stabilization/solidification methods, such as those based on cementitious and pozzolanic

materials, have been applied with limited success to treat soils with organic contaminants. Project 34

involved the development of a range of modified organophilic clays with the goal of overcoming these

limitations in an in situ stabilization/solidification application based on cementitious binders. Following

laboratory trials to develop the optimum combination of modified clays and other ingredients, the

technology was tested at field scale on a site contaminated with a variety of inorganic and organic

substances.

Project 29 involved a laboratory-scale investigation of the use of solid wastes, such as red muds and coal

fly ashes, to absorb toxic heavy metals and radionuclides from water (a fixation or stabilization process)

followed by solidification of the metal-loaded solid wastes in a cement-based system.

Both projects focused on the pre-solidification stabilization stage with the intention of providing

adsorptive media for organic and inorganic contaminants, respectively. Both are intended to be used with

cement-based solidification processes.

The projects differ in that the:

• Project 34 uses a tailor-made (possibly expensive) organophilic clay, while Project 29 seeks to use

readily available, inexpensive waste materials; and

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• Project 34 is intended for the treatment of soils, while the Project 29 is intended for the treatment

of effluents.

The projects are summarized below. Additional detail is provided in Appendix IV, Project Summaries.

8.2.1 Project 34: Chemical Fixation of Soils Contaminated with Organic Chemicals

(Envirotreat Process)

The Envirotreat process uses modified smectite clays that contain reactive species. The process is

primarily targeted at organic contaminants, but also has the capability to treat cationic and anionic heavy

metal species by a combination of ion-exchange processes and chemical interaction with pillaring agents

and other intercalatants. The technology uses modified continuous-flight auger drilling and injection

techniques. The treatment materials are injected in slurry form into the ground and mixed with the

contaminated soil in situ.

Commercially available organophilic clays are typically made by the substitution of quaternary

ammonium salts into phyllosilicate clay matrices (e.g., montmorillonite). The primary objective of this

project was to modify these clays through intercalation (i.e., substitution of the cations between clay

layers) to improve stabilization of organic contaminants by:

• increasing the size of the interlamellar spacing within the clays to accommodate large molecules,

such as polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs); to increase

the effective surface area; and to increase the potential reactivity by introducing selected pillaring

agents;

• optimizing the polarity of the interlamellar environment to increase the absorption and adsorption

of organic contaminants;

• providing a reactive environment on interlamellar clay surfaces to chemically bind contaminants

permanently; and

• providing an active medium for effective treatment of heavy metals (both cationic and anionic) and

other inorganics by cation exchange processes and/or interaction with the intercalated species (which

then can be immobilized within the cementitious matrix following alkaline precipitation).

An advantage of using tailored organoclays is that a clay can be manufactured to treat a specific group

of contaminants by manipulating the type and amount of intercalating agents used. Envirotreat's goal was

to produce a range of clays with varying hydrophobicity and chemical composition to deal with five

different groups of organic compounds.

Following laboratory trials to develop the clays and additional efforts to optimize the auger design, a

field trial was carried out on a site occupied since the turn of the century by a variety of industrial

operations, including a chemical waste “quarantine store,” chemistry laboratory, flammables store, battery

bank, engine testing areas, underground storage tanks, and nucleonic laboratory. Likely contaminants

included flammable materials, solvents, concentrated sulfuric acid, oils, gasoline, and radioactive species.

Site characterization seems to have been very limited in terms of the range of contaminants analyzed

and the number of samples (3) analyzed. The maximum value for PAHs (six carcinogenic compounds

selected by the World Health Organization [WHO]) was 12 mg/kg—well below the U.K. threshold value

for residential development (50 mg/kg for 16 USEPA PAHs). Maximum copper, lead, and zinc

concentrations were 635, 3,330, and 785 mg/kg, respectively.

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Prior to field operations, a laboratory program was conducted to determine the type of intercalated clay

to be used; the proportions of cement, fly ash, and clay for the grout; and the optimum soil:grout ratio.

The clay formulation used was Al3+ pillared and Fe3+ exchanged (spiked) and then treated with benzyl

quaternary ammonium salt. The modified clay was produced as a suspension at Birmingham University

and transported to the site in steel drums. The clay concentration was 20 g/L (2.5 times more dilute than

that used in laboratory treatment trials).

The grout was injected using a prototype auger fitted to a conventional piling rig that produces 900-mm

diameter columns either individually or overlapping. The columns were formed by advancing the auger

into the soil to the required depth of the column, mixing the soil in place during the auger descent, and

then injecting the grout slurry into the soil with simultaneous mixing on the auger withdrawal. The

overall volume increase, measured at the end of the second day, was about 1 m3

, which represents an

increase of about 6.5%. For this demonstration, columns with 50% overlap were chosen, and several

different optimized mixes were evaluated in adjacent columns. An area of 6 m2 to a depth of 2.5 m was

treated in the trial. Cores aged 50 days (taken at 44 days), 70 days (taken at 57 days), and 1 year

(presumed to have been taken at 57 days) from each column were tested in the laboratory against the

treatment criteria outlined below.

The effectiveness of the various treatments in the laboratory and field was assessed based on:

• unconfined compressive strength by an American Society for Testing and Materials (ASTM) method

(greater than 350 kPa after 28 days of curing);

• leachability, based on the USEPA Toxicity Characteristic Leaching Procedure (TCLP), which uses

an aggressive acid leaching medium, with respect to six WHO PAHs (total PAHs less than 10 μg/L

and benzo(a)pyrene less than 0.5 μg/L) and chromium, copper, lead, and zinc with target levels 50

times the U.K. drinking water limits; and

• a final leachate pH in the TCLP leachate (between 8-10 following 28 days curing) to ensure low

metal solubility (this was later amended to a pH of 7-11).

Durability (freeze/thaw and wet/dry) and permeability tests (less than 1x10-9 m/s) were used as secondary

evaluation criteria. ASTM test procedures were used for the initial freeze/thaw tests on laboratory

prepared materials, but the test method was subsequently modified as it was judged too harsh in relation

to typical U.K. weather conditions.

The results on the cores taken at 44 and 57 days were judged to be satisfactory. All unconfined

compressive strength values exceeded the target value of 350 kPa and were greater than the equivalent

(28-day) laboratory results. This was particularly true for the mixes containing quick lime. The total

concentrations of the six WHO PAHs in the leachates were all below 2 μg/L and often below the 0.02

μg/L detection limit. Also, the individual leachate values for benzo(a)pyrene were within the target value

of less than 0.5 μg/L. All results for chromium, copper, lead, and zinc were satisfactory. Subsequently,

more detailed analyses showed satisfactory performance with respect to a wider range of metals. The

samples survived a modified freeze-thaw test—the ASTM method being considered too aggressive

following the laboratory trials for U.K. conditions. The wet-dry test results were also satisfactory.

However, only one sample satisfied the permeability criterion of less than 1x10-9 m/s; this was probably

due to the presence of natural bentonite.

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Cored samples collected during the site trial were cured under laboratory conditions for 12 months. They

were wrapped in wet cloth and kept in a humidity room. The cores were 75-150 mm in diameter and

had a maximum length of 400 mm.

Samples from all mixes showed an increase in unconfined compressive strength for those cured for 12

months, compared to those cured for 70 days. Permeability values decreased as expected due to

continuing cement hydration processes. Wet-dry durability testing gave similar results after 12 months,

and freeze-thaw testing was largely inconclusive (all samples failed at very low temperatures as

previously observed).

8.2.2 Project 29: Sorption/Solidification of Selected Heavy Metals and Radionuclides onto

Unconventional Sorbents

Cadmium (II) (Cd2+), lead (II) (Pb2+) and copper (II) (Cu2+) are toxic heavy metals that pose a serious

threat to the ecology of receiving water bodies when discharged in industrial wastewater. Cesium-137

(

137Cs) and strontium-90 (90Sr), with half lives of 30 years and 28 years, respectively, pose significant

threats to the environment as a result of fallout from nuclear bomb tests and reactor accidents. In recent

years, land burial of radioactive wastes has become a common practice, posing a radioactive

contamination risk to groundwater. In Turkey, 137Cs became a matter of public concern after the

Chernobyl accident, especially due to contamination of tea-growing areas on the Black Sea coast. Milk

products and other biological materials containing 137Cs were also extensively investigated for possible

90Sr contamination.

Various treatment technologies have been developed for the removal of these metals from water. They

include ion exchange, electrodialysis, reverse osmosis, membrane filtration, sludge leaching,

electrowinning, solvent stripping, precipitation, and common adsorption. The cost of adsorptive metals

removal processes is relatively high when pure sorbents, such as activated carbon or hydrated oxides,

are used. Consequently, there is an increasing trend towards substitution of pure adsorbents with natural

byproducts or stabilized solid waste materials. Such materials may also be useful for constructing

“natural barriers” around radioactive waste disposal sites, especially for facilities involving shallow burial

of low-level wastes, to prevent the leakage of radionuclides from the facility to the environment.

The goal of this pilot study project was to develop cost-effective unconventional sorbents, preferably

metallurgical waste solids, for the removal of heavy metals and radionuclides from contaminated water.

The removal capacities of heavy metals (Cd, Pb, and Cu) and radionuclides (137Cs and 90Sr) and the

sorption modeling of red muds and fly ashes were studied. The irreversible nature of sorption needs to

be demonstrated to guarantee non-leachability of metals from the metal-loaded sorbents.

Metal uptake (sorption) and release (desorption) were investigated by thermostatic batch experiments

on coal fly ashes and on red muds, which are alkaline leaching wastes of bauxite from the Bayer process

for the manufacture of alumina. The materials were subjected to a variety of pretreatments prior to the

introduction of the contaminated solutions. The distribution ratios of metals between the solid sorbents

and the aqueous solution were determined as a function of sorbent type, equilibrium aqueous

concentration of metals, and temperature. The breakthrough volumes of the heavy metal solutions were

measured by dynamic column experiments to determine the saturation capacities of the sorbents. The

sorption data were analyzed and fitted to linear adsorption isotherms.

The heavy metal solutions contained up to 10,000 mg/L of Cd, Pb, or Cu made from the corresponding

nitrate salts. No further pH adjustment was made. Solutions containing 137Cs and 90Sr were made by

diluting flacons of standard solutions supplied by Amersham International, Ltd.

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The desorption studies were conducted using distilled water, saturated aqueous carbonic acid (pH=4.75),

and H2CO3/NaHCO3 buffer solutions (pH=7.0) to simulate carbonated groundwater conditions for the

purpose of analyzing risks around waste disposal sites.

The sorbents may serve as effective fixation agents for removing heavy metals from water prior to

solidification for disposal. Although stabilization tests were conducted on the fly ash and red muds, as

well as on the adsorbents after they were loaded with contaminating metals, the detailed results were

not described in the final project report. Solidification of the red muds and fly ash was accomplished

by adding them to a mixture of cement, standard sand, and carefully measured water. When metal-loaded

solid waste was added (up to 20% by mass) to Portland cement-based formulations, the fixed metals did

not leach out from the solidified concrete blocks over extended periods with the exception of Cu2+,

which reached a concentration of 0.4 mg/kg after 8 months in water of pH 8-9. In solid-waste

concentrations below 20%, the compressive strengths and shear strengths of the doped concrete did not

significantly differ from the control concrete. However, there is a critical weight percentage of 10-20%

additives above which the strength declines dramatically.

8.4 PERFORMANCE RESULTS

8.4.1 Project 34: Chemical Fixation of Soils Contaminated with Organic Chemicals

(Envirotreat Process)

Regardless of the success of laboratory trials, the field trial suffered from a number of deficiencies that

make it difficult to evaluate the effectiveness of the process. The characterization of the site in terms

of the contaminants present and their distribution was poor. The maximum PAH concentration (the total

of six WHO carcinogens) was 12 mg/kg compared to a threshold trigger value of 50 mg/kg (16 USEPA

compounds) for residential development and 1,000 mg/kg for commercial developments, suggesting that

the site was in no need of PAH treatment. In contrast, the metal concentrations were high relative to the

threshold trigger values. The greatest weakness, however, was the lack of any control mixes not

containing the modified clay; thus, the possibility that a similar satisfactory performance could have been

achieved in the absence of the clay cannot be ruled out. The detailed leaching results for metals are not

provided in the reports but it should be noted that the criteria applied (50 times U.K. drinking water

limits) were quite generous.

A calculation shows that the six WHO PAHs in the treated soil would be reduced to about 8.5 mg/kg

compared to 12 mg/kg in the soil due to dilution by the other ingredients. The concentration of modified

clay is about 500 mg/kg. Given the low solubility of the PAHs, the insolubility of the clay, and the

probable inefficient mixing, it seems unlikely the clay could have a profound effect on binding the

PAHs.

8.4.2 Project 29: Sorption/Solidification of Selected Heavy Metals and Radionuclides onto

Unconventional Sorbents

The laboratory study showed that:

• Bauxite wastes of alumina manufacture (i.e., red muds) are capable of removing the radionuclides

137Cs and 90Sr as well as other heavy metals from water. Acid- and heat-treated red muds are more

effective in Cs removal than water-washed red muds, but heat treatment is detrimental to the surface

hydroxyl sites, which are important for ion-exchange sorption of 90Sr. Cesium uptake is predominantly irreversible and exothermic and increases with the specific surface area of the sorbent. A rise in

pH favors the exchange sorption of Sr, while the specific adsorption of Cs is negatively affected.

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• Coal fly ashes from thermal power plants are capable of removing 137Cs and 90Sr, as well as other

heavy metals from water. Although acid treatment of fly ash did not result in an improved

adsorption capacity, acid treatment is recommended to prevent trace pollutant leach-out from the

adsorbent into water.

Red muds and especially fly ashes were shown to exhibit a high capacity for heavy metals. The sorption

sequence was Cu > Pb > Cd in accordance with the order of insolubility of the corresponding metal

hydroxides. The metals were held irreversibly and would not leach out into carbonic acid or bicarbonatebuffered solutions.

Metal-loaded solid wastes could be solidified to an environmentally safe form thereby serving the twofold objective of water treatment and solid waste disposal. Thus, the two-fold objective of heavy metal

fixation and metallurgical solid waste disposal could be achieved with the constraint that fly ashes better

serve the purpose of heavy metal fixation than red muds.

Red muds and fly ashes, along with other metallurgical solid wastes and clay minerals, may be utilized

for constructing “natural barriers” (active permeable barriers) around shallow-land burial sites of lowlevel radioactive wastes and heavy metal-containing products.

8.5 RESIDUALS AND EMISSIONS

8.5.1 Project 34: Chemical Fixation of Soils Contaminated with Organic Chemicals

(Envirotreat Process)

No information on residuals or emissions was provided. Likely emissions would be dust that presents

similar hazards to any cement-based system, and possibly volatile organic compounds if temperatures

in the mixed material rise too high (the hydration of cement and lime are exothermic processes).

8.5.2 Project 29: Sorption/Solidification of Selected Heavy Metals and Radionuclides onto

Unconventional Sorbents

No information on emissions was provided, but as noted above, prior treatment of the fly ash is

recommended to reduce the possibility that trace elements already present in the ash will leach into the

environment.

8.6 HEALTH AND SAFETY

8.6.1 Project 34: Chemical Fixation of Soils Contaminated with Organic Chemicals

(Envirotreat Process)

No specific information was provided on health and safety. However, the likely hazards are those

associated with any cement- or lime-based system and are primarily those that result from contact with

highly alkaline materials and from chrome in cement. If volatile organic compounds are emitted due to

heating of the mix, additional hazards would be expected.

8.6.2 Project 29: Sorption/Solidification of Selected Heavy Metals and Radionuclides onto

Unconventional Sorbents

No specific issues of health and safety are related to this process, other than those that would ordinarily

attend pretreatment processes. The reports provided no indication of the specific activity of fully loaded

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wastes and whether these activities might pose a health hazard, but the purpose of the treatment is, after

all, to concentrate radionuclides on the solid adsorbent.

8.7 COSTS

No information was provided on costs for either project.

8.8 FUTURE STATUS OF CASE STUDY PROCESSES AND TECHNOLOGY AS A WHOLE

The Envirotreat Process (Project 34) clearly has potential but needs to be employed in better designed

studies that are more likely to reveal the claimed benefits of the active ingredient. The findings of the

pilot field study fail to demonstrate that the technology can bind PAHs or other organic compounds.

The use of wastes as adsorbents needs to be followed up by larger-scale studies, leading in due course

to field trials under practical conditions.

8.9 REFERENCES

1. Harris, M.R., S.M. Herbert, and M.A. Smith, Remedial Treatment for Contaminated Land, Volume

IX: Ex-Situ Treatment of Contaminated Soils, Sediments and Sludges, Construction Industry Research

and Information Association (London) 1995.

2. Anderson, W.C. (editor), Stabilization/solidification, American Academy of Environmental Engineers

(Annapolis, MD) 1994.

3. Hinsenveld, M. Stabilization/Solidification Technologies, In: Demonstration of Remedial Action

Technologies for Contaminated Land and Groundwater, Final Report, Volume 1, pp 53-63, USEPA,

EPA/600/R-93/012a, 1993.

4. USEPA, Corrective Action: Technologies and Applications,

Seminar Publication, EPA/625/4-89/020, 1989.

5. USEPA, Innovative Treatment Technologies Overview and Guide to Information Sources, Office of

Solid Waste and Emergency Response, EPA/540/9-91/002, 1991.

6. Bishop, P.L., "Stabilization/Solidification of Contaminated Soils: An Overview," Proceedings of the

Third International KfK/TNO Conference on Contaminated Soil ’90, Arendt, F., M. Hinsenveld, and

W.J. van den Brink, W.J. (edits), Kluwer Academic Publishers (Dordrecht), pp 1265-1274, 1990.

7. Harris, M.R., S.M. Herbert, and M.A. Smith, Remedial Treatment for Contaminated Land, Volume

III: Site Investigation and Assessment, Construction Industry Research and Information Association

(London) 1995.

8. MacKay, M. and J.J. Emery, Practical Stabilization of Contaminated Soils, Land Contamination and

Reclamation, 1:3, pp 144-145, 1993.

9. Emery, J.J., "Stabilization of Industrial Sludge for Fill Applications," Volume 4, Proceedings Seventh

International Congress on the Chemistry of Cement (Paris), 1980.

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NATO/CCMS Pilot Study, Phase II Final Report

10. Barry, D.L., Treatment Options for Contaminated Land (Report to the Department of the

Environment), W.S. Atkins Research and Development (Epsom), 1982.

11. USEPA, Handbook on the In Situ Treatment of Hazardous Waste-Contaminated Soil, EPA/540/2-

90/002, 1990.

12. USEPA, International Waste Technologies/Geo-Con In Situ Stabilization/solidification, Applications

Analysis Report, EPA/540/A5-89/004, 1990.

13. USEPA, Hazardous Waste Control: Nomix® Technology, In: The Superfund Innovative Technology

Evaluation Program: Technology Profiles, Fifth Edition, pp 100-101, EPA/540/R-92/077, 1992.

14. USEPA, S.M.W. Seiko Inc: In Situ Solidification and Stabilization, In: The Superfund Innovative

Technology Evaluation Program: Technology Profiles, Fifth Edition, pp 156-157, EPA/540/R-92/077,

1992.

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Chapter 9: OTHER REMEDIATION TECHNOLOGIES

Diane Dopkin

Environmental Management Support, Inc., Silver Spring, MD, U.S.

9.1 INTRODUCTION

The projects included in this chapter (22, 39, 50, 51, 53, 55, and 56) were not covered in previous

chapters for the following reasons: (1) the project is still in the site investigation stage; (2) remedial

options have been selected, but not implemented; or (3) the selected remedial option does not fit into

the categories of technologies highlighted in the other technology chapters (in situ treatment, physicalchemical treatment, ex situ biotreatment, thermal treatment, or stabilization/solidification). The following

sections summarize the findings of these projects. Additional information on these projects is contained

in Appendix IV.

9.2 PROJECTS IN THE SITE INVESTIGATION STAGE

Projects 51 and 56 involve site investigations at contaminated industrial and military properties in the

Czech Republic and will continue into the remediation stage during Phase III of NATO/CCMS Pilot

Study.

9.2.1 Project 51: Sobéslav, South Bohemia Wood Treatment Plant

Since the 1870s, a wood processing plant has been operating on the outskirts of the town of Sobéslav,

located 120 km south of Prague, Czech Republic. Wood products such as railway sleepers and telegraph

poles were treated at the Sobéslav wood processing plant by immersion in boiling tar (“black”

impregnation) or by coating with a mixture of heavy metal salts (“white” impregnation).

In 1990, following a decision to install and upgrade existing process equipment, a site investigation was

performed to determine the extent of soil and groundwater contamination resulting from industrial

operations at the plant. This investigation was completed in December 1996. Soil and groundwater

contaminated with polycyclic aromatic hydrocarbons (PAHs) and metals were identified in an area of

approximately 1-2 km2

. The contamination resulted from on-site disposal of tar sludges in poorly lined

pools, discharge of untreated effluent into the Lužnice River, and discharges of chemicals from treated

products staged at the site prior to transportation.

Initial concerns about site pollution centered on the foul odors emanating from local drinking water

wells. The odors prompted an investigation by the local environmental health authority, which examined

the results of biological oxygen demand (BOD), chemical oxygen demand (COD), and non-polar

extractable organic analyses of surface water and groundwater samples. The more comprehensive

investigation initiated in 1990 included a detailed site walkover survey, aerial imaging, inspection of

plant life, installation and logging of monitoring wells, chemical sampling of soil and groundwater, and

pump testing to determine subsurface permeability. Although originally intended to be completed in 14

months, the investigation was extended to 35 months because of financial, analytical, and regulatory

difficulties.

During the walkover survey, the principal sources of contamination were identified as a leaking creosote

oil storage tank and seepage from unlined disposal lagoons in the southeast part of the site. Nearly 100

boreholes were drilled, and sandy to sandy clay soils overlying sedimentary clays were found to underlie

the site. Monitoring of the groundwater indicated a light non-aqueous phase liquid (LNAPL) layer up

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to 0.7 m thick at the site. Extensive analysis of soil and groundwater samples confirmed elevated

concentrations (unspecified) of PAHs, heavy metals, and phenols.

An initial investigation of remedial options was carried out by a German consultancy, which studied the

effectiveness of biotreating the contaminated soils. Results showed that an initial decrease in PAH

concentrations was followed by a greater increase in concentrations, which destroyed the degrading

micro-organisms. The study concluded that microbial activity had caused rapid desorption of

contaminants and increased bio-available concentrations to intolerably high levels. Although more

success was achieved during bench-scale testing using in situ groundwater biotreatment, the technique

was unsuccessful during field-scale testing. As a result, it was concluded that soil encapsulation, in

combination with pumping and treating groundwater with gravel filters, was the most cost-effective

remediation solution.

9.2.2 Project 56: Spolchemie a.s.—Mercury-Contaminated Site

The town of U ̋ sti nad Labem lies in the a region of North Bohemia known as the “black triangle”

because of the severity of its environmental problems. The Spolek pro chemické a hutni vyroba

(Company for Chemical and Industrial Production), also known as “Spolchemie,” is one of the most

contaminated sites in this region. Spolchemie was founded in 1856 for the production of chlorinated lime

and sodium bicarbonate. The company has since produced pesticides, including DDT and “Agent

Orange,” and a variety of other chemicals. More than 30 separate production facilities are known to have

operated at the site, which occupies over 1,000 x 5,000 m2 (>500 hectares or 1,000 acres).

Mercury has been used in electrolysis operations at Spolchemie since 1890. Based on an environmental

audit of the site, it is estimated that the total release of mercury at the site has been greater than 500

metric tons. Liquid mercury has been observed during soil excavations.

Site investigations have been conducted near the electrolysis plant to assess mercury contamination in

soil and groundwater. Mercury concentrations in nine groundwater samples collected in January 1996

ranged from <0.1 μg/L to 154.1 μg/L, and concentrations in 39 soils samples ranged from <0.0001

mg/kg to 707 mg/kg. Concentrations of all but one of the groundwater samples exceed 0.1 μg/L, which

is the Ministry of Environment's Category A threshold concentration for mercury; four samples exceed

5 μg/L, which is the Category C threshold. Furthermore, nine of 39 soil samples exceed the Category

A threshold concentration of 0.3 mg/kg for mercury in soil; six samples exceed the Category C threshold

of 10 mg/kg.

Up to several hundred micrograms per liter of chlorinated hydrocarbons and slightly elevated

concentrations of zinc and copper were also detected in samples at Spolchemie. Remedial options are

being studied.

9.3 PROJECTS FOR WHICH REMEDIAL OPTIONS HAVE BEEN SELECTED, BUT NOT

IMPLEMENTED

The site characterization and risk assessment stages of Project 55 have been completed, and bioventing

and biosparging have been selected to remediate the site.

9.3.1 Project 55: Czechowice Oil Refinery Project

This project involves a working partnership between the U.S. Department of Energy (DOE) and the

Institute for Ecology of Industrial Areas (IETU), an independent organization under the Polish Ministry

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of Environmental Protection. Each phase of the project aims to demonstrate the technology and decisionmaking processes involved in site remediation.

The first project initiated by the partnership was the environmental characterization, risk assessment, and

remediation of the Czechowice Oil Refinery, which has operated for nearly 100 years near the city of

Katowice in southern Poland. The refinery uses a catalytic cracking process to refine crude oil. Wastes

from the cracking process were deposited in site lagoons, which are now filled with a thick viscous

sludge. Leakage of the lagoons has contaminated soil and groundwater with several organic compounds.

Environmental characterization of the refinery will consist of a two-phased expedited site characterization

approach using low-cost, simple rapid-response technologies to obtain general site information, followed

by quantitative sampling using direct push technologies for data collection. Risk assessment will involve

the development and refinement of potential exposure scenarios. The scenarios will be combined with

the expedited site characterization results to quantify potential risks from the site to humans and the

environment. The estimates of risk will be compared to appropriate benchmark concentrations for the

contaminants.

Based on preliminary site information, bioventing and biosparging have been proposed to remediate the

lagoons. Bioventing involves the injection of oxygen and nutrients into the subsurface to aerobically

stimulate the indigenous microorganisms to degrade hydrocarbons to carbon dioxide and water. Vertical

injection wells will be installed around the perimeter of the lagoons to aerate and remediate the

contaminated vadose zone. Biosparging will be conducted to treat the lagoon sludge. Biosparging is

similar to bioventing except that the air and nutrients are injected into a liquid, in this case a lined basin

filled with process water. Sludge that has been pH-adjusted or mixed with a surfactant will be added to

the basin in batches. In the implementation of both remediation technologies, the level of microbial

activity, pH, contaminant concentrations, and rate of degradation will be carefully monitored.

9.4 PROJECTS FOR WHICH THE SELECTED REMEDIAL OPTION DOES NOT FIT IN THE

CATEGORIES OF TECHNOLOGIES HIGHLIGHTED IN THE OTHER TECHNOLOGY

CHAPTERS

Projects 22, 39, 50, and 53 involved remedial options not covered by the technologies detailed in the

previous chapters of this report. Project 22 describes the recovery of jet fuel from contaminated

groundwater; in situ bioremediation is proposed to treat residual contamination in the unsaturated zone,

but has not yet been implemented. Project 39 involves the ex situ treatment of groundwater contaminated

with dissolved organic compounds using a chemical oxidation technology.

Project 50 involved demonstration of a groundwater pump-and-treat system coupled with a pervaporation

system to treat groundwater contaminated with dissolved organic contaminants. In addition, in situ rotary

steam and air stripping were demonstrated for the treatment of contaminated soil. In situ bioremediation

has been proposed for further treatment of soil; however, the demonstration has not yet been conducted.

Project 53 involved both laboratory- and pilot-scale studies of in situ biotreatment, using aerobic and

anaerobic zones to mineralize tetrachloroethene (PCE) to ethene.

9.4.1 Project 22: Environmental Evaluations of Former Soviet Military Bases in Hungary

After the withdrawal of the Soviet army from Hungary in 1990, the Hungarian Ministry for Environment

conducted an environmental assessment and damage survey following a method acceptable to both the

Hungarian and Soviet governments. Tököl airbase was one of the sites identified as needing prompt

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remediation because it is located just 600 m from the Danube River and lies atop of the aquifer that

supplies the village of Halasztelek with about 5% of its municipal drinking water. Site investigations

determined that the groundwater was contaminated by free phase and dissolved hydrocarbons from a jet

fuel storage area. Contaminated groundwater from the airfield was migrating slowly towards the

Halasztelek water supply wells.

Recovery operations at Tököl began in August 1991. Recovery of free product from groundwater was

accomplished by depressing the water table to accelerate the flow of groundwater toward large diameter

recovery wells where product was separated using 150 mm diameter Filter Scavenger pumps. By June

1993, approximately 224,000 liters of jet fuel were recovered from 279,000 m3 of pumped groundwater.

By April 1994, the volume of recovered jet fuel was about 700,000 liters.

Remediation at Tököl was accomplished in cooperation with the Danish Agency of Environmental

Protection. The total cost was estimated at U.S.$600M (1994). The study concluded that although

immediate risks to the Halasztelek water supply was reduced, jet fuel sorbed to soil in the unsaturated

zone is still present and poses a long-term source of groundwater contamination. Pilot scale in situ

bioremediation was successful and was recommended as an effective method for further reducing risks

to groundwater quality.

9.4.2 Project 39: Management of Soil Vapors at the Basket Creek Site

The Basket Creek Site, located in Douglassville, Georgia, is an abandoned surface impoundment used

in the 1960’s for the disposal of industrial wastes. The disposed wastes were ignited accidently and

burned for several days in 1970. The USEPA initiated emergency action at the site in 1991. Analyses

of soil samples revealed concentrations of toluene, methyl ethyl ketone, methyl isobutyl ketone in

concentrations exceeding 30%; concentrations of trichloroethylene and tetrachloroethylene of up to 8,000

mg/kg; and concentrations of mercury and lead of 400 mg/kg and 5,000 mg/kg, respectively.

Approximately 765 m3 of contaminated soil was present with total organic concentrations ranging from

5-10%.

An in situ soil vapor extraction (SVE) treatability study determined that the soil was not sufficiently

permeable for in situ SVE to be viable, and low temperature thermal desorption was rejected due to the

low flash point of the soil vapor (150°C), which resulted in ignition of a soil sample during the

treatability study. Based on the treatability results, ex situ SVE was selected to treat the contaminated

soil.

Contaminated soil was excavated from the site within a 60-foot by 120-foot (18.3 m by 36.6 m)

ventilated metal enclosure to prevent the escape of untreated vapors. The excavated soil was screened

to remove rock and debris; the screened soil was stockpiled, and ambient air was pumped through the

stockpile via 4-inch (10-cm) diameter slotted horizontal well screens.

Extracted vapors from excavation and SVE were passed through a bag-house for the removal of

particulates and treated with a thermal oxidizer. The thermal oxidizer operated at temperatures of 816-

871°C and had a greater than 95% removal efficiency.

In total, approximately 1,500 m3 of soil were excavated and treated. In addition, 100 tons of screened

rocks and debris, 18 yd3 (13.8 m3

) of excavated metal and crushed drums, and 4,250 gallons (16,086

liters) of decontamination water were disposed at appropriate off-site facilities.

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The total cost of the project was $2 million (1993), which was $1 million less than the original estimate

in 1992. The project was interesting in that the soil was not treatable by SVE in situ, but could be

treated by venting ex situ after excavation and screening.

9.4.3 Project 50: Integrated Rotary Steam Stripping and Enhanced Bioremediation for In

Situ Treatment of VOC-Contaminated Soil (Cooperative Approach to Application of

Advanced Environmental Technologies)

This project involves technology demonstrations at the Department of Energy's Pinellas Northeast Site,

located in Largo, Florida, USA. Concentrations of chlorinated volatile organic compounds (VOCs) in

the sandy surficial aquifer at the site range from 10-1,000 mg/L. In January 1995, the following three

technologies were selected for pilot tests at the Pinellas site:

(1) groundwater pump and treat with a pervaporation system to remove VOCs from the pumped

groundwater while eliminating air emissions and the need for costly groundwater pre-treatment;

(2) in situ rotary steam and air stripping to treat the highest concentrations of VOCs in soil and

reduce them to a level of 100 mg/kg; and

(3) nutrient injection to enhance in situ anaerobic bioremediation of soil with VOC concentrations

of 100 mg/kg or less.

A potential cost savings of U.S.$5-10 million was anticipated over the proposed baseline remedial

design, which was a standard 30-year pump-and-treat system using groundwater recovery wells and an

air stripper. Furthermore, the proposed baseline remedial design was not expected to reduce the most

concentrated areas of VOCs to below drinking water standards.

Pervaporation Technology Evaluation

Evaluation of the pervaporation pilot test was conducted from 1995-1996. Two recovery wells pumped

groundwater to the system, which used membranes to allow VOCs to preferentially permeate. Transport

of VOC vapors through the membrane was induced by maintaining a lower vapor pressure on the

permeate side of the membrane than on the side of the influent groundwater. This pressure difference

was achieved by cooling the permeate vapor to make it condense.

The pilot system was capable of treating 1-2 gallons of groundwater per minute. Approximately 6,250

gallons of groundwater with VOC concentrations ranging from 500-1,000 parts per million (ppm) were

treated during the pilot test. Effluent contaminant concentrations were reduced to 1-4 ppm under

optimum operating conditions; however, the efficiency of the system was lowered due to membrane

fouling caused by the precipitation of iron gel. Moderate success was achieved by modifying the system

and adding chemicals to reduce membrane fouling. The only wastes produced during the pilot test were

the permeate and the spent filters used to inhibit membrane fouling. VOCs were successfully

concentrated in the permeate, eliminating air emissions. Full-scale system capital costs for the

pervaporation system to treat 20 gallons per minute are expected to range from U.S.$200,000-275,000;

operating costs are expected to range from U.S.$10-20 per 1,000 gallons (3,785 liters) of treated water.

Rotary Steam and Air Stripping Technology Evaluation

Evaluation of the rotary steam and air stripping pilot test is currently being conducted. The stripping

system injects steam and hot air through a rotating auger to volatilize VOCs sorbed onto soil particles.

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The off-gases are transported by the injected steam and air to a metal hood at the ground surface where

they are treated using a catalytic oxidation system for the destruction of contaminants and an acid-gas

scrubber to eliminate air emissions.

Thus far, the system has effectively reduced the concentrations of chlorinated VOCs in soil from 1,000-

6,000 ppm, to 100-300 ppm, which was the goal for this site. However, several operational problems

were experienced with the total system. In particular, the catalytic oxidation system was unable to handle

the quantity of the vapors generated by the stripping system. As a result, some vaporized VOCs initially

escaped from the metal hood. This problem was subsequently controlled by reducing the injection

pressures. The only wastes generated by the system were from the scrubber. The initial results of the

pilot test indicate that the operational costs will range from U.S.$70-200/yd3 (U.S.$92-260/m3

).

Nutrient Injection to Enhance In Situ Anaerobic Bioremediation

The in situ anaerobic bioremediation system recently began operation and has not yet been evaluated.

The system involves a series of horizontal wells and infiltration galleries to control the hydraulic gradient

and supply nutrients to the contaminated zone.

9.4.4 Project 53: In Situ Bioremediation of Chloroethene-Contaminated Soil

In the Netherlands, between 20-30% of heavily contaminated sites have chlorinated hydrocarbons—in

particular, trichloroethene (TCE) and PCE—as a principal constituent. On some sites, the depth to

contamination makes ex situ treatment technically difficult and uneconomical. Therefore, there is a need

to develop in situ remedial techniques for this type of contamination. Biotreatment is particularly

attractive since it offers the potential for remediation without generating any secondary hazardous waste

for further treatment or disposal. However, biodegradation of chloroethenes is technically and

microbiologically complex, and might prove difficult to achieve under field conditions. This Pilot Study

project reports on the development of an in situ biotreatment for chloroethenes from bench-scale studies

to a pilot-scale field application.

Technical Concept

The Tauw Milieu approach to treating chloroethenes exploits both aerobic and anaerobic microbial

processes. Although chloroethenes such as PCE are persistent under aerobic conditions, they can be

dechlorinated sequentially by anaerobic bacteria to TCE, dichloroethene (DCE), vinyl chloride, and

ultimately to ethene. Since the dechlorination of DCE and vinyl chloride are the rate-limiting steps, these

compounds are accumulated under anaerobic conditions as intermediate breakdown products of PCE.

In contrast to PCE, however, less-chlorinated ethenes can be co-metabolically mineralized by aerobic

bacteria. The Tauw Milieu process degrades PCE through stimulation of bacteria in spatially separated

aerobic and anaerobic zones. PCE is degraded anaerobically to TCE and DCE, which are transported

downstream to an aerobic zone where they are mineralized to ethene.

Laboratory Studies

By February 1996, the process had been demonstrated and verified for PCE at the bench scale. These

studies showed that under anaerobic conditions, using formate and methanol as carbon and electrondonor sources respectively, PCE and TCE were readily dechlorinated to DCE and other intermediaries.

In addition, using toluene or phenol as a co-substrate, TCE, DCE, and vinyl chloride were readily

degraded aerobically. Flask studies with indigenous bacteria from a proposed pilot-scale test site had

similar results.

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In order to evaluate degradation kinetics, a series of column experiments were performed using 0.7-L

columns of site soil through which 200 mL of site groundwater was recirculated. The soil column was

operated anaerobically, spiked with PCE, and supplied with formate or methanol as a carbon source and

electron donor. PCE concentrations initially decreased due to sorption onto column material, but

dechlorinated breakdown products were noted approximately three weeks after start-up. Although

degradation was observed using both formate and methanol, it was concluded that methanol would be

used for the pilot-scale system because of its lower cost and more stable pH profile. The aerobic column

was set up in a similar way to the anaerobic column. It was spiked with PCE and its breakdown

products (TCE, DCE, and vinyl chloride). The daughter products were readily degraded with the addition

of phenol to the column, but PCE degradation was not observed.

Pilot-Scale Study

The pilot-scale remediation study was conducted from August 1995 to September 1996 at a former dry

cleaning facility near the town of Breda. Soil and groundwater was contaminated with PCE over an area

of 1,800 m2 to a depth of 10 m. Concentrations of PCE in groundwater ranged up to 10,000 μg/L. The

unsaturated zone was remediated using soil vapor extraction, and the saturated zone and groundwater

were remediated by a combination of aerobic and anaerobic biodegradation.

The anaerobic biodegradation zone was created by the extraction and injection of groundwater (up to

250 m3 per day) to which methanol and nutrients were added. A total of about 1,100 kg of methanol was

injected. By carefully controlling the hydrogeological environment, anaerobic conditions were created

within the recirculating “groundwater loop.” Downstream of this loop, aerobic biodegradation was

supported by slow infiltration of phenol (acting as a co-metabolite) through a series of wells. A well

downstream of the anaerobic treatment zone was used to extract up to 150 m3 of groundwater per day,

in order to prevent the contamination spreading and to provide water for the phenol infiltration process.

Extensive monitoring was conducted to determine the effectiveness and kinetics of the degradation

processes and to mitigate the migration of the contamination plume. Methanol was detected in all

monitoring wells in the anaerobic zone, in concentrations ranging from 120 to 800 μmol/L. As soon as

the methanol was detected, anaerobic degradation was observed. PCE was degraded rapidly to DCE;

TCE, vinyl chloride, and ethene were present but did not accumulate significantly.

Under anaerobic conditions, PCE was dechlorinated at rates comparable to those found in the laboratory,

and evidence of complete anaerobic degradation to ethene was found. The aerobic process also proved

successful, with complete degradation of phenol and DCE. The limiting factor associated with in situ

biodegradation of chloroethenes appears to be the availability of suitable electron donors rather than the

presence of microorganisms.

Prognosis

The pilot study proved so successful that the site owner is continuing the remediation, which is expected

to take two to three years.

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Chapter 10: INTEGRATION OF TECHNOLOGIES

Kai Steffens

Probiotec GmbH

10.1 INTRODUCTION

Experience shows that contaminated sites frequently cannot be remediated by a single technology.

Complex contamination problems require the combination of different technologies for either different

contaminated areas and media or for a specific medium exhibiting complex contamination.

However, remediation strategies employing a single treatment technology and those employing a

combination of technologies are commonly more complicated and more expensive than is removal to

a landfill. Consequently, not only technical effectiveness (in terms of ability to achieve remediation

objectives, time requirements, potential environmental impacts, and cost), but also “political” (policy)

factors will influence the choice of strategy. These policy considerations may lead to adoption of

complex treatment systems that otherwise might be rejected in terms of short term costs alone (assuming

comparable technical effectiveness).

In Chapter 2, the terms “integrated” and “mixed” are used to describe combinations of technologies that

are used as part of an overall remediation strategy. In the Phase II Pilot Study, 23 projects used a single

technology, 19 involved an integration of technologies, and seven used different technologies in parallel

(“mixed”).

The term “integrated” refers to approaches involving process integration where two or more technologies

are used simultaneously or in series to treat a specific problem. The term “mixed“ refers to projects

involving two or more technologies to treat different contaminated areas or media at a site as part of an

overall remedial strategy. The individual technologies applied in both the integrated and the mixed

projects are discussed in detail in the other chapters in this report.

This chapter focuses on projects in which treatment technologies were integrated to treat a contaminated

material in two or more stages. The goal is to discuss identified benefits, problems, and general

constraints.

The Pilot Study projects involving integration of treatment technologies are listed and briefly described

in Section 10.3. The general characteristics of the projects are summarized in Section 10.4 Performance

results of the integration are discussed in Section 10.5, while factors and limitations to consider for

determining the applicability of technology integration are dealt with in Section 10.6. Cost information

is provided in Section 10.7. Finally, general conclusions are discussed in Section 10.8.

10.2 BASIC OPTIONS AND CLASSIFICATION OF APPROACHES

Effective and efficient treatment of environmental contamination requires tailor-made solutions meeting

the specific requirements of the media to be treated, of the contaminants to be removed or destroyed,

and of the policy framework within which the project is to be implemented. In many projects, the

contamination problem can be adequately addressed by applying a single treatment technology. However,

problems may occur due to one or more technical or organizational factors:

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NATO/CCMS Pilot Study, Phase II Final Report

10.2.1 Technical Factors

• Difficult-to-treat media, such as soil with high proportion of fine-grained material; mixed solids (soil,

ashes, slags, brick, debris, concrete, plastics, wood, etc.); solids with a high proportion of organic

matter (e.g., peat); low-permeability soils and sediments; fine or uneven distribution of contaminants

(i.e., giving rise to low bioavailability); or large volumes of contaminated material requiring

treatment.

• Contaminants that are difficult to treat due, for example, to physical properties (e.g., low solubility);

chemical properties (e.g., not biodegradable); presence of complex contaminant mixtures (e.g., metals

and organic compounds).

10.2.2 Organizational Factors

• Policy (e.g., generation of secondary waste that would have to be landfilled)

• General project constraints, such as budget; time constraints; space constraints; or lack of community

acceptance (e.g., due to high emissions).

The limitations of the “single” technologies are discussed under their respective chapters in this report.

Frequently, combinations of technologies can overcome these limitations. In many cases, efforts are

made to reduce the amount of material requiring expensive treatment by separating fractions of materials

that can be reused without further treatment or with limited effort. In other cases, materials or

contaminants are difficult to treat, which means that the limitations of a single technology are evident

early in the development of the remediation strategy. In these cases, means of modifying the material’s

physical and chemical conditions have to be identified and evaluated in order to allow treatment at all,

or to optimize cost and results.

The organizational factors mentioned above are commonly reduced to the “policy” requirement to avoid

generating secondary wastes that would have to be landfilled.

Technology integration can be generally classified into methods involving

• separation of fractions for volume reduction or to apply different downstream treatments; or

• increasing the availability of contaminants for treatment by mobilizing of contaminants in the

medium to be treated; modifying the chemical or physical properties of contaminants; or employing

treatment trains for sequential removal/treatment of different types of contaminants.

In practice, a combination of these options may be employed in an integrated treatment system to deal

with particularly complex contamination.

Separation of different fractions may be carried out to reduce the volume to be treated using a more

expensive technology or to be treated at all; to separate out fractions that need to be treated differently.

Separation is usually achieved through dry physical separation (e.g., crushing or sieving) or wet physical

separation (e.g., soil washing or other wet mechanical separation processes or flotation with or without

chemical pretreatment). Besides separating out the more contaminated fine grained concentrate, creating

a “clean” coarse fraction may be intended when applying wet mechanical separation processes. One

group of integration options is based on the principle of washing off the contaminants and the (highly)

contaminated fine particles from the surfaces of the coarser particles, leaving the coarse fraction

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NATO/CCMS Pilot Study, Phase II Final Report

relatively “clean.” A second group of options uses physical techniques to separate fractions by exploiting

differences in the physical properties (e.g., specific gravity or surface hydrophobicity).

Mobilization of contaminants may be achieved by altering the medium to be treated. Examples include

• in situ methods, such as through fracturing, steam injection, air sparging, or soil flushing with

agents; and

• ex situ methods, such as crushing clay-clumps.

Mobilization may also be achieved by modifying the contaminants to increase availability to microbial

degradation by concentrating or pretreating the contaminants (e.g., partial oxidation of organics).

Treating combinations of different contaminants (e.g., organics and metals) usually will require

application of different processes in sequence. Table 10.1 lists the factors limiting effective treatment

with only one technology and the options to overcome these limitations.

Table 10.1: Factors Limiting Effective Treatment with Only One Technology and the General

Options to Overcome the Limitations

Limiting Factor

Options to Overcome Limitation

Separation Mobilization of

Contaminants

Sequential

Treatment

Soil with high fines

Mixed solids

Solids with high proportion of organic

material

In situ treatment of low-permeability

sediments

Fine or uneven distribution of

contaminants (low bioavailability)

Large volumes to treat

Low solubility contaminants

Non-biodegradable contaminants

Complex mixtures of contaminants

10.3 CASE STUDIES CHOSEN

The 15 Pilot Study projects reviewed for this Chapter are listed in Table 10.2. Additional information

on the projects is provided in the brief descriptions that follow. Further information is available in the

project summaries found in Appendix IV.

This Chapter focuses on the integration of technologies. The individual technology elements, which make

up the integrated technologies discussed in this chapter, are described and analyzed in detail in the

respective technology-based chapters.

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NATO/CCMS Pilot Study, Phase II Final Report

Table 10.2: Projects Involving Integration of Treatment Technologies

Project Description Goal of

Integration

1 Trial of air sparging of a petroleumcontaminated aquiferField trials of air sparging combined with

soil vapor extraction to determine the

increase of extracted VOCs

Mobilization of

contaminants

9 Field demonstration of an in situ

process for soil remediation using well

points

Field demonstration of a combined in situ

soil flushing and bioremediation technology

for BTEX and petroleum hydrocarbons

Mobilization of

contaminants

10 Integrated treatment technology for the

recovery of inorganic and organic

contaminants from soil

Integrated ex situ classification and solvent

enhanced soil washing process for metals

and PAHs; separation of metal particles by

classification; solvent extraction of PAHs

and hydrometallurgical leaching of metals

from a slurry (pilot-scale)

Mixed contaminants requiring

different

treatment

13 Rehabilitation of a site contaminated

by tar substances using a new on-site

technique

Integrated soil washing and two-stage

thermal treatment of highly tar-contaminated

fines (full-scale, thermal unit: 1 ton/hr

operating capacity)

Volume

reduction

15 Combined chemical and microbiological treatment of coking sites/

bioremediation of soils from coal and

petroleum tar distillation plants

Microbiological treatment of aromatic

hydrocarbons with and without oxidizing

pretreatments (bench-scale)

Increase

availability of

contaminants

19 Cleaning of mercury-contaminated soil

using a combined washing and

distillation process

Integrated soil washing and vacuum distillation plant used to treat mercury contaminated soil and debris (full-scale, 150 tonnes/

day)

Volume

reduction

24 Combined remediation technique for

soil containing organics: Fortec®

Combined hydrocyclone separation,

photochemical treatment, and bioremediation

(demonstration-scale, 300 m3 reactor)

Increase

availability of

contaminants

26 Treatment of creosote-contaminated

soil (soil washing and slurry phase

bioreactor)

Combined soil washing and slurry phase

bioreactor (pilot-scale, 1 ton/hr washing, 600

dm3 reactor)

Volume

reduction

27 Soil washing and chemical

dehalogenation of polychlorinated

biphenyl (PCB)-contaminated soil

Combined soil washing and chemical

dehalogenation (pilot/bench scale, 1.5 ton/hr

washing, bench-scale reactors)

Volume

reduction

31 Decontamination of metalliferous

mining wastes

Laboratory tests of a combination of

flotation and metal-leaching processes (pilotscale)

Volume

reduction

32 CacitoxTM soil treatment process Tests of combined application of soil

washing (for physical separation) and metal

leaching (pilot-scale, 10 kg/hr)

Volume

reduction

33 In-pulp decontamination of soils,

sludges, and sediments

Tests of combined application of soil

washing (for physical separation) and metal

leaching (bench-scale)

Volume

reduction

36 Enhancement techniques for ex situ

separation processes particularly with

regard to fine particles

Tests of combined application of wet soil

separation techniques and biological

treatment of the contaminated fines fraction

(bench-scale)

Volume

reduction

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Project Description Goal of

Integration

42 In situ pneumatic fracturing and

biotreatment

Pneumatic fracturing in low-permeability and

over-consolidated sediments increases

permeability and improves the conditions for

in situ remediation (SITE demonstration)

Increase

availability of

contaminants

47 In situ electro-osmosis (LasagnaTM

Project)

Fracturing in low-permeability and overconsolidated sediments increases

permeability and improves the conditions for

in situ remediation, e.g., by electro-osmosis

(demonstration-scale)

Increase

availability of

contaminants

10.3.1 Project 1: Field Trial of Air Sparging of a Petroleum-Contaminated Aquifer

Goal: Mobilization of contaminants to increase removal rate.

Three field trials were carried out at a gas station site in Adelaide, Australia, to determine the effect of

air sparging when applied in combination with soil vapor extraction (SVE). Air sparging caused a

substantial increase in the amount of extracted contaminants in the short term. However, the rate slowed

down within just a few days. This effect probably resulted from a mobilization of contaminants from

the immediate vicinity of the boreholes. The areas and layers with higher permeability were assumed

to exhaust fairly quickly, while the lower permeability layers were only slightly affected by sparging.

The zone of influence was limited to between 3 m and 9 m from the sparging well.

10.3.2 Project 9: Field Demonstration of an In Situ Process for Soil Remediation Using

Well Points

Goal: Mobilization of contaminants to increase removal rate. Treatment of residual concentration with

second technology.

The field demonstration was carried out at a site contaminated with benzene, toluene, ethylbenzene, and

xylenes (BTEX) and aliphatic hydrocarbons. The treatment process consisted of a recirculation system

with injection and extraction wells. During soil flushing, a surfactant/co-surfactant solution was used to

mobilize the contaminants, which were separated in an above-ground effluent treatment plant. The

remaining hydrocarbon contamination was to be subjected to microbial degradation enhanced by the

injection of nutrients and air or hydrogen peroxide into the well points.

10.3.3 Project 10: Recovery of Inorganic and Organic Contaminants from Soil

Goal: Integration of different physical and chemical separation steps suitable for different

contaminants in a treatment train.

A bulk soil sample from two industrial sites in Canada was collected for a pilot-scale evaluation of this

integrated technology. After breaking down clay clods in a wet scrubber, the slurried soil was sorted by

particle size, density, or magnetic susceptibility to produce a contaminant concentrate that was to be

recycled off site. The remaining slurry was subjected to a leaching process involving solvent extraction

for polycyclic aromatic hydrocarbon (PAH) removal and a hydrometallurgical treatment involving

leaching metals selectively and recovering them using metal-selective adsorbents. The pilot tests were

reportedly successful in producing a soil suitable for further use. Full-scale remediation of one of the

sites was decided on using a 600 tonnes/day plant. Estimated costs are U.S.$75/tonne.

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10.3.4 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using a New

On-Site Technique

Goal: Volume reduction of the material treated thermally, and application of different treatment

technologies suitable for different grain size fractions of soil.

This on-site remedial demonstration project combining excavation of tar-contaminated soil followed by

on-site ex situ thermal desorption was carried out at an old gasworks site in a densely populated area

of Copenhagen. Soil and debris surrounding two tar reservoirs were excavated in a tent and subsequently

treated in a combined soil-washing and thermal-desorption system. Soil washing was used to provide

a volume reduction step by producing clean fractions in the particle size ranges >50 mm and 2-50 mm

through screening and high-pressure spray washing. The contaminated fraction (<2 mm) was treated

using a two-stage thermal desorption process. In the first stage water and volatile substances were

evaporated from contaminated materials. The off-gas was treated using a particulate dust trap and an air/

oil/water separator and condenser. The second stage, operating at higher temperatures, was used to

volatilize the heavier tar substances, which were recovered in an air/tar condenser

10.3.5 Project 15: Combined Chemical and Microbiological Treatment of Coking Sites/

Bioremediation of Soils from Coal and Petroleum Tar Distillation Plants

Goal: Pretreatment of contaminants to optimize biodegradation rates.

PAH-degrading bacteria were identified and the practicality of using bioremediation for PAHs in soil

was evaluated. Furthermore, an oxidation-based pretreatment was examined to assess whether subsequent

bioremediation was enhanced. Very limited information was provided on this project and on the success

of the oxidizing pretreatments. Considerable additions were required to observe any increased

degradation of PAHs. There are indications that ferrous sulfide was used as an oxidizing catalyst.

10.3.6 Project 19: Cleaning Mercury-Contaminated Soil Using a Combined Washing and

Distillation Process

Goal: Volume reduction of the material that was to be treated thermally, and application of different

treatment technologies suitable for different grain size fractions of soil.

The Marktredwitz Chemical factory in Germany was established in 1786 and manufactured various

mercury compounds (including agrochemicals) and mineral acids. Buildings, soil, and groundwater were

heavily contaminated with mercury. A distillation unit was used in combination with a soil washing plant

that separated the highly contaminated silt/clay soil fractions to form a pretreatment concentrate for

thermal treatment. The sand and rubble fraction was disposed as clean fill. The fine fraction (grain size

ranging from <100 μm to <8 mm) was transferred to the vacuum distillation unit. The treated soil was

water cooled in a rotating drum to an average temperature of <50°C and recombined with the coarsegrained material from the soil washing plant.

10.3.7 Project 24: Combined Remediation Technique for Soil Containing Organics: Fortec

Goal: Volume reduction of material that is to be treated in downstream steps, and pretreatment of

contaminated concentrate to optimize biodegradation rates.

The system combines hydrocyclone separation of soil fractions resulting in separated coarse fractions,

which are either “clean” or can be subjected to additional soil washing. The slurry carrying the fine

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NATO/CCMS Pilot Study, Phase II Final Report

fraction can be treated in a photochemical (UV/H2O2) treatment step if persistent organic contaminants

(e.g., PAHs) are to be treated. The UV/H2O2 treatment partially oxidizes the organics and transforms

these compounds into biodegradable fragments. This photochemical pretreatment may be skipped if

organics are present, since they are more easily biodegraded. The final treatment step of the slurry is

a slurry-bioreactor, which is operated in batch mode.

10.3.8 Project 26: Treatment of Creosote-Contaminated Soil (Soil Washing and Slurry

Phase Bioreactor)

Goal: Volume reduction of the material that is to be treated in downstream steps.

Pilot-scale testing was done using a 1 tonne/hr soil washing unit. “Clean” coarse material was removed.

Soil washing was used as a pretreatment for froth flotation studies, which showed that a cationic

collector and frother removed high percentages of PAHs from the soil. PAH-contaminated slurry was

subjected to a subsequent bioreactor treatment in a pilot-scale unit.

10.3.9 Project 27: Soil Washing and Chemical Dehalogenation of PCB-contaminated Soil

Goal: Volume reduction of the material that is to be treated in downstream steps.

A soil washing unit with an operating capacity of 1.5 tonnes/hr was used for cleaning and separation

of a coarse grain-size fraction. The fines were treated further in a double air flotation cell. The

contaminated sludge from the flotation process was used for bench-scale testings of chemical

dehalogenation. Systems from three different vendors were tested, two of which (both closed reactors)

were successful. Detailed information on the dehalogenation testings was not presented.

10.3.10 Project 31: Decontamination of Metalliferous Mining Wastes

Goal: Volume reduction of the material that is to be treated in downstream steps.

Laboratory-scale studies of mineral processing techniques were carried out on lead- and zinc-containing

spoils from abandoned mine sites in Wales. Separation testing was conducted using dense media (“sinkand float”) and froth flotation cells. Subsequently, leaching tests were done using various chemical

agents. Results show that leaching of unprocessed material is significantly more effective than leaching

of processed material.

10.3.11 Project 32: CacitoxTM Soil Treatment Process

Goal: Volume reduction of the material that is to be treated in downstream steps.

The proprietary reagent converts insoluble or adsorbed contaminants into soluble complexes. Pilot-scale

studies used a plant with a capacity of 10 kg/hr to leach heavy metals and radionuclides from soil.

During application of this technology, soil washing should be applied as a pretreatment step to reduce

the volume by separating out a fine-grained contaminant concentrate.

10.3.12 Project 33: In-pulp Decontamination of Soils, Sludges, and Sediments

Goal: Volume reduction of the material that is to be treated in downstream steps.

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NATO/CCMS Pilot Study, Phase II Final Report

Laboratory- and bench-scale studies of metal leaching processes were carried out using a 10-kg sample

of soil contaminated with copper, chromium, zinc, and arsenic. It is indicated that a preliminary soil

washing process should be used for initial volume reduction by separation of a fine-grained concentrate.

The results of the leaching tests show that arsenic was the contaminant most difficult-to-treat, requiring

multiple acid leaching to achieve low residual concentrations. Other trials were done with mercurycontaminated soil, including the investigation of a thermal option (heating the material to around 800°C)

to achieve regulatory targets.

10.3.13 Project 36: Enhancement Techniques for Ex Situ Separation Processes

Particularly with Regard to Fine Particles

Goal: Volume reduction of the material that requires further treatment or is to be landfilled.

Laboratory- and pilot-scale tests were done with two soils contaminated with organics. The study

focused on the fate of highly contaminated fine particles in a wet separation processes. Subsequent tests

were conducted using a laboratory-scale slurry bioreactor for treatment of the fines. The study concludes

that wet separation techniques (“soil washing”) can be beneficially applied if a substantial fraction of

the soil of grain size >0.002 mm is contaminant free, and if material <0.002 mm is less than 30-35%

by weight of the original feed soil.

10.3.14 Project 42: In Situ Pneumatic Fracturing and Biotreatment

Goal: Improvement of conditions for subsequent in situ treatment.

A field-scale pilot study was done under the USEPA’s Superfund Innovative Technologies Evaluation

(SITE) Program. Low-permeability and over-consolidated sediments were subjected to pneumatic

fracturing (by pressurized air) to increase the permeability of the soil to liquids and vapors. In the field

demonstration, permeability was increased by up to 40 times within an effective radius of about 6 m.

This technology can improve the conditions for in situ treatment of low-permeability sediments by SVE

or biodegradation, for example. The results of the field test combining fracturing and bioremediation are

promising.

10.3.15 Project 47: In Situ Electro-Osmosis (LasagnaTM Project)

Goal: Improvement of conditions for subsequent in situ treatment.

The overall concept of the LasagnaTM technology is to introduce treatment zones (zones of high

permeability containing treatment agents) into contaminated areas. Electro-kinetic mechanisms carry

water and contaminants through these zones for treatment in situ or after extraction. To improve

conditions for in situ treatment in low-permeability sediments, hydraulic or pneumatic fracturing may

be employed.

10.4 REVIEW OF CASE STUDIES AS A GROUP

In eight of the 15 Pilot Study projects employing integrated technologies, the primary goal of integration

was to reduce the volume of the material requiring expensive treatment, such as thermal treatment of

organics and mercury (in two projects) or leaching of metals (in three projects). In other cases, wet

physical separation processes were applied to form a fine-grained contaminant concentrate that was

subjected to further treatment: microbial degradation in bioreactors (in two projects) and chemical

dehalogenation of PCBs. Information on various aspects of the projects is summarized in Table 10.3.

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NATO/CCMS Pilot Study, Phase II Final Report

Table 10.3: Goal of Combination, Input Materials in Terms of Medium Treated, Contaminants

Present, Types of Technologies Combined and Scale of Project

Project Input Materials Contaminants Technologies

Combined Scale

Separation of Fractions

13 Rehabilitation of a site

contaminated by tar

substances using a new

on-site technique

Soil and debris

(fraction <2 mm)

Tar Soil washing and

two-stage thermal

treatment

Full-scale, thermal

unit: 1 ton/hr

operating capacity

19 Cleaning of mercurycontaminated soil using a

combined washing and

distillation process

Soil and debris

(fraction 0.1-8 mm)

Mercury Soil washing and

vacuum distillation

Full-scale,

150 tonnes/day

26 Treatment of creosotecontaminated soil (soil

washing and slurry phase

bioreactor)

Sandy soil PAHs Soil washing and

slurry-phase

bioreactor

Pilot scale,

1 ton/hr washing,

600-dm3 reactor

27 Soil washing and

chemical dehalogenation

of PCB-contaminated soil

Soil and debris

(fraction <0.1 mm)

PCBs Soil washing and

chemical

dehalogenation

Pilot/bench-scale,

1.5 ton/hr

washing, benchscale reactors

31 Decontamination of

metalliferous mining

wastes

Mine spoils Pb, Zn Flotation and

metal leaching

Laboratory tests

32 CacitoxTM soil treatment

process

Most testings with

fine particle soils

Heavy metals,

radionuclides

Soil washing and

metal leaching

Pilot-scale, 10

kg/hr

33 In-pulp decontamination

of soils, sludges, and

sediments

No data Cu, Cr, Zn, As,

Hg

Soil washing and

metal leaching

Bench-scale

36 Enhancement techniques

for ex situ separation

processes particularly

with regard to fine

particles

2 Soils with fines

(<0.063 mm)

contents of 43% and

62%

Diesel fuel,

PAHs

Wet soil

separation and

biological

treatment

Laboratory- and

pilot-scale

Mobilization of Contaminants to Enhance Treatment

1 Trial of air sparging of a

petroleum-contaminated

aquifer

In situ (water table

at 7.5 m depth)

VOCs, gasoline Air sparging and

SVE

Field trials

9 Field demonstration of an

in situ process for soil

remediation using well

points

In situ BTEX,

petroleum

hydrocarbons

Soil flushing and

bioremediation

Field demonstration

Increase Availability of Contaminants to Treatment

15 Combined chemical and

microbiological treatment

of coking sites/bioremediation of soils from

coal and petroleum tar

distillation plants

Soil Aromatic

hydrocarbons

Oxidizing

pretreatments/

microbiological

treatment

Bench-scale

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NATO/CCMS Pilot Study, Phase II Final Report

24 Combined remediation

technique for soil

containing organics:

Fortec

Sandy soil/fines PAHs,

chlorophenol

Hydrocyclone

separation and

photochemical

treatment and

bioremediation

Demonstration

scale, 300-m3

reactor

42 In situ pneumatic

fracturing and

biotreatment

Low permeability

sediments

Benzene,

toluene, and

xylene

Pneumatic

fracturing and

biotreatment

SITE

demonstration

47 In situ electro-osmosis

(LasagnaTM Project)

Low permeability

sediments

- Fracturing and

electro-kinetics

Field

demonstration

Sequential Removal of Different Types of Contaminants

10 Integrated treatment technology for the recovery

of inorganic and organic

contaminants from soil

Soil Cu, Pb, Zn,

PAHs

Classification

and solvent

enhanced soil

washing and

leaching

Pilot-scale

Mobilization of contaminants was the goal in two projects. Both were in situ processes targeting an

increase of the amount of contaminants extracted by conventional methods like SVE and groundwater

pump-and-treat approaches. Both technologies were applied at field demonstration scale.

Low availability of contaminants to treatment was the reason that four projects modified the physicalchemical properties of the contaminants. Two of these involved an oxidizing pretreatment process for

organics in slurries. In one of these cases, the slurry had been generated by using a wet mechanical

separation process. Unfortunately, the reported data are rather limited in both cases. An evaluation of

the pretreatment effect is therefore restricted to some global assumptions.

Only one of the reviewed projects involved a combined technological approach to a matrix containing

mixed contaminants (organics and metals). The pilot-scale tests of these integrated technologies were

reported to be successful, although the reported data sets are limited.

10.5 PERFORMANCE RESULTS

10.5.1 Overview

The effectiveness of integrating treatment technologies should be judged on the basis of their ability to

achieve the goals of the overall treatment system. However, the primary technical factor for evaluating

the performance of the integration is the degree to which the goals of the integration itself (e.g.,

reduction in the volume of material to be subjected to downstream treatment) are achieved. Table 10.4

lists the categories of the projects reviewed in this chapter together with criteria that can be employed

for the performance evaluation of integration. The costs of integrating the technologies are also discussed

below. Tables 10.5 to 10.8 show the key data for the performance evaluation for the categories.

Information was very limited for some projects.

10.5.2 Separation of Fractions

The integrated technologies involving separation of fractions succeeded in reducing the volume of the

material requiring treatment in more expensive or technically more complicated downstream treatment

processes. In Projects 19, 27, 31, and 36, a significant portion of the soil was separated in soil washing

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NATO/CCMS Pilot Study, Phase II Final Report

Table 10.4: Categories of Integration of Technologies and Respective Criteria

Category Example criteria

Separation of fractions • Volume reduction achieved

• Concentration in separated fractions

Mobilization of contaminants to enhance treatment • Increase of contaminant mobilization in the

medium

Increase of availability of contaminants for treatment • Increase of destruction caused by pretreatment

Sequential removal of different types of contaminants • Interferences reducing different treatment effects

Table 10.5: Performance Data of the Separation of Fractions Category

Project Contaminants

Volume

Reduction

(%)

Contaminant Concentrations (mg/kg)

Input for

Pretreatment

Output of

Pretreatment

Input for

Downstream

Treatment

Output of

Downstream

Treatment

13 Rehabilitation of a site

contaminated by tar

substances using a new

on-site technique

Tar No data No data Coarse: 13-35 mg/kg

“total tars”

Fines: 1,500-

83,000 mg/kg

“total tars,”

median value

11,000 mg/kg

(1.1 wt %)

median value

22 mg/kg

“total tars”

19 Cleaning of mercurycontaminated soil using

a combined washing

and distillation process

Mercury About

30%

Average:

500 mg/kg Hg

peaks: 5,000

mg/kg Hg

7.9-23 mg/kg Hg 1,000-4,000

mg/kg Hg in

soils

Average in

January 1995:

20 mg/kg Hg

26 Treatment of creosotecontaminated soil (soil

washing and slurry

phase bioreactor)

PAHs No data No data No data No data Flotation: 90-

95% PAH

removal

(sandy soil),

20-90% PAH

removal (clay

soil);

bioreactor:

97% PAH

reduction after

6 days

27 Soil washing and

chemical

dehalogenation of PCBcontaminated soil

PCB 60% 50-300 mg/kg Coarse: <10 mg/kg;

fines (<0.1 mm): no

data

250 mg/kg < 1 mg/kg

31 Decontamination of

metalliferous mining

wastes

Pb, Zn 90% 20 wt% Pb,

15 wt% Zn

<2 wt% metals in

light fraction;

32 wt% Pb, 5 wt%

Zn in heavy

concentrate

No data Removal rates

from untreated

material:

NaOH: 25-92

% Pb, 3-23%

Zn; H2SO4: 2-

33% Pb, 12-

64% Zn; much

lower removal

from

pretreated

material: 2-5%

“metals”

removed

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NATO/CCMS Pilot Study, Phase II Final Report

Project Contaminants

Volume

Reduction

(%)

Contaminant Concentrations (mg/kg)

32 CacitoxTM soil treatment

process

Heavy metals,

radionuclides

No data No data No data No data Metals

exceeded

Dutch “B”

values; 98%

removal of

organics

33 In-pulp

decontamination of

soils, sludges, and

sediments

Cu, Cr, Zn, As No data No data No data Cu: 360, Cr:

621, Zn: 414,

As: 1,204 mg/

kg

Cu: 22, Cr: 74,

Zn: 68, As:

112 mg/kg;

multiple acid

leaching: As

650 down to

22 mg/kg

36 Enhancement

techniques for ex situ

separation processes

particularly with regard

to fine particles

Two samples:

1) Diesel

2) PAHs

1) fraction

>0.01mm,

68-72%

2) fraction

>0.01mm,

78%

1) 3,000-4,000

mg/kg TPH,

4 mg/kg PAHs

2) 2,000-3,000

mg/kg TPH,

200-300 mg/kg

PAHs

1) fraction >0.01

mm: 200-290 mg/kg

TPH (3-4 hydrocyclone repasses)

2) fraction >0.01

mm, 4,200 mg/kg

TPH, 320 mg/kg

PAH

1) Fraction

<0.01 mm,

12,000 mg/kg

TPH

2) fraction 0-

0.063 mm,

413 mg/kg

PAH

1) fraction

<0.01 mm,

2,300 mg/kg

TPH

2) fraction 0-

0.063 mm, 214

mg/kg PAH

or flotation processes. The flotation tests in Project 31 resulted in a potentially recyclable metal-rich

concentrate leaving the “light” fraction as an input material for further processing in a metal-leaching

process. This process needs to be optimized to increase contaminant removal. The same is true for

Projects 32 and 33, which also involved leaching processes as a downstream treatment.

The volume reduction effects of the soil washing processes are critically dependent on the fines content

of the original feed soil and the distribution of contamination in the different grain size fractions. In

Projects 19 and 27, volume reduction did not reach the anticipated level. In Project 19, this was caused

by higher-than-expected contamination of the fine-to-medium size fraction, which therefore could not

be treated with the required effect by soil washing alone; it had to be subjected to thermal treatment

together with the fines. The “cutting grain size” of the soil washing had to be increased, resulting in a

larger amount of separated fines.

In Project 27, the fine-grained portion of the feed soil was reported to be much higher than anticipated.

Nonetheless, the reduction by 60% in this case would result in significant savings of costs and effort

during the downstream treatment.

The target volume reduction, or “separation of fractions,” was achieved by the different approaches.

However, in the soil washing projects, removing contaminants from the coarse fraction was an additional

goal. It was difficult to achieve cleaning levels and analytically determine the extent of contaminant

removal. Although the reported data sets in this respect are limited, it can be stated that in Projects 13,

19, 27, and 36 (total petroleum hydrocarbon [TPH] sample), a significant cleaning effect was achieved.

In other cases, either no data were reported or the coarse fraction still showed elevated levels of

contaminant concentrations (e.g., Project 36, sample 2).

10.5.3 Mobilization of Contaminants

Performance data for this category are provided in Table 10.6. Only for one of the two projects of this

category were data reported that can be evaluated regarding the effect of combination of technologies.

The field trials of in situ air sparging in Project 1 showed that preferred flow paths of air in the

subsurface were exhausted very rapidly when SVE was supplemented with air sparging. After additional

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NATO/CCMS Pilot Study, Phase II Final Report

air sparging was applied, the contaminant yield of SVE increased very rapidly and significantly, but

dropped after about 30 hours to very low values.

Table 10.6: Performance Data of the “Mobilization of Contaminants to Enhance Treatment”

Category

Project Contaminants Status Before

Mobilization

Status After

Mobilization Degree of Increase

1 Trial of air sparging of a

petroleum-contaminated

aquifer

volatile organic

compounds

(VOCs),

gasoline

Total

hydrocarbons:

initially: 0.5-0.8

kg/day, before

sparging: 0.1-0.2

kg/day

Total

hydrocarbons:

0.8-1.5 kg/day

dropped after

30 hours to

<0.1 kg/day

About ten times for

about 30 hours.

After 30 hours, drop

due to exhaustion of

preferential flow

paths

9 Field demonstration of an in

situ process for soil

remediation using well points

BTEX,

petroleum

hydrocarbons

No data No data No data

From the projects results, it cannot be determined if preferred flow paths were created by air sparging,

or if they were also present and active during the “conventional” SVE. In both cases, air sparging was

beneficial:

• If the preferred flow paths are caused by air sparging, it can be concluded that air sparging is not

a suitable method to enhance an evenly distributed removal of contaminants from a sedimentary

formation by SVE.

• If these flow paths are present no matter if air sparging is applied or not, SVE would be a longer

lasting effort to exhaust these paths and not more. Thus, the trials would have shown in a very short

period of time that SVE does not affect the entire subsurface but only parts of it.

In the future, air sparging could be an option to check the effectiveness of long-term SVE efforts under

the conditions of the particular project.

10.5.4 Increase of Availability

Performance data for projects involving an increase of availability are given in Table 10.7. The effect

of technology combinations in this category is very difficult to evaluate based on the reported data.

Projects 42 and 47 involved site or medium pretreatment. In these cases, fracturing was used—or should

be used—as a method to allow in situ treatment of densely packed sediments with low permeability. It

is unlikely that in situ treatment of these sediments without fracturing would be possible. Therefore,

given that in situ treatment is the only way to handle the problem, the pretreatment by fracturing can

be assumed successful if there is any treatment effect at all. In Project 42, pneumatic fracturing was

shown to increase permeability by up to 40 times. Thus, this appears to be a useful means to apply in

situ processes to a much wider range of cases than in the past.

The oxidizing pretreatment in Project 24 showed a significant increase in biodegradability of PAHs.

PAHs were partly oxidized by physical-chemical treatment (UV/H2O2) and were thus more available for

microbial degradation in a slurry-bioreactor process. Test results for chlorophenol were interpreted as

showing the same effect as the PAH results. It is remarkable that the pretreatment process-step is an

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NATO/CCMS Pilot Study, Phase II Final Report

Table 10.7: Performance Data of the “Increase of Availability of Contaminants to Treatment”

Category

Project Contaminants Without

Pretreatment

With

Pretreatment

Degree of

Increase

15 Combined chemical

and microbiological

treatment of coking

sites/bioremediation of

soils from coal and

petroleum tar

distillation plants

PAHs, phenols,

cyanides

No data PAH decreased

from 800 to 200

(after 12 months);

phenols: 75%

degradation (after 7

weeks); cyanides:

50% removal (after

2-3 months)

no data; info

that

considerable

additions were

required to

observe

increased

degradation

24 Combined remediation

technique for soil

containing organics:

Fortec

Petroleum

hydrocarbons

PAHs

Chlorophenol

Petroleum

hydrocarbons

decreased from 400-

5,000 mg/kg down

to 100 mg/kg in 3-8

days

PAHs: no degradation observed

Chlorophenol:

decreased from 200

to 100 mg/kg in 24

days

Petroleum

hydrocarbons: same

as without

pretreatment

PAHs: decreased

from 30 mg/kg to

5-10 mg/kg in 15

days

Chlorophenol:

decreased from 160

to 60 mg/kg in 24

days

Petroleum

hydrocarbons:

no difference

detectable

PAHs: pretreatment allowed

degradation

Chlorophenol:

increase unclear

42 In situ pneumatic

fracturing and

biotreatment

BTEX No treatment

possible

79% reduction in

soil-phase BTEX

Fracturing

increased

permeability by

up to 40 times

within 6 m

radius

47 In situ electro-osmosis

(LasagnaTM Project)

trichloroethene

(TCE)

Vertical electrodes

were used.

Control plot (no

treatment): TCE

decreased from 89.9

to 49.5 mg/kg

TCE decreased

from 72.6 to 1.1

mg/kg

In the future,

horizontal

electrodes will

be placed by

fracturing

optional part of the capabilities of the soil treatment center in this project. This combination is a

beneficial way to improve flexibility in soil treatment and to overcome impediments to microbial

degradation of PAHs.

10.5.5 Sequential Removal of Contaminants

Performance data for projects involving sequential treatment are given in Table 10.8. In Project 10, an

ex situ classification was combined with a solvent-enhanced soil washing process for metals and PAHs.

The separation of metal particles by sorting resulted in a metal-rich concentrate of the fine particles.

Unfortunately, the concentrate was not characterized in deeper detail in the project report. After this

treatment, the remaining soil contained only 7% of the initial lead content, meeting the regulatory limits

of either 1,000 mg/kg for industrial use or 500 mg/kg for residential use.

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Table 10.8: Performance Data of the “Sequential Removal of Different Types of Contaminants”

Category

Project Contaminants Removal in Step 1 Removal in Step 2

10 Recovery of inorganic

and organic contaminants

from soil

Cu, Pb, Zn,

PAHs

Metal concentrates for

potential recycling

contained 55% by weight

of iron

lead was reduced to 7% of

the initial content

Benzo(b)fluoranthene:

decreased from 14 to 4

mg/kg, Zn from 4,000

down to 360 mg/kg, Cu

was not affected by

treatment

The solvent extraction of PAHs from the remaining slurry resulted in significant removal of benzo-(b)-

fluoranthene and a successful hydrometallurgical leaching of zinc. Further optimization should focus on

improving removal of other metals. This project is an example of treatment of different types of

contaminants in sequential steps. The composition and other properties of the treated material were not

reported.

10.6 FACTORS AND LIMITATIONS OF INTEGRATED TECHNOLOGIES

10.6.1 Separation of Fractions

In this category, technologies like soil washing and flotation are included as pretreatment processes.

Important factors to consider, limitations, and integration into treatment trains are discussed below.

Separation by Soil Washing

The portion of fines present in the feed soil and the distribution of contaminants in different grain sizes

determine the volume reduction that can be achieved. If contaminants mainly adhere to fine particles,

and the soil washing process minimizes “misplaced” fines, the volume reduction can be significant.

Minimizing misplaced fines, (in the coarse fraction) together with the efficiency of washing contaminants

off the surface of coarser particles, are the critical factors for the residual contamination in the coarse

fraction.

Separation by Flotation

The portion of material to be removed by exploiting the differences in physical-chemical properties must

be significant. The separated “heavy” material—i.e., metal concentrates—must be very suitable for

metallurgical processes. The flotation process should not hinder downstream processes like leaching of

metals from the “light” fraction, solvent-extraction, or microbial degradation of organics. An example

of interferences between the pretreatment and the downstream treatment of the light fraction by metalleaching was given in Project 31. No information was given on the suitability of recycling of

concentrates.

10.6.2 Mobilization of Contaminants to Enhance Treatment

The examples for this category show a potential to improve the treatment of proven technologies like

in situ SVE and groundwater pump-and-treat systems. The effect itself and the duration of the effect may

promote clean-up efficiency and may provide information on conclusions about the future course of the

chosen remedial approach.

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NATO/CCMS Pilot Study, Phase II Final Report

The critical factors for applying SVE in combination with air sparging are the degree to which the

contaminant yield can be increased and the development of this increase. If low soil permeability is the

reason for low yields of extracted contaminants, air sparging might not improve extraction. Project 1

shows that the presence (or formation) of preferred flow paths governs the conditions for this approach.

The other example of an attempt to mobilize contaminants and increase extraction by groundwater

pumping by using surfactants or co-surfactants (Project 9) raises two issues:

• whether increase in solubility from the introduction of the surfactant into the aquifer is always

desirable—this particular issue is of critical importance in discussions with water-control authorities;

and

• the possibility of impediments to microbial degradation caused by the surfactant enhanced extraction

pretreatment should be evaluated in laboratory trials at a reasonable investment of resources.

10.6.3 Increase of Availability of Contaminants to Treatment

The main characteristic of the technology combinations in this category is that without the preliminary

treatment of the subsurface or contaminants, contaminant removal would not be possible. Therefore, the

evaluation of the factors and limitations of the combination of the technologies applied can be limited

to the respective issues brought up in the discussions of the single technologies in the other chapters of

this report.

10.6.4 Sequential Removal of Different Types of Contaminants

This category is represented by Project 10, in which a solvent-enhanced soil washing process for metals

and PAHs was the downstream treatment for the separation of metal particles by sorting. The main

factor is the hindering of the downstream extraction or leaching caused by the flotation process’s effects.

The example shows that different leaching process steps probably have to be applied for different metals.

Another factor is the extent to which the pretreatment process can lower the contaminant concentration

levels. Because of the high cost of downstream treatment agents and the severe damage they cause to

the soil structure, the largest potential for optimization of this technology combination is considered to

be the preliminary wet separation process.

10.7.5 General and Concluding Aspects Regarding Integration of Technologies

Factors and Limitations for Ex Situ Treatment

In the projects involving ex situ treatment, thermal treatment, microbial degradation, and chemical

treatment were applied as downstream processes to the wet, mechanically separated fine fractions. Thus,

one of the main characteristics of the wet mechanical separation processes, the generation of highly

contaminated concentrates was matched with technologies targeting these secondary waste streams. Other

ex situ projects involved pretreatment to enhance microbial degradation of organics and sequential

treatment of metals and organics.

Besides the general critical factors for the pretreatment of the soil stated above, the following factors

are important for integrated technology application in practical clean-up projects:

• Interference of physical and chemical pretreatment that hinder or complicate downstream treatment.

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NATO/CCMS Pilot Study, Phase II Final Report

• Availability of two or more compatible technologies in terms of their technological “readiness.”

• Throughput capacities per time unit of the technologies must match as well as possible to allow

smooth handling of materials on the site and to avoid interim storage and multiple handling of

materials.

• Condition and properties of materials that have undergone thermal treatment or multiple solvent- and

acid-leaching.

Factors and Limitations for In Situ Treatment

The in situ projects reviewed involved enhancement of treatment by mobilizing contaminants or

improving the subsoil conditions. The critical factors for the application of the in situ pretreatment

technologies of this group are discussed above and in the respective chapter of this report. For the

integration of technologies, the following factors and limitations are important:

• availability of two or more compatible technologies in terms of their technological “readiness.”

• cost-effect ratio of the enhancing technology.

• duration of the positive effect.

• environmental impact of substances introduced into the subsurface.

• control of the process, increasingly complicated in combinations of in situ technologies.

In the projects reviewed, a combination of technologies has been shown to make treatment possible, to

increase treatment efficiency, and to adapt the remedial approach to policy requirements such as the

avoidance of secondary wastes that would have to be landfilled.

Especially in the latter respect, the requirement to minimize residues is promoting the application of

integrated technologies. The cost of additional pretreatment or downstream-treatment, however, can be

considered to be the main hurdle for integrated technologies application. Additional cost factors include

additional investigation of treatment options, investment cost for additional plants or equipment, cost for

longer project duration, cost for interim storage and additional handling of material, and fees for

treatment of material in treatment centers.

The policy framework in a region or a country for the decisions in a particular remedial project can be

considered the critical factor for having a real option either to landfill or to treat residues. In some cases

of site clean-up, contaminated soil is disposed at municipal waste landfills. In these cases, prices range

from U.S.$80-150/tonne. If contaminated soil or treatment residues are to be handled as hazardous

wastes, landfilling in state-of-the-art hazardous waste landfills costs about U.S.$ 500-800/tonne. In

Project 27, costs for incineration of PCB-contaminated material was reported to be U.S.$5,000-7,500/

tonne. In the last two cases, many efforts of integrating remedial technologies would be competitive. If

the decision either to treat the soil or to dispose it in a low-cost landfill is more or less left to the

responsible project personnel, in most cases no expensive treatment will be carried out.

In the international remedial marketplace, two factors are under discussion:

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NATO/CCMS Pilot Study, Phase II Final Report

• How many follow-up costs (e.g., monitoring and maintenance of closed landfills) should be included

in the landfilling fees (what is “maintenance” and for how long must it be continued)?

• Should contaminated soil be disposed at municipal waste landfills or at hazardous waste landfills?

The policy decisions made in these respects set the framework for soil treatment. Costs for integrating

technologies in site cleanup, in most cases, are higher than landfilling. Therefore, policy decisions must

support decontamination by establishing a policy for minimizing disposed wastes by treatment.

10.7 COSTS

As shown in Table 10.9, only very limited information was provided on the costs of the studied or

applied technologies. One of the reasons may have been that most of the technologies were only applied

in bench- or pilot-scale testing. In the two full-scale applications of wet mechanical soil separation and

subsequent thermal treatment of the fines fraction (Projects 13 and 19), cost data were reported for the

entire clean-up project. A breakdown of cost showing the relative portions of the two treatment steps

was not reported.

10.8 GENERAL CONCLUSIONS

The examples of technology integration in the Phase II Pilot Study show that significant progress has

been achieved by efforts to:

• optimize cost and energy consumption by reducing materials volumes to be treated thermally;

• improve the conditions for microbial degradation of contaminants;

• improve the conditions to permit treatment of difficult-to-treat media in situ;

• achieve higher removal rates; and

• avoid landfilling of residues.

Although many of the technological approaches to integration of remedial technologies are still at benchor pilot-scale, there is a broad spectrum of promising approaches and technologies. The review of

application factors has shown that the limitations inherent in many single technologies can be

compensated for by using integrated technologies. Therefore, it can be stated that integrated treatment

technologies are needed to handle complex projects of site remediation better, faster, and (in the longterm) more cheaply.

10.9 ACKNOWLEDGEMENTS

The author wishes to gratefully acknowledge:

• The German Federal Ministry for the Environment, Nature Conservation, and Nuclear Safety for

providing financial resources for the preparation of this chapter.

• Prof. Harald Burmeier, representing the Fachhochschule Nordostniedersachsen, Suderburg

(University of Applied Studies and Research), for providing substantial input and helpful comments.

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Table 10.9: Cost Data (to the extent available)

Project Information on Costs

Separation of Fractions

13 Rehabilitation of a site contaminated

by tar substances using a new onsite technique

Project costs are discussed in Chapter 7 of this report; no

breakdown of costs for soil washing and thermal treatment were

provided.

19 Cleaning of mercury-contaminated

soil using a combined washing and

distillation process

Treatment costs were reported by vendor to be about U.S.$320/

tonne, no further breakdown of costs for soil washing and thermal

treatment provided.

26 Treatment of creosote-contaminated

soil (soil washing and slurry phase

bioreactor)

Cost estimates per cubic meter for the remediation of the site:

U.S.$160 for soil handling; U.S.$300 for soil washing; U.S.$530 for

biological treatment.

27 Soil washing and chemical

dehalogenation of PCB-contaminated

soil

Bench- and pilot-scale washing tests: U.S.$70,000; 2 tonnes/hr

washing plant: capital cost U.S.$750,000, operation (including

materials handling and analytical costs) U.S.$380/tonne; cost of

dehalogenation: not yet presented.

31 Decontamination of metalliferous

mining wastes

No data available.

32 CacitoxTM soil treatment process No data available.

33 In-pulp decontamination of soils,

sludges, and sediments

No data available.

36 Enhancement techniques for ex situ

separation processes particularly

with regard to fine particles

Based on a bench-scale test sample; treatment cost for a dieselcontaminated soil was estimated roughly to be U.S.$50-80 in a 20-

tonne/hr plant.

Mobilization of Contaminants to Enhance Treatment

1 Trial of air sparging of a petroleumcontaminated aquiferNo data available.

9 Field demonstration of an in situ

process for soil remediation using

well points

No data available.

Increase Availability of Contaminants to Treatment

15 Combined chemical and

microbiological treatment of coking

sites/bioremediation of soils from

coal and petroleum tar distillation

plants

No data available.

24 Combined remediation technique for

soil containing organics: Fortec

No data available.

42 In situ pneumatic fracturing and

biotreatment

No data available.

47 In situ electro-osmosis (LasagnaTM

Project)

Estimate: U.S.$52-118/m3 for TCE at an approx. 0.5-km2 site with

contamination 12-15 m deep (direct costs of application only).

Sequential Removal of Different Types of Contaminants

10 Integrated treatment technology for

the recovery of inorganic and organic

contaminants from soil

Estimate for full-scale plant (500,000 tonnes to treat): Cdn$100/

tonne

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Chapter 11: REMEDIATION TECHNOLOGY RESEARCH NEEDS

Michael A. Smith

M.A. Smith Environmental Consultancy

11.1 INTRODUCTION

In preparing this report, the authors identified several technology research needs that would be beneficial

to:

• countries in the formulation of national research programs;

• the Phase III CCMS study in scoping its future work; and

• the selection of individual projects for a Phase III study.

Technologies are frequently classified as emerging, innovative, or established. However, what is viewed

as innovative in one country may be regarded as established in another, and what is considered

established in one country may not be used widely in others because of doubts about effectiveness.1 The

term “innovation” often applies to an application of a technology rather than to the principles underlying

the technology. While developing truly innovative technologies remains an important goal, such a focus

should not divert attention from the need for better information and understanding of established

processes and for ensuring that their capabilities are fully realized in practice.

A great wealth of knowledge is available on many technologies, such as soil vapor extraction,

bioventing, bioremediation, and stabilization/solidification, enabling authoritative guidance to be provided

on good practice for many situations. The difficulty is getting this knowledge applied to the myriad of

small projects where these technologies are used. This is not to say that continued research is not

required, but that the barriers to the application of research results must also be tackled. This is not

unique to contaminated land. In areas such as construction, there is a constant battle to ensure that good

practice, established on the basis of past research, is adhered to by practitioners.

As in all areas of research, a variety of topics such as the following need to be recognized:

• Basic scientific research, not directed specifically to solving problems posed by contaminated

land—basic science researchers may have an idea of the potential relevance of their work, but

relevance is not the immediate driving force;

• Strategic applied research of a fairly basic nature into such things as biodegradation mechanisms

and the behavior of contaminants in soil;

• Strategic research leading to a better understanding of how a process works so that

improvements can be made;

• Feasibility testing of concepts derived from basic research;

1 An example is stabilization/solidification. While widely applied in the United States, this technology has only

limited application to date in Western Europe.

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NATO/CCMS Pilot Study, Phase II Final Report

• Pilot-scale and field testing of potentially useful technologies; and

• Development of a new concept or process as a result of a problem discovered during site

investigation for which no adequate technology exists.

Soil and groundwater remediation industries have been established in a number of countries, and in some

cases, as in soil washing in Germany and the Netherlands, some of the plants can be regarded as third

generation. Innovation can be driven by operators seeking to extend the physical and chemical range of

materials that can be treated and effectiveness of treatment, and to lower processing costs so that they

can compete in an increasingly challenging market. Such research by commercial interests is of a

proprietary nature and will only slowly reach the wider scientific and technical community.

Promising technologies can sometimes find rapid application before fullly understanding the processes

involved, and subsequent improvements can follow after initial application. Soil vapor extraction, electroremediation, and more recently, active treatment barriers, are examples of such technologies.

In practice, some research needs represent very broad concepts, whereas others relate to improvements

or extensions required for particular technologies. For example, the USEPA identified in 1993 a lack of

technologies for in situ treatment of contaminated groundwater (1).

More recently, a general need has been identified for treatments that are less costly and extensive, which

means they are less dependent on technology and energy, and are likely to have less impact on other

costs. Ideally, treatments should harness time and natural processes to the wheel of remediation. Such

treatment methods have been discussed by Bardos and van Veen (2). These considerations are

particularly appropriate to the large-scale pollution problems in Central and Eastern European countries.

Existing methods are generally too costly for the pollution problems in these countries. Similarly, in

many developing and less developed countries, existing technologies are too expensive. Owners and

operators of industrial facilities, also have a need for similar methods once they have taken the measures

necessary to avoid immediate legal liabilities.

It is important to recognize that scale has a major influence on the costs of any process. The size of

many treatment plants has been limited by the need to be transportable, or at least mobilizable. Even

the largest soil washing plants only handle about 150,000 tonnes/year. This capability is small compared

to, for example, mineral processing plants, where capabilities of 1 million metric tons/year are not

uncommon. This brings into play several factors, such as how remediation is organized and the relative

importance of the costs and environmental impacts of transportation (e.g., to a central transport facility),

compared to those of the actual treatment process.

Cement kilns are used for disposal of hazardous wastes, used oil, and even vehicle tires in parts of

Europe (the energy content is the attraction). In Canada, waste foundry sands and power station fly ash

are used as silica sources. In the United Kingdom, colliery wastes have been used as sources of fuel,

silica, and aluminum. The possibility of using cement plants as a means of treating contaminated soils

merits further investigation, taking into account that the process usually requires large volumes of

reasonably consistent material to ensure product quality and that performance is very sensitive to low

concentrations of some metals in the cement clinker. Obviously, limits on atmospheric emissions would

have to be met and it is important to recognize that the burning of hazardous wastes in cement kilns is

controversial in some countries.

In Western Europe the use of a fast-fix, intensive treatment approach is often driven by the need to

redevelop an area. Remediation is a step in the redevelopment process rather than the end objective. For

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NATO/CCMS Pilot Study, Phase II Final Report

instance, the need to rejuvenate brownfield sites is becoming increasingly important in policy and

research in the United States and has always been a driver in parts of Canada (e.g., the greater Toronto

area of Ontario). In these cases, the overall costs and value of the development can have a greater

influence on the selection of a remedial strategy than the direct remediation costs alone. Time (a costly

commodity to developers) is often an overriding factor leading to the use of off-site strategies, such as

simply excavating and disposing off site, rather than on-site in situ or ex situ treatment.

Although a great range of technologies now exists, many technologies such as bioremediation will only

work on a limited group of contaminants and may be hindered by the presence of other substances (e.g.,

metals hindering the bioremediation of organic compounds). Few technologies can deal with such mixed

contamination, and increasingly, integrated treatment systems are being used. These may involve

sequential treatment in a treatment train or parallel treatment of different fractions following an initial

separation step. This trend is apparent in the Phase II study—20 projects involved the use of integrated

technologies.

Some contamination problems occur on such a scale and are so complex that containment is the only

technically and economically viable solution. However, the effectiveness of containment systems (e.g.,

cover systems, vertical barrier walls) can be reduced with time and require long-term monitoring, repair,

replacement during operation. Containment systems would be more attractive if low cost, minimal

methods could be found to reduce the pollution potential of the contained materials during the lifetime

of the containment system. This situation is very similar to the deliberately constructed mixed waste

landfill that has a finite lifetime. Although highly controversial in other countries, the concept of the

“flushing landfill bioreactor,” which is gaining acceptance in the United Kingdom, is relevant. Research

that brings this concept to practical use will in turn aid the development of methods for dealing with old

“problem” hazardous waste sites.

11.2 LESSONS FROM PREVIOUS NATO/CCMS STUDIES

An objective when preparing the final reports of the CCMS Pilot Studies on remediation technologies

has been to identify research and development requirements as well as the general lessons learned. For

the report on the Phase I Pilot Study (3), the authors of individual chapters initially took on this task and

then met to further refine their ideas. Their conclusions are:

• There is a continuing need for development of new technologies and use of common research

protocols;

• Scientific understanding of processes is essential in order to ensure against formation of harmful

end products;

• Standardization of analytical methods is needed; and

• Techniques are required to remove contamination beneath urban structures without significant

disturbance to on-going activities.

The conclusions that were technology specific are listed in Box 11.1 (note that variants of some of these

appear in Chapter 12 as conclusions of the Phase II Pilot Study, together with supporting reasons for

their inclusion).

Several technologies, especially in situ treatments, either fail to destroy or remove contaminants or are

based on principles of immobilization or transformation (e.g., stabilization/solidification processes). The

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long-term performance of these technologies needs to be better understood in terms of risk management

and appropriate environmental quality criteria to be applied during monitoring.

Box 11.1: Conclusions from Phase I Study Indicating a Need for Research2

• The long-term effectiveness of solidification/stabilization processes has not been proven,

especially when these processes are applied under field conditions;

• Electro-reclamation deserves to be extensively investigated—no other technology currently

shows the same potential for treating clay soils;

• Pump and treat is a limited technology for remediating aquifers;

• Scaling up the bioremediation process from the laboratory to the field is difficult;

• Further research is needed on bioavailability and residual concentrations achievable in

bioremediation;

• A mass balance approach to remediation is desirable;

• Uniform data collection is needed to enhance technology transfer; and

• Continuation of the current NATO/CCMS Pilot Study should also include cleanup criteria,

project design methodologies, and documentation of completed remediation projects.

11.3 THE PRESENT STUDY

The projects included in the Phase II Pilot Study do not necessarily provide a true reflection of research

and development needs. However, they do have certain characteristics that possibly provide some

indication of where current interest lies. For example, interest can be identified in:

• coal carbonization sites and the chemicals typically associated with them, such as polycyclic

aromatic hydrocarbons (PAHs), and mixtures of coal-tar chemicals such as creosote;

• in situ treatment methods;

• methods to treat chlorinated solvents;

• ex situ methods for treating metal contamination;

• residuals left after biotreatment;

• all forms of bioremediation; and

• active barriers.

2 The wording in the report has been slightly amended for clarity.

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NATO/CCMS Pilot Study, Phase II Final Report

There are, however, significant gaps in the coverage of the projects. For example, there are very few

projects on groundwater cleanup (although a number of projects dealt with groundwater as part of an

overall remediation strategy). This may, of course, simply be a reflection of a lack of innovative

technologies and their practical applications.

Taking discussions at meetings into account, the general areas where research might be directed are:

• In situ methods for soil treatment, particularly for metals and mixed contaminants;

• In situ methods for groundwater treatment;

• Means for improving the effectiveness and speed of operation of pump-and-treat systems;

• Extensive treatments, requiring fewer resources, but possibly taking more time to achieve a given

level of risk reduction;

• Means of reducing the pollution potential within a contained site through low intensity processes

for the purpose of extending the life of the overall system and achieving an overall

environmental improvement in the long term;

• Test facilities where technologies, considered to have potential negative environmental impacts,

can be tried out at field scale under controlled conditions;

• Improved methods for stabilization/fixation or solidification of organic chemicals;3

• Long-term studies of stabilized/solidified materials, especially the products of in situ treatment;

and

• Better techniques to characterize sites before remediation and to perform evaluations, particularly

of in situ treatments.

The discussion at the Berlin meeting regarding the proposed Phase III study indicated an interest in

including containment systems (e.g., cover systems or vertical barrier walls) within the scope of the

study. There remains a dearth of information on long-term performance, and laboratory and field studies

are required. However, it is important to recognize that these studies must be long-term in nature and

might require 20 or more years to complete. Despite the widespread use of covers in the United

Kingdom, and some research in the early 1980s and currently at the Building Research Establishment,

there is little or no long-term field monitoring.

Additional areas of study that might merit attention include:

• A feasibility study on the use of cement kilns to dispose or treat contaminated soils in Eastern

and Central Europe (Note: As stated above, there is controversy about the burning of hazardous

wastes in kilns in some countries);

3 A conclusion of the Phase I study and various U.S. studies is that the performance of cement-based

stabilization/ solidification processes is one of physical occlusion only, which means there is no chemical

change or fixation of organic species. Project No. 34 tests a method of binding organic chemicals to

organophilic clay minerals before solidification.

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NATO/CCMS Pilot Study, Phase II Final Report

• Investigation of the importance of time (for equilibrium reactions to occur) and the intensity of

mixing in the treatment of soils contaminated with organic chemicals using organophilic clays

and other adsorbents as a prelude to solidification; and

• Development of cost-effective technologies (including sorption and solidification) applicable in

less developed countries as well as highly developed NATO-member countries (e.g., using

readily available wastes as treatment agents).

11.4 REFERENCES

1. U.S. Environmental Protection Agency, In Situ Treatment of Contaminated Ground Water: An

Inventory of Research and Field Demonstrations and Strategies for Improving Ground Water

remediation, 1993.

2. Bardos R.P. and H.J. van Veen, “Review of longer-term or extensive treatment technologies,” Land

Contamination and Reclamation, 1996, 4(1), pp 19-36.

3. U.S. Environmental Protection Agency, NATO/CCMS Pilot Study: Demonstration of Remedial Action

Technologies for Contaminated Land and Groundwater, Final Report, Volume 1, 1993, EPA/600/R93/012a.

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NATO/CCMS Pilot Study, Phase II Final Report

Chapter 12: CONCLUSIONS AND RECOMMENDATIONS

Michael A. Smith

M.A. Smith Environmental Consultancy

Stephen P. James and Walter W. Kovalick, Jr.

U.S. Environmental Protection Agency

12.1 INTRODUCTION

The Phase II Pilot Study once again demonstrated the benefits of exchanging technical and economic

information on technologies for the remediation of contaminated land and groundwater. This chapter

presents the conclusions and recommendations of the Phase II Pilot Study and contains:

• general conclusions arising from the Pilot Study (12.2);

• general conclusions about remediation and technology transfer (12.3);

• research needs (12.4—see also Chapter 11); and

• the formal recommendations to CCMS arising from this Pilot Study (12.5).

The conclusions are based on the deliberations of the Study Group, results of case studies, expert speaker

presentations, special studies carried out by Fellows of the Pilot Study, and the experience and expertise

of the individual chapter authors.

A number of the conclusions closely parallel those of the previous phase of the Pilot Study (1), further

affirming their importance.

12.2 GENERAL CONCLUSIONS

1) Involvement of more countries led to better and wider awareness of the problems posed by

contaminated land.

A total of 23 countries were involved in the Pilot Study, and 14 contributed projects. The increased

number of countries participating in Phase II undoubtedly increased the overall value and impact of

the technology exchange process. Although more countries took part largely as recipients of

technology information rather than as contributors, the representatives of these countries brought new

insights and priorities to the Pilot Study and were able to make valuable contributions to the

discussions.

2) Presentation of additional full-scale experiences was helpful.

A number of the participants found the case studies involving full-scale remediation, as opposed to

demonstration-, pilot- or bench-scale studies, to be particularly valuable.

3) In a number of countries, remediation strategies are moving from technology-intensive treatment

processes to greater recognition of land use management and extensive approaches, such as natural

attenuation. Further research into these approaches is needed.

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NATO/CCMS Pilot Study, Phase II Final Report

It was apparent during the Pilot Study that there is increasing interest in land use management and

extensive approaches to remediation. While these approaches can be as effective as more intensive

methods, they may take longer to complete. Extensive approaches demand fewer resources and are

less costly; thus, they can be viewed as more sustainable. Extensive remediation options, which are

less dependent on technology and energy inputs, etc., and are likely to have less impact on other

aspects of economic activity, are needed. Cost considerations are particularly appropriate for lessdeveloped countries having pollution problems that would be prohibitively expensive to treat using

technology-intensive processes.

Consideration of the overall potential environmental, social, and economic impacts of planned

remedial actions are of increasing interest and the subject of formal study in some countries. It

should be noted that taking these issues into account can both increase the level of clean up required

(e.g., in situations where “fit for current or immediate future use” is a prime criterion) and lessen

the level of clean up required (e.g., in a situation where multi-functional land use might otherwise

be required or where groundwater has no economic value).

4) The intended future use of a site is increasingly a determining factor when setting clean-up

objectives and selecting a remediation strategy.

This conclusion reflects the convergence in thinking between those countries that have always seen

land use as an important factor and those that have tended to set clean-up requirements irrespective

of the future use of the land. Consideration of future land use can lead to a better allocation of

scarce resources.

5) All remediation activities require proper operation and management.

The success of field demonstration and treatability studies is not enough to ensure success of the

remediation activities. The overall effectiveness of a remediation scheme, which may include many

interrelated elements of civil engineering works and soil and groundwater clean-up technologies, will

depend heavily on the care with which the individual technologies are operated in the field. Site and

operating conditions may change over time, and skilled people are needed to adjust technologies to

these changes or discontinue them if they do not meet expectations. Similarly, a strong quality

assurance program needs to be in place, and activities must be carried out by a dedicated and

effective management team.

6) Whenever possible, the wider environmental impacts of a chosen remedial strategy should be

considered during remedial selection.

Short-term performance goals should not be the sole factor in technology selection when developing

a remediation strategy. Some remediation strategies may only be effective over a longer time frame,

but may have lower environmental impacts during implementation (e.g., reduced traffic, lower

emissions, and lower energy requirements) .

12.3 GENERAL TECHNICAL CONCLUSIONS

7) Integrated treatment systems are frequently needed for site remediation.

Contamination at many sites can be complex, with different contaminants in different media and

areas. Multi-technology solutions are required for the effective remediation of such sites. Many of

the Phase II projects involved the use of integrated or mixed technologies (see Chapters 2 and 10).

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NATO/CCMS Pilot Study, Phase II Final Report

Modular integrated treatment systems can provide system flexibility by allowing optimization of

specific process units to treat different contaminants of varying concentrations within various media.

This modular arrangement also allows the addition or withdrawal of processing units within the

system and the opportunity to insert and evaluate new or upgraded technologies as they become

available. Modular systems require additional up-front design, but may result in lower capital and

operating costs than conventional one-technology approaches.

The integrated systems approach also applies to sites where there are multiple areas of contamination

and where it is more practical to use specific technologies on each area, rather than trying to make

one technology solve all of the contamination problems (see Chapter 2).

8) Energy efficiency practices influence plant design resulting in varying processing costs between

countries. This may make cost comparisons between countries difficult and leads to the choice of

different technologies to address similar problems.

Variable factors, such as the cost of energy and labor, not only influence operating costs, but also

plant design and associated capital costs. These factors must be taken into account when considering

the application of a technology in a country other than the one in which it was developed.

9) Independent evaluation and verification of technologies and uniform data collection are needed for

effective technology transfer.

The NATO/CCMS Pilot Studies have shown the benefits to be gained from well-designed,

supported, executed, and documented field demonstrations of treatment technologies that are

independently evaluated and verified. Such field demonstrations not only help to confirm the

strengths and limitations of a technology, but also provide a credible basis for technology transfer

and application.

There is a critical need for the establishment of a uniform data reporting methodology for

demonstration projects, etc. Various database systems are available and in use; however, input of

consistent data into these systems and easy access to them will benefit all users. Critical information

needed in these databases includes:

• a minimum data set concerning the site's geological and hydrological setting, the types and

concentrations of contaminants present, etc.

• the clean-up standards used to provide the basis for selecting remediation strategies and for

assessing their effectiveness. The clean-up standards are important because there are currently

no internationally adopted standards or guidelines, and those applicable in one nation or state

may not be pertinent in another.

The identification and/or development of standard protocols for demonstration projects was one of

the objectives of the Phase II Pilot Study. This objective was not achieved, but it was addressed, in

part, by one of the CCMS Fellows and will be considered further in the Phase III Pilot Study.

10) Consensus on analytical methods and quality assurance is needed.

There is a lack of consensus on analytical methods used within the worldwide contaminated-land

community and often within individual countries. As a result, there can be confusion between or

within countries about meaning of the data and how the data were obtained and analyzed. Under

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NATO/CCMS Pilot Study, Phase II Final Report

such circumstances, data can be misinterpreted or appear inconclusive. A greater level of confidence

in the interpretation of data could be established if there were worldwide acceptance of analytical

methods.

In addition, greater attention is needed in the areas of experimental design and quality assurance and

quality control (QA/QC) for identifying data needs and data quality, which in turn determine the

analytical methods. Programs to evaluate new analytical techniques and update analytical standards

would further benefit the contaminated-land community. One forum addressing this issue is the

International Organization for Standardization (ISO) Technical Committee 190 for soil quality.

11) Scientific understanding of processes is essential to avoid forming harmful end-products and

byproducts, ensure process optimization, avoid unwanted transfer of contaminants to other media,

and understand the limits of technical performance.

The demonstrated removal of contaminants from contaminated media is not a sufficient basis for

implementing a treatment technology because toxic intermediates, byproducts, and residuals may

be formed during treatment. A thorough understanding of the treatment process mechanisms

involved is required in order to avoid such undesirable occurrences.

12) Field treatability/pilot studies should be conducted under the range of potential field conditions they

might be realistically applied. Test facilities are required where technologies considered to have

potential negative environmental impacts can be field-scale tested under controlled conditions.

The complex physical and chemical nature of the subsurface environment makes both laboratory

testing and pilot-scale field evaluations (treatability studies) essential elements of a successful

approach to remediation. Generally, either bench-scale or pilot-scale studies in the laboratory need

to be followed by pilot-scale or full-scale field evaluations. These evaluations should indicate

whether the technology is applicable to the contaminated medium and should provide information

on the optimal level of treatment effectiveness that the technology can achieve. Bench-scale and

pilot-scale evaluations must be tailored to each specific application in order to obtain the maximum

amount of credible data at a minimum cost and establish the basis for follow-on field evaluations.

13) Field-scale studies aimed at understanding phenomena such as transport of contaminants and

natural attenuation are needed. International collaboration on this effort would increase the value

and diversity of conditions studied and lead to quicker application of results.

Studies of this type are already taking place, particularly in North America. Field laboratories in

which controlled release of contaminants is permitted would be particularly valuable.

14) Technology scale-up problems need to be addressed in design and testing.

Care must be taken in translating technologies from bench- to pilot-scale to demonstration-scale or

full-scale so that all aspects of the scale-up are taken into account. The scale-up of pilot-scale

systems to full-scale operating systems can often result in unforeseen difficulties that need to be

addressed in the design. For instance, design variables (e.g., wall effects, mixing efficiencies, flow

patterns, fugitive emissions, and retention times) can change as a result of system scale-up. To

overcome some of these problems (particularly for technologies that are not widely used), operating

flexibility can be built into the system by modular design, by providing the ability to vary feed rates,

and by providing surge capacity at various points throughout the system.

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NATO/CCMS Pilot Study, Phase II Final Report

15) Long-term monitoring of assumed permanent remediation may be necessary to ensure that clean-up

goals are met.

Construction of soil and groundwater remedies is not the endpoint for determining whether

environmental protection concerns have been satisfied. Focused, long-term monitoring is essential

to ensure that the required remedies are properly implemented, operated, and maintained and

ultimately are successful. This, in turn, requires that long-term oversight is provided by well-trained

personnel and that the necessary institutional controls are put in place to ensure that monitoring is

conducted and appropriate responses to the results of monitoring are taken.

Limiting monitoring to the period in which remediation goals and objectives are first achieved may

yield misleading results. It has been demonstrated both in “pump-and-treat” groundwater systems

and soil vapor extraction systems that “bounce back” can occur as contaminants held in less

permeable zones diffuse out to re-contaminate the apparently clean (and more permeable) zones.

Monitoring must be continued until such phenomena no longer occur to a significant extent.

16) Assessment, remedy selection, and implementation records should be preserved.

A major challenge in evaluating the effectiveness of current and emerging technologies is that there

are usually insufficient data available to evaluate them (particularly for in situ remediation

strategies). Therefore, it would be advantageous to remediation planners if site investigation and

assessment records and the rationale for selecting the remediation strategy are preserved for future

reference and evaluation. Such records are valuable in property transactions and in determining the

suitability of land for a particular use subsequent to remediation. It is also important that the records

reflect “as-built” or “as-operated” systems, rather than just the design intentions.

17) Although treatment and permanent solutions are widely sought, some contamination problems occur

on a scale and complexity for which containment may be the preferred technical and economicallyviable solution. Further information sharing among countries is needed to determine the long-term

effectiveness and state of development of containment systems.

Containment systems can be expected to decline in effectiveness with time, require long-term

monitoring, and possibly require repair or replacement.

18) Studies related to stabilization/solidification processes are required in respect to:

• improved methods for stabilization/solidification of organic chemicals;

• long-term performance of stabilized/solidified materials, especially the products of in situ

treatment;

• the importance of time (to permit equilibrium reactions to occur) and the intensity of mixing in

the treatment of soils contaminated with organic chemicals using organophillic clays and other

adsorbents as a prelude to solidification; and

• development of cost-effective technologies applicable in less-developed countries as well as

highly-developed NATO-member countries (e.g., using readily available wastes as treatment

agents).

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NATO/CCMS Pilot Study, Phase II Final Report

12.4 RESEARCH NEEDS

19) Future work on the NATO/CCMS Pilot Study should include the formulation of the overall scope

of a Phase III CCMS study and the selection of individual projects for inclusion in a Phase III

study.

20) As in all areas of research, it is necessary to recognize that research of a variety of types is

required.

For example:

• basic scientific research not directed specifically to solving the problems posed by contaminated

land—although the researchers may have an idea of potential relevance, this is not the immediate

driving force;

• strategic applied research on such topics as biodegradation mechanisms and the behavior of

contaminants in soil;

• strategic research leading to a better understanding of how a process works so that improvements

can be made;

• feasibility testing of concepts derived from more basic research;

• pilot-scale and field testing of possible technologies; and

• development of a new concept or process as a result of a problem discovered during site

investigation for which no adequate technology exists.

21) Further research is required into the remediation of coal carbonization sites and the chemicals

typically associated with them, such as polycyclic aromatic hydrocarbons (PAHs) and mixtures of

coal tar chemicals.

22) Further research is required into:

• in situ methods for soil treatment particularly for metals and mixed contaminants;

• in situ methods for groundwater treatment, including active barriers;

• improving the effectiveness and speed of pump-and-treat systems; and

• better techniques for site characterization before remediation and for performance evaluation—

particularly of in situ treatments.

12.5 RECOMMENDATIONS TO CCMS

1) The CCMS is invited by the Pilot Study Directors to commend this Phase II Pilot Study Final Report

to the NATO Council for approval.

All the participants in this phase of the study are commended for their professionalism, technical

expertise, and cooperation. The Pilot Study Directors particularly thank the two co-pilot countries,

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NATO/CCMS Pilot Study, Phase II Final Report

Germany and The Netherlands, for their assistance. The CCMS Fellows are complimented on their

technical quality and personal input to the Pilot Study. The Expert Speaker activities were a major

success in stimulating discussion among participants. Over and above the technical successes of the

Pilot Study, a camaraderie was established between participants leading to extensive exchanges of

information outside of the Pilot Study. The progress of the Study was reported via formal interim

reports and numerous papers published in technical journals, and conference proceedings published

in North America, Europe, and Australia. Consequently, the CCMS is invited to commend the Final

Report to member governments and to the governments of the North Atlantic Cooperation Council

(NACC) countries drawing their attention to the technical information, conclusions, and

recommendations it contains.

2) The CCMS is requested to encourage participation of NATO and non-NATO countries in the

continuation study (Phase III Pilot Study).

The participation of NACC and other non-NATO countries has been a feature of the Phase II Pilot

Study with mutual benefit to all involved. The Pilot Study co-pilots will continue to elicit formal

participation by additional countries known to have contaminated land and groundwater programs.

CCMS is requested to draw the attention of member countries to the way in which formal

participation can open doors for researchers, regulators, and others from within and outside

government to high quality technology and information exchange activities and to an extensive

network of professional contacts. The CCMS is asked to encourage member countries to adopt

formal observer status, even if the countries wish to have only minimal active participation at an

official level.

3) The Phase III Pilot Study should maintain liaison with related international activities on

contaminated land.

The benefits to all participants has been enhanced by the parallel activities in policy-orientated areas

(e.g., the International Working Group on Contaminated Land and the Common Forum on

Contaminated Land) and technical areas such as risk assessment through the European Union’s (EU)

Coordinated Action on Risk Assessment for Contaminated Sites (CARACAS) and soil quality

through the ISO Technical Committee 190. Liaison should be extended in the Phase III study to

include the EU’s Network for Industrially Contaminated Land (NICOLE), the European

Environment Agency’s Soil Topic Centre, the World Health Organization’s European Centre for

Environment and Health and others involved in this technical area. Close liaison should be continued

with NATO/CCMS Pilot Studies dealing with contamination of military installations.

4) The Phase III Pilot Study should publish an annual progress report and, as appropriate, periodic

technical reports on selected topics.

Preparing a technical report summarizing several years' work requires a considerable effort on the

part of all concerned. It involves not only critical review of submitted information, but also the

gathering of additional technical information and liaison with country representatives and project

authors. Furthermore, there is a considerable editorial effort required to combine the individual

contributions into a coherent final report. Preparation of the Final Report for this and the preceding

Pilot Studies (1,2) has been possible because of the efforts of the volunteer writing teams.

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NATO/CCMS Pilot Study, Phase II Final Report

The remediation of contaminated soil and groundwater is a rapidly evolving field so that there is

a risk that much of the information provided in the Pilot Study report will already be out of date

by the time of publication. It is therefore recommended that this issue be addressed by:

• preparation of an annual report that could be widely distributed and serve as a working tool for

participants to monitor the progress of the Pilot Study, including the introduction and completion

of individual projects;

• the publication from time to time of technical and non-technical reports on specific topics as

seems appropriate; and

• the use of other channels of publication, such as technical journals and conference publications,

to ensure rapid dissemination of the results of individual projects and of the Pilot Study as a

whole.

12.6 REFERENCES

1. U.S. Environmental Protection Agency. NATO/CCMS Pilot Study, Demonstration of Remedial Action

Technologies for Contaminated Land and Groundwater, Final Report, Volume 1, EPA/600/R93/012a, 1993.

2. Smith, M.A. (editor). Contaminated Land: Reclamation and Treatment, Plenum (London) 1985.

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NATO/CCMS Pilot Study, Phase II Final Report

Appendix I

COUNTRY REPRESENTATIVES
NATO/CCMS Pilot Study, Phase II Final Report

Country Representatives (1998)

COUNTRY CONTACT

AUSTRALIA Gillian King Rodda

Manager, Contaminated Sites

Environment Protection Group

Environment Australia

PO Box E305

Kingston ACT 2604

tel: 61-2-6274-1114

fax: 61-2-6274-1164

E-mail: gillian.king.rodda@ea.gov.au

AUSTRIA Nora Auer

Federal Ministry of Environment, Youth and Family Affairs

Dept. III/3

Stubenbastei 5

A-1010 Vienna

tel: 43/1-515-22-3449

fax: 43/1-513-1679-1008

E-mail: Nora.Auer@bmu.gv.at

BELGIUM Jacqueline Miller

Groupe d’Étude Habitat/territoire

Brussels University

Avenue Jeanne 44

1050 Bruxelles

tel: +32/2-650-3183

fax: +32/2-650-3189

E-mail: jmiller@resulb.ulb.ac.be

CANADA Harry Whittaker

Emergencies Engineering Division

Environment Canada

3439 River Road

Ottawa, Ontario, K1A OH3

tel: 613/991-1841

fax: 613/991-1673

E-mail: harry.whittaker@etc.ec.gc.ca

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NATO/CCMS Pilot Study, Phase II Final Report

COUNTRY CONTACT

CZECH REPUBLIC Jan Švoma

Aquatest a.s.

Geologicka 4

152 00 Prague 5

tel: 420/2-581-83-80

fax: 420/2-581-77-58

E-mail: aquatest@aquatest.cz

DENMARK Inge-Marie Skovgård

Contaminated Land Division

Danish Environmental Protection Agency

29 Strandgade

DK-1401 Copenhagen K

tel: 45/3-266-0100 - direct 45/32660397

fax: 45/3-296-1656

E-mail: ims@mst.dk

FRANCE René Goubier

Polluted Sites Team

ADEME

BP 406

49004 Angers, Cedex 01

tel: +33/41-204120

fax: +33/41-872350

GERMANY Volker Franzius

Umweltbundesamt

Bismarkplatz 1

D-14193 Berlin

tel: +49/30-8903-2496

fax: +49/30-8903-2285 or -2103

HUNGARY Pál Varga

National Authority for the Environment

Fö u.44

H-1011 Budapest

tel: 36/1-457-3530

fax: 36/1-201-4282

E-mail: vargap@kik.ktm.hu

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NATO/CCMS Pilot Study, Phase II Final Report

COUNTRY CONTACT

NETHERLANDS H. Johan van Veen

The Netherlands Integrated Soil Research Programme

P.O. Box 37

NL-6700 AA Wageningen

tel: 31/317-484-170

fax: 31/317-485-051

E-mail: anneke.v.d.heuvel@spbo.beng.wau.nl

NEW ZEALAND Raymond Salter

Resource Management Directorate

Ministry for the Environment

84 Boullcott Street

P.O. Box 10362

Wellington

tel: 64/4-917-4000

fax: 64/4-917-7523

e-mail: rs@mfe.govt.nz

NORWAY Bjørn Bjørnstad

Norwegian Pollution Control Authority

P.O. Box 8100 Dep

N-0032 Oslo

tel: 47/22-257-3664

fax: 47/22-267-6706

E-mail: bjorn.bjornstad@sftospost.md.dep.telemax.no

REPUBLIC OF

SLOVENIA

Branko Druzina

Institute of Public Health

Trubarjeva 2-Post Box 260

6100 Ljubljana

tel: 386/61-313-276

fax: 386/61-323-955

E-mail: branko.druzina@ivz.sigov.mail.si

SWEDEN Ingrid Hasselten

Environmental Protection Agency

Biekholmsterrassen 36

S-106 Stockholm

tel: +48/8-698-1179

fax: +48/8-698-1222

E-mail: inh@environ.se

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COUNTRY CONTACT

SWITZERLAND Bernhard Hammer

Federal Office of the Environment, Forests and Landscape

Federal Department of the Interior

Buwal Laupenstrausse 20

3003 Bern

tel: +41/31-322-6961

fax: +41/31-382-1546

TURKEY Resat Apak

Instanbul University

Faculty of Engineering

Avcilar Campus

Avcilar

34840 Instanbul

tel: 90/212-5911-998

fax: 90/212-5911-997

E-mail: rapak@istanbul.edu.tr

UNITED KINGDOM Ian D. Martin

Environment Agency

Olton Court

10 Warwick Road

Olton, West Midlands

tel: 44/121-711-2324

fax: 44/121-711-5830

E-mail: ianmartin@environment-agency.gov.uk

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NATO/CCMS Pilot Study, Phase II Final Report

COUNTRY CONTACT

UNITED STATES Stephen C. James

U.S. Environmental Protection Agency

National Risk Management Engineering Laboratory

26 Martin Luther King Drive

Cincinnati, OH 45268

tel: +1/513-569-7877

fax: +1/513-569-7680

E-mail: james.steve@epa.gov

Walter W. Kovalick, Jr.

U.S. Environmental Protection Agency

Technology Innovation Office

401 M Street SW (5012W)

Washington, DC 20460

tel: +1/703-603-9910

fax: +1/703-603-9135

E-mail: kovalick.walter@epa.gov

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Appendix II

CCMS FELLOWS
NATO/CCMS Pilot Study, Phase II Final Report

NATO/CCMS Fellows1

FELLOW SUBJECT

Robert M. Bell

Technical Director

Hyder Consulting

c/o Ty Isa Farm

Garth Road

Glan Conway LL28 5TE

Colwyn Bay

United Kingdom

tel: +44/(0)1492-580-950 (home)

+44/(0)1928-579-955 ext. 53015 (work)

E-mail: bob.bell@hyder-con.co.uk

Quality management systems in the remediation of

contaminated land

Maria Teresa Chambino

INETI

ITA/DTA

Azinhaga dos Lameiros a Estrada do Paco do Lumiar

1699 Lisboa Codex

Portugal

tel: +35/1-1-716-4211

fax: +35/1-1-716-0901

Important issues about the Portuguese situation

Domenic Grasso

Department of Civil Engineering

University of Connecticut

Storrs, CT 06269-3037

USA

tel: +1/860-486-2680

fax: +1/860-486-2298

E-mail: grasso@eng2.uconn.edu

Hazardous waste site remediation

Mary R. Harris

Monitor Environmental Consultants Ltd.

Blakelands House

400 Aldridge Road

Birmingham

B44 8BH

United Kingdom

tel: +44/(0)121-356-5533

fax: +44/(0)121-356-5222

E-mail: mary.harris@monitorec.co.uk

Economic/cost data issues related to innovative

environmental restoration technologies

1 For information about the CCMS Fellowship Programme, contact NATO's Scientific and Environmental Affairs

Division in Brussels at Tel: +32/2-707-4111 or FAX: +32/2-707-4232. Information can be found on the World

Wide Web at http://www.nato.int/science. Invitations for applications are extended each year through national

NATO coordinators.

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NATO/CCMS Pilot Study, Phase II Final Report

FELLOW SUBJECT

Merten Hinsenveld

TSM Business School

University of Twente

P.O. Box 217

7500 AE Enschede

The Netherlands

tel: +31/53-489-8009

fax: +31/53-489-4848

E-mail: m.hinsenveld@tsm.utwente.nl

Changing approaches to remediation

Maria Jose Macedo

Hovione - Sociedade Quimica SA

Qt. S. Pedro

Sete Casas

Loures

Portugal

tel: +35/1-1-982-9000

fax: +35/1-1-983-6801-1406

Use of remedial clean-up technology in Portugal

Robert Siegrist

Colorado School of Mines

Environmental Science and Engineering Division

1500 Illinois Avenue

Golden, CO 80401-1887

USA

tel: +1/303-273-3490

fax: +1/303-273-3413

E-mail: rsiegris@mines.edu

In situ remediation of organics: process design,

treatment efficiency, and performance assessment

Michael A. Smith

68 Bridgewater Road

Berkhamsted

Hertfordshire

HP4 1JB

United Kingdom

tel: +44/1442-871500

fax: +44/1442-870152

E-mail: Michael.A.Smith@BTinternet.com

Contributed to preparation of the final report

Kai Steffens

PROBIOTEC gmbh

Schillingsstrasse 333

D 52355 Düren-Güzenich

Germany

tel: 49/2421-69090

fax: 49/2421-690961

E-mail: info@probiotec.ac-euregio.de

Concepts of quality management in testing and

monitoring of innovative technologies for remedial

actions on contaminated land and groundwater

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NATO/CCMS Pilot Study, Phase II Final Report

FELLOW SUBJECT

Hans-Joachim Stietzel

Bundesministerium für Umwelt, Naturchutz und

Reaktorsicherheit

Postfach 120629

D-53048 Bonn

Germany

tel: 49/228-305-3432

fax: 49/228-305-2398

E-mail: Hans-Joachim.Stietzel@metronet.de

Innovative approaches used on large remediation

projects in Germany

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NATO/CCMS Pilot Study, Phase II Final Report

Appendix III

GUEST SPEAKERS
NATO/CCMS Pilot Study, Phase II Final Report

During the Phase II Pilot Study, meetings were held at which numerous experts were invited to make

presentations related to the overall objectives of the study. Most of these invitees and the titles of their

presentations are listed below.

Guest Speakers

GUEST SPEAKER TITLE OF PRESENTATION YEAR

Jens Nonboe Andersen

Rambøl, Hannemann & Højlund

Denmark

Danish assistance in the remediation of Tököl Airbase

(Hungary)

1994

Baldur Barczewski

Grundwasser u.

Germany

Research facility for subsurface remediation 1994

James Barker

Waterloo Centre for

Groundwater Research

Ontario, Canada

Controlled in situ groundwater treatment 1994

Prof. Harald Burmeier

WCI Umwelttechnik GmbH,

Germany

Permeable treatment beds 1997

David Cooper

U.S. EPA

Office of Emergency and

Remedial Response

USA

Risk Assessment in Superfund 1997

Patrick Davoren

Department Primary Industries

and Energy

Canberra, Australia

Rehabilitation of former British nuclear test sites at

Maralinga, South Australia

1996

Dr. Wolfgang Dott

Institut fur Hygiene und

Umweltmedizin, Aachen

Germany

Strategies for in situ bioremediation 1996b

Marco Estrela

Instituto de Soluadura e

Qualidade, Centro de

Technologias Ambientais

Portugal

Use of remedial clean-up technology in Portugal 1997

Ayse Filibei

Dokuz Eylul University

Turkey

Solidification of fly ash samples coming from a solid

waste incineration plant

1993

Jan Freijer

University of Amsterdam

The Netherlands

Prediction and optimization of the abiotic environment

in landfarms to enhance biodegradation of

hydrocarbons

1994

Karsten Hupe

Technical University of

Hamburg-Harburg

Germany

Biological soil remediation 1996b

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GUEST SPEAKER TITLE OF PRESENTATION YEAR

Steven Hutchins

U.S. EPA

Office of Research and

Development

Ada, Oklahoma

USA

Field demonstration of bioremediation under

anaerobic conditions of a fuel-contaminated aquifer

1997

Rune Dyre Jespersen

Technical Soil Cleaning

Denmark

Electrodialiytic soil remediation (EDSR) 1996

Harald Kasamas

CARACAS Office

Vienna, Austria

CARACAS—The Concerted Action on Risk

Assessment for Contaminated Sites (in the European

Union)

1996b

1997

Nic Korte, Gary Jacobs, and

Tony Palumbo

Oak Ridge National Laboratory

USA

In situ remediation employing redox processes in

reactive barriers and zones

1997

Walter Kovalick, Jr.

U.S. EPA

Technology Innovation Office

USA

Overview of in situ treatment options for metalscontaminated soils

1996b

Walter Kovalick, Jr.

U.S. EPA

Technology Innovation Office

USA

Treatment walls 1996

Andrew Langley

Environmental Health Branch

Australia

The interface between risk assessment and

remediation: choosing a method of risk assessment

appropriate for Australia

1996

Andrea Leeson

Battelle-Columbus

USA

Results of bioventing studies at over 100 field sites 1994

James Mantle

Rust PPK

Australia

Oil terminal remediation: integration of free product,

dissolved phase and soil vapor recovery and treatment

1996

Dr. Ewa Marchwinska

IETU

Poland

Environmental issues in Poland 1997

Igor Marvan

Grace Dearborn, Inc.

Canada

Evaluation of six near-real-time analytical methods 1996

Mark McNamara

Clough Engineering Group

Australia

Introduction to the Homebush Bay regeneration

project

1996

Annemieke Nijhof

TAUW Milieu bv.

The Netherlands

The NOBIS project 1996b

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NATO/CCMS Pilot Study, Phase II Final Report

GUEST SPEAKER TITLE OF PRESENTATION YEAR

Annemieke Nijhof

TAUW Milieu bv.

The Netherlands

Risk assessment bottlenecks 1996b

Mark Noll

Applied Research Associates,

Inc.

Dover AFB

USA

Groundwater remediation field laboratory 1996b

Anna Orlova

University of Maryland

USA

Soil contamination in Russia 1996b

Paul Richter

New Jersey Department of

Environment and Energy

USA

Selection of remedial technologies 1993

Inge-Marie Skovgård

Environmental Protection

Agency

Denmark

The new Danish assistance to Central and Eastern

Europe

1994

Thomas Stauffer

U.S. Air Force

USA

Natural attenuation/degradation of aromatic

hydrocarbons

1996

Brian Ullensvang

U.S. EPA, Region 9

USA

Design and construction of an on-site leachate

treatment plant at the Operating Industries, Inc.,

landfill

1992

Paul Van der Heidje

Colorado School of Mines

USA

The role of modeling in risk assessment and site

remediation engineering

1997

Vilma Wisser

Tauw Milieu bv.

The Netherlands

Contaminated land in industrialized countries 1993

Ken Wangerud

U.S. EPA, Region 8

USA

On-site risk assessment and remediation planning at

lead-contaminated sites in Romania

1997

Geoffrey Williams

British Geological Survey

United Kingdom

Natural attenuation at the U.K. Villa Farm 1997

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NATO/CCMS Pilot Study, Phase II Final Report

Appendix IV

PROJECT SUMMARIES

These summaries are published in a separate document

available on the Internet from:

http://clu-in.com

http://www.nato.int/ccms
NATO/CCMS Pilot Study, Phase II Final Report

Appendix V

FELLOW STUDIES
NATO/CCMS Pilot Study, Phase II Final Report

PREFACE

This Volume of the Final Report of the Phase II Pilot Study on the remediation of contaminated land

and groundwater contains contributions from CCMS Fellows who took part in the study. They are

reproduced directly from the texts provided by the authors: they have not been edited other than to put

them into a common format. Contact addresses for the Fellows are provided at the end of the volume.

These papers do not represent the entirety of the contribution of the Fellows to the Pilot Study. Each

Fellow attended one or more of the international meetings and played an active part in discussions at

the meetings. In addition, a number of the Fellows have contributed to the preparation of the Final

Report by writing technology-related chapters (see Volume 1) and preparing extended project summaries

(see Volume 2).

The CCMS Fellowship Programme provides grants towards the travel and subsistence costs of

individuals conducting small studies related to on-going CCMS Pilot Studies. Recipients are encouraged

to attend meetings of the study group with which they are associated. Fellwoships are awarded annually

in response to applications through national CCMS coordinators. For more information on this and other

CCMS programmes, such as the Study Visit Programme, please contact:

CCMS Secretariat

NATO Scientific Affairs Division

B-1110 Brussels

Belgium

tel. +32/2-707-4619

fax. +32/2-707-4232

Information can also be obtained through national CCMS coordinators and on the World Wide Web at:

http://www.nato.int/science.

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Quality Management Systems and the Remediation of Contaminated Land

Dr. R.M. Bell, Hyder Consulting, and Mr. Richard Failey, SGS Environment,

Colwyn Bay, U.K.

1. INTRODUCTION

Quality Management Systems (QMS) are required to be established for the remediation of contaminated

land and waste containment in the expectation that the system will provide a consistent, and maintainable

operation which results in a piece of land that is fit for use and that all information upon which decisions

are made is reliable.

Quality Management Systems (QMS) are used where a contract between two parties requires the

demonstration of capability and assurance to provide the design and supply of a product or service. The

aim is to prevent nonconformity by using a system comprising components and elements subject to

Quality Control and Quality Assurance.

QMS like any system requires a policy, set of objectives and a method of measurement and review to

ensure targets are being met. QMS in the remediation of contaminated land requires a plan giving the

methods used, responsible parties and a system for identifying a non-conformance and implementation

of corrective action.

Quality Assurance (QA) is achieved through planned auditing/inspection of components of the system

against predetermined targets to give confidence that product or service requirements are being met, i.e.,

it is prevention rather than detection of non-conformance.

Quality Control (QC) is the ongoing measurement of conformance to ensure objectives and targets set

by the system are being reached. QC aims to achieve conformity through quantified measurement against

predetermined specifications which may include product standards, etc.

The most common method of ensuring QA/QC is by auditing which determines whether activities

comply with planned arrangements through the assessment of objective evidence. This is discussed later

under verification.

For the remediation of contaminated land a QMS will comprise a three phase system:

• Pre-works design and specification;

• On site operations including materials testing, site sampling and analysis; and

• Post works verification, ongoing monitoring, and guarantees.

Environmental Management Systems (EMS) are a method by which organisations can demonstrate

environmental performance through controlling the impact of their products and services. Many

organisations conduct environmental reviews or audits, but an EMS gives assurances that environmental

performance is in accordance and will continue to meet with the organisations environmental policy and

objectives. Examples include the ISO 140001; and the European Eco-Management and Auditing Scheme

(EMAS) which requires the publication of an auditable statement on the organisations concerns with the

environment.

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The essential elements of an EMS are that the system is based upon the evaluation of environmental

effects, from which all policies, targets, and procedures are based, and that the system is auditable. An

EMS follows QMS principles of control, calibrate, and verify, but also requires continual improvement

in environmental performance.

2. LAND REMEDIATION

EMS in land remediation allows for effective site management and policing of issues and allows the site

manager to pre-empt future problems. One assumes the land remediation process itself is a measure of

continual improvement. The first step in establishing an EMS is a preliminary environmental review

which needs to cover four key areas:

• Legislative requirements of proposed operations; Evaluation of significant effects;

• Examination of existing management practices;

• Assessment of feedback systems in dealing with incidents.

These key areas are considered in relation to internal site management issues, as well as external factors

such as neighbouring land use, road network, planning constraints, etc.

Important elements of any EMS relating to land remediation and waste containment include:

• Policy documents must incorporate principles of Economically Viable of Application of Best

Available Technology (EVABAT). In the U.K., this would include adoption of the waste

management hierarchy outlined in Department of Environment Waste management Paper No.28,

1991.

• Procedures for waste containment sites will be those outlined in the site working plan and licensing

conditions. For proprietary processes, the procedures relating to site controls are usually outlined in

an Environmental Impact Assessment required as part of planning permission.

• Responsibility includes the identification of management representatives, training of personnel, and

instructions to subcontractors. Current U.K. legislation requires the nomination of a ’Fit and Proper

Person’ as representative of waste management expertise; the EMS, however, requires demonstration

of appropriate training at all levels of staff which critically impinge on day to day operations.

• Evaluation of Environmental Effects requires the operator to identify, evaluate, and control all

significant environmental effects. These are to be registered in a “live” document that will be

auditable. Effects to be evaluated include direct effects from operations which may have already

been assessed using risk management principles during the site investigation or site licensing. There

also needs to be consideration of indirect effects which are generally more esoteric and may include

unmanageable issues such as nearest neighbours, or site location and access. The effects from

abnormal operations and accidents also need to be identified and evaluated. This is normal for sites

subject to an EIA under U.K. planning regulations.

The aim of the EMS is to manage significant environmental effects; however, there is guidance as to

what is meant by ’significant’ in any current certified system. The determination of a significant effect

is relative in all cases and can only be adjudged through transparent reasoning.

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NATO/CCMS Pilot Study, Phase II Final Report

• A Management Programme will be progressive and a chance to emphasise the positive aspects of

site management and evidence of the application of EVABAT.

• Operational Control is required on an activity from which a significant effect arises and that any

control mechanism is verified. Clear recognition of non-conformance is therefore required for

controls to be effective. For site remediation, operational controls are incorporated in the first phase

of site remediation, site design and construction/remediation methods. This also includes the

establishment of acceptance criteria for each activity that causes a significant effect.

• Verification and corrective actions are to ensure that operational controls are effective. This usually

comprises regular sampling and monitoring regimes during the second and third phase of site

remediation.

• Management Review principles are adopted for EMS as a normal part of QMS to ensure performance

reaches targets. It is the system that is reviewed and not the raison detre for the operation or site

works, since this will have been established in the Environmental Effects Evaluation.

3. U.K. EXPERIENCE

There are currently no formal systems for QMS in the U.K. for site remediation; we still rely largely

on caveat emptor as a means of absolving responsibility. Out of fifteen remediation contractors in the

U.K., only two specifically stated that they have an identifiable QMS in place to ensure the site

remediation process is reliable and that reliability can be demonstrated.

Planning legislation and licensing generally provide checks in the quality of site remediation, although

this can result in major differences in the reasoning for adopting site remediation techniques and the

interpretation of what is acceptable. In many cases, site remediation may be dictated by local politics

and the understanding of local council officers and not necessarily EVABAT/BATNEEC or a proper

evaluation of risk.

For large scale remediation schemes, an Environmental Impact Assessment and accompanying statement

are required. There are obvious and numerous licensing and regulation requirements, particularly for

waste containment as a means of site clean up which will soon be subject to taxation.

Section 78 of the Environment Act 1995, to be implemented in April 1996, allows the regulator to serve

a remediation notice and establishes responsible parties and the means by which remediation will be

undertaken. The courts, however, are not the best place to start the remediation process and the quality

of site remediation may not be uppermost in the polluters mind when paying court fines.

Some contractors and consultants operate a QMS system in accordance with IS09000 and there are

numerous product standards for materials used in the site remediation process.

However, for the U.K. there is currently no standard procedure for documentation for verification of

remedial action.

The Welsh Development Agency (WDA) (the government agency in Wales for remediation and

redevelopment) have produced a Manual on the Remediation of Contaminated Land with the purpose

of outlining its policy and objectives on the quality of land remediation projects.

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NATO/CCMS Pilot Study, Phase II Final Report

The WDA’s aim of land remediation is to ensure economic regeneration and environmental improvement

can take place using appropriate technical procedures, the effectiveness of which are confirmed through

appropriate management procedures. This will demonstrate to investors and regulators that remediation

has been carried out to a sufficiently high standard.

It is the WDA’s principal policy that remediation schemes comply with legislation and present residual

environmental health risks that are low as are reasonably practicable according to existing and proposed

site use, local setting, and technical and financial constraints. That is, the quality of land remediation

is based upon the principles of risk management and provides a complete record of site remediation.

The manual sets out guidance on procurement associated with site investigations, design

and selection criteria for technologies and materials, and gives guidance for requirements for detailed

design and verification.

The main documentation are the Outline Strategy Document (OSD) and Final Strategy Document (FSD).

The aim of the OSD is to ensure that site design considers and incorporates Best Practicable

Environmental Options and should fulfil those planning requirements for an Environmental Statement,

particularly the review of alternatives and the assessment of risks through accidents and abnormal

operations. In establishing the best practicable environmental option for remediation, the OSD will also

fulfil[ those requirements for an effects evaluation identified in ISO 14000. The FSD sets out the

requirements for auditing mechanisms to verify the quality of remediation with the eventual aim of

providing a Certificate of Completion that can be substantiated.

The site remediation process typically involves a consultant undertaking site investigations and designing

remedial works; a contractor undertaking the remedial works; regulatory authorities ensuring regulatory

compliance; a site owner/operator for whom the works are carried out; financial institutions or funding

bodies and solicitor to ensure contractual obligations are met. Further to this, an independent verifier of

works is often employed. These parties require a clear understanding of the remediation process and their

liabilities as well as clarification of any future obligations. A standard documented procedure is therefore

warranted.

Elements for documentation of verification procedures include:

• Description of site conditions and contamination;

• Hazard identification and risk assessment;

• Definition of remedial objectives and standards;

• Selection of preferred strategy;

• Site design for preferred technique;

• Tender preparation and contract documents;

• Variations to works; and

• Certificate of completion and warranties.

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NATO/CCMS Pilot Study, Phase II Final Report

The above elements need to be part of, or referenced in a Verification Report which should provide a

clear understanding of:

• The rationale for remedial action;

• Nature of works carried out;

• Key decisions and responsibilities;

• Regulatory compliance;

• Post remediation status of site; and

• Performance of site works.

The environmental performance of site works will be measured against objectives and standards

established in the first phase of remediation. The first phase of the remediation process also needs to

demonstrate:

• BATNEEC

• Practicality

• Guarantees of performance through demonstration on other sites

• Acceptance of technique by statutory authorities

For the second and third phase of the remediation quality controls will be implemented through an

agreed sampling and monitoring programme. Where a documented EMS has been established,

verification can be limited to an appraisal of whether commitments have been carried out. Otherwise

specific sampling programmes and protocols are required to ensure predetermined standards have been

met.

Most financial and funding institutions require independent measurement to ensure the quality of site

remediation. The establishment of a standard documented procedure will almost certainly provide

substantiated evidence that controls were in place during the entire remediation process and therefore

site warranties can be accepted as collateral.

4. CONCLUSIONS

In the U.K., QMS for site remediation is informal and variable and there is currently no consistent

system by which developers, regulators and funders can have confidence in. Pressure from developers,

legal and financial institutions has resulted in the issue being addressed by government agencies such

as the WDA and the Department of Environment.

By adopting QMS principles, this allows us to build in consistency, reliability, and independent

verification of the remediation process. Such principles may be set out in an EMS which brings together

all phases and elements of site remediation into a reasoned, documented, and measurable or auditable

system that gives objective evidence of verification. This in turn allows all parties in the remediation

process to have a clear understanding of their obligations and can give value to site warranties.

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Groundwater Contamination in Portugal: Overview of the Main Problems

Maria Teresa Chambino, Instituto Nacional de Engenharia e Tecnologia Industrial (INETI),

Instituto de Tecnologias Ambientais/Dep. Tecnologias Ambientais, Portugal

1. INTRODUCTION

Nowadays in Portugal, there is a progressive degradation of soils and groundwater, mainly as a

consequence of the population growth and industrial development of the last decades. Quite often waste

and wastewater treatment plants are not created according to the new needs and industrialists and farmers

are not yet conscious of the dangers of the uncontrolled deposition of wastes or use of excessive

amounts of fertilizers and pesticides.

Nevertheless soil and groundwater contamination are not yet a priority in Portugal compared to other

european countries. To overcome these problems the creation of a national program of characterization

of soil and groundwater contaminated sites and also the intervention of local authorities is of great

importance.

This paper presents a national overview of the main groundwater contaminated problems. The case of

the industrial site of Estarreja is specifically mentioned because it is a very important one and the most

systematically characterized .

2. MAIN POLLUTION SOURCES

2.1 Industry

The principal industries causing major pollution problems are food processing, pulp and paper,

chemistry, textile, and cattle breeding. These together account for 90% of the total pollution produced.

The major contributions are from pulp and paper (20.9%), textile (12.4%), olive oil (10.6%), pig

breeding (10.2%), wine and derivatives (4.7%), synthetic resins (4.5%), yeast (4.2%), and oil refineries

(3.4%).

Industry is responsible for the consumption of around 16% (800 million m3

) of the total water consumed.

Around 80% of this water is consumed in North region and Lisbon area.The sectors consuming most

are textiles and tanning (≅ 45%) and pulp and paper, and printing (≅ 25%). The slaughter houses,

tanning, extractive industry and steel works are not important at a national level, but may be important

regionally.

2.2 Agriculture

Agriculture is an important pollution source due to the intense activity in certain areas and the excessive

use of pesticides and fertilizers that contribute to the degradation of superficial and groundwater.

The total yearly water consumption in agriculture is around 3,800 million m3 (≅ 77% of total

consumption). Of this, the North region has 31%, Lisbon area 35%, Centre 17%, Alentejo 14%, and

Algarve 3%.

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2.3 Urban Areas

The public water supply is ≅ 7% of total consumption or 360 million m3

. 67% of this water is for

domestic consumption, 20% for industrial consumption, and 13% for public sector. Portugal has a

consumption of 100 L/inhab/day, which is less than most other european countries. The dependency of

domestic and industrial water supply on groundwater is indicated in Figure 1.

3. MAIN PORTUGUESE REGIONS WITH SERIOUS PROBLEMS OF GROUNDWATER

Figure 1: Dependency of domestic and industrial supplies on groundwater

POLLUTION AND OVEREXPLOITATION

The main problems are presented here. Due to its relevance the Estarreja case, in centre region, is

described in detail in Section 4 below. A general problem is the groundwater contamination by most of

the landfills, in particular in Estarreja, Almada/Seixal and Sines.

3.1 North Region

3.1.1 Organic and Industrial Pollution in River Cávado Sediments

This is an important industrial area. The main activity is textiles but paper, ceramics, food processing,

and slaughter houses are also important.

The water from the Borralha mines contaminates the river with cadmium and copper. Some urban areas

also dispose of their domestic effluents to the river.

An investigation of the river sediments revealed high levels of cadmium, copper, lead, chromium, nickel,

and zinc.

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The groundwater revealed organic contamination. In the nearby urban area of Barcelos 69% of the water

is bacteriologically unsuitable and only 11.5% is chemically unsuitable. This means the water has good

quality in the origin, but becomes contaminated along the way.

3.1.2 Domestic and Industrial Pollution in the Sediments of the Rivers Ave and Affluent

The same situation as the previous one. Contamination by cadmium, chromium, copper, lead, and zinc.

The main industry is textiles, which absorbs around 70% of all the people employed in industry in the

area.

Most of the industrial wastewaters are discharged directly and without any treatment into the rivers. The

situation with regard to sewage discharges the situation is quite similar.

3.2 Centre Region

3.2.1 Lowering of Piezometric Levels in the Baixo Vouga Aquifer

During recent decades, piezometric levels have fallen by tens of meters. From only 1989 to 1993, the

level decreased 5.5 m. Chloride levels over 500 mg/L were detected in the part of the area closer to the

sea.

3.2.2 Industrial Pollution in Caldas de S.Jorge

Toys industrial units, with chromium and nickel plating operations have disposed around 500 L/week

of their effluents, over the years, into wells and on land near the industries. The main pollutants were

chromium, nickel, cyanide, copper, and zinc, and the contamination reached the groundwater.

3.2.3 River Sediments

Near Águeda there are about 120 industrial units with anodizing surface treatments mainly chromium,

nickel, and zinc plating. Around 80-90% of these units have infiltrated their effluents in the soil. The

sediments of river Águeda are contaminated with heavy metals. The sediments of the river Criz

(Tondela) are polluted by effluents of aviculture.

3.3 Lisbon Area

3.3.1 High Nitrate Concentrations

Nitrate levels between 74 and 471 mg/L have been detected in river Sizandro valley. High nitrate levels

were detected in Rio Maior (325 mg/L), Seixal (274.5 mg/L), Almeirim (226.1 mg/L), and Torres

Vedras (203.5 mg/L).

3.3.2 Disposal Area of Almada

Domestic and industrial wastes were disposed in the old disposal site, with no impermeabilization. The

groundwater are contaminated with heavy metals of industrial origin.

3.3.3 Ridge of Mountains of Aires and Candeeiros

Over the years domestic waste was thrown in pits and this contaminated the groundwater.

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3.3.4 Alcanena

The tanning industry is concentrated in Alcanena, representing 75% of the national production.The

wastewater rejection over the years has contaminated the aquifers near the water lines. A wastewater

treatment plant has now been installed, but there remains the problem of sludges and wastes highly

saturated with chromium.

Due to the industry concentration in this area, it was decided to install a collective treatment plant to

treat the domestic and industrial effluents of almost all the industrial units. The sludges from the

treatment have been deposited on the soil, with no control for over six years.

A new landfill is being built consisting of three impermeable pools. Some sludges are being transferred

to the first pool with 61,000 m3

, located 100 m from the treatment plant. This plant is going to be

enlarged to produce 60 m3

/day of sludges that will be deposited in the two lagoons with 122,000 m3.

This sludge and waste transfer to the landfill has created atmospheric pollution problems with chromium

acid, hydrogen sulphide, and methylmercaptan.

3.4 Alentejo Region

The main problem in this region is nitrate contamination of groundwater. In the Évora area, around 50%

of the groundwater analysis performed indicate values exceeding the limit value of 50 mg/L. The nitrate

level is also high in Beja.

3.5 Algarve Region

3.5.1 Nitrate

Nitrate levels over the limits were detected in several river sediments, due to agriculture and effluent

disposal.

3.5.2 Groundwater salinization

Several areas around the south coast have problems of groundwater salinization. Besides the problems

of salinization by overexpoitation of the aquifers, salinization also occurs due to the leaching of

saliferous rocks. The main contaminated (saline ?) aquifers are shown in the map in Figure 2.

4. GROUNDWATER CONTAMINATION IN ESTARREJA

4.1 Main Chemical Units

4.1.1 The general situation

This area is one of the most industrialized in the country and presents serious problems of soil and

groundwater contamination due to over forty years of presence of an important chemical complex, with

precarious methods of effluent and waste disposal.

The chemical industrial area of Estarreja includes mainly the following industrial concerns: Quimigal,

Uniteca, and Cires. The first unit to be installed was Quimigal, in 1952, followed by Uniteca in 1959

and Cires in 1963. There is a great interdependence among these units, with exchanges of raw material

and subproducts.

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This industrial area is regarded as a threat to the environment due to the wastes and effluents produced.

Figure 2: Main contaminated aquifers

Furthermore, it is located on highly permeable soils with a groundwater level that is periodically high,

and near an area of intense agricultural activity highly dependent on groundwater.

Over the years these units have been rejecting large quantities of waste directly on the soil: Uniteca

sludge deposit, 60,000 tonnes; Cires sludge deposit, 300,000 tonnes; and the Quimigal sludge deposit,

80,000 tonnes. These wastes were deposited with no impermeabilization measures.

Until recently, the effluents were disposed to a not impermeable ditch, transporting over several

kilometers arsenic, mercury and other heavy metals and inorganic compounds to the Estarreja river

branch. Some compounds infiltrated through the bottom of the ditch have contaminated the local

groundwater. In addition, during periods of with heavy rain or disposal of large effluent volume, the

effluents have overflown the agricultural land near the ditch.

A few years ago, a pipe was built for effluent transport. Although the ditch has officially ceased to be

used for effluent rejection, effluents with nitrobenzene were detected during a sampling campaign

performed in 1992.

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The atmospheric pollution and the deposition on the soil of several metals and sulphur dioxide from

gaseous emissions will increase the soils acidification.

The effects of this industrial area are felt until the Aveiro estuary, 20 km away, where high levels of

mercury were detected.

The groundwater contamination has reached such a level in many wells that the municipality has been

forced to distribute water for domestic use. Nevertheless the water distribution is not enough for

agricultural purposes.

The volume of groundwater withdrawn over the years has lowered the piezometric level and induced

a gradual salinization. So the industrial units were forced to capture water from the river nearby

(corresponding to 90% of their needs), and use groundwater during summertime.

4.1.2 Quimigal

This plant has been producing, ammonium sulphate since 1952, nitric acid and ammonium nitrate since

1974 and aniline from mononitrobenzene since 1978. The main raw material was pyrites for sulphuric

acid production. This production is now stopped for economic reasons.

Over the working decades, we can foresee the impact of the atmospheric emissions of sulphur dioxide

and sulphuric anhydride, arsenic, mercury, and other metals and the effluents and waste rejection. Some

years ago, a gas treatment system was installed but no protection was made for soil or groundwater. The

dust from the treatment was gathered with the other sludges and wastes.

Waste Production

Around 80,000 tonnes of wastes and sludges were produced over the years—mainly dusts from gaseous

effluents treatments with heavy metals, and sludges from primary treatment contaminated with arsenic

and ashes.

Main Contaminants

• In liquid effluents: aniline, ammonia, arsenic, mononitrobenzene, and benzene

• In wastes: arsenic, lead, zinc, vanadium, other heavy metals

Effluent Treatment

• Incineration for effluent rich in organic matter and activated carbon for inorganic effluents.

• Settling

Raw Materials

• Ammonia, potassium chloride, pyrite, solid sulphur, phosphates, benzene

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4.1.3 Uniteca

This plant produces sodics and chlorates from rock salt through electrolytic cells, using graphite anodes

and mercury cathodes. Some mercury goes to the environment, mainly due to cleaning of the cells,

cleaning of the pavements near the electrolysis area, and wastewater treatment sludges

Nowadays in the European Community, the most important producers of alkaline chlorides no longer

use mercury cells. Nevertheless in Uniteca they are still being used, although there exists a new line with

membrane technology that avoids pollution with mercury.

Main Contaminants

• Liquid effluents with mercury, suspended solids, and sulphuric acid

• Sludges with mercury

• Atmospheric pollutants: sulphur dioxide, nitrogen oxide, particles, mercury, and hydrochloric acid

Raw Materials

Raw materials include sodium chloride, mercury, sodium carbonate, and sulphuric acid. There is a plan

to install a process for mercury removal from the liquid effluents, lowering the mercury level from 25

mg/L to 0.025 mg/L. In the Portuguese legislation, the mercury level allowed in wastewaters is 0.001

mg/L.

4.1.4 Cires

This plant produces synthetic resins, mainly PVC (polyvinyl chloride).

Main Contaminants

• Liquid effluents with vinyl chloride and mercury

• Sludges with calcium hydroxide, wastewater sludges

Effluents Treatment

The effluents are stored in two lagoons before going to the treatment plant. The lagoons are not

impermeabilized and so vinyl chloride can contaminate the groundwater.

Raw Materials

• Hydrochloric acid, vinyl chloride, mercury chloride, and sodium hydroxide

4.2 Sampling

Two different sampling campaigns were performed for groundwater and soil characterization, from 1992

to 1994. In the first campaign, in 1992, samples were collected only from 37 wells and three ditches

covering an area of 15 km2 around the industrial units. In the second campaign, in 1993/94, samples

were collected in 39 monitoring holes. The depth of sampling was in average 5.5 m.

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These data allowed the characterization of the groundwater and the identification of the major pollution

plume, only with season concentration changes.

4.3 Results

4.3.1 Overview

The main concentration values were detected near the industrial units, in the ditches and in the sludges

deposition areas. This concentration flows in the direction of the quaternary aquifer flow, from east to

west. So the highest concentrations are found west of the industrial area. The concentration levels found

in monitoring holes are higher than those found previously in wells. Due to the nonexistence of

legislation for groundwater in Portugal, the comparison is made with legislation for water for human

consumption.

4.3.2 Heavy Metals

Mercury

High values of mercury were found reaching 745 μg/L (the legislation value is 1 μg/L). The areas where

this happened are near the effluent rejection ditches and west of the industrial area.The total mercury

concentration is higher than the dissolved mercury, revealing that mercury is adsorbed by small particles.

A map of mercury concentrations is provided in Figure 3.

The origin of the mercury is mainly the sludge disposal area of Uniteca. Those sludges have mercury

levels from 100-500 mg/kg. In the area where these high mercury levels were detected, the water cannot

be used for human consumption.

Arsenic

High concentrations in groundwater were found, reaching 6,760 μg/L, compared the legislation level was

50 μg/L. The high levels of arsenic come from the sludge disposal area of Quimigal. Also the effluents

from Quimigal presented high levels of arsenic. From 1987 to 1991, the industry effluent had maximum

levels of arsenic of 38,000 μg/L. The average values were 8,355 μg/L and the effluent value allowed

in legislation is 1,000 μg/L.

Zinc

The origin of the zinc is the sludge disposal area. The main pollution area is west of this area and

reaches 204 mg/L, compared to the limit of 0.1 mg/L. Also, near the ditches the values are important.

Iron

The higher concentrations are near the ditches, reaching values of 61 mg/L (legislation value of 0.2

mg/L). So we can see that the heavy metals reach high contamination levels in groundwater.

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4.3.3 Anions

Figure 3: Groundwater mercury contamination

Chlorides

The chloride concentrations reach higher values (highest value = 36,540 mg/L) than the legislation

permits (25 mg/L) all over the sampling area. The origin is probably the sludges from Uniteca, which

present chloride values of 7 to 11% in the 60,000 tonnes of sludges. Also, the effluents from Quimigal

present high chloride values, reaching an average between 1987 and 1991 of 630 mg/L.

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Sulphates

Values over three times the legislation limit were found: values of 900 mg/L compared to the limit of

250 mg/L. The origin is the sludge from Uniteca, where calcium sulphate is 10 to 14% of the sludges,

and the effluents from Quimigal that reach values of 2,300 mg/L, compared to the legislation limit of

2,000 mg/L. Some of the sulphate might have been reduced to sulphide and be responsible for the smell

characteristic of the waters in this area.

Nitrates

Values exceeding the legislation value (50 mg/L) were found near the ditches, reaching values of 325

mg/L. Their origin is the effluent rejection and also the fertilization for agriculture. The effluent rejection

between 1987 and 1991 reached values of 5,116 mg/L, hundred times the legislation value.

4.3.4 Organic compounds

There is no mention of organic compounds in the Portuguese legislation for water for human

consumption so reference is made below to international legislation.

Nitrobenzene

In three of the monitoring holes, the level was higher than the U.S.legislation limit for groundwater (20

μg/L), reaching the high value of 2,520 μg/L. This hole is very near to the ditches, indicating the

importance of effluents disposal as a source.

Benzene

The high value of 85.7 μg/L was reached in the same hole where nitrobenzene also reached the

maximum (the limit in USA legislation is 5 μg/L). These two compounds are present in Quimigal

effluents. The sampling campaigns allowed the detection of the area where contaminant concentrations

are higher than the legislation permits. This area is illustrated in Figure 4.

4.4 Solutions Proposed

The Estarreja problem is a complex one due to the long time over which disposals have taken place

(over forty years) and the dispersion of contaminants over a large area. Before the decontamination of

the area, the first step should be the removal and treatment of the main pollution sources: i.e., the

sludges disposal area of Quimigal and Uniteca and the liquid effluent disposal to the ditches.

For the moment, the sludges disposal area should be covered to prevent the rain entering and consequent

leaching and a physical isolation of the area through the injection, in the land and until near the aquifer,

of walls preventing the pollutants migrating. Also, effluent disposal through the ditches should be

stopped and wastewater treatment should also be installed.

There is a project from the Estarreja Municipal Government to treat the wastes by “Chemical Fixation

and Solidification.” The sludges from Quimigal and Uniteca would be mixed with Cires sludges, which

are more inactive (mainly calcium hydroxide) and would be used as material for encapsulation.The

sludges and wastes would finally be deposited in a landfill.

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In addition to the measures listed above, decontamination of the groundwater is essential. The polluted

Figure 4: Main polluted areas

groundwater should be removed and should be treated, to prevent the pollution spreading. Through the

method developed by Javandel and Tsang (1986) the volume and extraction flow and number and

position of capture holes were established. The volume to be removed should be 7 x 106 m3

, and the

extraction flow should be 17,797.5 m3

/day

The time necessary to perform this operation will be around 400 days. This decontamination will remove

the elements not adsorbed in the surrounding soil. The groundwater should be treated in wastewater

treatment plants and afterwards be reintroduced again in the aquifer or used in agriculture or industry.

This groundwater pollution case is the most important and also the most studied one in Portugal. In 1995

a governmental law (DR 19/7/95) established that Estarreja was a critical area for pollution and industrial

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security. For management of industrial wastes, an Integrated System of Waste Treatment (SITRI) was

programmed for the country.

In Estarreja should be installed an incineration unit, together with a project for soil and groundwater

decontamination (Project ERASE) and a project for industrial and domestic wastewater treatment (Project

AMRIA). Also, priority should be given in Estarreja to the installation of clean technology industries.

The incineration installation is somewhat delayed because the NIMBY mentality (not in my backyard)

arrived quickly in Portugal, and through 1995 great opposition was made by the population to the

installation of incineration units or landfills.

5. RESEARCH PROJECTS

In Portugal, very few research projects are dedicated to the problems of groundwater and soils

contamination, and those there are mainly are master theses in the universities. One of the few existing

projects is a European Community project “Experimental Evaluation of Remediation Techniques for

Contaminated Coke Oven Sites.” The partners are Siderurgia Nacional, Instituto de Ciência e Tecnologia

dos Materiais (ICTM) and Deutshe Montan Tecnologie (DTM).

INETI is subcontracted by ICTM, one of the partners. INETI’s activities concern characterization of the

contamination of soils and groundwater in the coke oven site of Siderurgia Nacional by the Institute of

Environmental Technologies (ITA); and strategies for microbial remediation of coke oven contaminated

sites by the Institute of Biotechnology, Chemistry and Food Technologies (IBQTA).

The contamination of soil at operational coke oven sites is due to organic and inorganic toxic compounds

such as mono-aromatic hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), phenols, cyanides,

heavy metals, and ammonia. This contamination may be a source of groundwater pollution, especially

when the water table is at shallow depths. Due to the fact that the contaminated site is located near an

estuary, the tide effect can cause a groundwater gradient towards the surface water and cause superficial

water pollution problems.

The objective of this research project is to select the most effective biological treatment technology to

remove phenols, PAHs, and cyanides from contaminated coke oven plant sites still in operation and also

to analyse the groundwater contamination. The program of work was:

• Identification of organic contaminated areas;

• Development of sampling program for soils and groundwater;

• Characterisation of soils and groundwater; and

• Determination of biological treatment efficiencies.

Regarding ITA’s activities, the characterisation of soil contamination as well as the mapping of the

extent of pollution was carried out. Individual samples of soil representative of each geological layer

were collected in order to obtain information about the lithology and the contamination of the area.

Twelve trenches were dug with a mechanical excavator, almost all were dug until groundwater level was

reached.

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The contamination found in the coke oven site is mainly due to tar at the top of the first layer. Coke

oven tar is an extremely complex mixture, the main components of which are polycyclic aromatic

hydrocarbons (PAHs), highly toxic. Fluoranthene, phenanthrene, and pyrene have been detected as major

contaminants.

Due to their high chemical stability and low water solubility, the PAHs have low mobility and persist

as soil contaminants. The PAHs were identified by reverse phase high performance liquid

chromatography, and values exceeding 1,000 mg/kg of fluoranthene, phenanthrene and pyrene were

detected. The phenols and total cyanides reached 25.3 mg/kg and 1,420 mg/kg, respectively.

The tar contamination was mapped. In most places tar contamination is only at the surface, but in some

sampling points, it has reached deeper layers down to groundwater level.

In lower soil layers the presence of ammonia was detected in the groundwater in all the trenches. This

contamination is due to ancient accidental spillage and probably also to pipe leaks. In the next project

phase, groundwater contamination is going to be characterised.

Regarding the bioremediation studies, the objective was to determine the potential for bioremediation

of the microbial communities indigenous of the coke oven site through the evaluation of their abilities

to degrade PAHs, particularly those detected as major contaminants. Tests already performed indicate

that mixed culture selected and enriched from soil native microbial populations have the ability to

degrade the predominant PAHs contaminants fluoranthene, phenanthrene, and pyrene.

6. BIBLIOGRAPHY

Gonçalves, E. e Boaventura, R., (1989), Sediments as Indicators of River Ave Contamination by Heavy

Metals, International Symposium on Integrated Approaches to Water Pollution Problems, SISIPPA,

Lisboa.

Grupo de Investigação de Águas Subterrâneas, (1992), Metodologias para a Recuperação de Águas

Subterrâneas e Solos Contaminados, Partes A e B, LNEC.

Grupo de Investigação de Águas Subterrâneas, (1994), Metodologias para a Recuperação de Águas

Subterrâneas e Solos Contaminados, Partes C, D, E e F, LNEC.

Grupo de Investigação de Águas Subterrâneas, (1995), Desenvolvimento de um Inventário das Águas

Subterrâneas de Portugal, LNEC.

Lobo Ferreira,J.P., (1989), A Groundwater Pollution Case Study: Rio Maior, International Symposium

on Integrated Approaches to Water Pollution Problems, SISIPPA, Lisboa.

Milheiras Costa, A., (1989), Águeda como Exemplo de Solução Integrada de Poluição, 1as Jornadas sobre

Indústria e Ambiente, INETI.

Monteiro, H. e Boaventura, R., (1989), Distribuição de Metais Pesados nos Sedimentos da Bacia

Hidrográfica do rio Cávado, International Symposium on Integrated Approaches to Water Pollution

Problems, SISIPPA, Lisboa.

Plano Nacional da Política de Ambiente, (1994) , M. do Ambiente e Recursos Naturais.

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NATO/CCMS Pilot Study, Phase II Final Report

Santiago,M.F. e Corte-Real Frazão, A., (1993), Lamas das Águas Residuais Industriais - Caso da

Indústria dos Curtumes, Seminário sobre Tratamento e Destino Final de Lamas de Águas Residuais,

LNEC e DGQA.

Sepúlveda, I., (1994), Soil Contamination and Decontamination: Overview of the Portuguese Situation,

Land Contamination & Reclamation, Vol. 2, No. 2.

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Critical Review of Air Sparging and In Situ Bioremediation Technologies

Domenic Grasso, The School of Engineering, University of Connecticut, Kenneth L Sperry,

Envirogen, Lawrenceville, NJ, and Susan Grasso, Environ, Princeton, NJ

1. INTRODUCTION

This review consists of the identification, classification, and analysis of issues of concern (or “critical

issues”) frequently encountered during the application of air sparging/biosparging, bioventing,

biostimulation, and biorestoration remediation technologies. This review was prepared for the NATO

Committee on the Challenges of Modern Society, which is evaluating emerging environmental

remediation technologies, in an effort to facilitate future applications of these technologies.

The review utilized a case study approach and included more than 400 sites located in the United States,

Australia, Canada, and Europe. Case studies included bench-, pilot-, and full-scale applications of these

technologies, and explored remediation at a wide variety of sites including:

petroleum processing/handling facilities;

wood preserving plants;

manufactured gas plants;

military installations; and

industrial/chemical manufacturing facilities.

At a majority of the sites reviewed, organic compounds in soil and groundwater were the target of

remediation. Elevated levels of heavy metals and inorganic compounds were, however, also present at

many of the sites reviewed. In general, seven classes of compounds were frequently encountered: (1)

aliphatics; (2) substituted benzenes; (3) polycyclic aromatic hydrocarbons; (4) polychlorinated biphenyls;

(5) pesticides/insecticides/herbicides; (6) inorganics; and (7) metals.

Critical issues identified in the case studies were categorized according to scale (macro, meso or micro).

A macroscale issue was generally defined as a factor that may complicate the selection and

administration of a remedial technology. Meso- and microscale issues were generally defined as factors

that may adversely affect the performance of a remedial technology. More specifically, mesoscale issues

were related to the physical geologic and hydrogeologic properties of the subsurface, and microscale

issues pertained to biological and physicochemical processes. The review focused primarily on the

detailed evaluation of meso- and microscale critical issues most frequently associated with the

remediation technologies of interest.

Overall, critical issues (macro, meso, and micro) were reported in approximately 35% of all cases

reviewed. More specifically, critical issues were observed with the following frequency for each

technology:

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Technology Total Number Sites with Percentage of Sites

Air sparging/biosparging 87 18 21%

Bioventing 101 31 31%

Biostimulation 67 29 43%

Biorestoration 104 47 45%

The actual number of case studies where critical issues were encountered may be much greater as there

may be reluctance to report such information. The primary types of critical issues observed for each

technology are summarized below.

2. AIR SPARGING/BIOSPARGING

Air sparging/biosparging consists of injecting air (or other gases) under pressure directly into

groundwater-saturated aquifer materials. The objective is to facilitate contaminant transfer from an

aqueous phase (groundwater) to a gaseous phase (in situ air stripping) which is subsequently transported

to the overlying unsaturated zone and removed by traditional soil vapor extraction (SVE) techniques.

In addition to volatilization, air sparging fortuitously stimulates microbial degradation of contaminants

by increasing the concentration of dissolved oxygen in the subsurface (biosparging).

Mesoscale critical issues were observed most frequently followed by macro-scale critical issues.

Reported macroscale issues were associated with regulatory acceptance of these technologies due to their

limited use. A very limited number of air sparging and biosparging case studies reported microscale

issues.

While some of the mesoscale issues observed were related to contaminant distribution and site

hydrogeology, those relating to site geology were observed to most severely compromise air sparging

and biosparging performance. In these cases, geologic stratigraphy (such as lenses of low or high

permeability material), and small variations in soil permeability resulted in preferential air channeling

and poor air distribution through tortuous and asymmetrical air flow pathways.

Preferential air flow reduced the effectiveness of air sparging and biosparging because large

portions of the targeted remediation zone were bypassed by the sparge air.

3. BIOVENTING

Bioventing induces air movement through the unsaturated soil to enhance aerobic biodegradation of

contaminants by supplying oxygen to soil microorganisms. Air movement is usually induced by forced

(active) aeration using injection and extraction wells.

Similar to air sparging/biosparging, mesoscale critical issues were observed most frequently followed

by macro-scale critical issues. Reported macroscale issues were associated with regulatory approval and

acquisition of regulatory permits. Relatively few of the bioventing case studies provided information

detailed enough to accurately identify microscale critical issues. Where microscale critical issues were

observed, however, they were likely associated with biological and/or physicochemical limitations that

adversely affected biodegradation kinetics.

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Mesoscale critical issues observed to most adversely affect system performance were related to site

geology and hydrogeology. More specifically, the effectiveness of bioventing was reduced when the

delivery of oxygen to indigenous microorganisms was hindered by: (1) low permeable soils; and (2)

excessive soil moisture content.

Fine-grained soils (silts and clays) which have a low intrinsic soil gas permeability and a high

field capacity (potential for high soil moisture content) were found to be especially problematic

in the application of bioventing. The combination of these factors decrease effective soil gas

permeability and increase the potential for oxygen diffusion limitations.

4. BIOSTIMULATION

Biostimulation refers to the enhancement of aerobic biodegradation of contaminants in the unsaturated

zone (above the water table) through the addition of electron acceptors, electron donors, and nutrients.

In the case studies reviewed, these amendments were typically delivered to the subsurface using water

or air as a carrier fluid.

Macroscale and microscale critical issues were observed with equal frequency in biostimulation case

studies, while mesoscale critical issues were observed to a lesser degree. Macroscale critical issues

included: (1) difficulty in obtained regulatory approval for use of the technology; and (2) difficulty

obtaining discharge to groundwater permits. The primary mesoscale issue observed involved the nonuniform delivery of components required to enhance aerobic biodegradation as a result of geologic

heterogeneity.

Microscale critical issues were most often associated with biological and physicochemical processes,

however, in many case studies differentiating between these mechanisms was not possible. The following

were observed:

(1) Biological microscale issues were related to contaminant biodegradation potential, microorganism

metabolic requirements, and contaminant toxicity.

(2) Physicochemical critical issues were related to reduced contaminant bioavailability deriving from

either mass transfer kinetics or dissolution rate limitations.

The predominance of microscale critical issues in the biostimulation case studies reviewed was a

reflection of the contaminant type targeted for remediation. In contrast to the majority of the air

sparging/biosparging and bioventing case studies reviewed, a wide range of large polycyclic aromatic

hydrocarbons (PAHs) were the target of remediation at the majority of biostimulation case studies

reviewed.

The insoluble and nonvolatile nature of PAHs targeted for remediation in many of the

biostimulation case studies makes them more recalcitrant to biodegradation (and volatilization)

than the lower weight aliphatic and aromatic hydrocarbons that were typically the target of

remediation in the air sparging/biosparging and bioventing case studies discussed.

5. BIORESTORATION

Biorestoration refers to the injection of fluids containing electron acceptors, electron donors, or nutrients

into the saturated zone (below the water table) to stimulate in situ aerobic or anaerobic biodegradation.

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Macroscale critical issues were observed most frequently in the biorestoration case studies reviewed, and

typically involved: (1) difficulty in obtained regulatory approval for use of the technology; and (2)

difficulty in monitoring biorestoration performance.

Mesoscale critical issues were most often related to site hydrogeology. Groundwater flow velocity, as

determined by hydraulic conductivity and hydraulic gradient, was an important factor in the successful

application of biorestoration, as expected.

In formations with low groundwater velocities, the areal extent of biodegradation was limited

because electron acceptors, electron donors, and nutrients were quickly consumed within the

immediate vicinity of injection wells.

Microscale critical issues were most often associated with biological processes in many of the

biorestoration case studies reviewed. Specific hindrances to system performance included:

(1) The biodegradation kinetics of some components of coal tar waste were observed to be rate

limiting.

(2) Microbial inhibition due to elevated levels of arsenic, lead, chromium, and dioxins was also

observed to potentially limit biodegradation.

The slow biodegradation rate of components of coal tar wastes was observed to limit system

performance in some of the biorestoration case studies reviewed. The biodegradation kinetics

of these compounds were potentially limited by contaminant bioavailability. In addition,

microbial inhibition due to elevated concentrations of arsenic, lead, chromium, and dioxins was

suspected of limiting biodegradation rates in some biorestoration case studies discussed.

6. MASS TRANSFER LIMITATIONS—A UBIQUITOUS CRITICAL ISSUE

Although many critical issues were observed to be specific to either air sparging/biosparging, bioventing,

biostimulation, or biorestoration, all the reviewed technologies have one at least one critical issue in

common: diffusion limited mass transfer. The theory and ramifications of diffusion limited mass transfer

were therefore explored in depth. The discussion focused on diffusion limitations:

(1) in bulk aqueous solution where advective flow is minimal or absent; and

(2) from within soil matrices to the surrounding bulk aqueous solution (sorption retarded diffusion).

6.1 Diffusion Limitations in Bulk Solution

In situ technologies discussed herein are inherently susceptible to diffusion limited mass transfer in the

bulk aqueous phase because each technology relies upon fluid flow to either:

(1) deliver components required to enhance biodegradation (electron donors, electron acceptors, and

nutrients); or

(2) to extract contaminants (such as volatilization in air sparging).

Fluid flow in most subsurface environments, however, is not uniform and heterogeneities in the

subsurface can result in preferential flow pathways. Outside these flow pathways, advective fluid flow

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may be minimal or absent. As a result, the primary mechanism for delivering components required to

enhance biodegradation or contaminant extraction in these areas may be governed by molecular

diffusion. A mathematical model was used to explore diffusion times required for oxygen and

contaminants under various subsurface conditions encountered in this review.

Modeling results indicated that extensive diffusion times (ca. years) are required for oxygen and

common contaminants to diffuse short distances (less than 1 m) in regions of the subsurface

where advective fluid flow is minimal or absent.

6.2 Sorption Retarded Diffusion

A sorption retarded diffusion limitation (i.e., diffusion from within the soil matrix to the surrounding

bulk aqueous solution) has been proposed as the primary mechanism responsible for the significant

“tailing effect” in contaminant concentrations which was observed in many of the case studies reviewed.

A bi-modal theory describing desorption from the soil matrix was combined with a radial diffusion

model of transport in an aqueous solution to simulate the tailing effect phenomena. Model simulations

assessed the effects of:

tortuous and constricting soil pores;

intra-particle porosity;

soil fraction organic carbon;

particle size; and

contaminant chemical properties.

Model simulations demonstrated that considerable time (ca. years) may be required to desorb

some contaminants from the soil matrix to the surrounding bulk aqueous solution. In addition,

the use of a Freundlich isotherm to represent non-linear sorption in select portions of a soil

matrix resulted in the prediction of significantly higher desorption times.

The ability to uniformly distribute fluid in the subsurface was frequently encountered as a limitation in

the application of the in situ technologies under review due to heterogeneous conditions commonly

present in the subsurface. Without this ability, accomplishing uniform and complete remediation is such

an environment can be difficult, due to diffusion limitations that may exist in the bulk fluid.

Additionally, in most of the case studies reviewed, soils had been contaminated for many decades prior

to remediation, suggesting that sorption retarded diffusion may be responsible for tailing phenomena

commonly observed. As previously discussed, this may severely limit the long-term performance of the

in situ remedial technologies reviewed.

7. REFERENCE

Grasso, Domenic, Kenneth L Sperry, and Susan Grasso. NATO Fellowship Project: A Critical Review

of Air Sparging and In Situ Bioremediation Technologies, The School of Engineering, University of

Connecticut (Storrs, Connecticut, USA) 1997.

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The Cost of Remedial Action

Dr. Mary R. Harris, Monitor Environmental Consultants Ltd, Birmingham, U.K.

1. INTRODUCTION

Considerable efforts have been made over recent years to identify and develop new technologies for the

treatment of contaminated soil and groundwater and to demonstrate their technical performance in the

field. Many of these technologies have the potential to transfer across international boundaries. Some

appear to offer the prospect of dealing with contamination on a “once-and-for-all,” as opposed to

“contain and control,” basis.

With some notable exceptions, however, there seems to be relatively little reliable information available

to landowners, regulators and practitioners on:

• the cost of different technologies, and how they may compare against more established or traditional

approaches;

• the key cost components of different technologies; and

• how the cost of treatment may be distributed over time.

A lack of reliable cost information can be as important as technical uncertainty in discouraging the wider

uptake and application of new technologies. For example:

• it encourages users to favour the selection of established methods and approaches, where technical

capabilities and costs are already well established and understood;

• it makes it difficult for users to predict at the outset (and with any acceptable degree of accuracy)

what the financial implications of a remedial project may be; and

• it makes it difficult for users to gauge short versus long-term costs and benefits when making

selection decisions, and to justify them financially.

Finally, a lack of information on the cost characteristics of new technologies can hamper their transfer

across international borders because users are unable to make the essential financial adjustments needed

to translate technology costs into a specific national context.

There are, of course, a number of practical difficulties in obtaining reliable financial information.

Examples include:

• commercial confidentiality (on the part of both clients and contractors) on the actual “value” of the

work done, rather the estimated or predicted cost;

• local or temporal cost variations due, for example, to fluctuations in local demand for remedial

goods and services; and

• other site specific factors, such as the nature of the contamination, scale of operations, duration of

the works, extent of other ground improvement or construction activities and their relationship with

remedial action.

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However, opportunities do exist for the systematic collection of financial information. Examples include

national and international research and demonstration programmes, such as this NATO/CCMS study,

and other publicly-funded remedial works, e.g., regulatory-led action and grant-aided redevelopment

schemes.

The development of standardised data collection and reporting procedures can help to ensure that

financial information is consistent, objective and informative. The aim of this Fellowship was to assist

in the development of reliable information on remedial costs and to improve the ability of technology

users to interpret and apply cost information.

2. OBJECTIVES

The main objective of the Fellowship was to develop a standardised framework for reporting information

on the costs of remediation that will:

• help to expand the currently relatively limited information base on remedial costs;

• assist in the international transfer of information on remedial costs;

• allow potential users of different remedial technologies to identify where the main cost burden is

likely to fall;

• alert potential users to the trade-offs (e.g., high capital/low aftercare versus low capital/high

aftercare costs) which may have to be made when selecting particular technologies; and

• help potential users of overseas technologies to identify those cost items (e.g., waste disposal,

energy, labour, etc.) which may vary significantly as a result of country-specific factors.

3. APPROACH

Draft guidance on reporting remedial costs has been developed (see Annex I) based on:

• the cost framework developed in support of the U.S. Environmental Protection Agency Superfund

Innovative Technology Evaluation (SITE) Program;

• research on remedial costs commissioned by the German Federal Environment Ministry; and

• work carried out by the U.S. Federal Remediation Technologies Roundtable Ad Hoc Working Group

on Cost and Performance.

The draft guidance was circulated to Pilot Study Country Representatives for comment. Some comments

have been received and have been incorporated into the current draft. This will be circulated to Pilot

Study members with a request for submission of cost information.

4. ANALYSIS AND REPORTING

It is hoped that sufficient cost data on individual Pilot Study Projects will be available to allow a simple

analysis of the broad cost characteristics of different types of technologies. The responses of Project

Leaders will also be used to refine the cost framework where necessary and to identify the key issues

to be addressed when attempting to interpret or apply cost information.

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It is intended that the findings of the Fellowship will be incorporated into the final Pilot Study report

in the form of a separate chapter on Remedial Costs.

5. ACKNOWLEDGEMENTS

The work reported here was carried out by means of written correspondence with other members of the

Pilot Study and through participation at the following Pilot Study Meetings:

Quebec City, Canada September 1993

Oxford, U.K. September 1994

Nottingham, U.K. May 1995

The assistance of other members of the Pilot Study, and the financial support of NATO and the U.K.

Department of the Environment are gratefully acknowledged.

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ANNEX I: Guidance on Reporting Information on Remedial Costs

A.1. INTRODUCTION

One of the aims of the Pilot Study is to provide information on the cost of remediating contaminated

soil and groundwater. This guidance has been prepared to assist project leaders in collecting and

presenting cost data on their technologies. The information obtained will be used to prepare a Chapter

on costs for inclusion in the Final Pilot Study Report. The guidance supplements that produced by Mike

Smith (see notes of the September 1994 Pilot Study meeting in Oxford) on overall reporting

requirements.

The guidance has been developed with reference to the U.S. Environmental Protection Agency Superfund

Innovative Technology Evaluation (SITE) programme cost framework, research on remediation costs

commissioned by the German Federal Environment Ministry and work carried out by the Federal

Remediation Technologies Roundtable Ad Hoc Working Group on Cost and Performance. Comments

from the Pilot Study Country Representatives have also been taken into account.

It is recognised that not all the projects in the Pilot Study programme will be able to provide cost data

at the level of detail shown; some projects are only just under way, and others are too remote from

commercial realisation to provide meaningful data. Nevertheless, the aim is to provide actual or

estimated costs for the full-scale operation of the technology.

A.2 OBJECTIVES

The main aims of providing cost data on remediation technologies through the NATO/CCMS Pilot Study

are to

• expand the relatively limited information base currently available;

• assist in the international transfer of information on remedial costs;

• inform potential users where the main costs are likely to fall when applying a particular technology;

and

• alert potential users to the trade-offs (e.g., high capital costs/low aftercare costs vs low capital

cost/high aftercare costs) that will have to made when selecting particular types of remedial

technology for use.

It has been suggested that the provision of cost data is of relatively limited value because actual remedial

costs are highly site-specific and some cost items (e.g., energy, labour, waste disposal) can vary

significantly from country to country. However, potential technology users can be made aware of the

limitations associated with the cost data and the need to make appropriate adjustments when attempting

to apply them in individual cases.

It is important therefore to document any important limitations applying to the cost data provided. All

assumptions used to derive cost estimates and any other information essential to the correct interpretation

of the data should be reported.

To facilitate the presentation and analysis of the data, costs should be in national currency and dated.

SI units (e.g., quantities of material treated) should be used throughout.

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A.3 COST BREAKDOWN

Where possible, data should be provided according to the generic cost breakdown provided in Table A.1.

This shows the different activities that might be carried out during the course of remedial action (left

hand column) against various cost elements (top row). It may be necessary to add activities/cost elements

when submitting data for individual technologies.

Sections A.4 and A.5 give a brief description of the intended scope of the activities/cost elements to be

covered in project submissions. A brief explanation of the items covered by the cost data actually

submitted should be provided.

Table A.1. Actual/Estimated Full-Scale Remediation Costs

Stage Activity Plant & Materials Laboratory Other

Pre-operational Legal approvals

Site Preparation

Mobilisation

Sub-total

Operational Excavation/extraction

Pre-treatment

Processing

Waste treatment/disposal

Monitoring

I. process control

I. legal compliance

Modification and repair

Public relations

Sub-total

Post-operational

Sub-total

TOTAL

A.4 ACTIVITIES

A.4.1 Pre-Operational Stage

Legal approvals: Costs involved in obtaining regulatory approval for the installation/operation of the

remedial technology. Requirements are likely to vary widely depending on the (national) regulatory

framework, the technology involved and site-specific factors but they will typically include: approval

for installing/constructing items of plant & equipment; consents to make permitted discharges (e.g., to

air, water, sewer); permission to abstract water (e.g., for groundwater remediation work); provision of

environmental impact statements, etc.

Site preparation: Costs involved in preparing the site to receive all necessary plant & equipment. Typical

items to be included are: provision of site security/access; site leveling; provision of hardstanding/storage

areas; ground and surface water protection measures; provision of site services, etc.

Mobilisation: Costs involved in transferring, setting up and commissioning all necessary plant and

equipment.

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A.4.2 Operational Stage

Excavation/extraction: Cost of removing contaminated solids/liquids from the ground prior to treatment

in on or off-site facilities.

Pre-treatment: Costs associated with storing/preparing material for treatment where this can be identified

as a separate part of the process. Typical pre-treatment activities include storing/conditioning, size

classification, grinding, dewatering, drying, etc., of feedstocks.

Processing: The cost of processing/treating contaminated material using physical, chemical, biological

techniques.

Waste treatment/disposal: Cost of transporting/treating/disposing of solid, liquid or gaseous wastes from

the process, including pollution control residues (e.g., spent activated carbon, scrubbing liquors, etc.).

Monitoring: All operational monitoring costs including that required to optimise/control the process (e.g.,

to maintain temperatures, mixing conditions, pH conditions) and ensure legal compliance (e.g., with

respect to atmospheric discharge limits, to protect the health and safety of the workforce).

Modifications/repair: Cost of modifying/repairing plant and equipment.

Public relations: The costs of informing/liaising with third parties, such as the local community.

A.4.3 Post-Operational Stage

Demobilisation/reinstatement: Cost of dismantling, decontaminating and removing items of plant and

equipment, and reinstating the site (where appropriate).

Monitoring: The cost of demonstrating that remedial objectives have been met including one-off

validation (e.g., demonstrating the quality of a product from a soil washing plant) and long-term

monitoring (e.g., demonstrating that an in situ treatment process has reached completion).

A.5 COST ELEMENTS

Plant and equipment: Plant and equipment costs may be reported as capital items (amortisation period

to be specified) or as plant hire costs.

Materials costs: These include all materials consumed during the course of remedial action. Typical

items include treatment chemicals, energy (electricity, diesel), water, health protection equipment,

monitoring equipment not otherwise specified.

Labour costs: These should be reported for all personnel involved in setting-up, operating and

completing the remedial operation. Consultancy and contracting labour costs should be reported

separately where possible. Travel and subsistence costs should be reported under the “other costs”

activity heading.

Analysis: All laboratory analytical support used before, during and after remedial action.

Other costs: All costs not otherwise specified. The items covered under this heading should be specified

and may include permitting/legal fees, travel and subsistence costs, loan charges, insurance, etc.

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Changing Approaches to Remediation1

Merten Hinsenveld, TSM Business School, University of Twente, Enschede, The

Netherlands

In the 1980s, large differences existed amongst the various countries in their approach towards

contaminated sites. By looking at the concentrations in their supposedly clean soils, the Dutch took a

straight forward approach and derived a single concentration per contaminant for a clean soil (so-called

A-value) and a concentration of a polluted soil for which prolonged exposure might lead to health effects

(so-called C-value). The Americans on the other hand choose a more site specific, but cumbersome and

disputable, risk approach. Both approaches were developed on the assumption that the problem of

contaminated sites was limited.

Initially, various countries adopted—with or without modifications—one of these extreme examples.

Experience made two points clear:

(1) the problem was not limited, and

(2) concentration based approaches as well as risk based approaches each have their specific advantages

and disadvantages.

Mixed approaches in various forms and the study of exceptions to the rule is now more common

practice.

Improved understanding of the mechanisms with which the subsoil and the groundwater can and does

cope with a contamination, is changing the approach towards remediation rapidly. With particular

reference to intrinsic bioremediation, the scientific and the regulatory world are both changing from a

problem-solution approach towards a process-oriented approach. Contamination in this approach is more

a process that might be altered, stopped or monitored, than it is a problem.

Finally, the realisation that the tremendous cost of remediation may not be in balance with its benefit,

has provided a growing incentive to the development and use of methods that can weigh the various

cost/benefit elements (economy, environment, health, spacial use) of contaminated sites to provide a tool

for integrated decision making.

1 This fellowship is still in progress and will be extended into the new Pilot Study on remediation starting in 1998.

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Use of Remedial Clean-Up Technology in Portugal

Maria José Macedo, Hovione - Sociedade Quimica SA, Loures, Portugal

1. INTRODUCTION

Until recently there was no experience of remedial clean-up of industrial sites in Portugal. Lisbon is

organizing the 1998 World Exposition (EXPO'98) and a site located East of the city was chosen to host

the exposition. This site was formerly occupied by the Petrogal, BP, Mobil and Shell petroleum

companies. Principal activities at the site included petroleum refining and storage, causing soil and

groundwater contamination in several distinct areas. Prior to the existence of the petroleum companies

at the site, there was a sulphuric acid producing plant that caused, in a determined area, contamination

of the soil by arsenic.

ISQ made an audit to the decontamination of this site. A brief description of the decontamination work

is presented.

2. SOIL REMEDIATION AT THE EXPO'98 SITE

The soil was contaminated by several petroleum originated pollutants (benzene, toluene, ethylbenzene,

and xylenes and total petroleum hydrocarbons [TPH]) and arsenic from a previously existent sulphuric

acid plant.

For the site clean-up, several techniques were considered, namely:

• thermal treatment;

• stabilisation;

• soil-vapour extraction;

• biological treatment; and

• excavation and landfilling.

Excavation and deposition in a controlled landfill was finally chosen since it was the technique that

presented a better cost/benefit ratio. Prior to the start of the excavations an excavation plan was prepared.

In this excavation plan, excavation activities to be carried out were described area by area, completed

with drawings and cross-sections. Each excavation area was staked out first, based on the results of the

delineation investigation and the modifications that were included in the excavation plan.

Excavation was done in two phases. After completing a first topographical survey of the area, the noncontaminated soil was excavated. The limits of the non-contaminated soil were determined during

excavation by means of an oil detection pan. The excavated non-contaminated soil was placed in

stockpiles in the vicinity of the excavated area.

The quantity of excavated non-contaminated soil was determined after doing a second topographical

survey. Excavation of contaminated soil proceeded according to the remediation goals.

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In general, the extent of contamination was quite similar to the expected extent. A total of approximately

300,000 m3 of soil was excavated and landfilled.

The contaminated soil was transported to a landfill. The new designed landfill was situated at the eastern

part of the existing Beirolas landfill in Moscavide, Lisbon. The landfill was constructed with

recompacted clay layers, geotextiles, geonets and liners, to provide a secure storage facility for

contaminated soil. The contaminated soil was transported to the landfill by truck.

There were also large amounts of free product and a large quantity was removed. In total approximately

400 m3 of free product was recovered and removed by tanker truck.

In order to properly excavate to the required depth dewatering of certain excavated areas was necessary.

The water was pumped into a temporary water treatment plant.

The water treatment plant consisted of the following components:

• collection sump with pumps;

• oil/water separator;

• aeration container;

• compost container for treatment aeration air;

• buffer basin for temporary storage;

• sandfilters;

• active-carbon filters;

• end buffer container;

• watermeter; and

• discharge hose to existing sewer.

The contaminated groundwater entered into the oil/water separator, where free product and groundwater

were separated. The free product accumulated in the separator was removed regularly by tankertruck.

The groundwater then entered the aeration container, in which the volatile compounds were dispersed

into the air. The contaminated air was led into the compost container for bio-cleaning. The treated

groundwater was discharged into the buffer basin.

From the buffer basin the water was pumped through the sand filters and the active carbon filters and

then discharged via the end buffer container into the existing sewer. The discharged water was regularly

sampled and analysed. The concentrations of TPH and volatile organic compounds (VOCs) never

exceeded the allowed concentrations.

In total, approximately 5,200 m3 groundwater was treated in the temporary plant.

3. CONCLUSIONS

This is the only case of soil remediation of a previously industrial site in Portugal.

There are some studies being made for the assessment of soil and groundwater contamination in

industrial sites but no remedial actions have been made. One example of a study area is the chemical

complex of the Estarreja industrial area, in Oporto district.

The processing industry, namely the chemical industry, is, in Portugal, the major source of industrial

contamination. Until recently, the solid wastes originating from there were deposited, without any control

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or protective measures in municipal landfills or in landfills belonging to the companies, as was the case

of the Estarreja chemical complex. Thus, there is a large contaminated area with solid wastes from

several production processes.

In 1991, the Environment Ministry started a project aiming to study an adequate methodology for

remediation of contaminated groundwater and soil. The objectives of this study were:

• selection of a study area with problems of soil contamination by industrial wastes

• assessment of present situation, in terms of soil and water quality: (1) elaboration of hydrogeological

studies; and (2) risk analysis

• elaboration of recommendations for the resolution of the problems of the selected area

This study has been made but no remedial actions have started.

At present, there are two factors that make the adoption of state of the art technologies slower in

Portugal than in more industrialised countries:

• the difficult financial situation of Portugal—made worse by the recession in all Europe—does not

allow large investments in remedial projects; and

• the awareness level of the Portuguese population is still extremely low.

The delay that Portugal suffered in its economic development can, however, in the long term become

an advantage, because, due to the low industrialisation in this century, there are not contaminated sites

in such a large number and proclivity (throughout the country) as for instance in Germany. In addition,

it is still possible to avoid strategic errors (future problems) by applying appropriate legislative,

administrative and technological measures.

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Experiences with the Performance of In Situ Treatment Technologies

Dr. Robert L. Siegrist, Environmental Science & Engineering Division, Colorado School of

Mines

1. INTRODUCTION

The overall goal of this study is to explore international experiences gained with the performance of in

situ treatment technologies for contaminated soil and groundwater and to determine the cleanup achieved

as related to time and cost expended compared to predictions made when the in situ technology was

selected. The types of sites of interest include those commonly encountered and where in situ

technologies have been employed. These sites include those contaminated with petrochemicals such as

benzene and/or chlorocarbons such as trichloroethylene. The types of technologies commonly applied

include soil vapor extraction and air sparging for source treatment and increasingly treatment barriers

for interception and plume migration control. As originally conceived, this work is being accomplished

by literature review and critical analysis complemented by interactions with delegates at NATO Pilot

Study meetings and through personal inquiries and correspondence.

While performance of in situ treatment technologies can be assessed with regard to various measures,

one critical question relates to how well did the technology achieve the cleanup goal initially prescribed

in terms of time and cost predictions that were made initially when the technology was selected. This

question is a critical one. The selection, design, and implementation of in situ technologies requires

knowledge of their ability to achieve various cleanup goals and at what cost over what time. If large

expenditures in terms of cost and time are made but the technology does not achieve the goal, then it

could be speculated that savings could have been realized with no loss in risk reduction actually

achieved, if a more realistic goal had been initially prescribed. In so doing, the savings in cost and time

could have been allocated to other sites and overall the reduction in risk in a jurisdiction might have

been greater.

Work on the project started with attendance at the Adelaide meeting of the Phase II Pilot Study held in

February 1996 and will continued into the Phase III Pilot Study.

2. PROJECT SCOPE AND CONCEPTS

For contaminated sites, a conceptual model for risk is generally considered to include several key

elements:

(1) a source of contamination,

(2) transport/fate in the soil and ground water environment, and

(3) the receptors and their exposure pathways and dose-response properties (Figure 1).

If the risk is deemed unacceptably high, risk management is often implemented to reduce or eliminate

the source, beneficially modify the transport/fate properties, or cut-off the exposure of receptors. For

these purposes, in situ remediation technologies are often preferred because they can be implemented

over larger areas with lower site disruption, with lower worker exposure, and generally at lower cost.

Achieving risk reduction via in situ technologies often requires a reduction in concentration and/or mass

of contaminants somewhere prior to exposure occurring.Figure 2 presents a graphical illustration of

contaminant concentration as related to time and cost.

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In most remediation cases, extensive time and expense are devoted to characterizing a site, assessing the

Figure 1: Conceptual Model Components for an Organically Contaminated Site and In Situ Remediation to

Achieve a Reduction in Risk

risk associated with the nature and extent of contamination present, and selecting and implementing a

remedial action to achieve a prescribed cleanup goal. However, less effort is often expended to evaluate

technology performance over time and to document cleanup goal achievement versus the time and cost

incurred. Such a critical review of technology performance is needed however, to ascertain whether

investments made in characterization, assessment, and remedial action implementation are justified by

the benefits achieved.

Information is being gathered on in situ technologies to enable a critical evaluation of the treatment

efficiency and the risk reductions that have been claimed to be achieved and whether there is adequate

information to support these claims. Moreover, the study will attempt to determine whether the initially

established cleanup goals were in fact achieved at the cost and time predicted. The study will also

explore whether resources could have been more effectively expended by treating more sites to less

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stringent goals that were in fact all that was achieved even when more stringent goals were initially

established.

Figure 2: Illustration of the Relationship Between In Situ Remediation Performance Predictions versus Actual

Achievement as Related to Time and Cost of Remediation

The project will contribute to the objectives of the Pilot Study by providing an independent and critical

understanding of the use of in situ treatment technologies, methods used for their process control, and

their true performance in achieving cleanup goals and associated risk reductions.

Editorial Note:

In addition to the CCMS Fellowship study described here, Dr. Siegrist hosted the meeting of the Phase

II Pilot Study held in Golden, Colorado in March 1997. In addition, during the meeting he made a guest

speaker presentation on In situ remediation of DNAPLs in low permeability media.

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