May 2004 

Technologies for Treating MtBE and Other Fuel Oxygenates 

U.S. Environmental Protection Agency 

Office of Solid Waste and Emergency Response 

Office of Superfund Remediation and Technology Innovation 

Washington, DC 20460 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

TABLE OF CONTENTS

LIST OF ACRONYMS AND ABBREVIATIONS .................................................................................vi

FOREWORD.............................................................................................................................................vii

NOTICE AND DISCLAIMER ...............................................................................................................viii

ACKNOWLEDGMENT .........................................................................................................................viii

1.0 INTRODUCTION.......................................................................................................................1-1

1.1 What is the Purpose of This Report? ...............................................................................1-1

1.2 Who is the Intended Audience of This Report? ...............................................................1-1

1.3 What Information Sources Were Used to Prepare This Report? .....................................1-1

1.4 Considerations About the Performance and Cost Data Included in This Report.............1-2

1.5 Report Organization.........................................................................................................1-4

2.0 BACKGROUND .........................................................................................................................2-1

2.1 What are Fuel Oxygenates? .............................................................................................2-1

2.2 What Are the Sources of Oxygenates in the Environment?.............................................2-2

2.3 What is the Prevalence of Contamination by Oxygenates in the Environment? .............2-3

2.4 What are the Concerns About Contamination with Oxygenates?....................................2-4

2.5 How Are Oxygenates Assessed in the Environment?......................................................2-5

2.6 How Do Oxygenates Migrate in the Environment?.........................................................2-6

2.7 How Do the Properties of Oxygenates Affect Treatment? ..............................................2-7

2.8 What Types of Technologies are Used in the Treatment of Soil, Groundwater, and 

Drinking Water Contaminated with Oxygenates? .........................................................2-10

2.9 How Are Technologies Used to Treat Soil and Water Contaminated 

with Oxygenates?...........................................................................................................2-10

2.10 What Additional Technical Considerations are Associated with Remediating Sites 

Contaminated with Oxygenates? ...................................................................................2-11

3.0 COMPARISON OF TREATMENT TECHNOLOGIES ........................................................3-1

3.1 What Types of Remediation Technology Projects were Considered 

in this Comparison? .........................................................................................................3-1

3.2 How Did These Remediation Technologies Perform?.....................................................3-2

3.3 What Did These Remediation Technologies Cost? .........................................................3-3

3.4 What Factors Should Be Considered When Identifying Technologies to Treat Fuel 

Oxygenates?.....................................................................................................................3-5

4.0 TREATMENT TECHNOLOGIES ...........................................................................................4-1

4.1 Air Sparging.....................................................................................................................4-2

4.1.1 What is Air Sparging?.........................................................................................4-2

4.1.2 How Do the Properties of MtBE and Other Oxygenates Affect Treatment?......4-2

4.1.3 How is Air Sparging Applied to Treat Oxygenates? ..........................................4-3

4.1.4 What Types of Projects Involve Air Sparging for Oxygenates?.........................4-4

4.1.5 How Has Air Sparging Performed in Treating Oxygenates?..............................4-5

4.1.6 What Costs Have Been Associated with Using Air Sparging

in Treating MtBE? ..............................................................................................4-6

i 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

4.1.7 What Factors May Affect the Performance and Cost of Oxygenate Treatment 

Using Air Sparging? ...........................................................................................4-7

4.1.8 Conclusions.........................................................................................................4-8

4.1.9 Example Projects ................................................................................................4-9

4.2 Soil Vapor Extraction ......................................................................................................4-9

4.2.1 What is Soil Vapor Extraction? ..........................................................................4-9

4.2.2 How Do the Properties of MtBE and Other Oxygenates Affect Treatment?....4-10

4.2.3 How is Soil Vapor Extraction Applied to Treat Oxygenates? ..........................4-10

4.2.4 What Types of Projects Involved Soil Vapor Extraction

to Treat Oxygenates? ........................................................................................4-13

4.2.5 How Has SVE Performed in Treating Oxygenates? .........................................4-14

4.2.6 What Costs Have Been Associated with Using SVE in Treating MtBE?.........4-15

4.2.7 What Factors May Affect the Performance and Cost of Oxygenate Treatment 

using SVE? .......................................................................................................4-15

4.2.8 Conclusions.......................................................................................................4-16

4.2.9 Example Projects ..............................................................................................4-17

4.3 Multi-Phase Extraction ..................................................................................................4-17

4.3.1 What is Multi-Phase Extraction? ......................................................................4-17

4.3.2 How Do the Properties of MtBE and Other Oxygenates Affect Treatment?....4-17

4.3.3 How is MPE Applied to Treat Oxygenates?.....................................................4-18

4.3.4 What Types of Projects Involve MPE for Treating Oxygenates?.....................4-19

4.3.5 How Has MPE Performed in Treating Oxygenates? ........................................4-20

4.3.6 What Costs Have Been Associated with Using MPE in Treating MtBE? ........4-21

4.3.7 What Factors May Affect the Performance and Cost of Oxygenate Treatment 

using MPE?.......................................................................................................4-21

4.3.8 Conclusions.......................................................................................................4-22

4.3.9 Example Projects ..............................................................................................4-22

4.4 In Situ Bioremediation ...................................................................................................4-23

4.4.1 What is Bioremediation?...................................................................................4-23

4.4.2 How Do the Properties of MtBE and Other Oxygenates Affect Treatment?....4-24

4.4.3 How is Bioremediation Applied to Treat Oxygenates? ....................................4-26

4.4.4 What Types of Projects Involved Bioremediation to Treat Oxygenates?.........4-28

4.4.5 How Has In Situ Bioremediation Performed in Treating Oxygenates? ............4-29

4.4.6 What are the Costs of Using In Situ Bioremediation to Treat Oxygenates? .....4-30

4.4.7 What Factors May Affect the Performance and Cost of Oxygenate Treatment 

using In Situ Bioremediation?...........................................................................4-31

4.4.8 Conclusions.......................................................................................................4-31

4.4.9 Example Projects ..............................................................................................4-32

4.5 In Situ Chemical Oxidation............................................................................................4-34

4.5.1 What is In Situ Chemical Oxidation?................................................................4-34

4.5.2 How Do the Properties of MtBE and Other Oxygenates Affect Treatment?....4-34

4.5.3 How is In Situ Chemical Oxidation Applied to Treat Oxygenates? .................4-35

4.5.4 What Types of Projects Involve In Situ Chemical Oxidation 

for Oxygenates? ................................................................................................4-37

4.5.5 How Has In Situ Chemical Oxidation Performed in Treating Oxygenates?.....4-38

4.5.6 What Are the Costs of Using In Situ Chemical Oxidation to Treat MtBE? .....4-39

4.5.7 What Factors May Affect the Performance and Cost of Oxygenate Treatment 

using In Situ Chemical Oxidation? ...................................................................4-39

4.5.8 Conclusions.......................................................................................................4-40

4.5.9 Example Projects ..............................................................................................4-41

4.6 Groundwater Pump-and-Treat and Drinking Water Treatment .....................................4-41

ii 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

4.6.1 What is Groundwater Extraction for Pump-and-Treat and Drinking Water 

Treatment? ........................................................................................................4-41

4.6.2 How Do the Properties of MtBE and Other Oxygenates Affect Groundwater 

Extraction? ........................................................................................................4-42

4.6.3 How is Pump-and-Treat Applied to Treat Oxygenates? ...................................4-42

4.6.4 What Projects Have Involved Pump-and-Treat for Treating Oxygenates?.......4-43

4.6.5 How Has Pump-and-Treat Performed in Treating Oxygenates? ......................4-43

4.6.6 What Costs Have Been Associated with Using Pump-and-Treat in Treating 

MtBE?...............................................................................................................4-45

4.6.7 What Factors May Affect the Performance and Cost of Oxygenate Treatment 

Using Pump-and-Treat? ....................................................................................4-46

4.6.8 Conclusions.......................................................................................................4-47

4.6.9 Example Projects ..............................................................................................4-48

4.7 Treatment of Extracted Groundwater Used in Pump-and-Treat and Drinking Water

Treatment Systems.........................................................................................................4-48

4.7.1 What is Above-Ground Treatment for Extracted Groundwater?......................4-48

4.7.2 How Do the Properties of MtBE and Other Oxygenates Affect Treatment?....4-49

4.7.3 How are Technologies Used for Above-Ground Treatment of Oxygenates? ...4-51

4.7.4 What Projects Have Been Used for Above-Ground Treatment of Extracted

Groundwater?....................................................................................................4-53

4.7.5 How Has Above-Ground Treatment Performed in Treating Oxygenates? .......4-54

4.7.6 What Costs Have Been Associated with Using Pump-and-Treat in Treating 

MtBE?...............................................................................................................4-54

4.7.7 What Factors May Affect the Performance and Cost of Above-Ground Treatment

for Oxygenates? ................................................................................................4-55

4.7.8 Conclusions.......................................................................................................4-55

4.7.9 Example Projects ..............................................................................................4-56

4.8 Other Treatment Technologies: Phytoremediation, PRBs, and Thermal Treatment ....4-58

4.8.1 What Other Technologies are used to Treat MtBE and Other Oxygenates? ....4-58

4.8.2 How Is Phytoremediation Used in Treatment of Oxygenates?.........................4-58

4.8.3 How Are PRBs Used in Treatment of Oxygenates? .........................................4-59

4.8.4 How Is In Situ Thermal Treatment Used for Remediation of Oxygenates? .....4-60

4.8.5 What Factors may Affect the Performance and Cost of Phytoremediation, PRBs, 

or Thermal Treatment? .....................................................................................4-61

4.8.6 Conclusions.......................................................................................................4-61

5.0 NON-TREATMENT REMEDIES ............................................................................................5-1

5.1 Excavation........................................................................................................................5-1

5.2 Free Product Recovery.....................................................................................................5-2

5.3 Monitored Natural Attenuation........................................................................................5-2

5.4 Institutional Controls .......................................................................................................5-3

6.0 REFERENCES............................................................................................................................6-1

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 Technologies for Treating MtBE and Other Fuel Oxygenates 

LIST OF TABLES 

2-1 State Cleanup Levels for Fuel Oxygenates in Groundwater .........................................................2-5

2-2 Properties of Fuel Oxygenates and Other Fuel Constituents ........................................................2-8

3-1 Description of MtBE Remediation Technology Projects (323 Projects) ......................................3-2

3-2 Performance Data for Completed MtBE Remediation Technology Applications (105 

Applications1

 Providing Data) ......................................................................................................3-2

3-3 Duration of Completed MtBE Remediation Technology Applications (89 Applications 

Providing Data) .............................................................................................................................3-3

3-4 Total Project Cost1 Data for MtBE Remediation Technology Applications (127 

Applications Providing Data)........................................................................................................3-4

3-5 General Factors to Consider When Identifying a Remediation Technology for Sites 

Contaminated with Fuel Oxygenates ............................................................................................3-5

3-6 General Factors to Consider When Selecting a Remediation Technology for Sites 

Contaminated with Fuel Oxygenates ............................................................................................3-6

4-1 Types of Technologies Used to Treat MtBE and Other Fuel Oxygenates....................................4-1

4.1-1 General Information on 123 Air Sparging Projects ......................................................................4-5

4.1-2 Completed Air Sparging Projects - Performance Summary for 19 Projects.................................4-6

4.1-3 Ongoing Air Sparging Projects % Performance Summary for 104 Sites.......................................4-6

4.2-1 General Information on 138 SVE Projects*................................................................................4-13

4.2-2 Performance Summary for 19 Completed SVE Projects ............................................................4-14

4.2-3 Performance Summary for 119 Ongoing SVE Projects..............................................................4-15

4.3-1 Contaminant Properties Relevant to MPE ..................................................................................4-18

4.3-2 General Information on 13 MPE Projects...................................................................................4-19

4.3-3 Completed MPE Projects - Performance Summary for 3 Projects .............................................4-20

4.3-4 Ongoing MPE Projects - Performance Summary for 7 Sites ......................................................4-20

4.4-1 MtBE Biodegradation Mechanisms and Products ......................................................................4-26

4.4-2 General Information from 73 Engineered Bioremediation Projects ...........................................4-28

4.4-3 Completed In Situ Bioremediation Projects Performance Summary for 31 Projects..................4-29

4.4-4 Ongoing In Situ Bioremediation Projects Performance Summary for MtBE at 38 Sites............4-29

4.5-1 General Information on 21 In Situ Chemical Oxidation Projects ...............................................4-37

4.5-2 Completed In Situ Chemical Oxidation Projects - Performance Summary for 8 Projects..........4-38

4.5-3 Ongoing In Situ Chemical Oxidation Projects - Performance Summary for 13 Sites ................4-39

4.6-1 General Information about 100 Pump-and-Treat Projects ..........................................................4-43

4.6-2 MtBE Performance Summary for 21 Completed Pump-and-Treat Projects...............................4-44

4.6-3 MtBE Performance Summary for 62 Ongoing Pump-and-Treat Projects ..................................4-44

4.6-4 MtBE Performance Summary for 12 Ongoing Drinking Water Treatment Systems..................4-45

4.6-5 TBA Performance Data for 9 Pump-and-Treat Projects .............................................................4-45

4.6-6 Cost Summary for 43 Pump-and-Treat and Drinking Water Treatment Projects.......................4-46

4.7-1 Above-Ground Treatment Technologies Used at 70 Groundwater Pump-and-Treat 

Remediation and Drinking Water Treatment Projects ................................................................4-53

4.7-2 Cost Summary for Pump-and-Treat – By Aboveground Treatment Type..................................4-54

4.7-3 Estimated Range of Unit Costs for Above ground Treatment Technologies..............................4-55

4.8-1 General Information on 8 Projects Using Phytoremediation ......................................................4-59

iv 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

LIST OF FIGURES 

2-1 Molecular Structures of Common Fuel Oxygenates.....................................................................2-2

2-2 Physical Properties of Fuel Oxygenates Relative to Benzene.......................................................2-9

2-3 Relative Solubility and Henry’s Law Constants for Selected Fuel Oxygenates 

(Henry’s Law data for MtBE, TBA, and Benzene based on Zogorski et. al., 1997) ....................2-9

4.1-1 Ranges of Henry s Law Constants (Dimensionless) for Common Fuel Oxygenates....................4-3

4.2-1 Ranges of Vapor Pressures for Common Fuel Oxygenates ........................................................4-10 

4.4-1 Proposed Degradation Pathway of MtBE and Other Oxygenates 

(Church and Tratnyek, 2000) ......................................................................................................4-25 

4.4-2 Typical Zones Downgradient of Petroleum Contaminant Source ..............................................4-27

4.5-1 Stoichiometric Mineralization of Oxygenates Using Hydrogen Peroxide..................................4-34

4.7-1 Relative Ranges of Partition Coefficients for Fuels Oxygenates and BTEX..............................4-50

APPENDIX 

A MtBE Treatment Profile Data (see www.cluin.org/mtbe) 

v 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

LIST OF ACRONYMS AND ABBREVIATIONS

AST Aboveground storage tank NOM 

bgs Below ground surface NSCEP 

BTEX Benzene, toluene, ethylbenzene, and 

ClO

xylenes O3 

cfm Cubic feet per minute OCl2

- Chlorine dioxide O&M 

CLU-IN EPA’s Hazardous Waste CLeanUp Oxyfuel

INformation System ppmv 

PRB CO2 Carbon dioxide 

COD Chemical oxygen demand psi 

PVC cy Cubic yard RCRA DIPE Diisopropyl ether 

DL Detection limit 

RFG DPE Dual-phase extraction RO EPA United States Environmental 

ROI Protection Agency 

EtBE Ethyl tert-butyl ether S2O8

SC FRTR Federal Remediation Technologies scfm Roundtable 

SERDP Ft Feet/foot 

GAC Granular activated carbon 

SO4

-2 

gals Gallons SSTL gpm Gallons per minute SVE H2O2 Hydrogen peroxide TAA HP Horse power TAEE IC Institutional controls 

TAME K Hydraulic conductivity TBA LNAPL Light non-aqueous phase liquid TBF lbs Pounds 

TPE MC Mixed culture 

TSP MCL Maximum Contaminant Level 

USACE mg/L Milligrams per liter 

MNA Monitored natural attenuation 

UST MnO4 Permanganate UV mm Hg Millimeters of mercury 

MPE Multi-phase extraction VE/GE

MtBE Methyl tert-butyl ether VOC NAPL Non-aqueous phase liquid 

ND Non detect μg/kg 

NEIWPCC New England Interstate Water μg/L 

NO

Pollution Control Commission μm

3

-

 Nitrate ZOI 

Natural organic matter 

National Service Center for 

Environmental Publications 

Ozone 

Hypochlorite 

Operation and maintenance 

 Oxygenated fuel 

Parts per million by volume 

 Permeable reactive barrier 

Pounds per square inch 

 Polyvinyl chloride 

 Resource Conservation and 

Recovery Act 

 Reformulated gasoline 

Reverse osmosis 

Radius of influence 

 Persulfate 

 Single culture 

Standard cubic feet per minute 

Strategic Environmental Research 

and Development Program 

Sulfate 

Site specific target level 

Soil vapor extraction 

 Tert-amyl alcohol 

Tert-amyl ethyl ether 

 Tert-amyl methyl ether 

 Tert-butyl alcohol 

 Tert-butyl formate 

 Two-phase extraction 

 Trisodium phosphate dodecahydrate 

United States Army Corps of 

Engineers 

Underground storage tank 

 Ultraviolet 

 Vapor extraction/groundwater 

extraction 

Volatile organic compound 

Microgram per kilogram 

Microgram per liter 

 Micrometer 

Zone of influence 

vi 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

FOREWORD 

Fuel oxygenates, including methyl tert-butyl ether (MtBE), have been widely used in the United States for 

the past several decades as an additive to gasoline intended to either boost octane ratings or to reduce air 

pollution. The gasoline containing these oxygenates has been stored in aboveground and underground 

storage tanks at a wide range of facilities, including refineries, terminals, service stations, and by end 

users; and gasoline has been transported throughout the U.S. via pipeline, barge, rail, and truck. As a 

result of leaks and spills, MtBE, other fuel oxygenates, and other gasoline components have been found in 

soil and groundwater at these sites. Federal and state studies have found that these components, including 

MtBE, have reached drinking water sources in many locations, including areas where the use of 

oxygenated fuel has not been mandated. 

The U.S. Environmental Protection Agency (EPA) has identified several hundred MtBE-contaminated 

sites that have performed treatment of soil and groundwater to remove or destroy MtBE. Many of these 

sites have also treated other fuel components, primarily benzene, toluene, ethylbenzene, and xylene 

(BTEX), and some have treated fuel oxygenates other than MtBE. Although others have reported about 

treatment technologies for MtBE cleanup, only limited information has been published about cleanup of 

other oxygenates. These oxygenates include ether compounds, such as ethyl tert-butyl ether (ETBE), tertamyl methyl ether (TAME), diisopropyl ether (DIPE), and tert-amyl ethyl ether (TAEE), as well as 

alcohol compounds, such as tert-butyl alcohol (TBA), tert-amyl alcohol (TAA), ethanol, and methanol. 

This report provides an overview of the treatment technologies used to remediate groundwater, soil, and 

drinking water contaminated with MtBE and other fuel oxygenates. The treatment methods discussed 

include air sparging, soil vapor extraction, multi-phase extraction, in situ and ex situ bioremediation, in 

situ chemical oxidation, pump-and-treat, and drinking water treatment. Information in the report can be 

used to help evaluate those technologies based on their effectiveness at specific sites. The report 

summarizes available performance and cost information for these technologies, examples of where each 

has been used, and additional sources of information. 

This report may be useful to cleanup professionals and researchers; federal, state, and local regulators; 

remediation consultants; water treatment plant designers and operators; and other interested parties. The 

report is intended to be a screening tool that can be used to identify treatment technologies for soil, 

groundwater, and drinking water contaminated with MtBE and other fuel oxygenates. However, it should 

be considered only as a starting point for such an analysis. The applicability of a particular treatment 

technology is site specific, and depends heavily on factors such as site conditions and treatment goals. 

Decisions about the use of a specific treatment approach will require further analysis, possibly including 

treatability or pilot-scale studies. This report is not a guidance document and is not intended to prescribe 

specific treatment technologies for certain types of applications. It was written assuming that readers 

have a basic technical understanding of the treatment technologies and the chemistry discussed. 

 vii 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

NOTICE AND DISCLAIMER

Preparation of this report has been funded wholly or in part by the U.S. Environmental Protection Agency 

(EPA) under Contract Number 68-W-02-034. Mention of trade names or commercial products does not 

constitute endorsement or recommendation for use. A limited number of printed copies of Technologies 

for Treating MtBE and Other Fuel Oxygenates is available free-of-charge by mail or by facsimile from: 

U.S. EPA/National Service Center for Environmental Publications (NSCEP) 

P.O. Box 42419 

Cincinnati, OH 45242-2419 

Telephone: (513) 489-8190 or (800) 490-9198 

Fax: (513) 489-8695 

A PDF version of this report is available for viewing or downloading from the Hazardous Waste Cleanup 

Information (CLU-IN) system web site at http://www.cluin.org/mtbe. Printed copies of the report can 

also be ordered through that web address, subject to availability. For more information regarding this 

report, contact Linda Fiedler, EPA Office of Superfund Remediation and Technology Innovation, at 

(703) 603-7194 or fiedler.linda@epa.gov. 

ACKNOWLEDGMENT 

Special acknowledgment is given to the federal and state staff and other remediation professionals for 

providing information for this document. Their cooperation and willingness to share their expertise about 

treatment technologies used to address MtBE and other oxygenates encourages their application at other 

sites. 

 viii 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

1.0 INTRODUCTION 

1.1 What is the Purpose of This Report? 

This report provides an overview of treatment technologies used to remediate groundwater, soil, and 

drinking water contaminated with methyl tert-butyl ether (MtBE) and other fuel oxygenates. The purpose 

of this report is to: 

• Identify technologies used to treat MtBE and other fuel oxygenates 

• Help screen those technologies based on their effectiveness in treating particular media and 

contaminants under specific site conditions and application requirements 

• Provide available performance and cost information about the use of those technologies 

• Provide additional information relevant to the treatment of MtBE and other fuel oxygenates 

• Identify additional sources of information 

This report is intended to be a screening tool that can be used to identify treatment technologies for 

groundwater, soil, and drinking water contaminated with MtBE and other fuel oxygenates. However, it 

should be considered only as a starting point for such an analysis. The applicability of a particular 

treatment technology is site specific and depends heavily on factors such as site conditions and treatment 

goals. Decisions about the use of a specific treatment technology will require further analysis, possibly 

including treatability studies. 

The performance and cost data in the report can help cleanup professionals, site managers, remediation 

consultants, and others gain a broader understanding of the types of technologies that have been used to 

treat MtBE and other fuel oxygenates, as well as the types of information available from sites that have 

used those technologies. This report also provides information about the factors that potentially affect the 

performance and cost of those technologies. 

This report is not a guidance document and is not intended to prescribe specific treatment technologies for 

certain types of applications. It was written assuming that readers have a basic technical understanding of 

the treatment technologies and chemistry discussed. Readers requiring additional background 

information on the treatment of MtBE and other oxygenates are referred to the information sources listed 

in Section 6.0. 

1.2 Who is the Intended Audience of This Report? 

The information presented in this report may be useful to cleanup professionals and researchers; federal 

(Superfund and Resource Conservation and Recovery Act (RCRA) remediation site managers), state, and 

local regulators; remediation consultants; water treatment plant designers and operators; and other 

interested parties. 

1.3 What Information Sources Were Used to Prepare This Report? 

The sources of information used to prepare this report include EPA’s MtBE Treatment Profiles Website, 

located at http://www.cluin.org/products/mtbe, technical publications, and other industry sources. As 

discussed below and summarized in the text box on the following page, EPA’s treatment profiles website 

presents information about drinking water and remediation sites that treat soil and groundwater for MtBE. 

Additional information sources used to prepare this report included EPA reports, other technical 

publications, recent conference proceedings (such as from the National Ground Water Association and 

 1-1 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Battelle conferences), and contacts knowledgeable about projects involving remediation of MtBE, 

including project managers and vendors. A list of these sources is included at the end of this report, with 

specific sources cited throughout the body of the report. A complete summary of the project data 

included in this report is contained in Appendix A. EPA has provided a contaminant focus area for MtBE 

at www.cluin.org/mtbe. 

EPA’s MtBE Treatment Profiles Website 

EPA’s MtBE Treatment Profiles Website, available at www.cluin.org/products/mtbe, provides site-specific data 

about the use of in situ and ex situ technologies that have been used to treat MtBE in groundwater, soil, and drinking 

water. Profiles contain the following types of information, as available: project information, such as site 

background and setting, contaminants and media treated, and area of contamination and quantity treated; technology 

design and operation; cost and performance information, including cleanup goals; points of contacts; and references. 

Profiles are available for nearly one dozen types of technologies, and are updated/expanded several times a year. 

The profiles are based on information provided by site managers, regulatory officials, and technology providers, as 

well as from published reports and conference proceedings. The website can be searched using pick lists for 

selected parameters or by using a list of all available profiles. Each profile has a varying level of detail, depending 

on the data and information that was available. 

As of January 2003, the website contained information about 323 projects, including information about the 

technology used, project scale, performance, and cost. Twenty-nine of these projects reported data on other fuel 

oxygenates, including tert-butyl alcohol (TBA) for all 29 projects, tert-amyl methyl ether (TAME) for 3 projects, 

ethanol for 3 projects, and diisopropyl ether (DIPE) for 1 project. This report discusses information available as of 

January 2003; however, it should be noted that the web site since has been expanded to include information about 

additional projects; as of April 2004, the web site included a total of 390 projects. A summary of information about 

the 390 projects was presented at the National Ground Water Association conference on MtBE and Perchlorate, June 

4, 2004, in a paper titled “Application and Performance of Technologies for Treatment of MtBE and Other 

Oxygenates”, available at www.cluin.org/mtbe. 

The performance and cost data included in this report are primarily based on the database of information 

from 323 site cleanups (projects) that involved treatment of MtBE and other fuel oxygenates. No 

additional testing of technologies was performed during the preparation of this report, and no independent 

review was performed for the data in the database. Generally, the available information included 

information about technology design and operation, such as number and types of wells, additives, and 

flow rates, as well as use of multiple technologies for a given project. In addition, project scale (full, 

pilot, bench) and status (completed or ongoing) were typically identified. In some cases, only interim 

data for ongoing projects are available. 

1.4 Considerations About the Performance and Cost Data Included in This Report 

The treatment performance and cost data presented in this report provide users with: 

• Data from actual field applications, focusing on full-scale and relatively large field 

demonstrations, including design and operation information about use of treatment technologies 

at more than 300 projects 

• Information about both conventional and innovative technologies that have been used to

successfully treat MtBE

• Preliminary information about treatment of fuel oxygenates other than MtBE 

 1-2 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

• Lessons learned about the application of these technologies to cleanup media contaminated with 

MtBE and other fuel oxygenates 

The performance and cost data presented in this report are based on the data provided by project 

managers and others in the source materials used to prepare the treatment profiles website. There was 

variation among the profiles in the level of detail for performance and cost data by project. Many of the 

treatment profiles contained only limited information about treatment performance and cost, generally 

including a maximum concentration of MtBE for before-treatment and a maximum concentration aftertreatment. These concentrations often were limited to discussing how the treatment technology 

performed relative to the cleanup goals for the site. Most treatment profiles did not provide detailed 

performance data, such as MtBE concentration versus time over the duration of the project, or statistical 

evaluations of performance data with confidence limits. 

Treatment performance and cost are site specific and depend on many factors. These factors include site 

conditions (such as soil types, permeability, conductivity, redox conditions, and degree of heterogeneity), 

technology design and operation, and regulatory considerations such as cleanup levels. Additional factors 

include duration of the release (such as a gasoline leak), presence of down-gradient water supply wells, 

and distribution of contaminants in soil and groundwater. 

While EPA has not promulgated a federal cleanup level for MtBE, some states have established cleanup 

levels. However, as shown in Table 2-1, these vary by state, ranging from 5 to 202,000 μg/L, a difference 

of more than three orders of magnitude. Because of the variation in MtBE cleanup levels, after-treatment 

MtBE concentrations are reported based on information provided in the source documents, and are not 

compared against a common cleanup level for all projects. 

Projects generally reported concentrations of MtBE in groundwater or drinking water, with only limited 

projects reporting MtBE concentrations in soil. As such, the technology performance information in this 

report is presented primarily in terms of changes in concentration of MtBE in water. Performance data 

are shown as the highest concentration reported prior to beginning treatment and the highest concentration 

after treatment was completed (shown as “final concentration”). For projects that are ongoing, the final 

concentration shown is the most current concentration reported in the source document. Final 

concentrations identified in source documents as below a reported detection limit (DL), but which do not 

provide a DL, are shown in this report as non-detect (ND). 

For projects where more than one technology was used, such as a site that used air sparging, in situ 

chemical oxidation, and SVE, performance information is presented under each of the technologies used 

for that project. 

With regard to treatment cost data, this report provides a summary of available data based on information 

in the source materials. These cost data are intended to give a broad indication of the types of costs 

associated with cleanup projects, and users should be cautious about drawing conclusions about the cost 

of cleanup projects at specific sites based on these data. As discussed in more detail later in the report, 

very few projects provided sufficient information to calculate a unit cost for treatment. 

In addition, cost data are presented in terms of the total cost for cleaning up contaminated sites. In some 

cases, the specific components that make up the total cost were not provided in the source materials, such 

as for capital or operation and maintenance (O&M) activities. In other cases, the types of contaminants 

present at the sites, other than MtBE, were not identified in the source materials. Sites may have been 

contaminated with gasoline components such as petroleum hydrocarbons, as well as oxygenates, and the 

treatment costs reported could be for cleanup of gasoline components as well as the oxygenates. For 

 1-3 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

example, for a specific project, most of the cost for cleanup may be due to gasoline components other 

than oxygenates. 

EPA recently prepared a more detailed analysis of treatment cost for in situ treatment of fuel oxygenates. 

The paper, “Cost of In Situ Treatment of Fuel Oxygenates”, was presented at the National Ground Water 

Association conference on Remediation: Site Closure and the Total Cost of Cleanup, New Orleans, held 

November 13-14, 2003, and is available at www.cluin.org/mtbe. 

1.5 Report Organization 

The remainder of this report provides a summary of the information available about the treatment of 

MtBE and other fuel oxygenates at the 323 projects reviewed and from other industry sources. Chapter 2 

provides background information about fuel oxygenates, including information about their properties. 

Chapter 3 provides a comparison of the treatment technologies used to treat oxygenates, while Chapter 4 

includes technology-specific discussions for technologies used to treat soil, groundwater, and drinking 

water. Chapter 5 provides information about non-treatment remedies. Chapter 6 contains a list of the 

references used to prepare this report. A complete summary of the project data included in this report is 

contained in Appendix A, available through www.cluin.org/mtbe. This appendix is organized by 

treatment technology and contains a summary of key information for each project. 

 1-4 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

2.0 BACKGROUND 

2.1 What are Fuel Oxygenates? 

Fuel oxygenates are oxygen-containing compounds used as gasoline additives to increase octane ratings 

and produce cleaner burning fuel. The common oxygenates fall into two major chemical groups – ether 

compounds, consisting of organic compounds characterized by an oxygen atom linking two hydrocarbon 

groups; or alcohols, consisting of an alkyl group (such as methyl, ethyl, or isopropyl) bonded to a 

hydroxyl (oxygen-hydrogen) group. In addition to MtBE and ethanol, other common oxygenates include 

TBA, TAME, ethyl tert-butyl ether (EtBE), and DIPE. Tert-amyl ethyl ether (TAEE), tert-amyl alcohol 

(TAA), and methanol have also been used to a lesser extent. Figure 2-1 shows the molecular structure of 

commonly-used oxygenates. Some of these oxygenates could also be present in commercial formulations 

of other oxygenates as by-products or degradation products. For example, TBA is often found in 

commercial formulations of MtBE. 

Oxygenates came into widespread use in the U.S. in the late 1970s as an octane booster, replacing alkyl 

lead additives, which were being phased out in an effort to reduce lead emissions from vehicles. The use 

of oxygenates in gasoline was increased after the passage of the 1990 Clean Air Act Amendments that 

included requirements to increase the oxygen content of fuel to reduce air emissions. The amendments 

required the use of oxygenated fuel (Oxyfuel) with a minimum of 2.7 percent by weight oxygen in 39 

carbon monoxide non-attainment areas during wintertime and Reformulated Gasoline (RFG) with a 

minimum of 2.0 percent by weight during the remainder of the year (Blue Ribbon Panel on Oxygenates in 

Gasoline, 1999). 

In 1998, approximately 30 percent of all gasoline in the U.S. contained oxygenates. At that time, MtBE 

was the most common fuel oxygenate, present in more than 80 percent of oxygenated fuels. However, 

due to increasing restrictions on the use of MtBE, this percentage has decreased over the past several 

years. In 1998, ethanol was the second most common fuel oxygenate, present in about 15 percent of 

oxygenated fuels. Other oxygenates were used in the remaining 5 percent of oxygenated fuels. As of 

2002, 17 states and the District of Columbia were required to use gasoline that contains MtBE or other 

oxygenates to reduce air pollution. Recent surveys have found that MtBE is present in states that did and 

did not use RFG. MtBE has been found in gasoline, as well as heating oil and diesel fuel. Sources of 

MtBE included areas used for storage, transportation, and use (McGarry, 2002). 

The following documents contain additional information on the historic use of oxygenates: 

• Blue Ribbon Panel on Oxygenates in Gasoline. 1999. Achieving Clean Air and Clean Water: 

The Report of the Blue Ribbon Panel on Oxygenates in Gasoline. EPA 420-R-99-021. 

http://www.epa.gov/oms/consumer/fuels/oxypanel/blueribb.htm 

• EPA. 1998. MtBE Fact Sheet #3: Use and Distribution of MtBE and Ethanol. EPA Office of 

Underground Storage Tanks. EPA 625-K-98-001. September. 

http://www.epa.gov/swerust1/mtbe/mtbefs3.pdf 

 2-1 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Figure 2-1. Molecular Structures of Common Fuel Oxygenates 

CH3

 |

Methyl tert-butyl ether H3C– C– O– CH3

(MTBE) |

CH3 

CH3

 | Ethyl tert-butyl ether H3C– C– O– CH2 – CH3 (ETBE) | 

CH3 

CH3 

|

tert - Amyl methyl ether CH2

(TAME) |

H3C– C– O– CH3 

| 

CH3 

CH3 CH3

Diisopropyl ether | |

(DIPE) H3C– CH– O– CH – CH3

Ethanol H3C –CH2OH 

CH3 

| tert-Butyl alcohol 

(TBA) H3C – C – OH 

| 

CH3 

2.2 What Are the Sources of Oxygenates in the Environment? 

As discussed above, oxygenates have been widely used in the U.S. for the past several decades as an 

additive to gasoline intended to either boost octane ratings or to reduce air pollution. A significant 

proportion of the more than 100 billion gallons of gasoline used in the U.S. annually has contained MtBE 

 2-2 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

and other oxygenates at greater than 10 percent by volume. The volume of MtBE, ethanol, and other 

oxygenates used in RFG and Oxyfuel in 1997 was estimated to be about 11 million, 2 million, and 

700,000 gallons, respectively (White et al, 2002). The gasoline containing these oxygenates is stored in 

aboveground storage tanks (ASTs) and underground storage tanks (USTs) at a wide range of facilities, 

including refineries, terminals, service stations, and by end users; gasoline has been transported 

throughout the U.S. via pipeline, barge, rail, and truck. There are an estimated 3.7 million USTs in the 

U.S., including 700,000 regulated gasoline USTs at approximately 250,000 facilities and approximately 3 

million underground fuel storage tanks that are exempt from federal regulations (for example, certain 

farm and residential and home heating oil tanks) (Blue Ribbon Panel Report, 1999). Gasoline has been 

released to the environment through spills and leaks from ASTs and USTs, as well as from 

manufacturing, storage, and transport operations. 

2.3 What is the Prevalence of Contamination by Oxygenates in the Environment? 

MtBE has been detected nationwide in soil and groundwater. Federal and state studies have found that 

MtBE contamination has reached drinking water sources in many locations, including areas where the use 

of oxygenated fuel has not been mandated (GAO, 2002). This MtBE contamination has also been 

documented in surface water bodies resulting from direct spills, storm water runoff, and emissions from 

watercraft. The following federal and state studies contain additional information on the extent of 

contamination by MtBE: 

• GAO. 2002. Testimony Before the Subcommittee on Environment and Hazardous Materials, 

Committee on Energy and Commerce, House of Representatives, Environmental Protection, 

MtBE Contamination from Underground Storage Tanks, Statement of John Stephenson, Director, 

Natural Resources and Environment. GAO.02.753T. May 21. http://www.gao.gov/ 

• New England Interstate Water Pollution Control Commission (NEIWPCC). 2003. A Survey of 

State Experience with MtBE Contamination at LUST Sites. August. 

http://www.neiwpcc.org/mtbesum.pdf 

• Lawrence Livermore National Laboratory. 1998. An Evaluation of MtBE Impacts to California 

Groundwater Resources. UCRL-AR-130897. July 11. 

http://www-erd.llnl.gov/mtbe/pdf/mtbe.pdf 

• Maryland Department of the Environment. 2001. The Task Force on the Environmental Effects 

of MtBE. Final Report. December. 

http://www.mdarchives.state.md.us/msa/mdmanual/26excom/defunct/html/23mtbe.html 

Of the 44 states that reported testing for MtBE at leaking tank sites, 35 states reported finding MtBE in 

the groundwater at least 20 percent of the time they sampled for it. Twenty four states reported finding 

MtBE at least 60 percent of the time (GAO, 2002). 

Information about the prevalence of other oxygenates in the environment is limited. However, there is 

evidence that other oxygenates may be found at sites contaminated with MtBE; non-MtBE oxygenates 

were identified as a contaminant at 29 of the projects in the database. In addition, several surveys, 

including those identified below, have assessed the nature and extent of contamination with other 

oxygenates within the U.S. 

• U.S. Geological Survey. 2003. A National Assessment of Volatile Organic Compounds (VOCs) 

in Water Resources of the U.S. Summer 2003. http://sd.water.usgs.gov/nawqa/vocns/ 

 2-3 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

• American Water Works Research Foundation. 2003. Occurrence of MtBE and VOCs in 

Drinking Water Sources of the U.S. http://www.awwarf.org

• New England Interstate Water Pollution Control Commission (NEIWPCC). 2003. A Survey of 

State Experience with MtBE Contamination at LUST Sites. August. 

http://www.neiwpcc.org/mtbesum.pdf 

2.4 What are the Concerns About Contamination with Oxygenates? 

There have been several assessments of research concerning the health effects of MtBE and other 

oxygenated fuels (National Science and Technology Council, 1997; California EPA, 1999). Recently, 

results from research were published about a study of the movement of MtBE between tissues in human 

volunteers (Prah, 2004). EPA is currently updating its assessment of the health effects of MtBE. 

There is uncertainty as to what levels of MtBE in drinking water cause a risk to public health (GAO, 

2002). EPA has issued an advisory suggesting that drinking water should not contain MtBE in 

concentrations greater than 20 to 40 micrograms per liter (μg/L), based on taste and odor concerns, but 

has not issued a federal maximum contaminant level (MCL) for MtBE, which will be based on the 

ongoing EPA studies. 

In addition, 31 states have established standards, guidelines, advisory levels, or action levels (some based 

on the EPA advisory concentrations) for the maximum concentration of MtBE allowable in drinking 

water. Forty two states have established cleanup levels or guidelines (some site-specific) for MtBE in soil 

and groundwater, as shown at http://www.epa.gov/oust/mtbe/index.htm. MtBE drinking water standards 

range from 5 to 240 μg/L, with 90 percent of state standards less than or equal to 100 μg/L. Soil cleanup 

levels range from 5 to 280,000 μg/kg and groundwater cleanup levels range from 5 to 202,000 μg/L, 

considering both potable and non-potable uses for groundwater (EPA, 2003a; Delta Environmental 

Consultants, 2004; NEIWPCC, 2000). More than 75 percent of the states have groundwater cleanup 

values less than 100 μg/L. Delta Environmental Consultants http://www.deltaenv.com/ compiled the 

summary of state groundwater standards for EPA, and periodically updates their summary of the 

standards. 

Only limited information is available about the health risks of oxygenates other than MtBE. Fewer states 

have established standards and cleanup levels for these contaminants than for MtBE. Currently, there are 

no federal drinking water advisory or cleanup levels for these other fuel oxygenates. Several states have 

established, and some states have plans to establish, cleanup levels for other oxygenates (Delta 

Environmental Consultants, Inc., 2004). Table 2-1 summarizes the number of states that have cleanup 

levels for fuel oxygenates along with the range of cleanup levels established for each. 

 2-4 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Table 2-1. State Cleanup Levels for Fuel Oxygenates in Groundwater 

Fuel 

Oxygenate 

States with 

Cleanup Level 

(in 4/04) 

Lowest Cleanup 

Level (μg/L) 

Highest Cleanup 

Level (μg/L) 

MtBE 42 13 202,000 

TBA 11 12 11,000 

DIPE 7 0.438 20,000 

TAME 6 25 980 

ETBE 5 24 50 

Ethanol 6 50 1,900,000 

Methanol 11 50 16,000 

Note: Cleanup levels address both potable and non-potable sources of groundwater 

Source: Delta Environmental Consultants, Inc., 2004 

2.5 How Are Oxygenates Assessed in the Environment? 

Analytical methods for petroleum hydrocarbons (usually benzene, toluene, ethylbenzene, and xylenes – 

collectively BTEX) are well established and some of these protocols have been modified to include 

oxygenates as individual target compounds. Until recently, validated EPA analytical methods existed for 

only a few fuel oxygenates (specifically ethanol, methanol, and TBA). Methods that were developed for 

analysis of petroleum hydrocarbons in water samples may not be appropriate for fuel oxygenates for 

several reasons, such as analytical instruments may not routinely be calibrated for oxygenates, 

inappropriate methods may be used for sample analysis, detection limits (particularly for alcohols) may 

be higher than regulatory standards, or acid-catalyzed hydrolysis (breakdown) of ethers may occur during 

sample processing and analysis. In April 2003, EPA published a Fact Sheet (EPA, 2003a) that specifies 

the following steps that may be taken to address potential analytical problems with oxygenate analysis. 

EPA has found that using this approach consistently results in detection limits of 5 μg/L or lower for 

MtBE, TBA, ETBE, TAME, TAEE, TAA, DIPE, and acetone. 

• Routinely calibrate analytical methods for the suite of common fuel oxygenates 

• Use Method 8260 (GC/MS) or Method 8015 (GC/FID) for sample analysis 

• Modify sample preparation methods to increase sensitivity and decrease detection limits; in some 

cases, samples should be heated during the preparative phase, especially when analyzing for 

alcohols 

• Change the chemical preservation method to avoid the potential for ether hydrolysis; for example, 

using base preservation to raise the pH to greater than 11 (including use of trisodium phosphate 

dodecahydrate [TSP]), rather than acidification, would help avoid ether hydrolysis 

Other researchers have provided additional information related to the methods used for the analysis for 

fuel oxygenates. The following references provide more detailed information about this subject: 

 2-5 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

• White H., Lesnik B., Wilson J. 2002. Analytical Methods for Oxygenates. L.U.S.T.Line, 

Bulletin 42, New England Interstate Water Pollution Control Commission. pp 1-8. October. 

Discusses results from an EPA study to determine optimum conditions for purge-and-trap sample 

preparation for MTBE and other fuel oxygenates. 

http://www.epa.gov/oust/mtbe/LL42Analytical.pdf 

• Crumbling D.M., Lesnik B. 2000. Analytical Issues for MtBE and Related Oxygenate 

Compounds. L.U.S.T.Line, Bulletin 36, New England Interstate Water Pollution Control 

Commission. pp 16-18. Discusses relative appropriateness of using flame ionization detection 

and mass spectrometry with proper preparation techniques. 

http://www.epa.gov/oust/mtbe/LL36Methods.pdf 

• Halden, R. U., A. M. Happel, and S. R. Schoen. 2001. Evaluation of Standard Methods for the 

Analysis of Methyl tert-Butyl Ether and Related Oxygenates in Gasoline-Contaminated 

Groundwater. Environmental Science & Technology, Vol. 35, no. 7, pp.1469-1474. (Additions 

and Corrections, Vol. 35, no. 7, p.1560.) Presents results from a formal method evaluation, 

round-robin study, and a split-sample study (424 groundwater samples) that showed consistently 

good results for mass spectrometry and flame ionization detection, but not for photoionization 

detection. http://pubs.acs.org/ 

2.6 How Do Oxygenates Migrate in the Environment? 

MtBE and other oxygenates typically enter the environment blended with gasoline or other refined fuel 

products. However, these oxygenates migrate differently within the environment because of the 

differences in physical properties between oxygenates and the other components of gasoline, such as 

BTEX, of which benzene is typically the most common contaminant of concern. Table 2-2 contains a 

summary of some properties that influence the migration of MtBE and other oxygenates in the 

environment. As discussed later in this report, these physical properties also influence the treatability of 

MtBE and other oxygenates. 

Fuel oxygenates generally exhibit the following physical properties relative to benzene: 

• Greater tendency to partition into the vapor phase from the non-aqueous phase (vapor pressure) 

(with the exception of TBA, ethanol, and TAME) 

• Greater solubility in water 

• Lesser tendency to partition to organic matter in soil (soil adsorption coefficient) 

• Lesser retardation factor (slowing of migration with groundwater due to sorption to aquifer 

matrix) 

• Lesser tendency to partition into the vapor phase from the aqueous phase (Henry’s Law Constant) 

Because of their relatively higher vapor pressure, ether-based oxygenates in fuel will tend to volatilize 

from releases (non-aqueous phase) exposed to the open air more rapidly than benzene. Alcohol-based 

oxygenates will volatilize less rapidly than benzene. However, once fuel oxygenates enter the subsurface 

and become dissolved in groundwater (aqueous phase), they are significantly less volatile (lower Henry’s 

Constant) than benzene. Oxygenates are many times more soluble than benzene; concentrations of MtBE 

in groundwater as high as 1,000,000 μg/L are not uncommon. Also, because MtBE dissolved in 

groundwater will partition (as a function of its soil adsorption coefficient) to the organic matter in 

surrounding soil less readily than benzene, a dissolved MtBE plume typically migrates faster than a 

dissolved benzene plume (lower retardation factor). As a result, MtBE contamination can result in a 

 2-6 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

relatively larger groundwater plume, compared with plumes originating from gasoline constituents (EPA, 

2001a; Kinner, 2001). 

While all fuel oxygenates are more water soluble than other gasoline components (benzene), variations in 

molecular structures result in a range of physical properties and affect the way that each of them migrate 

in the environment. Figure 2-2 summarizes the physical properties discussed above for each of the 

common fuel oxygenates relative to benzene, which is most often the chemical of concern in gasoline. 

While the physical properties for each oxygenate is different, there are similarities among the alcohols 

and the ethers. For example, as shown on Figure 2-3, alcohol-based oxygenates have a relatively greater 

water solubility and much lower Henry’s Constant than the ether-based oxygenates. Other properties 

such as the soil partition coefficient, vapor pressure, and retardation factor do not adhere to these same 

groupings. 

2.7 How Do the Properties of Oxygenates Affect Treatment? 

As discussed above, the properties of MtBE and other oxygenates, including water solubility, vapor 

pressure, soil adsorption coefficient, retardation factor, and Henry’s Law Constant, affect their fate and 

transport in the environment relative to other contaminants. These same properties also affect the 

selection and design of remediation technologies used to address soil and water contaminated with 

oxygenates. In general, the same types of treatment technologies have been applied for treatment of 

BTEX and MtBE, however design and operating conditions for MtBE may not be the same as for 

treatment of BTEX. For example, carbon-based adsorption materials that work well for BTEX may not 

be effective for removal of MtBE. 

BTEX is most often the contaminant group targeted for treatment at gasoline spill sites, and in many cases 

the treatment systems have been specifically designed to reduce concentrations of benzene. In some 

cases, a treatment system designed to remove benzene can also remove the oxygenate contamination. 

However, because of the differences in the physical properties of oxygenates relative to benzene, certain 

oxygenates might not be effectively treated by a system designed to treat benzene. Also, because the 

physical properties of individual oxygenates also differ from one another, a treatment system designed to 

treat one oxygenate may not effectively treat another oxygenate. An overview of the effects of the 

physical properties of oxygenates on the effectiveness of various remediation technologies is included in 

Section 4. Primary considerations related to the treatment of oxygenates include: 

• The vapor pressures of most oxygenates, with the exception of ethanol, TBA, and TAME, can 

result in them being more readily volatilized from soil using certain technologies, such as soil 

vapor extraction (SVE) or multi-phase extraction (MPE) (EPA, 2001b; Kinner, 2001). 

• The relatively low Henry’s Constants (the ratio of a compound’s concentration in air relative to 

its concentration in water) of oxygenates can result in them being more difficult to strip from 

contaminated groundwater via air sparging or air stripping as part of a pump-and-treat remedy. 

• The presence of an ether bond or hydroxyl group in oxygenates results in these compounds being 

significantly less likely to partition to organic matter (Koc), such as in use of granular activated 

carbon (GAC) in pump-and-treat remedies. 

• Because they can be chemically oxidized or biologically degraded, chemical oxidation and 

biodegradation technologies (both in situ and ex situ) can be effective in the treatment of 

oxygenates. 

 2-7 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Table 2-2. Properties of Fuel Oxygenates and Other Fuel Constituents 

Chemical 

Pure Phase 

Solubility 

(mg/L) 

Solubility into 

H O from 2

Gasoline 

(mg/L)a Log Koc 

Vapor Pressure 

@25oC (1) @20oC (2) 

(mm Hg) 

Henry’s Law 

Constant 

(Dimensionless) 

Retardation Factor 

Molecular 

Weight 

(g/mol) 

Boiling 

Point 

(EC) 

Density 

(g/L) 

Octane 

Number 

Taste 

Threshold 

in Water 

(mg/L) 

Odor 

Threshold 

(ppm) 

Soil 

Condition 

A (4) 

Soil 

Condition 

B (5) 

Benzene 1,780 (1) <100 (2) 1.5-2.2 (1) 76-95.2 (1) 

73 (2) 

0.22 (1) 1.59 (8) 3.38 (8) 78.11 (1) 80.1 (1) 0.88 (2) 94 (2) 500 (2) 0.5 (2) 

MtBE 43,000-

54,300(1) , 

48,000 (2) 

5500 (2) 

3393 (6) 5241 (7) 

1.0-1.1 (1) 245-256 (1) 

240 (2) 

0.024-0.12 (1) 

0.018 @20oC 

1.09 (8) 1.38 (8) 88.2 (1) 55.2 (1) 0.74 (2) 110 (2) 20-40 (2) 0.053 (2) 

TBA Miscible (1), (2) 25,000 (2) 1.57 (1) 40-42 (1) 

41 (2) 

0.00048-0.00059 (1) 

0.00048 

1.31 (8) 2.25 (8) 74.1 (1) 82.4 (1) 0.79 (2) 100 (2) NA 21 (2) 

DIPE 2,039-9,000 

@ 20oC (1) 

804 (6) 

745 (7) 

1.46-1.82 (1) 149-151 @ 20oC 

(1) 

0.195-0.41 (1) 1.37 (8) 2.47 (8) 102.2 (1) 68 (1) 0.73 (3) NA NA NA 

ETBE 26,000 (1) 

12,000 (2) 

3300 (2) 

1018 (6) 

1365 (7) 

1.0-2.2 (1) 152 (1) 

130 (2) 

0.11 (1) 1.33 (8) 2.34 (8) 102.2 (1) 72.2 (2) 0.74 (2) 112 (2) 47 (2) 0.013 (2) 

TAME 20,000 (1) 

12,000 (2) 

2400 (2) 

1210 (6) 

1220 (7) 

1.3-2.2 (1) 68.3 (1) 

75 (2) 

0.052 (1) 1.47 (8) 2.89 (8) 102.2 (1) 86.3 (1) 0.77 (2) 105 (2) 128 (2) 0.027 (2) 

Ethanol Miscible (1), (2) 57,000 (2) 0.20-1.21 (1) 49-56.5 (1) 

44 (2) 

0.00021-0.00026 (1) 1.04 (8) 1.17 (8) 46.1 (1) 78.5 (1) 0.79 (2) 115 (2) NA 49 (2) 

Methanol Miscible (1) NA 0.44-0.92 (1) 121.6 (1) 0.00011 (1) 1.04 (8) 1.16 (8) 32.1 (1) 64.7 (1) 0.79 (3) NA NA NA 

Notes: NA - Information not availablea “Solubility into H O from Gasoline” data from the sources listed below are based on experimental results and estimates for typical gasoline blends 2 in contact with water; actual solubility into water 

from gasoline is dependent on the fraction of individual gasoline components and, therefore, may vary from the values presented in this table 

(1) Data from Zogorski et. al. “Fuel Oxygenates and Water Quality”. In Interagency Assessment of Oxygenated Fuels. NSTC. 1997. Data for MtBE for temp = 25 oC, unless otherwise stated. 

Additional information about affect of temperature on Henry’s Law constant in A. Fischer et. al. “Determination of Henry’s Law Constant for MtBE at Groundwater Temperatures”, Chemosphere 54 (2004) 689-694. 

(2) Data from “Achieving Clean Air and Clean Water: The Report of the Blue Ribbon Panel on Oxygenates in Gasoline,” September 1999 (3) Data from NIOSH Pocket Guide to Chemical Hazards (1990) (4) Soil Condition A: organic fraction foc = 0.001 mg/mg, bulk density = 1.75 kg/L, porosity = 0.25 (5) Soil Condition B: foc = 0.004 mg/mg, bulk density = 1.75 kg/L. porosity = 0.25 (6) Experimental results, ManTech Environmental Research (USEPA Contract 68-C-09-198) (7) Theoretical results, ManTech Environmental Research (USEPA Contract 68-C-09-198) (8) Data from “Guidelines for Investigation and Cleanup of MtBE and Other Ether-Based Oxygenates,” CalEPA, State Water Resources Control Board, March 2000 

2-8 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Figure 2-2. Physical Properties of Fuel Oxygenates Relative to Benzene 

Physical Property Magnitude Relative to Benzene 

0.0001 0.001 0.01 0.1 1 10 100 

 Solubility data not available 

ALCOHOLS 

ETHERS

Solubility into H2O from Gasoline (mg/L)

Log Koc (log l/kg)

Vapor Pressure 

Henry’s Law Constant 

Retardation Factor (Soil Condition A) 

1000 

Ethanol 

Methanol 

TBA 

MTBE 

ETBE 

TAME 

DIPE 

Figure 2-3. Relative Solubility and Henry’s Law Constants for Selected Fuel Oxygenates (Henry’s 

Law data for MtBE, TBA, and Benzene based on Zogorski et. al., 1997) 

0.450 

DIPE 

0.400 

Ethylbenzene 

0.350 

o-Xylene 

0.300 

Henry’s 0.250 Law Benzene Consent 0.200 

0.150 

ETBE 0.100 

TAME 0.050 

MTBE TBA Ethanol Toluene 

0.000 

100 161 175 534.8 804 2400 3300 5500 25000 57000 

Solubility in Water mg/L 

 2-9 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

2.8 What Types of Technologies are Used in the Treatment of Soil, Groundwater, and 

Drinking Water Contaminated with Oxygenates? 

Technologies that have been used to treat groundwater and soil contaminated with oxygenates include air 

sparging, SVE, MPE, in situ bioremediation, in situ chemical oxidation (ISCO), groundwater extraction 

and above-ground treatment (i.e., pump-and-treat or drinking water treatment), and phytoremediation. 

Above-ground treatment for extracted groundwater includes technologies such as air stripping, activated 

carbon, chemical oxidation, and bioremediation. Air sparging, SVE, and MPE rely generally on the use 

of air flow to remove contaminants, and are discussed before the other technologies. Bioremediation and 

ISCO rely on biological and chemical reactions to destroy MtBE and other oxygenates, while pump-andtreat and drinking water treatment rely primarily on physical and chemical parameters to separate MtBE 

and oxygenates from water. Other technologies discussed in this report, such as phytoremediation, in situ 

thermal treatment, and permeable reactive barriers, have also been used at sites contaminated with 

oxygenates, although less often at the sites in EPA’s MtBE database. Non-treatment remedies that have 

been used include excavation, free product recovery, monitored natural attenuation (MNA) and 

institutional controls (IC). These technologies are discussed in more detail in Sections 4 and 5 of this 

report. 

Additional sources of information that discuss treatment of MtBE using multiple technologies include the 

following: 

• Moyer, E.E. and Kostecki, P.T., Eds. 2003. MtBE Remediation Handbook. AEHS. Amherst 

Scientific Publishers. 

• Evaluation of MTBE Remediation Options. 2004. The National Water Research Institute. April. 

www.nwri-usa.org/. 

2.9 How Are Technologies Used to Treat Soil and Water Contaminated with Oxygenates? 

Remediation of a site contaminated with MtBE and other fuel oxygenates is often conducted using a 

phased approach. Often, the first phase of remedial action at a site focuses on protecting receptors at the 

site, such as nearby buildings or drinking water supplies. The second phase generally involves 

controlling the source of the contamination, for example excavation of leaking underground storage tanks 

(USTs) or contaminated soil, or free product removal. The next phase typically involves the active 

cleanup of residual and dissolved contamination using one or more treatment technologies. Active 

cleanup of residual and dissolved contamination often is followed by MNA (Jansen et. al., 2002). 

Technologies might be applied sequentially or simultaneously in different parts of a contaminated site, 

depending on the concentration of oxygenates and potential risks to receptors. For example, at a gasoline 

service station site with a leaking UST, excavation, free product removal, or SVE might be performed at 

the source area; air sparging, in situ chemical oxidation, or in situ bioremediation in the plume area (these 

technologies could also be used for source area treatment at some sites); or pump-and-treat as the plume 

gets closer to a receptor. If concentrations are sufficiently low, MNA might be used instead of an active 

bioremediation technology or pump-and-treat for the residual plume. When considering MNA as a 

potential remedy, remediation timeframe is an important factor to consider. Treatability studies (benchor pilot-scale) often are performed to evaluate how a technology would perform on the actual soil or 

groundwater at a site. The results of these studies are used in preparing a design for full-scale 

remediation (EPA, 1999b). 

 2-10 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

2.10 What Additional Technical Considerations are Associated with Remediating Sites 

Contaminated with Oxygenates? 

Other technical considerations related to remediation of sites contaminated with MtBE and oxygenates 

include contaminant concentration, cleanup goals, presence of other contaminants at the site, and sitespecific considerations that may affect the selection and design of treatment technologies. There tends to 

be wide variability in the range of concentrations of MtBE or other oxygenates in soil and groundwater at 

sites. The concentration of MtBE in contaminated groundwater and soil for the projects reviewed for this 

report ranged from 5 to 1,000,000 μg/L. In addition, soil and groundwater treatment goals for MtBEcontaminated sites are currently based on state-specific standards and risk-based levels that range from 5 

to 280,000 μg/L in soil and from 5 to 200,000 μg/L in groundwater. State-established primary drinking 

water limits for MtBE range from 5 to 240 μg/L (Delta Environmental Consultants, Inc., 2004). High 

contaminant concentrations at sites with low cleanup goals can result in the need for treatment 

technologies and system designs able to achieve higher removal efficiencies and more aggressive 

remediation. 

Many other factors can affect the performance and cost for implementing a technology at a given site, 

including the nature and extent of contamination, depth of contamination, physical and chemical 

characteristics of a site (such as dimensions and hydrogeology), design and operation of a treatment 

system, regulatory requirements, and logistical issues. Typically, these factors are quantified before an 

engineering level design is made for use of a technology at a given site. 

In addition, it is important to recognize that sites with spilled or leaked gasoline contain 200-300 distinct 

chemicals which can contaminate soil and groundwater; approximately 6-10% of the spilled/leaked 

gasoline typically consist of fuel oxygenates such as MtBE (McGarry, 2002). 

 2-11 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

3.0 COMPARISON OF TREATMENT TECHNOLOGIES 

This section contains a comparison of the following nine technologies that have been used to treat sites 

contaminated with MtBE and other fuel oxygenates: 

• Air Sparging 

• Soil Vapor Extraction (SVE) 

• Multi-Phase Extraction (MPE) 

• In Situ Bioremediation 

• In Situ Chemical Oxidation (ISCO) 

• Pump-and-Treat 

• Other Treatment Technologies 

o Phytoremediation 

o Permeable Reactive Barriers 

o In Situ Thermal Treatment 

The information used for this comparison is based primarily upon information reported for 323 MtBE 

remediation technology projects at EPA’s MtBE Treatment Profile Website, available at 

www.cluin.org/products/mtbe, as well as information available from published literature sources. This 

section provides a summary overview of these technologies and Section 4 includes more detailed 

information related to each individual technology, including a technology description, a discussion of 

how the properties of fuel oxygenates affect treatment, and more detailed information summaries related 

to the 323 projects in the dataset. 

3.1 What Types of Remediation Technology Projects were Considered in this Comparison? 

Information about 323 MtBE remediation technology projects was reviewed during the preparation of this 

report. These projects employed primarily air sparging, SVE, MPE, bioremediation, ISCO, and pumpand-treat to remediate MtBE and other oxygenates in groundwater and soil. Some sites also used 

phytoremediation, PRBs, or in situ thermal treatment. Table 3-1 summarizes the number of projects that 

used each of these technologies, as well as the scale (full-scale, pilot-scale, or bench-scale) and status 

(completed or ongoing) of the projects reviewed, and the number of projects for which performance and 

cost data were available. Among the six technologies, air sparging, SVE, bioremediation, and pump-andtreat were used more frequently to remediate groundwater and soil contaminated with MtBE and other 

oxygenates, and MPE, ISCO, phytoremediation, PRBs, and thermal treatment were used less frequently. 

Nearly 25 percent of the projects have been completed, with the remaining 75 percent ongoing. Eighty 

percent of the projects provided some type of performance data, and more than 30 percent provided cost 

data. Performance and cost data were provided most often for projects using air sparging, bioremediation, 

and pump-and-treat. 

 3-1 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Table 3-1. Description of MtBE Remediation Technology Projects (323 Projects) 

Technology 

Number 

of 

Projects 

Project 

Scale Project Status 

# of Projects 

with 

Performance 

Data 

# of Projects 

with 

Cost Data Bench Pilot Full Completed 

Ongoing 

Air Sparging 123 1 2 120 19 104 113 39 

Soil Vapor Extraction 138 0 1 137 19 119 129 24 

Multi-Phase Extraction 13 0 4 9 4 9 10 2 

Bioremediation 73 7 13 53 35 38 68 28 

In situ Chemical Oxidation 21 0 4 17 8 13 20 2 

Pump-and-treat 100 0 16 84 22 78 76 43 

Phytoremediation 8 3 4 1 5 3 1 0 

Permeable Reactive Barriers 6 0 2 4 4 2 4 0 

Thermal Treatment 1 0 0 1 1 0 1 0 

Note: Each project may involve use of one or more than one specific technology. 

Source: EPA, 2002a 

3.2 How Did These Remediation Technologies Perform? 

As shown on Table 3-1, performance data were available for all 323 of the MtBE remediation projects in 

the dataset. However, most of these projects with performance data are ongoing. To evaluate 

performance of specific technologies and projects, 105 completed projects with performance data were 

identified, along with the minimum, median, and maximum of the highest concentration of MtBE 

measured in the groundwater before treatment (initial) and after treatment (final), as shown in Table 3-2. 

Limited performance data were available about the projects that employed phytoremediation, PRBs, and 

thermal treatment, and are not presented in this table. A summary of the technology-specific data for 

these technologies is included in Section 4, with project-specific data provided in Appendix A. 

Table 3-2. Performance Data for Completed MtBE Remediation Technology Applications 

(105 Applications1

 Providing Data) 

Technology 

# of 

Completed 

Projects with 

Performance 

Data 

Initial MtBE Concentration 2 (μg/L) 

in Groundwater 

Final MtBE Concentration 2 (μg/L) 

in Groundwater 

Minimum Median Maximum Minimum Median Maximum 

Air Sparging 19 5 2,100 62,000 2 16 2,070 

Soil Vapor Extraction 23 5 2,600 44,400 2 21 3,200 

Multi-Phase Extraction 3 11 55 6,140 79 435 791 

Bioremediation 35 5 3,880 100,000 <1 30 33,000 

In situ Chemical Oxidation 8 55 11,700 475,000 5 75 68,400 

Pump-and-Treat 21 3 1,610 475,000 <1 11 68,400 

Notes: 

1 For projects where more than one technology was used, performance information is presented under each of the technologies used for the 

project. 

2 MtBE concentrations for all technologies are reported for groundwater. For technologies that affect soil (such as MPE and SVE), source 

materials provided information on MtBE concentrations in groundwater. For all projects, the highest concentration reported prior to 

beginning treatment (shown as “initial”) and the highest concentration after treatment was completed (shown as “final”) is provided. 

Source: EPA, 2002a 

 3-2 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

As discussed in Section 1, these performance data are based on the data provided by project managers and 

others in the source materials used to prepare the treatment profiles website. There was variation among 

the profiles in the level of detail for performance data. Many of the treatment profiles contained only 

limited information about treatment performance, generally including a maximum concentration of MtBE 

before-treatment and a maximum concentration of MtBE after-treatment. Most treatment profiles did not 

provide detailed performance data, such as MtBE concentration over the duration of the project, or 

statistical evaluations of performance data with confidence limits. 

As mentioned before, treatment performance is site-specific and dependent on many factors; thus it is 

difficult to extrapolate from one site to another. The data are provided to give a general indication of 

technology performance. These factors include site conditions (such as soil types, permeability, 

conductivity, redox conditions, and degree of heterogeneity), technology design and operation, and 

regulatory considerations, such as cleanup levels. Additional factors include duration of the release (such 

as a gasoline leak), presence of down-gradient water supply wells, and distribution of contaminants in soil 

and groundwater. 

Table 3-3 summarizes the duration of 89 completed remediation projects. Although project duration is 

dependent on a number of factors, such as extent of contamination and cleanup levels, the data from these 

89 projects show a relatively shorter median duration for projects using bioremediation or ISCO, 

compared with those using air sparging, SVE, pump-and-treat, or MPE. 

Table 3-3. Duration of Completed MtBE Remediation Technology Applications 

(89 Applications Providing Data) 

Technology # of 

Projects 

Project Duration (months) 

Minimum Median Maximum 

Air Sparging 18 3 22 75 

Soil Vapor Extraction 22 3 21 66 

Multi-Phase Extraction 1 45 

Bioremediation 24 <1 6 60 

In situ Chemical Oxidation 7 2 12 18 

Pump-and-Treat 17 <1 31 75 

Notes: 

1 For projects where more than one technology was used, information is presented under each of the technologies used 

for the project.

Source: EPA, 2002a 

3.3 What Did These Remediation Technologies Cost? 

Table 3-4 summarizes the cost information reported for 127 MtBE remediation technology applications. 

Only costs reported as total project costs are summarized in this table. Note that these include both 

completed and ongoing projects. Because of the wide variation in the components that were included in 

the reported total project costs, these data should only be used as a general reference about costs and 

should not be used as a sole basis to estimate costs for future MtBE remediation projects or to compare 

the cost of technologies. Additional information about the costs reported for the remediation technologies 

are provided in Section 4. 

 3-3 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Table 3-4. Total Project Cost1 Data for MtBE Remediation Technology Applications 

(127 Applications Providing Data) 

Technology # of Projects with 

Cost Data 

Total Project Costs Reported ($) 

Minimum Median Maximum 

In situ Chemical Oxidation 2 $60,000 $103,000 $146,000 

Bioremediation 30 $4,000 $137,000 $5,200,000 

Soil Vapor Extraction 24 $14,700 $206,000 $4,600,000 

Air Sparging 39 $13,700 $247,000 $1,050,000 

Multi-Phase Extraction 2 $130,000 $257,000 $383,000 

Pump-and-Treat 43 $65,000 $327,000 $4,000,000 

Note: 

1 For projects where more than one technology was used, cost information is presented under each of the technologies used for the project. 

Table includes total costs for completed projects, and costs to date for ongoing projects. Projects were of varying sizes, concentrations, and 

other site conditions. A summary of project-specific data for these technologies is provided in Appendix A. 

2 Total project cost included more than just the treatment cost, such as cost for ancillary treatment processes, monitoring costs, or source 

removal costs. The costs summarized in this table have not been normalized to account for the types of cost components included, locations 

of the projects, or the time when the costs were incurred (inflation factors, see EPA 2001c). For a majority of the applications, reported 

costs were based on actual incurred costs. However, for some applications, costs were estimated as projected full-scale costs based on a 

scale up of pilot- or bench-scale projects. 

Source: EPA, 2002a 

In addition, EPA recently prepared a more detailed analysis of treatment cost for in situ treatment of fuel 

oxygenates. The paper, “Cost of In Situ Treatment of Fuel Oxygenates”, was presented at the National 

Ground Water Association conference on Remediation: Site Closure and the Total Cost of Cleanup, New 

Orleans, held November 13-14, 2003, and is available at www.cluin.org/mtbe. 

As discussed earlier for performance data, the cost data are based on the data provided by project 

managers and others in the source materials used to prepare the treatment profiles website. There was 

variation among the profiles in the level of detail for cost data by project, with many of the treatment 

profiles containing only limited information about treatment cost. Treatment cost is site specific and 

depends on many of the same factors that also affect performance, such as site conditions, project scale, 

technology design and operation, and regulatory considerations. Therefore, these cost data are intended 

to give a broad indication of the types of costs associated with cleanup projects, and users should be 

cautious about drawing conclusions about the cost of cleanup projects at specific sites based on these 

data. As discussed later in the report, very few projects provided sufficient information to calculate a unit 

cost for treatment. 

For some of the treatment profiles, the specific components that make up the total cost were not provided 

in the source materials, such as for capital or operation and maintenance [O&M] activities. In other cases, 

the types of contaminants present at the sites, other than MtBE, were not identified in the source 

materials. Sites may have been contaminated with gasoline components such as petroleum hydrocarbons, 

as well as oxygenates, and the treatment costs reported are for cleanup of both the gasoline components as 

well as the oxygenates. For example, for a specific project, most of the cost for cleanup may be due to 

gasoline components other than oxygenates. 

Costs for most of these projects were provided as a total remedial cost. Some projects also included the 

cost for ancillary treatment processes, monitoring costs, or source removal costs in the total cost. For 

most of the projects, reported costs were based on actual incurred costs. For other projects, costs were 

estimated as projected full-scale costs based on a scale up of pilot-scale projects or on engineering 

 3-4 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

estimates. Because most of the costs for use of the treatment technologies are related to system design, 

installation, and startup, these partial or estimated costs may be relatively close to the eventual total 

project cost. However, the reported project costs should still be considered estimates because the cost 

components for each project are not consistent and it is possible that significant costs could be associated 

with system operation, maintenance, monitoring, and decommissioning. In addition, these cost data were 

not normalized to account for the project year or location. (Further information about normalizing cost 

data is provided in EPA 2001c). 

3.4 What Factors Should Be Considered When Identifying Technologies to Treat Fuel 

Oxygenates? 

Table 3-5 summarizes the general factors to be considered when identifying technologies to treat sites 

contaminated with fuel oxygenates. These general factors were developed based on data from the 323 

technology applications, as well as from the Remediation Technology Screening Matrix and Reference 

Guide published by the Federal Remediation Technologies Roundtable (FRTR), and other industry 

references. As shown in Table 3-5, these general factors include type of treatment, relative time to 

complete, and relative cost. 

Table 3-5. General Factors to Consider When Identifying a Remediation Technology for 

Sites Contaminated with Fuel Oxygenates 

Technology 

Type of Treatment Relative Time to 

Complete Relative Cost In situ/ 

Ex situ Media Source/ 

Plume 

Air Sparging In situ GW Plume Average Average to Lower 

Soil Vapor Extraction In situ Soil Source Average to Longer Lower 

Multi-Phase Extraction In situ Both Source Average Average to Higher 

In situ Bioremediation In situ Both Plume Average to Shorter Lower 

In situ Chemical Oxidation In situ Both Source Shorter Average to Lower 

Pump-and-Treat Ex situ GW Plume Longer Higher 

Phytoremediation In situ Both Plume Longer Lower 

Permeable Reactive Barriers In situ GW Plume Longer Lower 

In situ Thermal Treatment In situ Both Source Shorter Average 

Source: EPA 2002a and FRTR 2002 

Table 3-6 summarizes some of the general factors that are often considered when selecting a remediation 

technology for sites contaminated with fuel oxygenates. These include potential benefits (such as 

minimal site disturbance, integration with other treatment technologies, or applicability to challenging site 

conditions) and limitations (such as types of contamination not suited to treatment, undesired migration or 

transformation of contamination, or health and safety considerations). A more detailed discussion of 

specific factors for each technology is provided in Section 4. 

 3-5 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Table 3-6. General Factors to Consider When Selecting a Remediation Technology for Sites 

Contaminated with Fuel Oxygenates 

Technology Potential Benefits Potential Limitations 

Air Sparging • Causes minimal disturbance to site 

operations 

• May cause a lateral spread of dissolved or 

separate phase contaminant plume 

• Addition of oxygen to the subsurface may 

enhance aerobic biodegradation 

• Contamination may be transferred from 

groundwater to the vadose zone 

• Can be a cost-effective alternative for sites 

with groundwater contamination 

• Has limited applicability at sites with confined 

aquifers 

SVE • Reduces the potential for migration of vapors 

into buildings or leaching into groundwater 

• Low soil permeability or other heterogeneous 

conditions may reduce effectiveness 

• Causes minimal disturbance to site 

operations 

• Shallow depths to groundwater or fluctuations 

in groundwater table can cause upwelling and 

• Can be a cost-effective alternative for sites interference with airflow 

with soil contamination and, in some cases, 

free product 

• Off-gas typically requires treatment 

MPE • May increase groundwater recovery rates, • NAPL emulsions and VOC-laden vapors may 

compared to conventional pumping practices increase treatment requirements 

in equivalent settings • Initial start-up and adjustment periods may be 

• Can be used to recover free product relatively long 

• May be used to remediate the capillary fringe • Some MPE configurations have depth 

and smear zone limitations 

• Can be a cost-effective alternative for sites 

with contamination in both soil and shallow 

• Off-gas typically requires treatment 

groundwater 

In situ 

Bioremediation 

• Causes minimal disturbance to site 

operations 

• Presence of other organic contaminants may 

inhibit biodegradation 

• Often biodegradation can be enhanced by use 

of other technologies, such as air sparging, 

SVE, MPE, thermal, or ISCO 

• Degradation pathways for anaerobic processes 

not as well understood as aerobic pathways; 

anaerobic processes typically slower 

• Can be a cost-effective alternative for sites 

with contamination in both soil and 

groundwater 

• High concentrations of contaminants may be 

toxic and/or not bio-available 

• May be difficult to implement in lowpermeability aquifers 

• Re-injection wells or infiltration galleries may 

require permits or may be prohibited 

• Biodegradation pathways may be site-specific, 

potentially requiring pilot testing or 

treatability studies 

In situ Chemical 

Oxidation 

• Can be a cost-effective alternative for hot 

spots that may not be amenable to 

bioremediation 

• Relatively large amount of oxidant may be 

needed for treatment of large contaminant 

mass 

• Contaminants are treated rather than 

transferred to a vapor phase 

• May be low contact between oxidant and 

contaminant in heterogeneous conditions or in 

• Causes minimal disturbance to site areas with low permeability 

operations • Special precautions may be needed to protect 

worker health and safety during operation 

• Oxidation reactions may form toxic byproducts in the groundwater or in off-gases 

and off-gas may require capture and treatment 

 3-6 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Technology Potential Benefits Potential Limitations 

Pump-and-Treat • Can be a cost-effective alternative to treat an 

aquifer or to provide hydraulic containment 

for sites contaminated with fuel oxygenates 

• May require an extended operation and 

maintenance period 

• Cost of constructing, operating, and 

maintaining treatment system can be relatively 

high 

• Biofouling of extraction wells can reduce 

system performance 

• The typical design of common above-ground 

treatment systems may not be effective for 

oxygenates 

Phytoremediation • Can be a cost-effective alternative for 

remediating or containing relatively low 

concentration, shallow, and widespread soil 

or groundwater plumes 

• Limited information available about the 

specific processes used in phytoremediation 

that reduce concentration of fuel oxygenates 

• Typically lengthy startup period 

• Phytoremediation generally less applicable to 

higher concentrations or deeper groundwater 

plumes 

Permeable 

Reactive Barriers 

• Can be a cost-effective alternative for 

preventing the migration of contaminated 

groundwater plumes 

• May affect natural groundwater flow gradients 

at a site, potentially resulting in lateral or 

vertical migration of the contaminant plume 

• Requires a high degree of engineering for 

design and installation 

In situ Thermal • Can be a cost-effective alternative for • May not be cost-effective for use at small sites 

Treatment remediating source areas in soil or 

groundwater 

• Tends to remove oxygenates when used to 

treat other petroleum contaminants (such as 

petroleum hydrocarbons) 

such as service stations 

• Requires a high degree of engineering for 

design, installation, and operation 

Sources: EPA 2002a and FRTR 2002 

For practitioners of in situ technologies, note that EPA has issued a policy statement that reinjection of 

contaminated groundwater is allowed under RCRA section 3020(b) as long as certain conditions are met. 

This policy is intended to apply to remedies involving in situ bioremediation and other forms of in situ 

treatment. Under this policy, groundwater may be reinjected if it is treated aboveground prior to 

reinjection. Treatment may be by a "pump-and-treat" system or by the addition of amendments meant to 

facilitate subsurface treatment. Also the treatment must be intended to substantially reduce hazardous 

constituents in the groundwater (either before or after reinjection); the cleanup must be protective of 

human health and the environment; and the injection must be part of a response action intended to clean 

up the environment (EPA, 2000f). 

 3-7 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

4.0 TREATMENT TECHNOLOGIES 

This section summarizes available information on nine treatment technologies that have been applied to 

treat MtBE and other oxygenates in groundwater, soil, and drinking water. Table 4-1 provides a brief 

description of these technologies, along with each technology’s applicability to treat groundwater, soil, or 

both to treat oxygenates either in situ or ex situ. Groundwater contaminated with MtBE has most often 

been treated using air sparging, bioremediation, ISCO, pump-and-treat, and MPE. To date, soil 

contaminated with MtBE has been treated primarily with SVE. Drinking water contaminated with MtBE 

and other fuel oxygenates is typically treated using the same aboveground treatment technologies 

associated with pump-and-treat, such as air stripping, adsorption, chemical oxidation, or bioremediation. 

In addition to these treatment technologies, several non-treatment remedies (excavation, product recovery, 

and monitored natural attenuation) have been used to enhance MtBE source removal or plume 

management remedies and are discussed in Section 5. The remainder of this section provides information 

summarized from 323 MtBE-remediation technology applications (based primarily on EPA MtBE 

Treatment Profiles – see Section 1) that can assist in remedy selection at sites contaminated with MtBE 

and other fuel oxygenates. 

Table 4-1. Types of Technologies Used to Treat MtBE and Other Fuel Oxygenates 

Treatment Ground In Situ or 

Section Technology water Soil Ex situ Description 

4.1 Air Sparging ● In situ Injection of air into the groundwater to strip 

out VOCs 

4.2 SVE ● In situ Application of a vacuum to the soil to 

extract VOCs and treatment using 

aboveground processes 

4.3 MPE ● ● In situ Simultaneous extraction of VOCs from soil 

and free product/groundwater and treatment 

using aboveground processes 

4.4 In situ 

Bioremediation 

● ● In situ Addition of oxygen or other amendments to 

stimulate and enhance biodegradation 

4.5 In situ Chemical ● ● In situ Injection of chemicals such as ozone, 

Oxidation hydrogen peroxide, or permanganate into 

the subsurface to oxidize contaminants 

4.6 Groundwater ● Ex situ Extraction of contaminated groundwater for 

Extraction for 

Pump-and-Treat 

treatment prior to use or disposal 

and Drinking 

Water Treatment 

4.7 Above-Ground 

Treatment 

Technologies for 

Extracted 

● Ex situ Treatment of extracted groundwater using 

ex situ processes such as air stripping, 

adsorption, biological reactors, or oxidation 

Groundwater 

4.8 PRBs ● In situ Placement of a reactive zone that treats 

contaminants as groundwater flows through 

the zone 

Phytoremediation ● ● In situ Use of trees and other higher plants to 

remove or destroy contaminants 

In situ Thermal 

Treatment 

● ● In situ Use of heat to mobilize or destroy 

contaminants 

 4-1 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

4.1 Air Sparging 

Overview 

$ Injection of air into the groundwater to strip out volatile contaminants 

$ EPA’s MtBE Treatment Profiles dataset includes use at 123 sites to treat 

MtBE, often in conjunction with SVE 

$ Some oxygenates may be less amenable to air sparging than other volatile 

contaminants 

4.1.1 What is Air Sparging? 

Air sparging is an in situ technology that removes VOCs such as MtBE and other oxygenates from the 

groundwater through the injection of air, which induces a phase transfer of VOCs from a dissolved state 

to a vapor state that can be extracted from the subsurface or allowed to attenuate in the vadose zone. 

During air sparging, biodegradation of contaminants (including MtBE and other oxygenates) can also be 

promoted by the oxygen in the injected air. In some cases, pure oxygen or air amended with other gases, 

such as triethylphosphate (a nutrient), or butane or propane (cometabolic substrates), are injected to 

further promote biodegradation of contaminants. For the purpose of this report, technology applications 

that rely on biodegradation as a primary pathway for contaminant remediation are considered to be 

bioremediation projects, and are discussed in more detail in Section 4.4. 

4.1.2 How Do the Properties of MtBE and Other Oxygenates Affect Treatment? 

In an air sparging system, the primary mechanism for contaminant removal is the transfer of contaminants 

from the dissolved to the vapor phase. The extent to which this transfer can take place during air sparging 

depends on the Henry’s Law Constant, which is an indication of the extent to which each will partition 

between the dissolved state and the vapor state under equilibrium conditions. A contaminant with a 

greater Henry’s Law Constant is more readily stripped from groundwater by air sparging than one with a 

lower Henry’s Law Constant. 

Figure 4.1-1 shows the Henry’s Law Constants for the common fuel oxygenates. The Henry’s Law 

Constants in this table are shown as dimensionless values representing the ratio of the concentration in the 

vapor state compared to its concentration in the aqueous state at 25 ̊C. As shown on the table, all of the 

common oxygenates (with the possible exception of DIPE) have Henry’s Law Constants that are lower 

than those for benzene, toluene, ethylbenzene, and xylene (BTEX), which range from 0.22 for benzene to 

more than 0.3 for xylene. Because of this, an air sparging system designed to remediate BTEX may not 

adequately address oxygenates. Research has shown that the removal of MtBE requires 5 to 10 times 

more airflow than would have been used for BTEX alone (Fields et al., 2001). In addition, the etherbased oxygenates have Henry’s Law Constants that are about two to three orders of magnitude greater 

than those for alcohol-based oxygenates, suggesting that ether-based oxygenates, such as MtBE, can be 

removed more readily using air sparging than alcohol-based oxygenates, such as TBA. However, 

alcohol-based oxygenates may be more readily biodegraded (see Section 4.4) or may have less stringent 

(higher concentration) cleanup goals at some sites than ether-based oxygenates. Thus, it is possible that 

air sparging could be used to remediate sites contaminated with both alcohol-based and ether-based 

oxygenates. 

 4-2 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Figure 4.1-1. Ranges of Henry=s Law Constants (Dimensionless) for Common Fuel Oxygenates 

0.0001 

0.001 

0.01 

0.1 

1 

MtBE 

ETBE 

TAME 

DIPE 

TBA 

Ethanol 

Methanol 

Benzene 

Toluene 

Ethylbenzene 

Xylenes 

0.22 0.24 

0.35 0.31 

0.11 

0.023 

0.052 

0.195 

0.00048 

0.00021 0.00011 

0.12 

0.41 

0.00059 

0.00026 

Henry's Law Constant (Dimensionless) 

ALCOHOL OXYGENATES 

ETHER BTEX 

Notes: 

1. Henry’s Law Constants shown as dimensionless values representing the ratio of the concentration in the vapor state compared to its 

concentration in the aqueous state at 25 ̊C. 

2. Data from AGuidelines for Investigating and Cleanup of MtBE and Other Ether-Based Oxygenates@, CalEPA, State Water Resources 

Control Board, March 2000. 

4.1.3 How is Air Sparging Applied to Treat Oxygenates? 

During air sparging, compressed air is forced into the saturated zone through one or more injection points, 

such as vertical or horizontal wells or engineered trenches, screened beneath the water table. The injected 

air flows and rises through the saturated zone. As the injected air passes through groundwater containing 

dissolved volatile contaminants, these contaminants partition to the injected air based on their individual 

physical properties. In addition, oxygen present in the injected air will dissolve into the groundwater at 

the gas-water interface and diffuse into the surrounding groundwater, potentially stimulating 

biodegradation of contaminants. When the injected air reaches the vadose zone, it can be extracted using 

SVE. Extracted vapors may be treated using aboveground technologies (Section 4.2 discusses SVE and 

aboveground vapor treatment technologies) or is allowed to attenuate naturally in the vadose zone through 

dispersion and biodegradation. Air sparging has been used without SVE when contaminant 

concentrations are relatively low or potentially affected receptors are far from the area being treated 

(Symons and Greene, 2003). 

The design and configuration of air sparging systems to treat oxygenates varies widely based on sitespecific conditions and is typically established through pilot-scale testing to determine the radius of 

influence (ROI) or zone of influence (ZOI) of an air sparging well under site conditions. The ROI or ZOI 

is the area around an injection well where there is adequate sparge pressure and airflow to enhance the 

transfer of contaminants from the dissolved phase to the vapor phase. Spacing between air sparging wells 

typically ranges from 5 to 40 feet (ft), depending on the surrounding soil characteristics, and airflow rates 

commonly range from 1 to more than 40 standard cubic ft per minute (scfm). Pilot testing is typically 

 4-3 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

employed to determine an appropriate airflow rate (maximizing the ROI/ZOI while limiting the potential 

for unintended subsurface fracturing and over-mobilization of the contamination) for a given site. The 

flow of air through the sparging wells can be continuous or pulsed. Pulsed systems have been shown to 

increase mass transfer removal in some instances (EPA, 1995; FRTR, 2002; USACE, 1997). 

More detailed information relevant to the application of air sparging at sites in general or those 

contaminated with MtBE and other fuel oxygenates is available in the following documents: 

• Symons, Brian D., and J. Greene. 2003. “Soil Vapor Extraction, Bioventing, and Air Sparging”. 

In Moyer and Kostecki, Eds. 2003. MtBE Remediation Handbook. Amherst Scientific 

Publishers. 

• Naval Facilities Engineering Service Center. 2001. Final Air Sparging Guidance Document. 

NFESC Technical Report TR-2193-ENV. August 31. 

• U. S. Environmental Protection Agency. 2001. Development of Recommendations and Methods 

to Support Assessment of Soil Venting Performance and Closure. EPA 600-R-01-070. 

• U.S Army Corps of Engineers. 1997. USACE Engineering Manual: In Situ Air Sparging. 

EM 1110-1-4005. September 15. 

• American Petroleum Institute. 1995. In Situ Air Sparging: Evaluation of Petroleum Industry 

Sites and Considerations for Applicability, Design and Operation. Product Number I46090. 

May. 

4.1.4 What Types of Projects Involve Air Sparging for Oxygenates? 

From the 323 projects in EPA’s MtBE Treatment Profiles dataset, 123 projects were identified where 

MtBE was treated using air sparging alone or in conjunction with another technology. Information on the 

treatment of other fuel oxygenates during these 123 projects is limited; one project also reported TBA as a 

co-contaminant and another project reported TBA and ethanol as co-contaminants. 

Table 4.1-1 summarizes the scale and operational status for the 123 air sparging projects. The data used 

to compile this information was current at the time the profile for each project was compiled. It is 

possible that some projects shown as ongoing may now be completed. Short summaries for two projects, 

Air Sparging at Exxon and Mobil Service Stations in Smithtown, NY and Air Sparging at Eaddy Brothers 

Service Station in Hemingway, SC, are included at the end of this section, with additional information 

about all 123 projects provided in Appendix A. 

 4-4 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Table 4.1-1. General Information on 123 Air Sparging Projects 

Technology(ies) # of Projects Operational Status Scale 

Completed Ongoing Bench Pilot Full 

Air Sparging Only 13 3 10 0 1 12 

Air Sparging with SVE 74 2 72 0 0 74 

Air Sparging with Pump-andTreat 4 2 2 0 0 4 

Air Sparging with SVE and 

Pump-and-treat 

19 5 14 0 0 19 

Air Sparging with Multiple 

Technologies 

13 7 6 1 1 11 

TOTAL 123 19 104 1 2 120 

As shown in Table 4.1-1, most of the 123 air sparging projects were conducted at full scale (120 projects) 

and were ongoing (104 projects) at the time the profile was prepared. In addition, while most (87) of the 

projects used air sparging alone or in conjunction with SVE, 36 projects supplemented air sparging 

treatment with pump-and-treat or other technologies, such as MPE, bioremediation, free product recovery, 

and ISCO. 

The 123 air sparging projects primarily used vertical wells; three projects reported use of horizontal wells. 

For 69 projects for which information about the number of air sparging wells was available, 48 used 2 to 

8 wells per project, with a range of 1 to 30 wells. One project identified an ROI (27 ft). Three projects 

reported continuous airflow, two reported pulsed flow, and the remainder provided no information on the 

type of airflow. For the 74 projects that used air sparging with SVE, the number of SVE wells used 

ranged from 1 to 23 wells per project, with 30 projects in the range of 2 to 5 wells per project. Four of 

these 74 projects reported the type of air emission treatment used, with two reporting use of GAC, one of 

catalytic oxidation, and one of thermal oxidation. 

4.1.5 How Has Air Sparging Performed in Treating Oxygenates? 

The treatment performance data for 123 projects presented in Tables 4.1-2 and 4.1-3 show that air 

sparging (either alone or in combination with other technologies) has been used to reduce MtBE in 

groundwater from concentrations greater than 1,000,000 μg/L to less than 50 μg/L. The median project 

duration for the 19 completed sites ranged from 1 to 5 years. Although 2 of the 123 projects listed TBA 

as a co-contaminant, neither of these projects reported TBA concentrations before or after treatment; no 

data for other fuel oxygenates was reported. 

 4-5 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Table 4.1-2. Completed Air Sparging Projects - Performance Summary for 19 Projects 

Technology(ies) 

# of 

Projects 

Initial MtBE Concentration 1 

(μg/L) 

Final MtBE Concentration 1 

(μg/L) 

Median 

Project 

Duration 

Minimum Median Maximum Minimum Median Maximum (months) 

Air Sparging Only 3 230 1,600 62,000 5 27 980 18 

Air Sparging with 

SVE 

2 99 218 337 NR 57 

Air Sparging with 

Pump-and-Treat 

2 1,200 6,100 11,000 16 1,040 2,070 43 

Air Sparging with 

SVE and Pump-andTreat 

5 5 203 2,600 2 3 5 50 

Air Sparging with 

Multiple Technologies 

7 55 7,940 44,400 79 79 79 18 

Notes:

NR Information not provided 

1 Treatment performance data are based on the data provided by project managers and others in the source materials used to prepare the 

treatment profiles website, as shown in cluin.org/products/mtbe, and summarized in Appendix A. Appendix A shows the specific sites that 

are summarized here, along with technology design, operation, and performance data for each of the projects. 

2 Performance data are shown in terms of changes in concentration of MtBE in the groundwater, as provided in the reference materials and 

from the project contacts, except as noted. MtBE concentrations prior to beginning treatment (shown as “initial concentration”) and after 

treatment was completed (shown as “final concentration”) are provided. For projects where more than one technology was used, 

performance data are presented under each of the technologies used for the project. 

Table 4.1-3. Ongoing Air Sparging Projects B Performance Summary for 104 Sites 

MtBE Concentration Range 

# of Projects 

Reporting Initial 

MtBE 

Concentrations 

# of Projects with 

Last Reported 

MtBE 

Concentrations 

Greater than 100,000 μg/L 4 1 

Greater than or equal to 10,000 μg/L but 

less than 100,000 μg/L 

16 3 

Greater than or equal to 1,000 μg/L but 

less than 10,000 μg/L 

24 10 

Greater than or equal to 100 μg/L but 

less than 1,000 μg/L 

25 20 

Greater than or equal to 50 μg/L but 

less than 100 μg/L 

4 5 

Less than 50 μg/L 18 15 

4.1.6 What Costs Have Been Associated with Using Air Sparging in Treating MtBE? 

Project cost data were reported for 39 of the 123 air sparging projects in the dataset; these include data for 

both ongoing and completed projects. In most cases, the components that make up the project costs were 

not reported. However, other components, such as treatment, monitoring, design, oversight, and health & 

safety, may be included in the cost. Most (38 projects) of the reported costs were for ongoing projects 

and represent either a partial actual cost as of the time that the report was made or an estimated total 

project cost. 

 4-6 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

The median reported total cost for all air sparging projects was approximately $250,000, with most 

projects having a total cost between $100,000 and $350,000. For 7 of these projects that used air sparging 

alone, the total cost ranged from $20,000 to $345,000 per project. For the 17 projects that used air 

sparging with SVE, the total cost ranged from $27,000 to $1,051,000 per project. The total cost for 15 of 

the projects ranged from $96,000 to $672,000 per project. 

Because the area, volume, or mass treated was not consistently available for the 39 air sparging projects, 

no unit costs were calculated. The cost per volume of groundwater treated (identified as tons of saturated 

soil) was reported in one literature source as ranging from $20 to $50 per ton of saturated soil for air 

sparging in general (EPA, 1995). Another source identified the unit cost as $371,000 to $865,000 per 

hectare ($150,000 to $350,000 per acre) of groundwater plume treated for air sparging in general (FRTR, 

2002). The cost of air sparging generally is considered to be better than average, among the costs for 

remediation technologies, for treatment of contaminated groundwater (FRTR, 2002). Because of the 

relative airflow requirements necessitated by the lower Henry’s Law Constants of MtBE and other 

oxygenates, the unit costs for the remediation of sites contaminated with MtBE and other oxygenates 

could be at the upper end of these ranges. 

4.1.7 What Factors May Affect the Performance and Cost of Oxygenate Treatment Using Air 

Sparging? 

Because ether- and alcohol-based oxygenates exhibit different properties (specifically, Henry’s Law 

Constant) than other common fuel contaminants such as BTEX, their presence may affect the size and 

design of the air sparging system required to remediate the site and, as a result, the cost of remediation. 

Research has shown that the removal of MtBE (ether-based) requires 5 to 10 times more airflow than 

used for BTEX alone (Fields, et al., 2001). The other common ether-based oxygenates have higher 

Henry’s Law Constants than MtBE and are theoretically more amenable to treatment via air sparging 

(although still less amenable than BTEX components). The common alcohol-based oxygenates have 

Henry’s Law Constants two to three orders of magnitude lower than those of the ether-based oxygenates, 

and may theoretically require 100 to 1,000 times greater airflow. In practice, air sparging may not be 

feasible if high enough airflow rates cannot be achieved without causing unwanted subsurface fracturing 

or contaminant mobilization. However, the biodegradation potential of both ether- and alcohol-based 

oxygenates will also influence system design and may reduce the airflow and time required for 

remediation. 

In addition to the oxygenate-specific factors described above, additional variables may also affect the 

performance and cost of an air sparging system. These factors include the concentration, mass, and 

distribution of contaminants in the groundwater; subsurface geology and hydrogeology; cleanup goals; 

and requirements for site cleanup. For example, heterogeneity within the subsurface may result in 

preferential pathways that prevent injected air from contacting contaminated areas. These factors affect 

the number and spacing of air sparging wells, flow rates, and the length of time required for treatment, 

which typically will be determined during pilot testing. Air sparging also has potential to cause a lateral 

spread of dissolved or separate phase contaminant plumes. For example, in formations with laterallyoriented clays interbedded with sand, there is a possibility of spreading the contamination when using air 

sparging. 

 4-7 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

4.1.8 Conclusions 

Based on the information available from the air sparging MtBE treatment profiles, and other information 

contained in the reference documents reviewed in preparation of this report, the following conclusions 

may be made regarding the use of air sparging to remediate sites contaminated with MtBE and other 

oxygenates: 

Data from Air Sparging MtBE Treatment Profiles 

• Widely used to remediate groundwater contaminated with MtBE – it was employed at 123 of 323 

(38%) of projects in the dataset 

• Most often used alone or in conjunction with SVE (71% of air sparging profiles in dataset); to a 

lesser extent has been employed with pump-and-treat or other technologies 

• Employed to remediate MtBE in groundwater from concentrations greater than 1,000,000 μg/L to 

concentrations of less than 50 μg/L and has achieved MtBE concentration reductions greater than 

99 percent 

• Median project duration for different types of air sparging projects (including air sparging alone 

or in conjunction with SVE) ranged from 1 to 5 years 

• Median reported total cost was approximately $250,000, with most projects having a total cost 

between $100,000 and $350,000 

Treatability of MtBE and Other Oxygenates Using Air Sparging 

• Increased airflow (compared to a system employed to treat only BTEX) is required to physically 

strip common oxygenates using air sparging; based on their Henry’s Law Constants; ether-based 

oxygenates would require up to 10 times greater airflow and alcohol-based oxygenates would 

require 100 to 1,000 times greater airflow than the airflow required to physically strip the same 

mass of BTEX components 

• Air sparging often will promote further removal of oxygenates through biodegradation 

mechanisms (Refer to Section 4.4 – Bioremediation for more information) 

• The varied treatability of oxygenates in extracted vapors using off gas treatment technologies is 

an important design consideration if SVE is employed (Refer to Section 4.2 – Soil Vapor 

Extraction for more information) 

Other Potential Advantages of Applying Air Sparging (EPA, 1995; FRTR, 2002) 

• Generally considered to be easy to construct, operate, and maintain 

• Configurations can be designed to cause minimal disturbance to site operations 

• In some cases, such as areas of lower contaminant concentrations or in remote locations, 

contaminants stripped from the groundwater may be allowed to attenuate naturally in the vadose 

zone 

Other Potential Limitations to Applying Air Sparging (EPA, 1995; FRTR, 2002) 

• Often contaminants stripped from the groundwater must be extracted and treated aboveground 

using SVE 

• High airflow rates may result in unintended fracturing leading to non-uniform flow or shortcircuiting of injected air in the subsurface, or may result in unintended mobilization of 

contaminants as non-aqueous phase liquids (NAPL), dissolved in groundwater, or in soil gas 

• Has limited applicability at sites with confined aquifers and stratified layers; soil heterogeneities 

may limit effectiveness 

• Has potential to cause a lateral spread of dissolved or separate phase contaminant plumes 

 4-8 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

4.1.9 Example Projects 

Air Sparging at Exxon and Mobil Service Stations, Smithtown, NY 

A full-scale cleanup is being performed using air sparging, SVE, and groundwater pump-and-treat to prevent 

further off-site migration of MtBE, TBA, and BTEX in groundwater originating from two service stations in 

Smithtown, New York. The lithology of the site consists of fine to course grained sands with varying amounts 

of silt and fine gravel. At the Exxon service station, a 300-scfm air sparging system in conjunction with SVE 

was used to replace pump-and-treat remediation. Operation of the air sparging system began in April 2001, and 

was continuing to operate at the time when the profile for the project was updated (June 2003). Initial MtBE 

concentrations were 15,600 μg/L and initial TBA concentrations were 365 μg/L. The cleanup goal for MtBE is 

1,000 μg/L; progress toward meeting the cleanup goal was not reported (EPA, 2003). 

Air Sparging at Eaddy Brothers Service Station, Hemingway, SC 

A full-scale cleanup is being performed using air sparging and SVE to treat MtBE and other contaminants at a 

service station in Hemingway, South Carolina. Soil at the site consists of silty clays with clayey sand lenses. 

The SVE system consisted of 230 ft of horizontal SVE piping installed immediately below the asphalt parking 

lot surface of the site. Extracted vapors were treated using a thermal oxidizer. The air sparging system, which 

began operating two weeks after the SVE system was activated, consisted of 10 vertical sparging wells, each 

installed at a depth of 26 ft with 5 ft well screens. The wells were connected to an air sparge compressor 

operating at 68 to 70 pounds per square inch (psi). Site specific target levels (SSTLs) for this site ranged from 

5 to 80 μg/L per contaminant. As of June 2003, the maximum concentrations of MtBE and BTEX in the 

groundwater decreased, with the SSTLs being met for toluene, ethylbenzene, and xylenes. Maximum MtBE 

concentrations were reduced from more than 1,000,000 μg/L to 568 μg/L (a 99.99 % reduction), and maximum 

BTEX concentrations reduced to 9,690 μg/L. The cost for this application was $195,515 (EPA, 2003b). 

4.2 Soil Vapor Extraction 

Overview 

$ Application of a vacuum to soil to extract contaminated vapors 

$ EPA’s MtBE Treatment Profiles dataset includes use during 138 projects to 

treat MtBE or other oxygenates (used during additional projects as a 

component of SVE) 

$ Used to reduce concentration and mass of MtBE and other oxygenates in soil 

that may be a source of groundwater contamination 

$ Subsurface air flow may promote biodegradation of contaminants 

4.2.1 What is Soil Vapor Extraction? 

SVE is an in situ technology in which VOCs such as MtBE and other oxygenates are removed with soil 

vapor from the vadose zone. It involves the application of a vacuum to the soil to create a negative 

pressure gradient that induces subsurface vapor flow toward one or more extraction points. Soil vapors 

are collected from the extraction points and generally are captured and then treated with one or more 

aboveground treatment technologies prior to being discharged to the atmosphere. 

SVE is used to reduce the concentration and mass of MtBE and other oxygenates in the vadose zone, 

which reduces its potential to migrate as vapors into buildings or to act as a continuing source of 

groundwater contamination. SVE may also reduce groundwater contaminants through the enhanced 

evaporation of NAPL, volatilization of contaminants dissolved in pore water, and stimulation of 

biodegradation. SVE also is used as a component of air sparging or other systems to collect injected 

 4-9 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

gases that have stripped contaminants from groundwater. This section discusses SVE used for treatment 

of the vadose zone only. SVE used as a component of air sparging is discussed in Section 4.1. 

4.2.2 How Do the Properties of MtBE and Other Oxygenates Affect Treatment? 

In an SVE system, the primary mechanism for contaminant removal from the soil to the vadose zone is 

the volatilization of contaminants present in the pure or adsorbed phase onto soil into the vapor phase, as 

the vapor phase is continually extracted. The property that shows the extent to which this transfer can 

take place during SVE is vapor pressure, which provides an indication of the extent to which each 

contaminant will partition between the liquid phase and the vapor state at equilibrium conditions. 

Generally, a contaminant with a greater vapor pressure more readily volatilizes than one with a lesser 

vapor pressure. 

Figure 4.2-1 shows the vapor pressures, in units of millimeters of mercury (mm Hg), for the common fuel 

oxygenates as compared to BTEX. Generally, contaminants with vapor pressures greater than 10 mm Hg 

are considered to be amenable to treatment using SVE. As shown on the table, each of the common 

oxygenates have vapor pressures greater than 10 mm Hg, with ether-based oxygenates generally having 

greater vapor pressures than alcohol-based oxygenates. In addition, most of the common oxygenates 

(with the exceptions of TBA, TAME, and ethanol) have greater vapor pressures than BTEX, suggesting 

that they are more readily extracted using SVE than BTEX, which are commonly addressed with SVE. 

Figure 4.2-1. Ranges of Vapor Pressures for Common Fuel Oxygenates 

44 40 

149 

240 

130 

9.5 8.3

28.4 

76 

121.6 

56.5 

42 

256 

75 

0 

50 

100 

150 

200 

250 

300 

MtBE luene Ethyl Xylenes 

68.3 

95.2 

152 151 

ETBE TAME DIPE TBA Ethanol Methanol Benzene To benzene 

Vapor Pressure (mm Hg) 

ALCOHOL OXYGENATES 

ETHER OXYGENATES 

BTEX 

4.2.3 How is Soil Vapor Extraction Applied to Treat Oxygenates? 

During SVE, contaminated soil vapors are extracted by inducing a vacuum at one or more extraction 

points that are typically constructed as vertical vapor extraction wells. Horizontal extraction wells or 

trenches have also been employed as extraction points. In general, SVE is applied at depths ranging from 

10 to 50 ft bgs, but has been applied as deep as 300 ft bgs (EPA, 1995). Shallower applications typically 

 4-10 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

employ some manner of a surface seal to minimize short-circuiting of the system by ambient air. Typical 

flow rates for extracted soil vapors range from 60 to 700 cubic feet per minute (cfm). The vacuum 

pressures required at the top of the vapor extraction well (wellhead vacuum) to produce the desired vapor 

extraction rate typically range from 3 to 100 inches of water, and vary depending on soil permeability 

(FRTR, 2002; EPA, 1995). The ROI of an extraction well is used to determine the number and spacing of 

extraction wells. The ROI is the distance from an extraction well to the point at which a vacuum can be 

induced to enhance volatilization and extraction of contaminants from the soil. 

SVE is considered to be most effective in more homogeneous and higher permeability geologies because 

subsurface preferential pathways may result in short circuiting and tighter formations may minimize the 

radius of influence of extraction points. In general, vapor extraction points are designed and spaced to 

provide for a reduced pressure gradient throughout the contaminated zone. Remediation of MtBE and 

other oxygenates using SVE may also potentially benefit from aerobic conditions generated by subsurface 

air flow that may result in conditions that are amenable to in situ biodegradation of contaminants. At 

some sites, groundwater or free product extraction equipment may be incorporated into vapor extraction 

points. Extraction systems that incorporate the recovery of multiple phases are discussed in Section 4.3 

about multi-phase extraction and separate systems to recover these other phases are discussed in Section 

4.6 about groundwater pump-and-treat and Section 5.2 about product recovery. 

Extracted soil vapors, containing volatilized contaminants, are routed to an aboveground treatment system 

prior to being discharged to the atmosphere. The types of aboveground vapor treatment technologies that 

have been used for treating MtBE and other fuel oxygenates include the following (Symons and Greene, 

2003): 

• Adsorption – Processes in which vapor phase contaminants are adsorbed onto a medium, such as 

GAC or resin, as driven by equilibrium forces 

• Thermal Treatment – Processes in which vapor-phase contaminants are destroyed via hightemperature oxidation; primary categories of thermal treatment used to treat MtBE and other 

oxygenates include thermal oxidation, which employs a flame to generate the high temperatures 

needed to oxidize contaminants, and catalytic oxidation, which employs lower temperatures in the 

presence of a catalyst (typically platinum, palladium, or other metal oxide) to destroy 

contaminants 

• Biofilters – Processes in which contaminants are biodegraded in a fixed-film bioreactor, typically 

consisting of a bed of high surface area filter media, such as GAC, that acts as a support matrix 

for a thin film consisting of microbes that are acclimated to the biodegradation of MtBE or other 

contaminants 

The type of vapor treatment that is used will depend on factors such as the contaminant concentrations in 

the extracted vapors and the air emission discharge limitations for the site. Highly contaminated vapors at 

a site with stringent air emissions limitations may require a multi-step vapor treatment train, such as 

thermal oxidation followed by carbon adsorption. Less contaminated vapors at a site with less stringent 

air emissions limitation may require minimal or no vapor treatment. A significant amount of literature 

(some of which is listed as references at the end of this report) has been dedicated to the design of vapor 

treatment systems. Some of the key considerations for relevant to the treatment of MtBE and other 

oxygenates in extracted vapors are summarized below. 

 4-11 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Adsorption 

• Because of their equilibrium properties, MtBE and other oxygenates have a relatively low 

breakthrough concentration with bituminous coal-based GAC. Other, more preferentially 

adsorbed, contaminants in extracted vapor may reduce the capacity of GAC to remove MtBE and 

other oxygenates. In some cases, more absorbable contaminants may displace MtBE or other 

oxygenates that are already adsorbed. 

• Certain types of adsorption media have been shown to preferentially adsorb certain contaminants. 

For example, current research shows that, in some cases, coconut shell based GAC removes 

MtBE better than other GAC varieties (California MtBE Research Partnership, 1999). In 

addition, synthetic resins have been developed to preferentially adsorb some oxygenates, such as 

TBA, that are less absorbable by GAC. 

Thermal Treatment 

• As with the treatment of other contaminants, the presence of catalyst poisons, such as metals and 

other inorganics, in the vapor stream can reduce the effectiveness of catalytic oxidation. 

Biofilters 

• Biofiltration is a newer technology that has seen less frequent use, but becoming more popular for 

treating soil gas contaminated with MtBE and other oxygenates; currently they are used to treat 

relatively low concentrations of these contaminants 

One reference described the following rules of thumb for selecting vapor treatment (Fields and others, 

2001): 

• Thermal oxidation for VOC concentrations greater than about 2,000 parts per million by volume 

(ppmv) 

• Catalytic oxidation for VOC concentrations between about 100 and 2,000 ppmv 

• GAC treatment for VOC concentrations between about 35 and 100 ppmv 

• Direct discharge for VOC concentrations less than 35 ppmv 

More detailed information on the application of SVE at sites contaminated with MtBE and other 

oxygenates and in general is available in the following documents: 

• EPA. 2001. Development of Recommendations and Methods to Support Assessment of Soil 

Venting Performance and Closure. EPA 600-R-01-070. 

• Symons, Brian D., and J. Greene. 2003. Soil Vapor Extraction, Bioventing, and Air Sparging. 

In Moyer and Kostecki, Eds. 2003. MtBE Remediation Handbook. Amherst Scientific 

Publishers. 

• U. S. Army Corps of Engineers (USACE). 1995. USACE Engineering Manual: SVE and 

Bioventing. EM 1110-1-4001. 

 4-12 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

4.2.4 What Types of Projects Involved Soil Vapor Extraction to Treat Oxygenates? 

From the 323 projects listed in EPA’s MtBE Treatment Profiles dataset, 138 projects were identified 

where MtBE was treated using soil vapor extraction. Information on the treatment of oxygenates other 

than MtBE during these 138 projects is limited. Two projects reported treating these other oxygenates; 

one project reported TBA and one reported ethanol. 

Table 4.2-1 summarizes the scale and operational status for the 138 SVE projects. The data used to 

compile this information was current at the time the profile for each project was completed. Short 

summaries for two projects, SVE at Kansas Site U6-077-231, Atwood, KS and SVE at Creek & Davidson 

Site G: Service Station, CA, are included at the end of this section, with additional information about all 

138 projects provided in Appendix A. 

Table 4.2-1. General Information on 138 SVE Projects* 

Technology(ies) # of Projects 

Operational Status Scale 

Completed Ongoing Bench Pilot Full 

Soil Vapor Extraction Only 20 4 16 0 0 20 

Soil Vapor Extraction with Air 

Sparging 

74 2 72 0 0 74 

Soil Vapor Extraction with Air 

Sparging and Pump-and-Treat 

19 5 14 0 0 19 

Soil Vapor Extraction with 

Bioremediation 

1 0 1 0 0 1 

Soil Vapor Extraction with In 

Situ Chemical Oxidation 

2 1 1 0 0 2 

Soil Vapor Extraction with 

Multiple Technologies 

22 7 15 0 1 21 

TOTAL 138 19 119 0 1 137 

* Information about projects that used SVE with air sparging are discussed in Section 4.1. 

As shown in Table 4.2-1, most of the 138 SVE projects were full scale (137 projects) and were ongoing 

(119 projects) at the time that its profile was published. In addition, most of the projects used SVE in 

conjunction with air sparging (74), or SVE alone (20); the remaining projects supplemented SVE 

treatment with bioremediation, ISCO, pump-and-treat, or multiple technologies. 

The 138 SVE projects primarily used vertical wells; three projects used horizontal wells. For 23 projects 

for which information about the number of SVE wells was available, 20 used 2 to 8 wells per project, 

with an overall range of 1 to 16 wells. For the 74 projects that used air sparging with SVE, the number of 

SVE wells used ranged from 1 to 23 wells per project, with 30 projects in the range of 2 to 5 wells per 

project. Four of these 74 projects reported the type of air emission treatment used, with two reporting use 

of GAC, one of catalytic oxidation, and one of thermal oxidation. Eight of the SVE projects reported the 

types of aboveground treatment technologies that were employed to treat off gas containing MtBE and 

other oxygenates. For seven of these eight projects, thermal treatment was employed; six projects used 

catalytic oxidation and one project used thermal oxidation. One of the projects that used catalytic 

oxidation and one other project also used GAC adsorption to treat the SVE off gas. 

 4-13 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

4.2.5 How Has SVE Performed in Treating Oxygenates? 

Several approaches have been used to evaluate SVE performance for MtBE treatment, including 

analyzing the changes in MtBE concentrations in soil, soil vapor, or groundwater, or estimating the mass 

of contaminant removed. SVE is used to reduce the mass of contaminants that may leach or otherwise 

migrate from the vadose zone to the groundwater. This reduced leaching rate may result in lower 

concentrations of contaminants in groundwater, and the performance data provided here are for MtBE 

concentrations in groundwater (EPA, 2001b). 

The treatment performance data for 138 projects presented in Tables 4.2-2 and 4.2-3 show that SVE 

(either alone or in combination with other technologies) has been used to remediate MtBE in groundwater 

from concentrations greater than 100,000 μg/L to less than 50 μg/L and has achieved MtBE concentration 

reductions greater than 99 percent. The median project duration for the 19 completed sites ranged from 3 

months to 5 years. Table 4.2-2 provides a summary of specific projects with performance data for one or 

more projects. SVE with pump-and-treat had one completed project, however, no performance data was 

reported and therefore was not included in the table below. 

Table 4.2-2. Performance Summary for 19 Completed SVE Projects 

Technology(ies) 

# of 

Projects 

Initial MtBE Concentration 1 

(μg/L) 

Final MtBE Concentration 1 

(μg/L) 

Median 

Project 

Duration 

Minimum Median Maximum Minimum Median Maximum (months) 

Soil Vapor 

Extraction Only 

4 48 6,900 8,900 21 1,800 3,200 24 

Soil Vapor 2 99 218 337 NR 57 

Extraction with Air 

Sparging 

Soil Vapor 5 5 203 2,600 2 3 5 22 

Extraction with Air 

Sparging and Pumpand-Treat 

Soil Vapor 1 17,000 31 9 

Extraction with In 

Situ Chemical 

Oxidation 

Soil Vapor 7 4,151 10,800 44,400 NR 12 

Extraction with 

Multiple 

Technologies 

Notes:

NR Information not provided 

1 Treatment performance data are based on the data provided by project managers and others in the source materials used to prepare the 

treatment profiles website, as shown in cluin.org/products/mtbe, and summarized in Appendix A. Appendix A shows the specific sites that 

are summarized here, along with technology design, operation, and performance data for each of the projects. 

2 Performance data are shown in terms of changes in concentration of MtBE in the groundwater, as provided in the reference materials and 

from the project contacts, except as noted. MtBE concentrations prior to beginning treatment (shown as “initial concentration”) and after 

treatment was completed (shown as “final concentration”) are provided. For projects where more than one technology was used, 

performance data are presented under each of the technologies used for the project. 

 4-14 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Table 4.2-3. Performance Summary for 119 Ongoing SVE Projects 

MtBE Concentration Range 

# of Projects 

Reporting Initial 

MtBE 

Concentrations 

# of Projects with 

Last Reported 

MtBE 

Concentrations 

Greater than 100,000 μg/L 7 1 

Greater than or equal to 10,000 μg/L but 

less than 100,000 μg/L 

18 4 

Greater than or equal to 1,000 μg/L but 

less than 10,000 μg/L 

26 10 

Greater than or equal to 100 μg/L but 

less than 1,000 μg/L 

29 21 

Greater than or equal to 50 μg/L but 

less than 100 μg/L 

6 7 

Less than 50 μg/L 20 22 

4.2.6 What Costs Have Been Associated with Using SVE in Treating MtBE? 

Project cost data were reported for 24 of the 138 SVE projects in the dataset; these include data for both 

ongoing and completed projects. In most cases, the components that make up the project costs were not 

reported. However, it is likely that these incorporate different components, such as treatment, monitoring, 

design, oversight, and health & safety. Twenty two of these projects reported were ongoing; therefore 

costs represent either a partial actual cost as of the time that the report was made or an estimated total 

project cost. 

The median reported total cost for all SVE projects was approximately $206,000, with most projects 

having a total cost between $100,000 and $400,000. 

The unit cost of SVE was reported in one literature source as ranging from $10 to $40 per cubic yard of 

soil treated. This source identified the cost of SVE as generally better than average among the costs for 

remediation technologies for treatment of contaminated soil (FRTR, 2002). 

In another source, the unit cost of SVE ranged from $60 to nearly $350 per cubic yard of soil for projects 

treating less than 10,000 cubic yards of soil, to less than $5 per cubic yards for projects treating more than 

10,000 cubic yards of soil. This source also identified the unit cost as ranging from $300 to more than 

$10,000 per pound of contaminant removed for projects where up to 3,000 pounds of contaminant mass 

were removed, to less than $15 per pound removed for projects where larger quantities were removed 

(EPA, 2001c). These unit cost ranges represent treatment costs for use of SVE in general, and are not 

specific to its use for treatment of MtBE. 

4.2.7 What Factors May Affect the Performance and Cost of Oxygenate Treatment using SVE? 

Key factors that affect the performance and cost of a SVE system include: the concentration, mass, and 

distribution of contaminants in the soil; geology and heterogeneity of the subsurface; cleanup goals; and 

requirements for discharging emissions to the atmosphere. These factors affect the number of vapor 

extraction wells, vacuum level required, type of off-gas treatment, and length of time required for 

treatment (FRTR, 2002). 

 4-15 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

4.2.8 Conclusions 

Based on the information available from the SVE project MtBE treatment profiles and other information 

contained in the reference documents reviewed in preparation of this report, the following conclusions 

were identified regarding the use of SVE to remediate sites contaminated with MtBE and other 

oxygenates. 

Data from SVE MtBE Treatment Profiles 

• Has been used to remediate soil and groundwater contaminated with MtBE – it was employed at 

138 of 323 (38%) of projects in the dataset; of these, SVE was used at 74 projects in conjunction 

with air sparging 

• For projects without air sparging, has been used to remediate MtBE in groundwater from

concentrations greater than 100,000 μg/L to less than 50 μg/L and has achieved MtBE 

concentration reductions greater than 99 percent 

• Median project duration for different categories of projects (for example, SVE alone, SVE with 

pump-and-treat, etc.) ranged from 3 months to 5 years 

• Median reported total cost was approximately $206,000, with most projects having a total cost 

between $100,000 and $400,000 

Treatability of MtBE and Other Oxygenates Using SVE 

• All of the common oxygenates have vapor pressures that are greater than 10 mm Hg and are 

amenable to treatment using SVE, with ether-based oxygenates generally having greater vapor 

pressures than alcohol-based oxygenates 

• GAC adsorption may be less effective than other thermal treatment in removing alcohol-based 

oxygenates from SVE off gas 

Other Potential Advantages of Applying SVE (EPA, 1995; FRTR, 2002) 

• Removal of MtBE from soil generally is considered to be more cost-effective than removal of 

MtBE that has dissolved in the groundwater (EPA, 1995; FRTR, 2002). 

• Reduces the potential for MtBE to migrate as vapors into buildings or leach to the groundwater 

• Is relatively low cost compared with other remediation technologies 

• Causes minimal disturbance to site operations 

Other Potential Limitations to Applying SVE (EPA, 1995; FRTR, 2002) 

• Low soil permeability may limit vapor movement through the soil, reducing SVE effectiveness 

• At heterogeneous sites, contaminants may be difficult to extract from low permeability layers 

(soil vapors may be collected mainly from higher permeability layers, while contaminants may be 

present in lower permeability layers) 

• Shallow depths to groundwater or fluctuations in the groundwater table can cause upwelling and 

interference with airflow 

• May not be capable of reaching very stringent soil cleanup levels (soil concentrations may reach 

an asymptotic level that is higher than the cleanup level) 

 4-16 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

4.2.9 Example Projects 

SVE at Kansas Site U6-077-231, Atwood, KS 

A full scale cleanup was performed using SVE to treat MtBE from a UST site in Atwood, Kansas. Soil at the 

site consists of 1 to 18 ft of silt and clay overlying 18 to 50 ft of sand and gravel. The SVE system consisted of 

8 vapor extraction wells, installed to a depth of 12 ft bgs. Operation of the SVE system began in February 1994 

and the system is currently operational. As of June 2003, the concentration of MtBE in the groundwater has 

been reduced from 480 :g/L to 93 :g/L (an 80% reduction). The most recent cost data available depicts a total 

remediation cost of $298,040 (EPA. 2002a). 

SVE at Creek & Davidson Site G: Service Station, CA 

A full-scale cleanup was performed using SVE to treat MtBE and benzene from a UST leak at a service station 

in California. Soil at the site consists of 10 ft of clay overlying sand and gravel. The SVE system consisted of 

5 vapor extraction wells and a 700 cfm vacuum system. Thermal oxidation was used for off-gas treatment. 

After 2.2 years of SVE operation, the concentration of MtBE in the groundwater (measured in 11 monitoring 

wells) was reduced from as high as 8,900 :g/L to 21 :g/L and the concentration of benzene was reduced from 

670 :g/L to 0.5 :g/L (both more than 99% reductions). The thermal oxidizer destroyed greater than 95% of the 

VOCs in the off gases, and remediation at the site is reported to be complete. As of June 2003, the cost data 

available depicts a total remediation cost $140,000 (EPA. 2002a). 

4.3 Multi-Phase Extraction 

Overview 

$ Uses a combination of SVE and groundwater pump-and-treat to extract 

MtBE in soil vapor and groundwater, simultaneously 

$ EPA’s MtBE Treatment Profiles dataset included use at 13 sites to treat 

MtBE 

$ Is most applicable to fine-grained formations in the fine sand to silty sand 

range 

4.3.1 What is Multi-Phase Extraction? 

MPE is a generic term for technologies that extract VOCs such as MtBE and other fuel oxygenates from 

the subsurface in soil vapor and groundwater, simultaneously. In addition, it can be used to remove free 

product or other NAPLs. MPE is referred to by several other names in the technical literature. Examples 

of terms referring to MPE and its configurations are dual-phase extraction (DPE), two-phase extraction 

(TPE), and vapor extraction/groundwater extraction (VE/GE). In general, all of these configurations 

couple SVE with groundwater (and in some cases NAPL) extraction and employ some form of 

aboveground water and vapor treatment technologies (EPA, 1999a; FRTR, 2002). Groundwater pumpand-treat and aboveground water treatment technologies are discussed in more detail in Section 4.6 and 

SVE and aboveground vapor treatment are discussed in more detail in Section 4.2. 

4.3.2 How Do the Properties of MtBE and Other Oxygenates Affect Treatment? 

The primary removal mechanisms for MPE are volatilization with subsequent air advection for the vapor 

phase and dissolution and aqueous advection in groundwater. Vapor pressure, solubility, and 

organic/water partition coefficient are the primary properties of MtBE and other oxygenates that 

correspond to these removal mechanisms. In general, contaminants with higher solubility and vapor 

pressure and lower partition coefficients, such as fuel oxygenates, are more appropriate for removal using 

MPE than BTEX. As shown on Table 4.3-1, the properties of both ether- and alcohol-based oxygenates 

suggest that they may be more favorably removed from the subsurface by the vapor and groundwater 

 4-17 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

extraction components of MPE than BTEX constituents. One exception to this generalization is that 

certain alcohol-based oxygenates, specifically TBA and ethanol, may be less readily removed in the vapor 

phase because of their relatively low vapor pressures. 

MPE provides several advantages when compared with use of SVE or pump-and-treat alone. MPE 

provides for an increase in groundwater recovery rates, an increase in radius of influence in individual 

groundwater recovery wells, and recovery of shallow free product. By depressing the groundwater table 

in the vicinity of the extraction wells, MPE provides for remediation of the capillary fringe and smear 

zone, and remediation of volatile, residual contaminants located above and below the water table (EPA, 

1999a). 

However, while the contaminant properties are important considerations in the selection and design of an 

MPE system for a given site, the applicability of MPE is more dependent on media properties, primarily 

hydraulic conductivity (K), transmissivity, depth to water table, and soil moisture (EPA, 1999a). 

Table 4.3-1. Contaminant Properties Relevant to MPE 

Contaminant Category Solubility into H2O from 

Gasoline Range (mg/L) 

Vapor Pressure Range 

(mm Hg) 

Partition Coefficient 

(log l/kg) 

BTEX Constituents 3 – 100 8 – 95 1.5 – 3.2 

Ether-Based Oxygenates 

(such as MtBE) 750 – 5,500 68 – 250 1.0 – 2.2 

Alcohol-Based Oxygenates 

(such as TBA) > 25,000 40 – 120 0.2 – 1.6 

Source: Based on information in Table 2-2. 

4.3.3 How is MPE Applied to Treat Oxygenates? 

MPE can be implemented in a variety of configurations, including single pump, two pump, and 

bioslurping. In the single pump configuration, a single drop tube is employed to extract both liquid and 

vapor from a single well. The vacuum and liquid suction lift is achieved by one vacuum pump (liquidring pumps, jet pumps, and blowers are typical). In the two-pump configuration, a submersible pump is 

used for groundwater recovery in conjunction with a separate vacuum applied at the sealed wellhead. In 

this configuration, liquid and vapor streams are separate from one another. Depending on application, 

two-pump systems can use electric or pneumatic submersible pumps for groundwater recovery and liquid 

ring pumps or blowers to induce vacuum. Applications that recover free product or LNAPL typically use 

pneumatic submersible pumps for liquid recovery. Bioslurping uses the same configuration as for a 

single pump system, however the drop tube is set at, or just below, the liquid-air interface. The extraction 

point alternates from recovering liquid to air, emanating a slurping sound. This configuration has been 

effective in free product recovery, and also enhances in situ aerobic bioremediation, due to the increased 

airflow. 

In some configurations, the vacuum used in MPE increases the effective drawdown of groundwater (i.e., 

increase or lower the depth to groundwater table) locally near the pumped well. This has the affect of 

increasing exposed soil in the saturated zone and the removal of volatile contaminants located above and 

below the original water table. 

Extracted vapors and liquids commonly are treated aboveground. The types of technologies used for 

aboveground treatment are similar to those used for SVE and groundwater pump-and-treat, respectively, 

and are discussed further under those technologies. 

 4-18 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

More detailed information relevant to the application of MPE at sites in general or contaminated with 

MtBE and other oxygenates is available in the following documents: 

• U.S. Army Corps of Engineers. 1999. Engineering and Design: Multi-Phase Extraction (EM 

1110-1-4010). June 1. http://www.usace.army.mil/inet/usace-docs/eng-manuals/em1110-1-4010/ 

• U.S. Environmental Protection Agency. 1999. Multi-Phase Extraction: State of the Practice. 

Office of Solid Waste and Emergency Response. June. 

http://cluin.org/download/remed/mpe2.pdf 

• U.S. Environmental Protection Agency. 1997. Presumptive Remedy: Supplemental Bulletin, 

Multi-Phase Extraction Technology for VOCs in Soil and Groundwater. Office of Solid Waste 

and Emergency Response. April. http://clu-in.org/download/toolkit/finalapr.pdf 

4.3.4 What Types of Projects Involve MPE for Treating Oxygenates? 

From the 323 projects in EPA’s MtBE Treatment Profiles dataset, 13 projects were identified where 

MtBE was treated using MPE. Information on the treatment of other oxygenates during these 13 projects 

is limited; no projects reported treating other oxygenates. Table 4.3-2 summarizes the scale and 

operational status for the 13 MPE projects. The data used to compile this information was current at the 

time the profile for each project was completed. Short summaries for two projects, MPE at Service 

Station A, MD, and MPE at Sparks Solvent/Fuel Site, Sparks, NV, are included at the end of this section, 

with additional information about all 13 projects provided in Appendix A. 

Table 4.3-2. General Information on 13 MPE Projects 

Technology(ies) # of Projects 

Operational Status Scale 

Completed Ongoing Bench Pilot Full 

Multi-Phase Extraction Only 9 3 6 0 4 5 

Multi-Phase Extraction with 

Air Sparging 

2 1 1 0 0 2 

Multiple Phase Extraction with 

In situ Chemical Oxidation 

2 0 2 0 0 2 

TOTAL 13 4 9 0 4 9 

As shown in Table 4.3-2, most of the 13 MPE projects were full-scale (9 projects) and were on-going (9 

projects) at the time that its profile was published. Most of the projects (9) used multi-phase extraction 

only; the remaining 4 projects supplemented MPE with air sparging (2 projects) and ISCO (2 projects). 

Five of the projects (4 pilot scale and 1 full scale) used the Bubblex system, a patented method that 

simultaneously extracts vapor and water using a high vacuum. One full-scale project used a VE/GE 

system (used at 8 sites), and 1 full-scale project used total fluid extraction with advanced oxidation 

technology. The VE/GE systems used 4 to 17 VE wells, with average airflow rates ranging from 4.6 to 

18.5 scfm, and 2 to 8 GE wells, with pumping rates ranging from 0.11 to 0.67 gpm. 

As another example, a site in Fountain Valley, CA had an air sparge/SVE system installed which 

appeared to remediating a BTEX plume with the exception of one recalcitrant area. However, an 

MTBE/TBA plume developed which did not appear to be affected by the operation of the air sparge/SVE 

system. MTBE was reduced but the TBA concentration was found to be increasing. After conducting 

feasibility tests, a dual-phase extraction (MPE) system to remove and treat ground is being installed 

(O'Connell, 2004). 

 4-19 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

4.3.5 How Has MPE Performed in Treating Oxygenates? 

For the 13 projects identified from 323 MtBE treatment profiles, MPE treated MtBE with concentrations 

as high as 100,000 μg/L (JFK International Airport, Jamaica City, NY) and achieved as low as 50 μg/L in 

groundwater after treatment. None of the 13 projects listed TBA as a contaminant. Therefore, this 

section only highlights performance for MtBE. 

Tables 4.3-3 and 4.3-4 summarize performance data for 3 completed and 7 ongoing MPE projects. 

Because the dataset included relatively few completed projects with performance data, Table 4.3-3 

provides a summary of specific projects instead of a summary of minimum, median, and maximum 

concentrations. The reason for the increase in the MtBE concentration at the Tahoe Boat Company, CA 

site was not specified. 

Table 4.3-3. Completed MPE Projects - Performance Summary for 3 Projects 

Technology(ies) Site Name and Location Scale 

Initial MtBE 

Concentration 1 

(μg/L) 

Final MtBE 

Concentration 1 

(μg/L) 

Median 

Project 

Duration 

(months) 

Multi-Phase 

Extraction Only 

Site CA – X, Lawndale, CA Pilot 11 NR NR 

Multi-Phase 

Extraction Only 

Eight Service Stations MD – A, 

MD 

Full 6,140 791 NR 

Multi-Phase 

Extraction with Air 

Sparging 

Tahoe Boat Company, Lake 

Tahoe, CA 

Full 55 79 45 

Notes:

NR Information not provided 

1 Treatment performance data are based on the data provided by project managers and others in the source materials used to prepare the 

treatment profiles website, as shown in cluin.org/products/mtbe, and summarized in Appendix A. Appendix A shows the specific sites that 

are summarized here, along with technology design, operation, and performance data for each of the projects. 

2 Performance data are shown in terms of changes in concentration of MtBE in the groundwater, as provided in the reference materials and 

from the project contacts, except as noted. MtBE concentrations prior to beginning treatment (shown as “initial concentration”) and after 

treatment was completed (shown as “final concentration”) are provided. For projects where more than one technology was used, 

performance data are presented under each of the technologies used for the project. 

Table 4.3-4. Ongoing MPE Projects - Performance Summary for 7 Sites 

MtBE Concentration Range 

# of Projects 

Reporting Initial 

MtBE 

Concentrations 

# of Projects with 

Last Reported 

MtBE 

Concentrations 

Greater than or equal to 10,000 μg/L but 

less than 100,000 μg/L 

1 0 

Greater than or equal to 1,000 μg/L but 

less than 10,000 μg/L 

1 2 

Greater than or equal to 100 μg/L but 

less than 1,000 μg/L 

2 0 

Greater than or equal to 50 μg/L but less 

than 100 μg/L 

0 1 

Less than 50 μg/L 0 1 

Note: 

Performance data were not available for some sites 

 4-20 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

4.3.6 What Costs Have Been Associated with Using MPE in Treating MtBE? 

The total project cost was reported for 2 of the 13 MPE projects identified above. The completed Kings 

Beach Swiss Mart, CA project, which employed MPE alone, reported a total project cost of $130,000 and 

the completed Tahoe Boat Company, CA project, which employed MPE with air sparging, reported a 

total project cost of $383,000. Both of these total costs were the amounts reported by the state cleanup 

fund. Because the area, volume, or mass treated was not available for this project, a unit cost was not 

calculated. 

Little additional information was identified in the literature about the costs of using MPE for the treatment 

of MtBE and other oxygenates, or for other contaminants. The cost per volume of subsurface treated 

(identified as cubic yards of subsurface) was reported in one literature source as ranging from $36 to $170 

per cubic yard for sites contaminated with chlorinated solvents (EPA, 1999a). The cost of MPE generally 

is considered to be average, among the costs for remediation technologies, for treatment of contaminated 

groundwater (FRTR, 2002). However, project costs will likely be driven primarily by the aboveground 

treatment required. The cost of aboveground water treatment technologies is discussed in Section 4.6; the 

cost for aboveground vapor treatment is discussed in Section 4.2. 

4.3.7 What Factors May Affect the Performance and Cost of Oxygenate Treatment using 

MPE? 

When MtBE or other oxygenates are present and must be remediated at a site, MPE, either alone or in 

combination with other technologies, may be a suitable remediation approach. MPE affects mass removal 

by volatilization, dissolution, and advective transport. In general, if both SVE and groundwater pumpand-treat are potentially applicable technologies, then MPE may be considered as a remedial alternative. 

The performance of MPE is governed, primarily, by media properties and, to a lesser extent, by 

contaminant properties. MPE is most applicable to fine-grained formations in the fine sand to silty sand 

range (K = 10-3 to 10-5 centimeters per second) with low transmissivity (less than 200 gallons per day per 

foot). 

A typical result of conventional pumping in low conductivity and transmissivity formations is increased, 

and sometimes rapid, drawdown with steep gradients, with corresponding low recovery rates. This 

condition limits the influence of the conventional pumping well. MPE overcomes this limiting factor 

with the application of a vacuum. The vacuum enhancement of MPE also can overcome the capillary 

forces that can trap contaminants within the capillary zone. This allows better recovery of LNAPL, which 

tends to accumulate in the capillary zone at the air-water interface. 

In addition to the technology-specific factors described above, additional factors may also affect the 

performance and cost of any MPE system. These factors include: 

• The concentration, mass, and distribution of contaminants in the soil and groundwater 

• Geology, hydrogeology, and heterogeneity of the subsurface; cleanup goals 

• Requirements for air emissions and water discharges 

These factors affect the number and type of extraction wells, vacuum level, pumping rate, type of 

aboveground water and off-gas treatments, and length of time required for treatment (FRTR, 2002). More 

information about the factors that influence the performance and cost of air sparging systems in general is 

available in the references listed in this report. 

 4-21 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

4.3.8 Conclusions 

Based on the information available from the MPE project MtBE treatment profiles and other information 

contained in the reference documents reviewed in preparation of this report, the following conclusions 

were identified regarding the use of MPE to remediate sites contaminated with MtBE and other 

oxygenates. 

Data from MPE MtBE Treatment Profiles 

• Has been used to remediate groundwater contaminated with MtBE, but less frequently than some 

other technologies, such as air sparging and bioremediation – it was employed at 13 of the 323 

(4%) of the projects in the dataset 

• Most often used without in situ technologies (70% of projects in dataset); to a lesser extent has 

been employed in conjunction with air sparging or ISCO 

• Has been used to remediate MtBE in groundwater from concentrations greater than 100,000 μg/L 

to less than 50 μg/L and has achieved MtBE concentration reductions greater than 99 percent 

• Cost information is limited – total costs for two project in dataset were $130,000 and $383,000 

Treatability of MtBE and Other Oxygenates Using MPE 

• While the contaminant properties are important considerations in the selection and design of an 

MPE system for a given site, the applicability of MPE is more dependent on media properties, 

primarily hydraulic conductivity and transmissivity (EPA, 1999a). 

Other Potential Advantages of Applying MPE (EPA, 1999a) 

• Has potential for increase in groundwater recovery rates, compared to conventional pumping 

practices in equivalent settings 

• Has potential for increase in radius of influence of individual groundwater recovery wells 

• Has potential for recovery of free product or other LNAPL 

• Has potential for remediation of the capillary fringe and smear zone 

• Simultaneous remediation of soil vapors and groundwater 

• Effective on lower permeability soil sites 

Other Potential Limitations of Applying MPE (EPA, 1999a) 

• Potentially greater aboveground treatment requirements as a result of NAPL emulsions and VOCladen vapors 

• Initial start-up methods and adjustment period may be longer, compared to conventional practices 

• Potentially higher capital costs compared to conventional pumping approaches 

• Depth limitations to some MPE configurations 

4.3.9 Example Projects 

MPE at a Service Station MD-A, MD 

At a service station in Maryland, MPE was conducted using a VE/GE system that consisted of 10 VE wells and 

6 GE wells. The sites were located on coastal plain, and the soil consisted of sandy silts and clays. The average 

flow rates were 9.8 scfm in the VE wells and 0.24 gpm for the GE wells. The concentration of MtBE in 

groundwater was reduced from 27,027 μg/L to 32 μg/L over 3.5 years of system operation. The cleanup was 

reported as completed, however a cleanup goal was not provided (EPA, 2000c). 

 4-22 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

MPE at Sparks Solvent/Fuel Site, Sparks NV 

Since 1995, the Sparks Solvent/Fuel Site located in Sparks, Nevada, a remediation system consisting of MPE, 

air sparging, and SVE has been operational. The treatment system consists of 29 MPE wells, an oil-water 

separator, and a fluidized bed bioreactor, with an influent flow rate of 370 gpm and a retention time of 8 

minutes. Vapors are sent through a condenser, followed by a thermal oxidizer, before release to the 

atmosphere. Condensate is sent back through the oil-water separator. Performance data, available for the first 

650 days of site operation, showed a reduction in MtBE concentration across the bioreactor from 2,400 to 55 

μg/L. No data was provided for reduction of MtBE concentrations in the aquifer (EPA, 2000b). 

4.4 In Situ Bioremediation 

$ 

$ 

$ 

Overview 

Enhances the mechanisms that biologically degrade MtBE and other 

oxygenates in contaminated soil and groundwater 

EPA’s MtBE Treatment Profiles dataset includes use at 73 sites to treat 

MtBE; 12 of these sites also reported treating TBA 

Typically used to treat residual soil and groundwater contamination after 

contaminant source has been removed 

4.4.1 What is Bioremediation? 

Bioremediation is a process by which microorganisms, fungi, and plants metabolize pollutant chemicals. 

It has been used to treat oxygenates in soil and groundwater both in situ and ex situ. Generally, an 

engineered bioremediation system stimulates the biodegradation of contaminants through the introduction 

of electron acceptors (typically oxygen), electron donors (substrates or food sources), nutrients, or 

microbes that are acclimated to the contaminated soil or groundwater. These amendments are either 

introduced to the subsurface in situ or are added to extracted groundwater or excavated soil. A 

description of the various types of amendments is provided below (Wilson, 2003c). 

Amendments 

• Electron Acceptors – Oxygen is the most common electron acceptor used to promote 

biodegradation and is added in different ways including: in sparged air, through injection of a 

solid or liquid that generates oxygen, or through in situ electrochemical generation. Other 

electron acceptors, including nitrate, sulfate, and iron (III) compounds, may be added to support 

anaerobic biodegradation. 

• Electron Donors – In direct biodegradation pathways, the contaminant acts as the electron donor 

or substrate. However, during cometabolic degradation, a different electron donor is metabolized, 

resulting in the consequential oxidation of the contaminant. In some contaminated plumes, other 

electron donors, such as other constituents of gasoline, may also be present. In cases where they 

are not, and cometabolic degradation pathways are desired, electron donors may be added. 

• Nutrients – Nutrients, such as nitrogen and phosphorus and other trace elements, are necessary 

for cell growth because they are key biological building blocks. Addition of nutrients as a 

supplement helps ensure that concentrations of nutrients do not become a limiting factor for 

bioremediation. 

• Bioaugmentation – involves the addition of supplemental microbes to the subsurface where 

organisms able to degrade specific contaminants are deficient. Microbes may be grown from 

populations already present at a site or “seeded” from cultures grown in aboveground reactors or 

available commercially as cultivated strains of bacteria known to degrade specific contaminants. 

The application of bioaugmentation technology is highly site-specific and dependent on the 

microbial ecology and physiology of the subsurface (EPA, 1998b). 

 4-23 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

This section focuses on engineered in situ remediation technologies that use microorganisms to 

biodegrade pollutant chemicals. In situ bioremediation technologies are configured to either directly 

inject supplements into the contaminated media; to place the supplements in the pathway of groundwater 

flow; or to extract contaminated groundwater, amend it with supplements, and recirculate the amended 

groundwater through the contaminated zone (further information about groundwater extraction is 

provided in Section 4.6 about pump-and-treat). EPA policy regarding injection of supplements is 

discussed in Section 3.4. Some of the key considerations for various types of engineered in situ 

remediation systems are summarized below (EPA, 1998b). A discussion of ex situ applications of 

bioremediation, which focuses on biological treatment of extracted groundwater, is included in Section 

4.7 about treatment of extracted groundwater. 

Engineered Systems 

• Direct Injection Wells/Trenches – In a direct injection system, degradation is enhanced through 

the addition of microbes, nutrients, electron acceptors, or electron donors directly into the aquifer 

at injection points or directly into the soil. Direct injection technologies include those that 

employ injection wells or trenches through which supplements are introduced. Some common 

direct injection technologies use chemical or electrochemical means to increase the level of 

oxygen in the groundwater, or inject microorganisms that are specifically conditioned to 

degrading the contaminants of concern. The natural flow of the groundwater generally is not 

impeded, but is monitored to determine that the degradation of the contaminants and their 

daughter products is completed within an acceptable distance from the source. 

• Recirculation Systems – A recirculation system extracts contaminated groundwater from the 

site, adds to or amends the extracted water ex situ, and reinjects the “activated” water to the 

subsurface, generally upgradient of the contaminated zone. As an alternative, extraction and 

injection are performed at different elevations in a single well, creating vertical circulation. A 

groundwater recirculation configuration may be used to provide containment of a plume or to 

allow the addition of amendments in a more controlled environment. 

• Permeable Reactive Barriers – The placement of supplements in the pathway of groundwater 

flow constitutes a PRB, sometimes referred to as a treatment zone or “bio-barrier”. With a PRB 

approach, an active bioremediation zone is created by such methods as backfilling a trench with 

nutrient-, oxidant-, or reductant-rich materials, or by creating a curtain of active bioremediation 

zone through direct injection or groundwater recirculation at the toe of a plume. PRBs contain a 

contaminant plume by treating only groundwater that passes through it. 

The design and configuration of in situ bioremediation systems varies widely based on site-specific 

conditions. A treatability study or pilot-scale testing is often performed to determine the type and amount 

of amendments required to create and maintain the conditions optimal for biodegradation as well as to 

select the type of engineered system that is most suitable to introduce the amendments to the subsurface 

(EPA, 2000a). 

4.4.2 How Do the Properties of MtBE and Other Oxygenates Affect Treatment? 

Early studies on MtBE contamination of groundwater concluded that the compound was either nonbiodegradable or very resistant to biodegradation. However, more recent research has shown that MtBE 

can be degraded both aerobically and anaerobically, although anaerobic intrinsic degradation rates are 

relatively slow. The research has found that there are naturally occurring microbes capable of using 

MtBE as their sole carbon and energy source. Such microorganisms seem to be widespread, but are 

present natively in low numbers and take time to reach a sufficiently dense population to sustain MtBE 

degradation. As a result, cometabolic approaches are often considered for MtBE bioremediation, wherein 

an organic substrate (electron donor) that is readily degraded is added to the subsurface, resulting in the 

 4-24 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

consequential oxidation of MtBE. Because the ability of microorganisms to cometabolically degrade 

MtBE is consistently found in strains that are predisposed to catabolize structural analogs of MtBE, 

suitable co-substrates include simple branched and even non-branched alkanes such as propane and 

butane (Wilson, 2003a; Bradley, 2001; Vance, 2003; Hyman, 2000; Steffan et al, 1997). 

Although detailed comparative evaluations of the aerobic degradation rates of other fuel oxygenates have 

not been performed to date, the aerobic biodegradation rates of TAME, EtBE, DIPE, TBA, and TAA 

were observed to be of the same order of magnitude as the aerobic degradation rate of MtBE in one 

research study using a mixed culture (Church and Tratnyek, 2000). Together with the similarity of 

product chemical structure, these results suggest that the same or similar enzyme systems and pathways 

are responsible for the biodegradation of these oxygenates (see Figure 4.4-1 below) and that the 

bioremediation of fuel oxygenates other than MtBE therefore has similar constraints (EPA 2001a). 

Figure 4.4-1. Proposed Degradation Pathway of MtBE and Other Oxygenates 

(Church and Tratnyek, 2000) 

Successful field-scale applications of engineered bioremediation systems have been limited to the aerobic 

pathway, as opposed to the anaerobic pathway. The advantages of the aerobic pathway include: 

• More energy is derived by microorganisms from the aerobic metabolism of MtBE and other fuel 

oxygenates; consequently, MtBE degrading cultures grow more quickly under aerobic conditions 

• There are a number of aerobes that are known to use MtBE as a sole carbon and energy source; 

anaerobic pathways and the types of microorganisms involved are less well documented 

• Where the terminal electron acceptor is not present initially in sufficient quantity, addition of 

oxygen for aerobic bioremediation can be as simple as bubbling air into the aquifer; addition of 

electron acceptors for anaerobic bioremediation is more complex and can foster concerns 

regarding the toxicity and fate of the added material 

• Laboratory studies have provided inconsistent results regarding the degree to which MtBE is 

biodegraded anaerobically to end products and the extent to which other oxygenates are 

biodegraded under anaerobic conditions 

 4-25 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

However, the many pathways by which MtBE and other oxygenates may be biodegraded anaerobically 

have been the subject of recent research and ongoing studies. Table 4.4-1 highlights the various electron 

acceptors that are used in anaerobic bioremediation studies and contrasts the products of complete 

anaerobic degradation with those for aerobic metabolism. 

Table 4.4-1. MtBE Biodegradation Mechanisms and Products 

Zone Electron 

Donor 

Electron 

Acceptor 

Products of Complete 

Degradation 

Aerobic MtBE O2 CO2 and H2O 

Anaerobic 

Nitrate Reducing MtBE NO3 

- N2, NH3, CO2, and H2O 

Iron Reducing MtBE Fe+3 Fe+2, CO2, and H2O 

Sulfate Reducing MtBE SO4 

-2 H2S, CO2, and H2O 

Methanogenic MtBE CO2 CH4, CO2, and H2O 

While Table 4.4-1 lists the products of complete degradation of MtBE, incomplete degradation of MtBE 

and other oxygenates may also occur under certain conditions. Of specific note, TBA has been shown to 

be a degradation intermediate that may persist under anaerobic conditions (Vance et al, 2003). In some 

cases, this can result in MtBE plumes having a concentration of TBA in excess of the concentration of 

MtBE (Wilson, 2003a). A paper published as this report went to print (Schmidt, 2004) provides further 

information about the role of TBA in microbial biodegradation. Therefore, application of bioremediation 

approaches to MtBE and other oxygenates often have considered the complete pathway to end products 

and the possible stall of the bioremediation process at intermediates along that pathway. 

4.4.3 How is Bioremediation Applied to Treat Oxygenates? 

Bioremediation is applied to MtBE and other oxygenates in systems that range in complexity from not 

being engineered at all (natural biodegradation) to systems that are completely engineered, including the 

addition of conditioned microorganisms (bioaugmentation) and of nutrients as well as co-substrates and 

electron acceptors (biostimulation). Further, these systems can be based on aerobic or anaerobic 

pathways, or a sequential combination of these pathways. 

The rate at which natural biodegradation of MtBE and other oxygenates will occur at a site is affected by 

a number of site conditions, including groundwater chemistry, presence of other contaminants, and 

number of native microbes capable of degrading MtBE or other oxygenates. Whether the contaminated 

zone is aerobic or anaerobic (nitrate reducing, iron reducing, sulfate reducing, or methanogenic), and 

other chemical parameters (for example, pH, alkalinity, and inorganic content) will determine what types 

of microbes may be able to grow and what type of biodegradation pathway may be followed. Figure 4.4-

2 depicts the oxidative zones which may be present in a plume at a petroleum-contaminated site and 

illustrates how each of the anaerobic and aerobic pathways listed in Table 4.4-2 may be part of the natural 

biodegradation process. 

 4-26 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Figure 4.4-2. Typical Zones Downgradient of Petroleum Contaminant Source 

i Ni 3 i

Sul 4 i ioxi 2 i

i 

Source Zone 

Iron (III) Reduc ng Zone 

trate (NO ) Reduc ng Zone 

fate (SO ) Reduc ng Zone 

Carbon D de (CO ) Reduc ng (Methanogenic) Zone 

Oxygen Reduc ng Zone 

ANAEROBIC ZONE AEROBIC ZONE 

Source: Modified from Anderson, R.T. and D.R. Lovley 1997 

Multiple microbes that are capable of biodegrading oxygenates have been identified at sites contaminated 

with MtBE and other oxygenates. Whether such microbes are present at a specific site will affect the 

viability of natural biodegradation without the need for bioaugmentation. Where these microbes are 

present, natural biodegradation or limited biostimulation, such as air sparging to increase oxygen levels, 

may be effective in reducing the concentrations of MtBE and other oxygenates. However, other 

conditions must be conducive to support significant natural biodegradation. Typically, only those sites 

that have aerobic conditions in the contaminated zone because of shallow water tables and high rates of 

groundwater recharge have achieved significant natural biodegradation of MtBE and other oxygenates 

(Stocking et al., 2000). 

In some cases, the presence of other contaminants, such as benzene, has been shown to facilitate the 

natural biodegradation of MtBE and other oxygenates through co-metabolism. However, contaminants 

such as BTEX also may inhibit the biodegradation of oxygenates through the depletion of electron 

acceptors or nutrients, or may be preferentially used because of the relatively slow growth of oxygenatedegrading microorganisms (EPA, 2001a; Deeb and Kavanaugh, 2002). 

In addition, sites contaminated with alcohols such as ethanol also may inhibit the biodegradation of etherbased oxygenates such as MtBE through the depletion of electron acceptors or nutrients (da Silva, 2003). 

Fully-engineered systems for the bioremediation of oxygenates typically incorporate both biostimulation 

and bioaugmentation to accelerate the biodegradation process. Most commonly, these systems are based 

on the aerobic pathway so that the biostimulation component includes the addition of oxygen, through 

air/oxygen sparging or addition of oxygen releasing chemicals, as well as the addition of nutrients. The 

addition of oxygen through one of these means can be used to make the entire contaminant zone aerobic 

and thereby provide more uniform conditions for accelerated biodegradation. Maintaining high oxygen 

levels is especially important to effective aerobic biodegradation in that oxygenate-degrading organisms 

have been shown in research studies to require a higher concentration of oxygen. The bioaugmentation 

component is achieved by adding microbial cultures that are conditioned to degrade oxygenates either by 

being grown on these contaminants or by culturing isolated species that have the required enzymes. 

Bioaugmentation is often critical to the success of an engineered bioremediation system in that 

microorganisms capable of degrading oxygenates may not be present natively and are slow growers 

(Rittman, 2003, Wilson, 2003b). 

The use of anaerobic pathways may have engineering advantages under certain conditions, such as in 

treating oxygenate contamination in deep aquifers or source zones. Recent research and field studies have 

focused on the various anaerobic pathways for biodegradation of MtBE and other fuel oxygenates (Vance 

et al, 2003). However, the results of these studies in terms of oxygenate degradation efficiency have been 

 4-27 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

variable and no single anaerobic pathway has demonstrated consistent success for degrading oxygenates 

to end products, even in the laboratory environment (Finneran and Lovely, 2003e). Therefore, sitespecific treatability studies and pilot testing are generally performed if bioremediation using anaerobic 

pathways is to be considered at a site. 

Engineered systems may also incorporate the addition of a co-substrate to help establish an active 

microbial community and thereby accelerate the biodegradation of oxygenates. Hydrocarbon gases, such 

as propane and butane are one type of co-substrates that has been used in field applications due to the 

simplicity of injecting and diffusing a hydrocarbon gas (Steffan et al, 2003). Some proprietary 

technologies are based on the use of specific co-substrates and strains of microbes. 

4.4.4 What Types of Projects Involved Bioremediation to Treat Oxygenates? 

From the 323 MtBE projects in EPA’s MtBE Treatment Profiles dataset, 73 projects were identified 

where MtBE was treated using engineered bioremediation systems, either alone or in conjunction with 

another technology. Information on the treatment of other oxygenates during these 73 projects is limited, 

with a total of 12 of the 73 projects reporting TBA as a co-contaminant. 

Table 4.4-2 summarizes the scale and operational status for the 73 bioremediation projects. These 

projects include only engineered bioremediation systems and exclude projects that used natural 

biodegradation as part of a monitored natural attenuation approach (see Section 5.3 for a discussion of 

monitored natural attenuation). 

Table 4.4-2. General Information from 73 Engineered Bioremediation Projects 

Technology(ies) # of Projects 

Operational Status Scale 

Completed Ongoing Bench Pilot Full 

IN SITU PROJECTS 

Bioremediation Only 55 25 30 2 12 41 

Bioremediation with Air Sparging 2 0 2 0 1 1 

Bioremediation with Pump-andTreat 

1 0 1 0 0 1 

Bioremediation with SVE 1 0 1 0 0 1 

Bioremediation with Air Sparging 

and SVE 

6 6 0 0 0 6 

Bioremediation with Multiple 

Technologies 

1 0 1 0 0 1 

EX SITU PROJECTS 

Bioremediation Only 7 4 3 5 0 2 

TOTAL 73 35 38 7 13 53 

As shown in Table 4.4-2, 62 of the 73 bioremediation projects employed either in situ or ex situ 

bioremediation alone. However, 11 of the projects supplemented bioremediation treatment with air 

sparging, SVE, or pump-and-treat. Most of the bioremediation projects in the dataset were full scale (53 

projects) and were ongoing (38 projects) at the time that its profile was published. For the 40 projects 

specifying the type of MtBE biodegradation mechanism employed, 37 reported using the aerobic 

pathway, 1 project reported using cometabolic pathways, 1 project reported using a combination of 

aerobic and anaerobic pathways, and 1 project reported using a combination of aerobic and cometabolic 

pathways. Short summaries for two of these projects, In Situ Bioremediation at Port Hueneme - D, 

 4-28 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Oxnard, CA, In Situ Bioremediation at Sunoco Service Station, MA, and In Situ Bioremediation at South 

Beach Marina, Hilton Head, South Carolina, are included at the end of this section, with additional 

information about all 73 projects provided in Appendix A. 

4.4.5 How Has In Situ Bioremediation Performed in Treating Oxygenates? 

Tables 4.4-3 and 4.4-4 summarize performance data for the 35 completed and 38 ongoing in situ 

bioremediation projects that reported this information. The concentration of MtBE in groundwater prior 

to treatment was as high as 870,000 μg/L (ongoing project at Site NY - F), and as low as 10 μg/L (Main 

Street Shell Conway, SC and Speedway #226, North Charleston, SC). 

Table 4.4-3. Completed In Situ Bioremediation Projects 

Performance Summary for 31 Projects 

Technology(ies) 

# of 

Projects 

Initial MtBE Concentration 1 

(μg/L) 

Final MtBE Concentration 1 

(μg/L) 

Median 

Project 

Duration 

Minimum Median Maximum Minimum Median Maximum (months) 

In situ Bioremediation 

Only 

25 5 2,800 100,000 1 35 33,000 6 

In situ Bioremediation 

with Air Sparging and 

SVE 

6 4,151 10,800 44,400 NR NR NR 12 

Notes: 

NR Information not provided 

1 Treatment performance data are based on the data provided by project managers and others in the source materials used to prepare the 

treatment profiles website, as shown in cluin.org/products/mtbe, and summarized in Appendix A. Appendix A shows the specific sites that 

are summarized here, along with technology design, operation, and performance data for each of the projects. 

2 Performance data are shown in terms of changes in concentration of MtBE in the groundwater, as provided in the reference materials and 

from the project contacts, except as noted. MtBE concentrations prior to beginning treatment (shown as “initial concentration”) and after 

treatment was completed (shown as “final concentration”) are provided. For projects where more than one technology was used, 

performance data are presented under each of the technologies used for the project. 

Table 4.4-4. Ongoing In Situ Bioremediation Projects Performance Summary for MtBE at 38 Sites 

MtBE Concentration Range 

# of Projects 

Reporting Initial 

MtBE 

Concentrations 

# of Projects 

Reporting Posttreatment MtBE 

Concentrations 

Greater than 100,000 μg/L 1 0 

Greater than or equal to 10,000 μg/L but 

less than 100,000 μg/L 

12 1 

Greater than or equal to 1,000 μg/L but 

less than 10,000 μg/L 

11 3 

Greater than or equal to 100 μg/L but 

less than 1,000 μg/L 

4 3 

Greater than or equal to 50 μg/L but 

less than 100 μg/L 

0 1 

Less than 50 μg/L 5 5 

 4-29 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

The data presented in Table 4.4-3 and Table 4.4-4 shows that bioremediation (either alone or in 

combination with other technologies) has been employed to remediate MtBE in groundwater and soil to 

concentrations less than 50 μg/L and has achieved MtBE concentration reductions greater than 99 

percent. The median project duration for the 20 completed sites ranged from 6 months to 1 year. 

In addition to the performance data reported for MtBE, 8 of the 12 projects in the dataset that reported 

treating TBA using bioremediation also provided performance data. All 8 of these sites provided TBA 

concentration prior to bioremediation treatment (the highest initial concentration was 90,000 μg/L) and 2 

provided TBA concentrations following treatment (both achieved less than 5 μg/L). 

Because of the heightened interest in bioremediation of TBA, additional information was obtained about 

several of these sites. These data, provided in the online database, show that several sites were able to 

reduce the concentration of TBA, sometimes to less than its site-specific cleanup level. For example, at 

several sites in Texas, including Turtle Bayou Easement Area and Rural Area Disposal Area, in situ 

bioremediation was used in conjunction with other technologies such as SVE and in situ thermal 

desorption. At these sites, the concentrations of TBA were reduced to less than its cleanup goal, with 

concentrations after treatment ranging from 100 – 1,000 μg/L. At the Naval Base Ventura County, Port 

Hueneme, CA, in situ bioremediation was used in a biobarrier configuration, and the concentration of 

TBA was reduced from >1,000 to <5 μg/L (information about required cleanup levels was not provided). 

4.4.6 What are the Costs of Using In Situ Bioremediation to Treat Oxygenates? 

Project cost data were reported for 28 of the 73 bioremediation projects in the dataset; these include data 

for both ongoing and completed projects. In most cases, the components that make up the project costs 

were not reported. However, it is likely that the reported costs incorporate different components, such as 

treatment, monitoring, design, oversight, and health & safety. Most (21 projects) of the reported costs 

were for ongoing projects and represent either a partial actual cost as of the time that the report was made 

or an estimated total project cost. 

The median reported total cost for all bioremediation projects was approximately $125,000, with most 

projects having a total cost between $50,000 and $350,000. The total cost for all 28 projects reporting 

this information ranged from $4,000 to $5,200,000 per project, depending on scale, type of engineered 

application, and site conditions. For example, as shown in Section 4.4.8, at the Port Hueneme site, a 500­

ft wide biobarrier was constructed in a shallow sand aquifer and had an installation cost of $435,000, with 

first year O&M costs of $75,000. At a site in South Carolina, 3,000 gallons of a liquid microbial solution 

were injected through 40 monitoring and 15 injection points, for a total cost of $63,500. 

Because the area, volume, or mass treated was not consistently available for the 28 bioremediation 

projects, no unit costs were estimated. The cost per volume of subsurface treated (identified as cubic 

yards of subsurface) was reported in one literature source as ranging from approximately $170 to $330 

per cubic yard for in situ bioremediation in general. This source also reported unit costs for ex situ 

bioremediation ranging from $12 to more than $1,000 per cubic yard treated (EPA, 2001c). These results 

suggest that the cost for bioremediation is highly variable and depends on site-specific conditions and 

remedial goals. Overall, the cost of bioremediation generally is considered to be better than the average 

for applicable groundwater remediation technologies (FRTR, 2002). 

 4-30 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

4.4.7 What Factors May Affect the Performance and Cost of Oxygenate Treatment using In 

Situ Bioremediation? 

When oxygenates are present and must be remediated at a site, bioremediation, either alone or in 

combination with other technologies, may be a suitable remediation approach. Although both ether- and 

alcohol-based oxygenates are susceptible to biodegradation, the site conditions will determine whether 

bioremediation is an appropriate technology for a given site. Key factors that affect the performance and 

cost of bioremediation include: the concentration, mass, and distribution of VOCs in the soil and 

groundwater; geology, moisture content, mineral content, pH, temperature, the concentrations of terminal 

electron receptors and nutrients, as well as the presence of appropriate microbes, in the subsurface; 

cleanup goals; and requirements for site cleanup. These factors affect the design of bioremediation 

system, the biodegradation pathways that can be employed, and the amendments that must be added to 

enhance bioremediation (EPA, 1995; FRTR, 2002). 

Bioremediation generally is considered to be more suitable for the dissolved phase in groundwater plumes 

or low concentrations in soil rather than grossly contaminated source areas where free product may be 

present. Other technologies that incorporate free product removal, such as MPE and pump-and-treat, are 

generally considered more applicable to source areas. Therefore, source areas are typically treated 

through removal or another technology prior to application of bioremediation. Research is ongoing into 

the potential use of bioremediation near source areas. 

Because of the above factors, the design of a bioremediation system is typically based on significant site 

analysis and bench- and pilot-scale testing rather than the application of packaged treatment systems. 

More information about the factors that influence the performance and cost of bioremediation systems is 

available in the references listed in this report. 

4.4.8 Conclusions 

Based on the information available from the bioremediation project, MtBE treatment profiles, and other 

information contained in the reference documents reviewed in preparation of this report, the following 

conclusions may be made regarding the use of bioremediation to remediate sites contaminated with MtBE 

and other oxygenates: 

Data from Bioremediation MtBE Treatment Profiles 

• Used to remediate groundwater contaminated with oxygenates – it was employed at 73 of the 323 

of the projects in the dataset, primarily in the in situ mode 

• Most often used alone (92% of projects in dataset); to a lesser extent has been employed in 

conjunction with air sparging, pump-and-treat, or SVE 

• Employed to remediate MtBE in groundwater from concentrations greater than 100,000 μg/L to 

less than 50 μg/L and has achieved MtBE concentration reductions greater than 99 percent 

• Median project duration is approximately 1 year 

• Median reported total cost for all bioremediation projects in the dataset was approximately 

$125,000, with most projects having a total cost between $50,000 and $350,000 

Treatability of Oxygenates Using Bioremediation 

• Most research has focused on bioremediation of MtBE and TBA; information on biodegradation 

of other oxygenates is limited, but similar degradation pathways are employed for many 

oxygenates 

 4-31 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

• Presence of ethanol may affect the aerobic biodegradation of MtBE and lead to longer MtBE 

plumes. Recent research has indicated that ethanol can deplete available electron acceptors and 

stimulate methanogenesis. 

• Effective biodegradation of MtBE and other oxygenates has been reported in a variety of 

applications of the aerobic pathway; results for anaerobic pathways have been confined to 

laboratory studies and have not been consistent 

• Intermediate degradation products of MtBE and other oxygenates, such as TBA, may remain in 

the subsurface under natural conditions or when using anaerobic pathways 

• Oxygenate-degrading microorganisms are typically very slow growing; bench- and pilot-studies 

may be needed to confirm the applicability of bioremediation and to select an appropriate design 

Other Potential Advantages of Applying Bioremediation (EPA, 1995; EPA, 2000a) 

• Application involves equipment that is widely available and relatively easy to install 

• In situ systems create minimal disruption and/or disturbance to ongoing site activities 

• Time required for subsurface remediation using aerobic bioremediation may be shorter than time 

required for pump-and-treat 

• Is generally recognized as being less costly than other remedial options (for example, pump-andtreat or chemical oxidation) 

• Can be combined with other technologies (for example, bioventing, soil vapor extraction) to 

enhance site remediation 

• In many cases, does not produce waste products that require disposal 

Other Potential Limitations to Applying Bioremediation (EPA, 1995; EPA, 2000a): 

• Injection wells and/or infiltration galleries may become plugged by microbial growth or mineral 

precipitation. 

• Oxygenate-degrading microorganisms are typically slow growing and may not be present 

natively at all sites; pilot or treatability studies may be needed to confirm the applicability of 

bioremediation at a specific site 

• Bioremediation of source zones may take substantial time due to the presence of free product and 

lack of immediate bioavailability 

• Difficult to implement in low-permeability aquifers (hydraulic conductivity less than 10-4 

centimeters per second) 

• Re-injection wells or infiltration galleries may require permits or may be prohibited. Some states 

require permits for air injection 

• May require long-term monitoring and maintenance for bio-barrier type applications 

• Effective remediation may only occur in more permeable layers or channels within an aquifer 

4.4.9 Example Projects 

In Situ Bioremediation at Port Hueneme - D, Oxnard, CA 

A full-scale cleanup has been ongoing using in situ bioremediation to treat MtBE, BTEX, and TBA in 

groundwater at the Naval Base Ventura County, Port Hueneme in Oxnard, California. Geology at the site 

consists of a shallow sand aquifer bounded on the bottom by a clay aquitard, through which ground water flows 

at an average velocity of 1 ft/day. At a depth of 10-20 ft below ground surface (bgs), the 5,000- by 500-ft 

dissolved MtBE plume mixes with a smaller BTEX plume that originates from sands contaminated with 

residual nonaqueous phase liquid (NAPL). 

The in situ bioremediation system consists of a 500-foot-wide “bio-barrier”, which acts as a passive flowthrough system and was installed just downgradient of the NAPL plume. Contaminated groundwater 

containing dissolved MtBE, TBA, and BTEX travels through the bio-barrier and is injected with various 

combinations of oxygen, air, and conditioned microorganisms. Oxygen gas and bioaugmented sections are 

 4-32 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

located in the central core of the dissolved contaminant plume and air injections are used on the edge of the 

plume. Operation of the system began in the Fall of 2000. Initial MtBE, BTEX, and TBA concentrations in the 

groundwater plume were greater than 10,000 μg/L in the center of the plume. 

After 18 months, contaminant concentrations were reduced to less than 5 μg/L in monitoring wells 

downgradient of the bio-barrier and extending across the length of the bio-barrier. No significant differences in 

performance were observed for the differently operated sections of the barrier. Dissolved oxygen increased 

from a pre-injection concentration below 1 mg/L to 10-35 mg/L throughout the treatment zone, thereby 

increasing the potential for aerobic biodegradation to occur. In addition, increased dissolved oxygen levels 

upgradient of the treatment zone due to dispersion of the injected gas appear to cause upgradient reductions in 

MtBE and benzene concentrations. Peripheral monitoring wells have not shown an increase in contaminant 

concentrations, indicating that groundwater is flowing through and not around the bio-barrier. 

The biobarrier system includes 252 gas injection wells, 174 monitoring wells, 25 satellite gas storage tanks, 154 

solenoid valves, a 240 ft3/hr-capacity oxygen generator, automated timer circuits, and associated piping and 

electrical lines. The total installation cost of this equipment was $435,000; initial year (FY 01) O&M costs 

were $75,000 and are expected to continue for a service life of 40 years. A preliminary cost comparison with 

an existing pump-and-treat system at this site suggests savings of more than $34 million over the project life. 

The state regulatory agency recently approved continued use of this biobarrier and installation of a second 

biobarrier (at the toe of the plume) as the final remedy for the MtBE plume (Miller 2002, ESTCP, 2003). 

In Situ Bioremediation at Sunoco Service Station, MA 

A full-scale cleanup was performed using in situ bioremediation to treat MtBE and BTEX at a service station in 

Massachusetts. Soil at the site consists of a layer of sand and gravel underlain by peat, silt, and clay. The in 

situ bioremediation system consisted of 12 injection wells and two butane injection panels used to stimulate 

cometabolic aerobic biodegradation of the contaminants in groundwater. The system was operated between 

October 2000 and January 2001. MtBE concentrations were reduced from 370 to 12 μg/L and BTEX 

contamination in groundwater was reduced by approximately two orders of magnitude during the 4 month 

period (Global BioSciences, Inc., 2001). 

In Situ Bioremediation at South Beach Marina, Hilton Head, South Carolina 

A full-scale cleanup was performed using in situ bioremediation to treat MtBE, BTEX, and naphthalene in 

groundwater at a service station with leaking underground fuel storage tanks. At this site, groundwater is 4.32 

to 6.92 feet bgs, with an average hydraulic gradient of 0.078 feet/feet and with a calculated velocity of 6.42 feet 

per year. No confining units were identified at the site. 

The in situ bioremediation application at this site included injection of a liquid microbial solution into the 

subsurface through monitoring and injection wells. This solution includes microbes (Pseudomonas, Bacillus, 

and Corynebacterium), oxygen, emulsifier, surfactant, and nutrients. Five injections were conducted. Over 

3000 gallons was injected from February 1999 through September 2000 into approximately 40 wells and 15 

Geoprobe® injection points. As of September 2000, MTBE levels decreased by 96% (from 3,310 to 146 μg/L), 

while benzene decreased by 83% (2,571 μg/L to 435 μg/L); toluene by 66% (24,330 μg/L to 8,300 μg/L), and 

naphthalene by 84% (5,377 μg/L to 853 μg/L); xylene levels increased and were above pre-operational level as 

of September 2000. The system will continue to be operated until all target levels have been met. The total 

cost for the cleanup of this site is $63,500; no additional information on cost breakdown was available (FRTR 

2001). 

 4-33 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

4.5 In Situ Chemical Oxidation 

Overview 

$ Injection of an oxidant and other amendments to convert site 

contaminants into innocuous products such as carbon dioxide and water 

$ EPA’s MtBE Treatment Profiles Website dataset included use at 21 sites 

to treat MtBE 

$ Successful application depends on matching oxidant and delivery system 

to contaminants and site conditions 

4.5.1 What is In Situ Chemical Oxidation? 

In situ chemical oxidation (ISCO) is a technology in which an oxidant, and other amendments as 

necessary, is introduced into contaminated media to react with site contaminants such as MtBE, other fuel 

oxygenates, and other organic compounds, converting them to innocuous products, such as carbon 

dioxide and water. Typically, hydrogen peroxide (H2O2), ozone (O3), or permanganate (MnO4

-

) oxidants 

have been used to treat MtBE in soil and groundwater. Persulfate (S2O8

-

) compounds have also been used 

as chemical oxidants for treating MtBE. All of these chemicals react, either directly or through the 

generation of highly-reactive free radicals, such as OH•, and H•, or SO4

-

• with organic compounds such as 

MtBE to break hydrocarbon bonds and form degradation products such as alcohols, carbon dioxide, and 

water. In some applications, different oxidants may be used in combination, such as H2O2/O3, or in 

conjunction with catalysts, such as H2O2 in the presence of ferrous iron (Fenton’s chemistry or reagent), to 

enhance oxidation through the generation of free radicals. Depending on site conditions, oxidants may be 

introduced to the contaminated area using a variety of engineered approaches, including groundwater well 

injection, groundwater well recirculation, lance injection (jetting), PRBs, deep soil mixing, or soil 

fracturing (GWRTAC, 1999). 

4.5.2 How Do the Properties of MtBE and Other Oxygenates Affect Treatment? 

As with other organic and some inorganic contaminants, MtBE and other oxygenates are susceptible to 

degradation through oxidations reactions. If a sufficient amount and strength of oxidant and enough time 

are provided, all of the ether- and alcohol-based fuel oxygenates can be mineralized to carbon dioxide and 

water. For example, Figure 4.5-1 shows the equations for the stoichiometric mineralization of some of 

the common oxygenates through oxidation using hydrogen peroxide. 

Figure 4.5-1. Stoichiometric Mineralization of Oxygenates Using Hydrogen Peroxide 

ETBE, TAME, DIPE: C6H14O + 18 H2O2 Æ 6 CO2 + 25 H20 

MtBE: C5H12O + 15 H2O2 Æ 5 CO2 + 21 H20 

TBA: C4H10O + 12 H2O2 Æ 4 CO2 + 17 H20 

Ethanol: C2H6O + 6 H2O2 Æ 2 CO2 + 9 H20 

Methanol: CH3O + 5/2 H2O2 Æ CO2 + 4 H20 

Analogous equations can be derived for mineralization using other oxidants. However, the oxidation of 

MtBE or other oxygenates to carbon and water is a multi-step, multi-path process in which each step has 

different equilibrium and kinetic factors that govern the extent and rate that each reaction can take place. 

Not all oxidants have proven successful in mineralization of MtBE, leaving by-products such as tert-butyl 

formate (TBF) and TBA. The full spectrum of possible reaction intermediates and governing criteria 

 4-34 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

have not been determined for MtBE and the other oxygenates. However, in general, the greater number 

of carbon atoms in the oxygenate, the greater stoichiometric proportion of oxidant that will be required 

(under the same conditions) to fully oxidize it. For example, based on the equations in Figure 4.3-1, the 

complete mineralization of one pound of ETBE, MtBE, TBA, ethanol, and methanol would require 6.0, 

5.7, 5.5, 4.4, and 2.7 pounds of hydrogen peroxide, respectively (Kelley, Marley, and Sperry, 2002). 

While the above comparison (or similar comparisons for other oxidants) of the amount of oxidant 

required for different oxidants may hold under controlled laboratory conditions, the actual amount and 

type of oxidant that is necessary for the treatment of MtBE or other oxygenates at a given site will depend 

on numerous factors beyond the amount of contaminant present, including: 

• The amount and types of other contaminants (such as other petroleum constituents) that will also 

consume oxidant 

• The chemical composition of the soil and groundwater, specifically the amount of natural organic 

matter (NOM) and other reduced species, such as iron (II) or manganese (II); often analyzed as 

the chemical oxygen demand (COD) of the soil, or soil oxidant demand 

• The pH, alkalinity, and temperature of the treatment area; these conditions will affect equilibrium 

and kinetic constants defining the extent and rate that each oxidation step can take place 

• The potential for biodegradation of site contaminants or oxidation products 

• Hydraulic and geologic parameters, such as hydraulic conductivity, hydraulic gradient, and 

permeability, that will affect the migration and dissolution of the oxidant once it is introduced to 

the subsurface 

Because these factors can vary from site to site, typically field analyses of these parameters and benchand pilot-scale studies are conducted to determine the type and amount of oxidant required for a specific 

application. 

4.5.3 How is In Situ Chemical Oxidation Applied to Treat Oxygenates? 

During ISCO, oxidants and any necessary amendments are introduced to the treatment area with one or 

more of the available delivery approaches. Pilot-scale testing is often used to determine the type of 

amendment and delivery system used at a given site. EPA policy regarding injection of supplements is 

discussed in Section 3.4. Some of the key considerations for the common oxidants and delivery 

approaches are summarized below. 

Oxidants/Amendments 

• Hydrogen Peroxide (H2O2) – Hydrogen peroxide has been used alone or in combination with 

other chemicals (such as using ferrous iron as a catalyst to generate free radicals through Fenton’s 

chemistry) or with ultraviolet (UV) light. When used alone, hydrogen peroxide is typically 

injected as a concentrated solution (35-50%), which decomposes violently when contacting 

groundwater, generating heat and high volumes of gas. When using Fenton’s chemistry, the pH 

of the treatment area is typically maintained at acidic (pH < 4) conditions and a more dilute 

hydrogen peroxide solution is used. Hydrogen peroxide and iron catalysts are typically injected 

separately, such as through specific ports in an injection lance, or through injection wells, because 

free radicals tend to react rapidly and can dissociate if generated prior to injection. Excess 

 4-35 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

hydrogen peroxide that is not used in degrading organic compounds will rapidly degrade to water 

and oxygen (Leethem, 2001). 

• Ozone (O3) – Ozone is a highly reactive chemical that has been used to treat organic compounds 

in ex situ groundwater and drinking water treatment systems. It can also be used to treat MtBE in 

an ozone-air sparging system. This system injects ozone through tubing to a microporous sparge 

point designed to generate very small bubbles (“microbubbles”, approximately 50 micrometers 

(μm) in diameter), which have a high surface-to-volume ratio. Organic contaminants in 

groundwater, such as MtBE, volatilize into the ozone bubbles and are oxidized. Ozone that is not 

consumed degrades to oxygen. Ozone is often used in combination with other oxidants, such as 

hydrogen peroxide, to enhance oxidation through the generation of free radicals. If bromine is 

present in the treatment area, bromate generation, which can occur during ozonation, is typically 

monitored during treatment. 

• Permanganate (MnO4

-

) – Permanganate is often employed in the form of solid or a solution of 

potassium or sodium permanganate for groundwater treatment. It has a smaller oxidizing 

potential than ozone and hydrogen peroxide using Fenton’s chemistry, resulting in the relatively 

slower oxidation of MtBE and other oxygenates. However, permanganate has a longer half-life 

compared to the stronger oxidants, and persists in the environment for a longer time. The end 

product of permanganate oxidation is manganese dioxide, which, depending on the groundwater 

pH, can precipitate into the formation. Excessive precipitation may reduce soil permeability. 

• Other Oxidants – Combinations of the above oxidants and other oxidants such as persulfate 

compounds are also being used to treat MtBE and other oxygenates. These and other 

combinations and other oxidants are being developed to maximize the generation of highlyoxidizing free radicals, increase oxidant persistence, or otherwise enhance in situ oxidation. 

Delivery Approaches 

• Groundwater Well Injection – Oxidants may be introduced to the treatment zone through 

existing or new groundwater monitoring wells either as a liquid, gas, or solid. This method relies 

on the natural migration of oxidants from the well into the formation. Injection wells need to be 

adequately spaced to allow for oxidant delivery to the entire treatment area. 

• Groundwater Recirculation – A groundwater recirculation system may be used to extract 

groundwater from within or at the downgradient edge of the contaminated area, introduce 

oxidants and amendments aboveground, and reinject the groundwater upgradient of the treatment 

area. This approach can be used to increase the flow-through of oxidant through the treatment 

area, as well as to achieve downgradient containment of a contaminated groundwater plume. 

• Lance Injection, Jetting, Fracturing – Use of a high-pressure lance can create micro-fractures 

in soils that increase soil permeability and allow for direct injection of oxidants and amendments 

into a desired treatment area without the need for an existing or new groundwater well. 

• Soil Mixing – For lower permeability soils, soil mixing using tilling for shallow soil or an auger 

for deeper soil can be used to introduce oxidants to a treatment area. 

• PRB – Oxidants can be injected into the treatment zone of a PRB to oxidize the groundwater that 

flows through it. This approach can be used as a containment approach for a contaminated 

groundwater plume. Also, a PRB could be placed upgradient or within a treatment area allowing 

the oxidized groundwater leaving the PRB to flow through the treatment area. 

There are also technologies that use electrical or other forms of energy to generate oxidizing and reducing 

radicals in aqueous solution and thereby destroy contaminants such as MtBE and other oxygenates. 

These technologies include ultrasound and electron beam treatment, and are primarily used in ex-situ 

applications (see Section 4.6). Recently, however, ultrasound treatment has been proposed as a potential 

in-situ application by incorporating ultrasonic transducers into a robotic self-powered mining head 

(Chang and Yen 2000). 

 4-36 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Additional information relevant to the application of ISCO at sites in general or contaminated with MtBE 

and other oxygenates is available in the following documents: 

• Kelley, Marley, and Sperry, 2003. In Moyer and Kostecki, Eds. 2003. MtBE Remediation 

Handbook. Amherst Scientific Publishers. 

• Ground-Water Remediation Technologies Analysis Center. 1999. Technology Evaluation 

Report, In Situ Chemical Treatment (TE-99-01). Prepared by Yin, Y. and Allen, H.E. July. 

http://www.gwrtac.org/pdf/inchem.pdf 

• Interstate Technology and Regulatory Cooperation Work Group. 2001. Technical and 

Regulatory Guidance for In Situ Chemical Oxidation of Contaminated Soil and Groundwater. 

June. http://www.itrcweb.org/ISCO-1.pdf 

• Naval Facilities Engineering Service Center. Chemical Oxidation, In-Situ Technology Web 

Page. http://enviro.nfesc.navy.mil/erb/restoration/technologies/remed/phys_chem/phc-43.asp 

• Strategic Environmental Research and Development Program (SERDP). 2003. In Situ Chemical 

Oxidation Initiative. http://www.serdp-estcp.org/ISCO.cfm 

4.5.4 What Types of Projects Involve In Situ Chemical Oxidation for Oxygenates? 

From the 323 MtBE projects in EPA’s MtBE Treatment Profiles dataset, 21 projects were identified 

where MtBE was treated using in situ chemical oxidation. No ISCO projects reported treating other 

oxygenates. Four of the projects used ozone and 17 used hydrogen peroxide either alone or with Fenton’s 

chemistry. 

Table 4.5-1 summarizes the scale and operational status for the 21 ISCO projects. The data used to 

compile this information was current at the time the profile for each project was completed. Short 

summaries for two projects, Ozone Sparging at Former Service Station, Bucks County, PA and Fenton’s 

Chemistry at a Warehousing Facility, Union, NJ, are included at the end of this section, with additional 

information about all 21 projects provided in Appendix A. 

Table 4.5-1. General Information on 21 In Situ Chemical Oxidation Projects 

Technology(ies) 

# of 

Projects 

Operational Status Scale 

Completed Ongoing Bench Pilot Full 

In situ Chemical Oxidation Only 14 6 8 0 4 10 

In situ Chemical Oxidation with 

Air Sparging 

2 0 2 0 0 2 

In situ Chemical Oxidation with 

Pump-and-Treat 

1 1 0 0 0 1 

In situ Chemical Oxidation with 

SVE 

2 1 1 0 0 2 

In situ Chemical Oxidation with 

Multiple Phase Extraction 

2 0 2 0 0 2 

TOTAL 21 8 13 0 4 17 

 4-37 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

As shown in Table 4.5-1, most of the 21 ISCO projects were performed at full scale (17 projects) at the 

time that their profiles were compiled. Eight of the 21 projects were identified as completed, and the 

remaining 13 as ongoing. In addition, while most (14) of the projects used ISCO alone, 7 projects 

supplemented ISCO with air sparging, pump-and-treat, SVE, or MPE. 

4.5.5 How Has In Situ Chemical Oxidation Performed in Treating Oxygenates? 

Tables 4.5-2 and 4.5-3 summarize performance data for the 8 completed and 13 ongoing ISCO projects. 

The data presented in these tables show that ISCO (either alone or in combination with other 

technologies) has been used to remediate MtBE in groundwater from concentrations greater than 

10,000 μg/L to less than 50 μg/L and has achieved MtBE concentration reductions greater than 99 

percent. Because the dataset included relatively few completed projects with performance data, Table 

4.5-2 provides a summary of specific projects instead of a summary of minimum, median, and maximum 

concentrations. The median project duration for the 19 completed sites ranged from 9 to 18 months. 

None of the projects reported performance data for other oxygenates. 

Table 4.5-2. Completed In Situ Chemical Oxidation Projects - Performance Summary for 8 

Projects 

Technology(ies) Site Name and Location Scale 

Initial MtBE 

Concentration 1 

(μg/L) 

Final MtBE 

Concentration 1 

(μg/L) 

Median 

Project 

Duration 

(months) 

In situ Chemical 

Oxidation Only 

Former Maintenance and Repair 

Garage, NY – H, West Chester, 

NY 

Pilot 451 171 12 

In situ Chemical 

Oxidation Only 

Spill Site (Long Island, New 

York), Long Island, NY 

Pilot 6,300 79 2 

In situ Chemical 

Oxidation Only 

Service Station, PA – D, 

Warminster, PA 

Full 50,000 6.6 14 

In situ Chemical 

Oxidation Only 

Service Station, NJ – E, North 

Halden, NJ 

Full 403,000 1,430 2 

In situ Chemical 

Oxidation Only 

Garage, NJ – F, Island Heights, NJ Full 55 4 14 

In situ Chemical 

Oxidation Only 

Warehousing Facility in Union 

County New Jersey, NJ 

Full 6,400 70 NR 

In situ Chemical 

Oxidation with SVE 

Former Service Station, PA – A, 

Bucks County, PA 

Full 475,000 68,400 18 

In situ Chemical 

Oxidation with 

Pump-and-Treat 

North Texas Service Station, TX Full 17,000 31 9 

Notes:

NR Information not provided 

1 Treatment performance data are based on the data provided by project managers and others in the source materials used to prepare the 

treatment profiles website, as shown in cluin.org/products/mtbe, and summarized in Appendix A. Appendix A shows the specific sites that 

are summarized here, along with technology design, operation, and performance data for each of the projects. 

2 Performance data are shown in terms of changes in concentration of MtBE in the groundwater, as provided in the reference materials and 

from the project contacts, except as noted. MtBE concentrations prior to beginning treatment (shown as “initial concentration”) and after 

treatment was completed (shown as “final concentration”) are provided. For projects where more than one technology was used, 

performance data are presented under each of the technologies used for the project. 

 4-38 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Table 4.5-3. Ongoing In Situ Chemical Oxidation Projects - Performance Summary for 13 Sites 

MtBE Concentration Range 

# of Projects 

Reporting Initial 

MtBE 

Concentrations 

# of Projects with 

Last Reported 

MtBE 

Concentrations 

Greater than 100,000 μg/L 0 0 

Greater than or equal to 10,000 μg/L but 

less than 100,000 μg/L 

1 0 

Greater than or equal to 1,000 μg/L but 

less than 10,000 μg/L 

3 2 

Greater than or equal to 100 μg/L but 

less than 1,000 μg/L 

6 2 

Greater than or equal to 50 μg/L but less 

than 100 μg/L 

0 1 

Less than 50 μg/L 2 6 

4.5.6 What Are the Costs of Using In Situ Chemical Oxidation to Treat MtBE? 

The total project cost was reported for 1 of the 21 ISCO projects identified above. The completed Former 

Service Station, PA – A project, which employed used ISCO with SVE, reported a total project cost of 

$146,000. This cost was broken down further into $90,000 of capital cost and $56,000 of operation and 

maintenance cost. Because the area, volume, or mass treated was not available for this project, no unit 

cost was calculated. 

There is little additional information in the literature about the costs of using ISCO for the treatment of 

MtBE and other oxygenates, or for other contaminants. The cost per volume of subsurface treated 

(identified as cubic yards of subsurface) was reported in one literature source as ranging from $52 to $310 

per cubic yard in general (GWRTAC, 1999). The cost of ISCO generally is considered to be average, 

among the costs for remediation technologies, for treatment of contaminated groundwater (FRTR, 2002). 

4.5.7 What Factors May Affect the Performance and Cost of Oxygenate Treatment using In 

Situ Chemical Oxidation? 

When MtBE or other oxygenates are present and must be remediated at a site, ISCO, either alone or in 

combination with other technologies, may be a suitable remediation approach. Although both ether- and 

alcohol-based oxygenates are susceptible to chemical oxidation, the chemical, hydraulic, and geologic 

conditions of a given site will determine whether ISCO is a feasible option for treatment. For example, 

ISCO may not be economically feasible for sites with high concentrations of NOM or other constituents 

that may consume large amounts of oxidant. In addition, sites with low subsurface permeability may 

require more complex approaches, such as fracturing or soil mixing, to deliver the necessary oxidant to 

the treatment zone, potentially increasing costs. Other site characteristics, such as pH, alkalinity, and 

temperature will also affect system design and impact cost and performance. For example, for oxidants 

that have specific pH requirements, pretreatment of the aquifer with an acid solution to lower the pH is 

typically considered. In addition, off-gas generated by the chemical reactions in ISCO may require 

capture and treatment (Kelley, Marley, and Sperry, 2002). 

In addition to the technology-specific factors described above, additional factors may also affect the 

performance and cost of an ISCO system. These factors include: the concentration, mass, and distribution 

of contaminants in the groundwater; subsurface geology and hydrogeology; cleanup goals; and 

 4-39 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

requirements for site cleanup. For example, heterogeneity within the subsurface may result in preferential 

pathways that prevent injected oxidant from reaching the entire treatment area. 

Because of the above factors, the design of an ISCO system is typically based on pilot-scale testing rather 

than generic design equations. More information about the factors that influence the performance and 

cost of ISCO systems in general is available in the references listed in this report. 

4.5.8 Conclusions 

Data from In Situ Chemical Oxidation MtBE Treatment Profiles 

• Used to remediate groundwater contaminated with MtBE, but less frequently than some other 

technologies, such as air sparging and bioremediation – it was employed at 21 of the 323 (6.5%) 

of the projects in the dataset 

• Most often used alone (67% of projects in dataset); to a lesser extent has been employed in 

conjunction with pump-and-treat or other technologies 

• The cost common oxidant applied was hydrogen peroxide with ferrous iron (Fenton’s chemistry) 

• Used to remediate MtBE in groundwater from concentrations greater than 10,000 μg/L to less 

than 50 μg/L and has achieved MtBE concentration reductions greater than 99 percent 

• Median project duration is approximately 1 year 

• Cost information is limited – one project reported total project cost of $146,000 

Treatability of MtBE and Other Oxygenates Using In Situ Chemical Oxidation 

• All ether- and alcohol-based oxygenates susceptible to chemical oxidation 

• In general, the greater number of carbon atoms in the oxygenate, the greater stoichiometric 

proportion of oxidant will be required (under the same conditions) to fully oxidize 

• Applicability to given site based primarily on factors not related to type of oxygenate (that is, all 

oxygenates can be treated using chemical oxidation, but certain other site conditions, like high 

concentrations of native organic matter or low permeability, may make other treatment 

technologies more attractive) 

Other Potential Advantages of Applying In Situ Chemical Oxidation (EPA, 1995; FRTR, 2002) 

• Has potential to be used to target hot spots that may not be amenable to bioremediation 

• Has potential to achieve cleanup goals in relatively short amount of time (several months to a 

year) 

• Depth of application is only limited to the delivery approach used 

Other Potential Limitations to Applying In Situ Chemical Oxidation (EPA, 1995; FRTR, 2002) 

• Relatively large amount of oxidant may be needed for treatment of large masses of contaminant 

(oxidant does not target only the contaminants of concern) 

• May have low contact between oxidant and contaminant in heterogeneous media or in areas with 

low permeability 

• Special precautions may need to be taken to protect worker health and safety during operation 

(because of use of strongly oxidizing chemicals); also concentrated oxidant injection can result in 

violent subsurface reactions 

• Chemical reactions may form toxic by-products (such as bromate during ozone oxidation) in the 

groundwater 

• Off-gas may require capture and treatment 

 4-40 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

4.5.9 Example Projects 

Ozone Sparging at Former Service Station, Bucks County, PA 

At a former service station located in Bucks County, PA, remediation needed to be completed within nine 

months to facilitate the sale of the property. The cleanup approach used ozone sparging, pump-and-treat, MPE, 

and SVE to treat MtBE. Free product was removed prior to performing ozone sparging. The sparging system 

consisted of multiple, nested sparge wells in a treatment area of 180 ft by 150 ft, and used an ozone dosage of 

2.5 lbs/day at 2 scfm over a 4 month period. MtBE concentrations in groundwater were reduced from 17,000 

μg/L to 31 μg/L, which was below the cleanup level of 2,900 μg/L. The total cost reported for treatment was 

$146,000, consisting of $90,000 for capital and $56,000 for O&M (EPA, 2002a). 

Fenton’s Chemistry at Warehousing Facility in Union County New Jersey, Union City, NJ 

Groundwater at an operating warehousing facility in Union, NJ was contaminated with MtBE (concentrations 

up to 6,400 μg/L), TBA, and BTEX. Soil at the site consists of soft red shales interbedded with harder 

sandstones and minor amounts of conglomerate. After completing a pilot study, hydrogen peroxide and 

catalysts were injected at six points during three treatment cycles over a three-month period in mid-1996 (each 

cycle consisted of 15 days injection followed by 15 days without injection). MtBE concentrations in 

groundwater were reduced to less than 5 μg/L, which was below the cleanup level of 70 μg/L. Rebound was 

evaluated four months after treatment was complete; results remained below the cleanup level. There was no 

current cost data provided for this site (EPA, 2002a). 

4.6 Groundwater Pump-and-Treat and Drinking Water Treatment 

Overview 

$ Extraction of contaminated groundwater from the subsurface and treatment 

using one or more ex situ technologies 

$ EPA’s MtBE Treatment Profiles Website dataset includes use during 100 

projects to treat MtBE or other oxygenates 

○ 85 pump-and-treat projects 

○ 15 drinking water treatment projects 

$ Used to reduce the concentration and mass of MtBE or other oxygenates from 

groundwater or for hydraulic containment 

4.6.1 What is Groundwater Extraction for Pump-and-Treat and Drinking Water Treatment? 

Groundwater pump-and-treat involves the extraction of groundwater from a contaminant plume and the 

treatment of extracted water using one or more aboveground technologies. Drinking water treatment 

systems where the extracted water is contaminated with fuel oxygenates involves many of the same 

activities as groundwater pump-and-treat. In general, the methods for extraction of the groundwater are 

not linked to or limited by the aboveground (ex situ) treatment technologies. This section focuses on 

groundwater extraction, while the following section (Section 4.7) focuses on above-ground treatment of 

extracted groundwater, for both pump-and-treat and for drinking water treatment. 

The groundwater extraction component typically consists of multiple wells and/or trenches for extraction 

of groundwater and includes differential control of extraction rates from individual wells to optimize 

operation. Most groundwater extraction systems incorporate extraction wells that are installed within the 

contaminant plume downgradient from the source. These extraction wells are designed and controlled to 

act as a barrier to additional downgradient movement of the contaminant plume and, over a long period of 

time, to extract contaminant mass. Due to the water solubility of MtBE and other oxygenates, and the 

associated occurrence of significant quantities of contaminant mass in the dissolved phase, such 

 4-41 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

groundwater extraction systems have specific application to the remediation of plumes incorporating 

oxygenate contamination. 

4.6.2 How Do the Properties of MtBE and Other Oxygenates Affect Groundwater Extraction? 

The properties of MtBE and other oxygenates are relevant to both the extraction and treatment 

components of pump-and-treat. As discussed in Section 2.6, the properties of fuel oxygenates, 

specifically their relatively high aqueous solubility and low tendency to partition to organic matter, affect 

how they migrate with groundwater. As a result, oxygenates tend to become dissolved in and migrate 

with groundwater more readily than other petroleum contaminants such as BTEX. One consequence of 

this tendency that is beneficial to pump-and-treat remediation is that oxygenates are also more readily 

extracted with groundwater than other contaminants. 

4.6.3 How is Pump-and-Treat Applied to Treat Oxygenates? 

A pump-and-treat system consists of an extraction and a treatment component. Groundwater is typically 

extracted through vertical groundwater recovery wells although, in the last decade or so, horizontal wells 

and trenches have also been employed. Variables in the design of a typical system include (EPA, 2001d): 

• Types of extraction systems to be used 

• Number and location of extraction points 

• Design of extraction points (for example, diameter, depth and well screen interval) 

• Type of pumping apparatus to employ (for example, aboveground vacuum, submersible, 

pneumatic) 

• Design of a distribution system to transport extracted groundwater to the aboveground treatment 

system (for example, aboveground vs. underground piping or possible need for double-walled 

piping at RCRA-regulated sites) 

For the most part, the above considerations are not affected by the specific contaminants present at the 

site, but by site characteristics, such as plume distribution, hydrogeologic characteristics, and aboveground obstacles (such as buildings or active roadways). Typical extraction system construction 

materials, such as polyvinyl chloride (PVC) piping and stainless steel pumps, are appropriate for fuel 

oxygenates at typical contaminated groundwater concentrations. Groundwater extraction system 

optimization approaches at sites contaminated with MtBE and other oxygenates are similar to those used 

at other sites, such as use of phased construction, adaptive management of pumping rates, periodic 

modeling of the well arrays, and pulsed pumping (Li et al, 2003). 

A conventional pump-and-treat extraction system is typically designed to recover only groundwater. 

Integrated or separate systems have also been used to capture free product or contaminated vapor 

concurrently with groundwater. Extraction systems that incorporate the integrated recovery of multiple 

phases are discussed in Section 4.3 (MPE) and separate systems to recover these other phases are 

discussed in Section 4.2 about SVE and Section 5.2 about free product recovery. 

More detailed information relevant to the application of pump-and-treat at sites contaminated with MtBE 

and other oxygenates and in general is available in the following documents: 

• Cohen, R.M., J.W. Mercer, and R.M. Greenwald. 1998. EPA Groundwater Issue, Design 

Guidelines for Conventional Pump-and-Treat Systems. EPA 540/S-97/504. September. 

http://www.epa.gov/ada/issue.html. 

 4-42 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

• Li, Tie, U. Raaj, P.G. Patel, D.K. Ramsden, and J. Greene. 2003. “Groundwater Recovery and 

Treatment”. In Moyer and Kostecki, Eds. MtBE Remediation Handbook. Amherst Scientific 

Publishers. 

• California MtBE Research Partnership. 2000. Treatment Technologies for Removal of Methyl 

Tertiary Butyl Ether (MtBE) from Drinking Water, Second Edition. February. 

4.6.4 What Projects Have Involved Pump-and-Treat for Treating Oxygenates? 

From the 323 projects in EPA’s MtBE Treatment Profiles dataset, 85 projects were identified where 

MtBE in groundwater was remediated using pump-and-treat along with 15 additional projects that treated 

MtBE in drinking water (collectively referred to as pump-and-treat projects). Information on the 

treatment of other oxygenates was reported for 20 of these 100 projects: 16 projects reported TBA, 6 

projects reported TAME, 2 projects reported ethanol, and 1 project reported DIPE as a contaminant in 

addition to MtBE. 

Table 4.6-1 summarizes the scale and operational status for the 100 pump-and-treat projects. Short 

summaries for two complete pump-and-treat projects, Pump-and-treat at Christy Station, North 

Windham, ME and Pump-and-treat and SVE at Service Station NH-B, NH, are included at the end of this 

section. 

Table 4.6-1. General Information about 100 Pump-and-Treat Projects 

Technology(ies) # of Projects 

Operational Status Scale 

Completed Ongoing Bench Pilot Full 

Pump-and-Treat Only 45 12 33 0 13 32 

Pump-and-Treat with Air 

Sparging and SVE 

18 5 13 0 0 18 

Pump-and-Treat with SVE 14 1 13 0 1 13 

Pump-and-Treat with Air 

Sparging 

4 2 2 0 0 4 

Pump-and-Treat with Other 

Technologies 

4 1 3 0 1 3 

Drinking Water Treatment 15 1 14 0 1 14 

TOTAL 100 22 78 0 16 84 

Note: Fifteen (15) drinking water treatment projects are included 

As shown in Table 4.6-1, most of the 100 pump-and-treat projects were full scale (84 projects) and were 

ongoing (78 projects) at the time that its profile was published. In addition, while most (54%) of the 

projects used pump-and-treat alone, almost half supplemented pump-and-treat with air sparging, SVE or 

other technologies, such as phytoremediation, bioremediation, or ISCO. 

4.6.5 How Has Pump-and-Treat Performed in Treating Oxygenates? 

For the 100 pump-and-treat projects in the dataset, initial concentrations in groundwater were as high as 

475,000 μg/L (North Texas Service Station, TX). Concentrations after treatment were as low as nondetectable (the typical reporting limit for MtBE is 5 μg/L). Tables 4.6-2 through 4.6-5 summarize 

available MtBE and TBA performance data for pump-and-treat projects. 

 4-43 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

The data presented in Table 4.6-2 for 21 completed pump-and-treat projects (either alone or in 

combination with other technologies) shows that MtBE concentration reductions in groundwater of 

greater than 99 percent have been achieved in several projects. The median project duration for the 21 

completed sites ranged from 1.5 to 5.5 years. 

Table 4.6-2. MtBE Performance Summary for 21 Completed Pump-and-Treat Projects 

Technology(ies) 

# of 

Projects 

Initial MtBE Concentration 1 

(μg/L) 

Final MtBE Concentration 1 

(μg/L) 

Median 

Project 

Duration 

Minimum Median Maximum Minimum Median Maximum (months) 

Pump-and-Treat Only 

(groundwater) 

8 96 1,800 8,000 2 24 68 27 

Pump-and-Treat with 

Air Sparging and SVE 

5 3 10 390 2 3 4.8 50 

Pump-and-Treat with 

Other Technologies 

4 1,200 11,000 475,000 18 2,070 68,400 40 

Notes: 

1 Treatment performance data are based on the data provided by project managers and others in the source materials used to prepare the 

treatment profiles website, as shown in cluin.org/products/mtbe, and summarized in Appendix A. Appendix A shows the specific sites that 

are summarized here, along with technology design, operation, and performance data for each of the projects. 

2 Performance data are shown in terms of changes in concentration of MtBE in the groundwater, as provided in the reference materials and 

from the project contacts, except as noted. MtBE concentrations prior to beginning treatment (shown as “initial concentration”) and after 

treatment was completed (shown as “final concentration”) are provided. For projects where more than one technology was used, 

performance data are presented under each of the technologies used for the project. 

Treatment performance data for ongoing projects are shown on Tables 4.6-3 and 4.6-4, for pump-andtreat and drinking water treatment projects, respectively. Both types of projects treated groundwater with 

relatively high initial MtBE concentrations (greater than 100,000 μg/L). The available data show that 10 

of 11 drinking water treatment projects achieved treated MtBE concentrations of less than 50 μg/L, while 

the results for pump-and-treat were more widely distributed. 

Table 4.6-3. MtBE Performance Summary for 62 Ongoing Pump-and-Treat Projects 

MtBE Concentration Range 

# of Projects 

Reporting Initial 

MtBE 

Concentrations 

# of Projects with 

Last Reported 

MtBE 

Concentrations 

Greater than 100,000 μg/L 4 1 

Greater than or equal to 10,000 μg/L but 

less than 100,000 μg/L 

11 2 

Greater than or equal to 1,000 μg/L but 

less than 10,000 μg/L 

14 5 

Greater than or equal to 100 μg/L but 

less than 1,000 μg/L 

11 3 

Greater than or equal to 50 μg/L but 

less than 100 μg/L 

3 2 

Less than 50 μg/L 10 13 

 4-44 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Table 4.6-4. MtBE Performance Summary for 12 Ongoing Drinking Water Treatment Systems 

MtBE Concentration Range 

# of Projects 

Reporting Initial 

MtBE 

Concentrations 

# of Projects with 

Last Reported 

MtBE 

Concentrations 

Greater than 100,000 μg/L 3 0 

Greater than or equal to 10,000 μg/L but 

less than 100,000 μg/L 

2 0 

Greater than or equal to 1,000 μg/L but 

less than 10,000 μg/L 

5 0 

Greater than or equal to 100 μg/L but 

less than 1,000 μg/L 

1 1 

Greater than or equal to 50 μg/L but 

less than 100 μg/L 

0 0 

Less than 50 μg/L 1 10 

Table 4.6-5 provides a summary of treatment performance data for 9 pump-and-treat projects that 

provided performance data for TBA. Initial TBA concentrations were as high as 17,000 μg/L, with most 

after-treatment concentrations less than 50 μg/L. Due to the additional interest in TBA, a review of data 

for the 390 projects in the database as of April 2004 showed a total of 15 pump-and-treat projects 

reporting performance data for TBA. Most of these projects reported using the HiPOx process for 

treatment of extracted groundwater, with additional projects using GAC treatment. 

Table 4.6-5. TBA Performance Data for 9 Pump-and-Treat Projects 

Concentration Range 

# of Projects 

Reporting Initial 

Concentrations 

# of Projects with 

Last Reported 

Concentrations 

Greater than 100,000 μg/L 0 0 

Greater than or equal to 10,000 μg/L but 

less than 100,000 μg/L 

1 0 

Greater than or equal to 1,000 μg/L but 

less than 10,000 μg/L 

4 1 

Greater than or equal to 100 μg/L but 

less than 1,000 μg/L 

4 0 

Greater than or equal to 50 μg/L but 

less than 100 μg/L 

0 0 

Less than 50 μg/L 1 7 

4.6.6 What Costs Have Been Associated with Using Pump-and-Treat in Treating MtBE? 

Project cost data were reported for 43 of the 100 pump-and-treat projects in the dataset; these include data 

for both ongoing and completed projects. In most cases, the components that make up the project costs 

were not reported. However, it is likely that these costs incorporate different components, such as 

treatment, monitoring, design, oversight, and health & safety. Most (40 projects) of the reported costs 

were for ongoing projects and represent either a partial actual cost as of the time that the report was made 

or an estimated total project cost. 

 4-45 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Tables 4.6-6 summarize the cost information from these 43 projects, broken down by type of other 

technologies used in conjunction with pump-and-treat. 

Table 4.6-6. Cost Summary for 43 Pump-and-Treat and Drinking Water Treatment Projects 

Technology(ies) 

# of 

Projects

Total Cost Range ($) Median Total 

Reported Cost 

($) Minimum Maximum 

Pump-and-Treat Only 15 71,900 1,120,000 500,000 

Pump-and-Treat with Air Sparging and SVE 9 96,400 567,000 327,000 

Pump-and-Treat with Air Sparging 1 672,000 672,000 672,000 

Pump-and-Treat with SVE 7 160,000 624,000 339,000 

Pump-and-Treat with Other Technologies 1 65,000 65,000 65,000 

Drinking Water Treatment 10 119,000 4,000,000 245,000 

Another source reported the unit costs of pump-and-treat (based only on capital cost) as less than $20 per 

1,000 gallons per year for projects treating more than 20 million gallons of groundwater per year, and unit 

costs (based on O&M cost) as less than $5 per 1,000 gallons per year for projects treating more than 20 

million gallons of groundwater per year (EPA, 2001d). These unit costs represent treatment costs for use 

of pump-and-treat in general, and are not specific to the treatment of MtBE and other oxygenates. In 

another source, the cost of pump-and-treat generally is considered to be worse than average, among the 

costs for remediation technologies, for treatment of contaminated groundwater (FRTR, 2002). 

4.6.7 What Factors May Affect the Performance and Cost of Oxygenate Treatment Using 

Pump-and-Treat? 

Because of the high water solubility of oxygenates, groundwater extraction may be effective in removing 

a significant mass of these contaminants. Key factors that affect the performance and cost of the 

extraction component of a pump-and-treat system include: 

• The depth and accessibility of the plume; site hydrogeologic characteristics, such as aquifer 

permeability 

• The hydraulic conductivity, and flow gradient 

• Remedial goals for the site 

• The presence or prior removal of the contaminant source 

If groundwater contamination is deep or beneath areas (such as buildings and rail lines) where 

conventional vertical wells cannot be placed, innovative drilling techniques or more powerful extraction 

pumps may be required. Alternatively, shallow and accessible groundwater may be easily extracted using 

simple collection trenches. Hydrogeologic characteristics will define the number, design, and spacing of 

extraction points, with tighter formations typically requiring more extraction points for a given area. 

Groundwater flow characteristics and the number and spacing of wells will be the basis for determining 

the flow rate of groundwater that needs to be extracted to achieve the desired capture zone. Cleanup 

goals are also a factor. On-site containment goals may require only pumping from the downgradient edge 

of a plume, whereas a goal of complete aquifer restoration may require more well points pumping at a 

higher extraction rates. 

One of the most significant factors that affect cost and performance is whether the contaminant source 

area at a site is present. If a contaminant source area is allowed to continue to contribute to the 

groundwater plume, groundwater extraction may be required for much longer periods of time than if the 

 4-46 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

contaminant source is removed or treated prior to beginning groundwater pump-and-treat. Because they 

are relatively water soluble, oxygenates tend to dissolve in groundwater rather than form NAPL. When 

they do form NAPL, they float rather than sink, and thus form an LNAPL. Thus, removal or treatment of 

MtBE and other oxygenate source areas can be more straightforward than for other contaminants such as 

chlorinated solvents. 

4.6.8 Conclusions 

Based on the information available from the pump-and-treat projects listed in the MtBE Treatment 

Profiles Website dataset and other information contained in the reference documents reviewed in 

preparation of this report, the following conclusions were identified regarding the use of pump-and-treat 

to remediate sites contaminated with MtBE and other oxygenates. 

Data from Pump-and-Treat MtBE Treatment Profiles 

• Has commonly been used to remediate groundwater contaminated with MtBE and other 

oxygenates – it was employed at 85 of the 323 (26%) of the projects in the dataset (drinking water 

treatment projects represented an additional 15 projects in the dataset) 

• Most often used alone or in conjunction with air sparging and SVE; to a lesser extent, has been 

employed in conjunction with other technologies 

• Has achieved MtBE concentration reductions greater than 99 percent in several projects 

• Median project duration ranged from 1.5 to 5.5 years 

• Median reported total cost was approximately $500,000 for pump-and-treat alone 

Treatability of MtBE and Other Oxygenates Using Pump-and-Treat 

• Groundwater Extraction – Fuel oxygenates are relatively well suited to removal with extracted 

groundwater 

Other Potential Advantages of Applying Pump-and-Treat (EPA, 1995; FRTR, 2002) 

• Properties of MtBE (high water solubility and low organic/water partition coefficient) make it 

amenable to groundwater extraction 

• Can be used to remediate an aquifer or to provide for hydraulic containment 

Other Potential Limitations to Applying Pump-and-Treat (EPA, 1995; FRTR, 2002) 

• Long-term operation may be required to achieve remediation goals for large plumes, complex 

hydrogeologies, or if an active source remains in place 

• The cost of constructing, operating, and maintaining treatment systems is considered to be 

relatively high 

• Biofouling or mineral precipitation in extraction wells or treatment processes can reduce system 

performance 

 4-47 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

4.6.9 Example Projects 

The following two project descriptions incorporate examples of completed, full-scale applications of 

pump-and-treat technology to MtBE-contaminated sites: 

Pump-and-Treat at Christy Station, North Windham, ME 

MtBE was detected in groundwater at Christy Station, located in North Windham, Maine, soon after the fuel 

station was constructed in 1997. Between May and June 1998, a full-scale cleanup was performed using a 

pump-and-treat system that consisted of two extraction wells operating at a combined 3 gpm. Extracted 

groundwater was treated using shallow tray aeration followed by GAC, and the treated groundwater was 

disposed off site. Initial concentrations of MtBE in groundwater were as high as 6,000 μg/L, but MtBE 

concentrations stabilized at 300 μg/L with the operation of the pump-and-treat system. The goal was to reduce 

MtBE in the aquifer to concentrations less than 500 μg/L. Following aeration, MtBE in extracted groundwater 

was reduced to concentrations ranging from 10 to 30 μg/L and following GAC adsorption, MtBE was reduced 

to concentrations of less than 2 μg/L. A performance standard for extracted groundwater was not identified. 

The cost assessment for the remediation was $200,000, the capital cost for the pump-and-treat system was 

$60,000 and the O&M cost was $11,000 for 1 month of operation (Eremita, 2000). 

Pump-and-Treat and SVE at Service Station NH-B, Somersworth, NH 

During inventory measurements in September 1996, a gasoline station in New Hampshire, referred to as 

Service Station NH-B, detected a release of 2,100 gallons of gasoline. Soil at the site consists of 4 to 8 ft of 

sandy fill overlying 2 to 13 ft of glacial till, with bedrock occurring at 10 to 15 ft below ground surface (bgs). 

The depth to groundwater ranges from is 5 to 15 ft bgs. The site is characterized by fractured bedrock and a 

hydraulic gradient of 30 ft/1,000 ft. Remedial activities included the removal of 3 USTs, 860 tons of 

contaminated soil, 27,000 gals of groundwater containing 158 lbs of hydrocarbons, and 120 gals of light nonaqueous phase liquids (LNAPL). A pump-and-treat system consisting of 7 recovery wells screened to bedrock 

and operating at a total flow rate of 7.5 gpm was implemented. Extracted groundwater was treated using 

oil/water separation, filtration, and air stripping. The air stripper contained a 7 horse power (HP) blower which 

operated at 1,000 scfm. Maximum concentrations in the influent to the air stripper were 1,670,000 μg/L of 

MtBE and 439,000 μg/L of BTEX. SVE was conducted using 11 vertical wells and 4 horizontal wells, and a 15 

HP blower operated at 300 scfm and 3.5 to 5 inches of mercury. No vapor treatment was performed. As of 

January 2000, pump-and-treat system had removed 4,300 lbs of hydrocarbons and SVE had removed 2,976 lbs 

of hydrocarbons. They currently use performing enhanced bioremediation at the site. The current total 

remediation cost for this site is $590,000 (EPA, 2002a). 

4.7 Treatment of Extracted Groundwater Used in Pump-and-Treat and Drinking Water 

Treatment Systems 

• j

•

EPA’s MtBE Treatment Profiles Website dataset includes use at 70 pro ects to treat MtBE or 

other fuel oxygenates 

Common processes such as air stripping and adsorption may not be as effective for oxygenates 

as for common fuel components such as BTEX 

4.7.1 What is Above-Ground Treatment for Extracted Groundwater? 

The above-ground (ex situ) treatment technologies used for extracted groundwater are applied both in 

pump-and-treat systems and drinking water treatment systems. In general, the methods for extraction of 

groundwater are not linked to or limited by the type of above-ground treatment technologies. This section 

focuses on above-ground treatment of extracted groundwater, for both pump-and-treat and drinking water 

treatment, while the previous section (Section 4.6) focuses on groundwater extraction. This section also 

includes specific examples of treatment applications used in pump-and-treat and drinking water treatment 

systems. 

 4-48 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

The general types of aboveground technologies that have been used for treating extracted groundwater 

that is contaminated with MtBE and other oxygenates include the following (California MtBE Research 

Partnership, 2000): 

• Air Stripping – Processes in which contaminants are volatilized from water to air in an 

engineered system, such as a packed tower; treatment of the resulting contaminated vapor phase 

may also be required 

• Adsorption – Processes in which contaminants are adsorbed from water onto a medium, such as 

granular activated carbon (GAC) or resin, as driven by equilibrium forces 

• Chemical Oxidation – Processes in which contaminants are sequentially oxidized to less toxic 

products through the introduction of chemical oxidants or the creation of oxidizing conditions 

through other means, such as using ultraviolet (UV) radiation, electrical stimulation, or cavitation 

• Biotreatment – Processes in which contaminants are biodegraded in an engineered system, such 

as an attached growth or activated-sludge bioreactor 

4.7.2 How Do the Properties of MtBE and Other Oxygenates Affect Treatment? 

The properties of MtBE and other oxygenates affect their relative treatability in extracted water using 

different technologies. Air stripping, adsorption, oxidation, and biotreatment technologies are technically 

capable of and have been used to treat water contaminated with some or all of the fuel oxygenates. 

However, the properties of oxygenates versus other fuel contaminants such as BTEX, and the different 

properties of ether-based versus alcohol-based oxygenates, are important to consider when selecting and 

designing an above-ground treatment system. The effect of fuel oxygenate’ properties on treatment using 

each of the commonly used technologies is briefly discussed below. 

Air Stripping 

Similar to air sparging, air stripping relies on the volatilization of contaminants from the aqueous to the 

vapor phase. The property that shows the extent to which this transfer can take place during air sparging 

is the Henry’s Law Constant, which represents the extent to which a contaminant will partition between 

the dissolved state and the vapor state under equilibrium conditions. A contaminant with a greater 

Henry’s Law Constant is more readily stripped from water during air stripping than one with a lesser 

Henry’s Law Constant. The discussion in Section 4.1.2 related to the affect of the properties of fuel 

oxygenates on air sparging is also applicable to air stripping. As discussed in that section, all common 

fuel oxygenates (with the possible exception of DIPE) are less readily stripped than BTEX (based on their 

Henry’s Law Constants). Because of this, air stripping systems designed to treat oxygenates often are 

designed to allow for more air/water contact time than a system designed to treat BTEX constituents at 

the same concentrations. This is typically accomplished by use of a larger stripping tower or packing 

material with a higher specific surface area. As an illustration, based on their ranges of Henry’s Law 

Constants, ether-based oxygenates would require 5 to 10 times more air contact than BTEX to volatilize 

the same concentration of contaminant. Because of this, an air stripping system designed to treat BTEX 

may not be capable of adequately addressing ether-based oxygenates. Alcohol-based oxygenates are even 

more difficult, and in some cases impractical, to strip from groundwater. 

The properties of oxygenates may also affect the applicability and design of a system to treat the 

contaminated vapor effluent resulting from air stripping, if one is required. These affects are discussed in 

Section 4.2 about SVE. 

Adsorption 

In adsorption processes, contaminated water is contacted with a solid adsorption media, such as GAC or 

resin. Based on their equilibrium properties relative to the specific adsorption media, contaminants will 

 4-49 
1.5

1.6

2.0 2.0

1.0

1.0

1.3

1.5

1.6

0.2

0.4

3.2

2.2 2.2

1.1

1.8

1.2

0.9

2.2 2.3

3.0

0

0.5

1

1.5

2

2.5

3

3.5

MtBE ETBE TAME DIPE TBA Ethanol Methanol Benzene Toluene EthylbenzeneXylenes

Partition Coefficient (log L/kg)

ALCOHOL OXYGENATES

ETHER OXYGENATES BTEX

 Technologies for Treating MtBE and Other Fuel Oxygenates 

partition from the water to the solid until the system has reached equilibrium. The maximum 

concentration of a given contaminant that can be adsorbed is dependent on the type of adsorption media 

used, the specific contaminant and its concentration, concentrations of other substances in the water that 

may competitively adsorb, as well as other parameters such as temperature. Although the actual 

treatability of a contaminated water stream is dependent on all of these parameters, the relative treatability 

of MtBE and other oxygenates can be estimated based on their relative tendency to partition from water to 

an organic matrix. One common measure of this tendency is the organic carbon-based partition 

coefficient. Generally, contaminants with lower partition coefficients are less amenable to treatment 

using GAC or resin adsorption. Figure 4.7-1 shows the ranges of partition coefficients for ether- and 

alcohol based coefficients and BTEX. 

Figure 4.7-1. Relative Ranges of Partition Coefficients for Fuels Oxygenates and BTEX 

1.5 

1.6 

2.0 2.0 

1.0 

1.0 

1.3 

1.5 

1.6 

0.2 

0.4 

3.2 

2.2 2.2

1.1 

1.8 

1.2 

0.9 

2.2 2.3 

3.0 

0 

0.5 

1 

1.5 

2 

2.5 

3 

3.5 

MtBE ETBE TAME DIPE TBA Ethanol Methanol Benzene Toluene Ethylbenzene Xylenes 

Partition Coefficient (log L/kg)

ALCOHOL OXYGENATES 

ETHER OXYGENATES BTEX 

1.5

1.6

2.0 2.0

1.0

1.0

1.3

1.5

1.6

0.2

0.4

3.2

2.2 2.2

1.1

1.8

1.2

0.9

2.2 2.3

3.0

0

0.5

1

1.5

2

2.5

3

3.5

MtBE ETBE TAME DIPE TBA Ethanol Methanol Benzene Toluene EthylbenzeneXylenes

Partition Coefficient (log L/kg)

ALCOHOL OXYGENATES

ETHER OXYGENATES BTEX

As shown in Figure 4.7-1, the average partition coefficients for ether- and alcohol-based oxygenates are 

much lower than for BTEX. Based on this, it would be expected that adsorption systems designed only to 

treat BTEX may not be able to effectively address ether-based oxygenates, and that the lower molecular 

weight alcohol-based oxygenates would not be amenable to adsorption. 

Chemical Oxidation 

As discussed in Section 4.5 about in situ chemical oxidation, MtBE and other oxygenates are susceptible 

to degradation through oxidation reactions. If a sufficient amount and strength of oxidant and enough 

time are provided, all ether- and alcohol-based fuel oxygenates can be destroyed via chemical oxidation. 

However, the amount and type of oxidant that is necessary for the treatment of MtBE or other oxygenates 

at a given site will depend on numerous factors beyond the amount of contaminant present. These factors 

are discussed further in Section 4.5. 

There are also technologies that use electrical or other forms of energy to generate oxidizing and reducing 

radicals in aqueous solution and thereby destroy contaminants such as MtBE and other oxygenates. 

These technologies include electron beams and ultrasound. High-energy electron beams (E-beams) 

induce radiolysis (radiation driven splitting) of water to form oxidizing hydroxyl radicals (OH•) as well as 

reducing hydrated electrons (eaq-) and hydrogen (H•). Ultrasound technology relies on the breakdown of 

water molecules into oxidizing and reducing free radicals (OH• and H•) under the intense heat and 

4-50 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

pressures generated during ultrasound-induced cavitation. Both of these technologies have been 

demonstrated on the pilot scale in application to groundwater contaminated with MtBE (Kelley, Marley, 

and Sperry, 2003). 

Biotreatment 

As discussed in Section 4.4 about bioremediation, MtBE and other oxygenates are susceptible to 

biodegradation. For in situ biological treatment, the primary focus is on creating conditions that are 

conducive (sufficient electron acceptors, nutrients, microbes, and co-metabolite) to stimulate 

biodegradation. With aboveground biotreatment, the creation of these conditions is simpler because the 

treatment is occurring in a defined, controlled, and accessible system. However, the relative 

biodegradability of different contaminants, such as ether- and alcohol-based oxygenates, is an important 

consideration in the selection and design of a biotreatment component for a pump-and-treat system. 

These factors are discussed further in Section 4.4. 

4.7.3 How are Technologies Used for Above-Ground Treatment of Oxygenates? 

One or more above-ground technologies are typically used to treat extracted groundwater before 

reinjection or discharge to surface water or the sewer. Multiple technologies, or treatment trains, are 

commonly used at sites contaminated with MtBE and other oxygenates (for example, air stripping 

followed by GAC polishing). A significant amount of literature (some of which is referenced at the end 

of this report) has been dedicated to the design of above-ground treatment systems. Some of the key 

considerations relevant to treatment of MtBE and other oxygenates in extracted groundwater are 

summarized below (California MtBE Research Partnership, 2000). 

Air Stripping 

• A typical volumetric ratio of air to water for effective treatment of MtBE is at least 150 to 200 

parts air to 1 part water, greater than that required to solely remove BTEX. 

• Most states require the capture and treatment of air stripper off gas. Typical off-gas treatment 

technologies that are applicable to MtBE and other oxygenates are adsorption, thermal treatment, 

and biotreatment. These technologies are discussed in more detail in Section 4.2 about SVE. 

Adsorption 

• Because of their water solubility and low partition coefficients, MtBE and other oxygenates are 

difficult to adsorb on GAC. Other, more preferentially adsorbed, contaminants in groundwater 

may also reduce the capacity of GAC to remove MtBE and other oxygenates. In some cases, the 

more absorbable contaminants may even displace MtBE or other oxygenates that are already 

adsorbed. In addition, natural groundwater constituents, such as iron, manganese, or organic 

carbon may also consume adsorption capacity. Because of this, two or more GAC beds are often 

used in series so that contaminant breakthrough can be monitored in the first bed without risking 

the discharge of contaminants into the effluent. 

• Certain types of adsorption media have been shown to preferentially adsorb certain contaminants. 

For example, research has shown that, in some cases, coconut shell based GAC removes MtBE 

better than typical coal-based GAC. In addition, synthetic resins have been developed to 

preferentially adsorb some oxygenates, such as TBA, that are less absorbable by GAC. Often, 

adsorption processes also take advantage of the biodegradability of MtBE and other oxygenates 

by promoting bacterial growth on the adsorption media (refer to Section 4.4.3 about use of 

combined treatment technologies that employ adsorption and biological treatment). 

 4-51 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Chemical Oxidation 

• For the ex situ treatment of groundwater contaminated with MtBE or other oxygenates using 

chemical oxidation, most systems rely on processes that generate hydroxyl radicals, which are 

capable of completely oxidizing organic material to primarily carbon dioxide and water. 

Approaches that have been used to generate hydroxyl radicals for the oxidation of MtBE and 

other oxygenates include the following. In some cases, the treatment system has been tailored for 

aboveground application. In other cases (for example, ultrasonic cavitation and electron beam), 

the technologies have only been used in aboveground treatment systems. 

o Combination of hydrogen peroxide and UV light 

o Combination of hydrogen peroxide and ferrous iron (Fenton’s chemistry) 

o Combination of ozone and UV light 

o Combination of ozone and hydrogen peroxide (such as in the HiPOx system) 

o Ultrasonic Cavitation (using high-energy ultrasonic vibrations to generate high temperatures 

and pressures) 

o Electron Beam (using high energy electrons to split water molecules into free radicals) 

• The incomplete oxidation of MtBE and other oxygenates may result in the generation of 

undesirable intermediate products, such as TBF, TBA, and acetone. The design (oxidant dosage 

and contact time) should be adequate to achieve complete oxidation or additional treatment 

processes, such as GAC, may be used to address residual contamination. 

• The presence of other oxidant-consuming constituents in the feed water, such as iron, natural 

organic carbon, carbonates, bromide, and other contaminants, may require pretreatment of the 

feed stream, additional oxidant dosage, or more contact time to adequately destroy the MtBE and 

other oxygenates. 

Biotreatment 

• Biological treatment systems that incorporate mechanisms to retain sufficient biomass generally 

are applicable to groundwater containing lower concentrations of contaminants. These systems 

typically consider the limited supply of carbonaceous material (food) to sustain a viable 

population of degrading microbes. Attached growth bioreactors, and suspended growth 

bioreactors that incorporate membrane-based biomass separation systems, generally are 

appropriate for these applications. 

• Because the biological degradation rate of MtBE has been observed to be slower than for other 

common contaminants, such as BTEX, MtBE will typically be the rate-limiting contaminant that 

determines the necessary hydraulic retention time for a mixed contaminant system, since it will 

typically be the slowest to degrade (see additional discussion in Section 4.4 about relative rates of 

biodegradation among oxygenates). 

• Due to the difficulties involved in maintaining an adequate microbial mass in application to low 

concentrations of MtBE or other oxygenates in groundwater, treatability studies are often 

performed to confirm that extracted groundwater can be adequately treated in a bioreactor. 

Recently, some efforts have been made to combine treatment technologies that employ adsorption and 

biological treatment. Biological treatment technologies that use naturally occurring microorganisms have 

successfully treated MtBE-contaminated groundwater. However, these microorganisms do not grow 

efficiently on MtBE, and thus require a microbial retention mechanism. Granular activated carbon (GAC) 

serves as an attachment media that immobilizes microbes. Other retention mechanisms include 

permeable barrier membranes and reactive barriers. GAC is often promoted for its adsorption capability 

of environmental pollutants. However, in the presence of BTEX, the affinity of MtBE and TBA to adsorb 

to carbon is lowered. Consequently, GAC may not offer substantial adsorption capacity for MTBE or 

TBA. 

 4-52 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

More detailed information relevant to the application of above-ground treatment at sites contaminated 

with fuel oxygenates and in general is available in the following documents: 

• Cohen, R.M., J.W. Mercer, and R.M. Greenwald. 1998. EPA Groundwater Issue, Design 

Guidelines for Conventional Pump-and-Treat Systems. EPA 540/S-97/504. September. 

http://www.epa.gov/ada/issue.html. 

• Li, Tie, U. Raaj, P.G. Patel, D.K. Ramsden, and J. Greene. 2003. “Groundwater Recovery and 

Treatment”. In Moyer and Kostecki, Eds. MtBE Remediation Handbook. Amherst Scientific 

Publishers. 

• California MtBE Research Partnership. 2000. Treatment Technologies for Removal of Methyl 

Tertiary Butyl Ether (MtBE) from Drinking Water, Second Edition. February. 

4.7.4 What Projects Have Been Used for Above-Ground Treatment of Extracted 

Groundwater? 

From the 323 projects in the MtBE Treatment Profiles Website dataset, 85 projects were identified where 

MtBE in groundwater was remediated using pump-and-treat along with 15 additional projects that treated 

MtBE in drinking water (collectively referred to as pump-and-treat projects). 70 of these projects 

reported the type of above-ground treatment used, as shown in Table 4.7-1. Short summaries for three 

demonstration-scale projects of above-ground treatment technologies, High Biomass Retention Reactor, 

HiPOx Advanced Oxidation Technology, and High Energy Electron Beam, are included at the end of this 

section. 

Table 4.7-1. Above-Ground Treatment Technologies Used at 70 Groundwater 

Pump-and-Treat Remediation and Drinking Water Treatment Projects 

Aboveground Treatment 

Technology Employed 

# of Pump-andTreat Projects 

# of Drinking 

Water Treatment 

Projects Total # of Projects 

Air Stripping Only 8 3 11 

Air Stripping with Adsorption 9 1 10 

Adsorption Only 18 8 26 

Adsorption with Oxidation 1 2 3 

Oxidation Only 19 0 19 

Biotreatment Only 1 0 1 

TOTAL 56 14 70 

Notes:

Based on the data provided by project managers and others in the source materials used to prepare the treatment profiles website,

as shown in cluin.org/products/mtbe, and summarized in Appendix A. Appendix A shows the specific sites that are summarized

here, along with technology design, operation, and performance data for each of the projects.

As shown in the table, the projects in the dataset used adsorption most frequently, either alone or in 

combination with other technologies. Nine of the 39 projects that used adsorption reported information 

about the type of adsorption media that was used in the treatment system. Bituminous carbon was used 

for 4 projects; coconut shell carbon for 2 projects; and, organoclay carbon, resin, or biologically-enhanced 

GAC were used for one project each. Air stripping (21 projects) and oxidation (22 projects) were also 

used frequently. Three of the air stripping projects reported that catalytic oxidation was used for off-gas 

treatment. No other projects reported information about off-gas treatment. Two of the air stripping 

projects reported air-to-water ratios; they were 150:1 and 200:1. Most (21) of the oxidation projects 

 4-53 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

reported the type of oxidation that was employed. Hydrogen peroxide/ozone was used for 16 projects; 

hydrogen peroxide/UV was used for 3 projects; hydrogen peroxide alone and ultrasonic cavitation were 

used for one project each. 

As an example of above-ground treatment, a site in Mission Viejo, CA had an operating dual-phase 

extraction system withdrawing soil vapor and groundwater for treatment with oxidation and bioreaction, 

respectively. Initially, the major contaminant was TBA, with a lesser concern about MtBE. However, as 

the formation dried out and more porosity developed, the concentrations of BTEX were found to be 

climbing. Site consultants considered that if the BTEX exceeded the TBA/MTBE concentration for a 

long time period, then the bio-mass would prefer the BTEX and would lose its ability to consume 

TBA/MTBE. To address this concern, a "sacrificial" carbon canister containing 200 pounds of coconut 

carbon was installed ahead of the bio-reactor to remove the BTEX while allowing the TBA/MTBE to pass 

through and be remediated in the bio-reactor. While feeding approximately 1.5 gpm of a stream 

containing approximately equal concentrations of TBA/MTBE and BTEX, the stream exiting the carbon 

canister showed breakthrough for TBA in two days, the first time a sample was taken. The TBA entering 

and leaving the carbon canister showed no decrease in concentration after the first week. The BTEX took 

about 45 days to break through (O'Connell, 2004). 

4.7.5 How Has Above-Ground Treatment Performed in Treating Oxygenates? 

Of the projects in the database, four completed projects using pump-and-treat provided performance data 

for initial and final MtBE concentrations. Median concentrations were 27,000 μg/L for before treatment, 

and less than 1μg/L for after treatment. The median project duration for these projects was 14 months. 

Note that these treatment performance data are based on the data provided by project managers and others 

in the source materials used to prepare the treatment profiles website, as summarized in Appendix A. 

Appendix A shows the specific sites that are summarized here, along with technology design, operation, 

and performance data for each of the projects. For projects where more than one technology was used, 

performance data are presented under each of the technologies used for the project. 

4.7.6 What Costs Have Been Associated with Using Pump-and-Treat in Treating MtBE? 

Project cost data were reported for 12 pump-and-treat projects in the dataset based on type of aboveground treatment used; these include data for both ongoing and completed projects. In most cases, the 

components that make up the project costs were not reported. However, it is likely that these costs 

incorporate different components, such as treatment, monitoring, design, oversight, and health & safety. 

Most of the reported costs were for ongoing projects and represent either a partial actual cost as of the 

time that the report was made or an estimated total project cost. 

Table 4.7-2 summarizes the cost information from these 12 projects, broken down the type of aboveground treatment technologies used. 

Table 4.7-2. Cost Summary for Pump-and-Treat – By Aboveground Treatment Type 

Aboveground Treatment # of Total Cost Range Median Total 

Technology(ies) Projects Minimum Maximum Reported Cost ($) 

Air Stripping Only 6 74,000 1,200,000 545,000 

Air Stripping with Adsorption 3 216,000 1,180,000 339,000 

Adsorption Only 3 160,000 624,000 180,000 

TOTAL 12 450,000 3,000,000 1,060,000 

 4-54 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Table 4.7-3 summarizes ranges of projected unit costs estimated by the California MtBE Research 

Partnership for the treatment of different flow rates (60, 600, and 6,000 gallons per minute (gpm) of 

MtBE-contaminated water using air stripping, oxidation, and adsorption technologies. These results show 

that air stripping is less costly than either adsorption or oxidation, and that there are economies of scale 

with treatment of relatively larger quantities of water. 

Table 4.7-3. Estimated Range of Unit Costs for Above ground Treatment Technologies 

Technology Category 

$/1,000 Gallons Treated 

(60 gpm system) 

$/1,000 Gallons Treated 

(600 gpm system) 

$/1,000 Gallons Treated 

(6,000 gpm system) 

Minimum Maximum Minimum Maximum Minimum Maximum 

Air Stripping 1.66 3.20 0.30 1.09 0.13 0.64 

Adsorption 2.30 4.61 0.77 2.37 0.30 2.22 

Oxidation 2.18 4.11 0.57 2.08 0.32 1.59 

Source: The California MtBE Research Partnership, 2000 

4.7.7 What Factors May Affect the Performance and Cost of Above-Ground Treatment for 

Oxygenates? 

Once water contaminated with MtBE or other oxygenates has been extracted, the relative tendency to 

remain in the aqueous phase can make above-ground treatment more complicated than the treatment of 

other contaminants, such as BTEX. Key factors that may affect the cost and performance of aboveground treatment include: 

• The concentrations of oxygenates and other contaminants 

• Extracted groundwater flow rates 

• Other groundwater chemistry parameters that may interfere with treatment, such as natural 

organic carbon, iron, manganese, hardness, alkalinity, pH; effluent water and off-gas discharge 

standards 

These factors may influence the specific above-ground treatment technology that is selected, the possible 

need for multiple above-ground treatment processes (treatment trains), and the need for pre-treatment of 

groundwater or post-treatment of off-gas. Also, as with the extraction component, the presence of an 

active source area may result in the need for long-term operation of above-ground treatment systems. 

4.7.8 Conclusions 

Based on the information available from the projects listed in the MtBE Treatment Profiles Website 

dataset and other information contained in the reference documents reviewed in preparation of this report, 

the following conclusions were identified regarding the use of above-ground treatment for sites 

contaminated with MtBE and other oxygenates. 

Treatability of MtBE and Other Oxygenates Using Above-Ground Treatment 

• Air Stripping – Treatment of ether-based oxygenates may require greater air to water ratios than 

treating only BTEX; treatment of alcohol-based oxygenates may be impractical 

• Adsorption – Ether-based oxygenates are less readily removed than BTEX using GAC and some 

alcohol-based oxygenates may not be adsorbable at all; synthetic resins that more selectively 

remove fuel oxygenates are available 

 4-55 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

• Chemical Oxidation – Fuel oxygenates can be destroyed using hydroxyl radical oxidation; 

oxidant dosage and contact time based more on overall oxidant demand of extracted groundwater 

than types of oxygenate contaminants 

• Biotreatment – Fuel oxygenates can be biodegraded given adequate retention time in a 

bioreactor with a sufficient mass of conditioned microbes 

• In general, above-ground treatment systems can be more readily controlled and monitored to 

optimize the removal of MtBE and other oxygenates than in situ treatment systems 

Other Potential Limitations to Applying Above-Ground Treatment (EPA, 1995; FRTR, 2002) 

• The cost of constructing, operating, and maintaining treatment systems is considered to be 

relatively high 

• Biofouling or mineral precipitation in extraction wells or treatment processes can reduce system 

performance 

4.7.9 Example Projects 

The following two project descriptions relate to demonstrations of innovative ex situ treatment systems 

for groundwater contaminated with MtBE and other oxygenates: 

Biodegradation of MtBE in a High Biomass Retention Reactor: Demonstration Study at Pascoag, RI 

A pilot-scale specialized Biomass Concentrator Reactor (BCR), an activated sludge type bioreactor that uses a 

membrane-based biomass separation system, was tested for the aerobic biodegradation of MtBE. The BCR 

design encompasses an aeration chamber housing a high surface area porous polyethylene membrane system 

that retains all of the biomass within the aeration chamber. Its simple operation and low maintenance 

requirements may render it economically more feasible than other water treatment technologies. The water flux 

through the membrane relies completely on gravity. The system includes 30 membrane compartments, with 

each one removable for cleaning. 

The BCR was used in a demonstration at a Pascoag, RI abandoned gasoline station where substantial amounts 

of gasoline have leaked into the groundwater, contaminating it with MtBE, TBA, TAME, TAA, DIPE, TBF, 

acetone, methanol, ethanol, and BTEX. The objective of the study was to demonstrate the effectiveness of the 

BCR in treating MtBE, other oxygenates, and BTEX to near or below detectable limits. The BCR was operated 

at the Pascoag site for nearly 6.5 months at up to 5 gpm. Average influent concentrations of volatile organic 

compounds were: MtBE, 6,500 μg/L; TBA, 69 μg/L; TAME, 1,130 μg/L; TAA, 130 μg/L; DIPE, 36 μg/L; 

TBF, 29 μg/L; acetone, 480 μg/L; methanol, 300 mg/L; and the sum of BTEX, 3,700 mg/L. Effluent 

concentrations were very low despite continual flow interruptions from the source wells. Over the entire 

project, including flow interruptions and non-steady-state flow conditions, MtBE in the effluent averaged near 9 

μg/L (< 5 μg/L during 5 gpm steady state flow conditions without flow interruptions), TBA, 0.5 μg/L; TAME, 

1.4 μg/L; TAA, ~0.06 μg/L; DIPE, 0.05 μg/L; TBF, 0.02 μg/L; acetone, 6.6 μg/L; methanol, 2 μg/L; and sum of 

BTEX, 1.3 μg/L. Non-purgeable organic carbon (NPOC) was reduced by close to 50%. A detailed cost 

analysis has not yet been conducted (Venosa 2003). 

Demonstration of the HiPOx Advanced Oxidation Technology for the Treatment of 

MTBE-Contaminated Groundwater at Port Hueneme, CA 

The HiPOx technology is an advanced oxidation process that incorporates high-precision delivery of ozone and 

hydrogen peroxide to chemically destroy organic contaminants while minimizing bromate formation. A MtBEcontaminated groundwater (initial MtBE concentration of 748 μg/L) from the Ventura County Naval Base in 

Port Hueneme, CA was used to evaluate this technology. Due to extremely high concentrations of bromide in 

the feed water (1.3 mg/L) and the desire to limit bromate formation, a pilot-scale system was operated with 630 

ozone injector ports in series, as part of EPA’s SITE program. 

 4-56 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

The HiPOx process achieved greater than a 99.87 percent reduction in MTBE concentration and easily met the 

treatment goal of reducing the concentration of MtBE to below 5 μg/L. However, significant concentrations of 

MtBE degradation intermediates and oxidation by-products were present in the final effluent. TBA was 

produced early during the chemical oxidation process. Its concentration was diminished by further oxidation, 

reaching below its regulatory limit of 12 μg/L in two of the three runs. Acetone was generated and a sizable 

percentage was left unoxidized in the final effluent (>100 μg/L). Bromate concentrations in the effluent 

exceeded the drinking water standard of 10 μg/L for all three runs. 

A model calculation showed that the HiPOx system may have been fully successful in limiting bromate 

formation under the chosen oxidant doses if the influent bromide concentration was 0.56 mg/L, or less. Since a 

bromide concentration of 0.56 mg/L is still extremely high for a drinking water source, the HiPOx system 

appears to hold promise for destroying MTBE and its oxidative byproduct TBA while controlling bromate 

formation, even in waters that have high bromide concentrations (Speth and Swanson 2002). 

Application of High Energy Electron Beam (E-Beam) to the Treatment of MtBE-contaminated Groundwater 

at Port Hueneme, CA 

A demonstration of the high-energy electron injection (E-Beam) technology in application to groundwater 

contaminated with MtBE and with BTEX was conducted at the Naval Base Ventura County, Port Hueneme, 

CA, as part of EPA’s SITE program. The E-beam technology destroys organic contaminants in groundwater 

through irradiation with a beam of high-energy electrons; the oxidizing radicals that are generated by the Ebeam react with and destroy organic contaminants, including MtBE and its breakdown products. 

Results of two weeks of steady state operation at an E-beam dose of 1,200 kilorads (krads) indicated that MtBE 

and BTEX concentrations in the effluent were reduced by greater than 99.9 percent from influent concentrations 

that averaged over 1,700 μg/L MtBE and 2,800 μg/L BTEX. Further, the treatment goals for the demonstration, 

which were based on drinking water regulatory criteria, were met for all contaminants except for TBA, a 

degradation product of MtBE. Dose experiments indicated that TBA was not consistently reduced to below the 

treatment goal of 12 μg/L although the results indicated that tBA by-product formation decreased as dose 

increased. Acetone and formaldehyde were the two most prevalent organic by-products that were formed by Ebeam treatment, with mean effluent concentrations during the two-week steady state testing of 160 and 125 

μg/L, respectively. Bromate was not formed during E-beam treatment. 

An economic analysis of the E-beam treatment system indicated that the primary costs are for the E-beam 

equipment and for electrical energy. The estimated cost ranged from over $40 per 1000 gallons for a small-scale 

remedial application to about $1.00 per 1000 gallons for a larger-scale drinking water application (Venosa and 

Swanson 2002). 

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 Technologies for Treating MtBE and Other Fuel Oxygenates 

4.8 Other Treatment Technologies: Phytoremediation, PRBs, and Thermal Treatment 

Overview 

• Other technologies that have been used to treat MtBE and other 

oxygenates include: 

○ Phytoremediation (8 projects in dataset) 

○ Permeable Reactive Barriers 

○ Thermal Treatment 

4.8.1 What Other Technologies are used to Treat MtBE and Other Oxygenates? 

In addition to the technologies discussed earlier in this chapter, three additional technologies 

(phytoremediation, PRBs, and thermal treatment) have also been used to treat MtBE and other oxygenates 

in soil and groundwater. Phytoremediation is a category of treatment technologies that employ plants (or 

in some cases fungi) to conduct remediation. Treatment during phytoremediation can be accomplished 

through one or more natural processes, including enhanced bioremediation in the rhizosphere (plant root 

zone), phyto-stabilization of contaminants by organic plant material, plant uptake, plant metabolism, and 

phytovolatilization (volatilization through plant leaves) (EPA, 2000g). PRBs are subsurface barriers that 

remediate groundwater as it passes through an engineered treatment zone. For the treatment of MtBE and 

other oxygenates, treatment zones that use bioremediation processes are most common (EPA, 2002e). 

Thermal treatment is a generic term that applies to technologies that use heat to mobilize, extract, or 

destroy contaminants either in situ or ex situ. While these technologies were applied less frequently, they 

may represent viable treatment options at some sites contaminated with MtBE and other oxygenates. 

4.8.2 How Is Phytoremediation Used in Treatment of Oxygenates? 

Properties -- 

Phytoremediation, as it applies to MtBE and other oxygenates, is a relatively new remedial approach and 

many of the removal and degradation pathways are currently being studied. However, it is known that 

phytoremediation relies on multiple processes to accomplish the removal of contaminants from shallow 

groundwater. Each of these processes is affected by different chemical properties as well as site-specific 

conditions. The biodegradability of oxygenates affects their treatment in the rhizosphere, where the 

conditions support an abundance of metabolically-active bacteria and fungi that may enhance contaminant 

degradation. The relatively high solubility and low organic partition coefficients (discussed earlier in this 

section) of oxygenates generally limits significant removal through phyto-stabilization, but facilitates 

removal through root uptake. In addition, volatility and Henry’s Constants may affect the removal 

through phytovolatilization (Chard and others, 2001). 

Application – 

The manner that phytoremediation can be applied to treat MtBE and other fuel oxygenates is highly 

variable, based on the site conditions, specific contaminants to be treated, cleanup goals, and other 

factors. Information relevant to the application of phytoremediation at sites contaminated with MtBE and 

other oxygenates is available in the documents: 

• EPA. 2000. Introduction to Phytoremediation. Office of Research and Development. EPA 600-

R-99-107. February. 

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 Technologies for Treating MtBE and Other Fuel Oxygenates 

• Chard, J., A.M. Ferro, and J. Greene. 2001. “Recent Advances in Phytoremediation of MtBE 

Groundwater Plumes”. Contaminated Soil, Sediment, and Water. Spring. 

• Landmeyer, J. E., D. A. Vrblosky and P. M. Bradley. 2000. “MtBE and BTEX in Trees above 

Contaminated Groundwater”. Battelle International Conference on Remediation of Chlorinated 

and Recalcitrant Compounds, Monterey, CA. 

• Newman, Lee and Charles Arnold. 2003. “Phytoremediation of MTBE – A Review of the State 

of the Technology”. In Moyer and Kostecki, Eds. MtBE Remediation Handbook. Amherst 

Scientific Publishers. 

• Rubin, E. and A. Ramaswami. 2001. “The Potential for Phytoremediation of MtBE”. Water 

Res. 35(5): 1348-1353. 

Projects – 

From the 323 MtBE treatment profiles, 8 projects were identified where MtBE was treated using 

phytoremediation. These projects used various approaches, including hybrid poplar trees, Monterey pine, 

oak, eucalyptus, and engineered wetlands. 

Table 4.8-1 summarizes the scale and operational status for the 8 projects in the dataset that used 

phytoremediation. The data used to compile this information was current at the time the profile for each 

project was completed. Further information about these projects is provided in Appendix A, including 

available performance data. 

Table 4.8-1. General Information on 8 Projects Using Phytoremediation 

Technology # of Projects 

Operational Status Scale 

Completed Ongoing Bench Pilot Full 

Phytoremediation 8 5 3 3 4 1 

Costs – 

No total project cost data were reported for any of the projects in the dataset that employed 

phytoremediation technology. 

4.8.3 How Are PRBs Used in Treatment of Oxygenates? 

Properties -- 

A PRB is a treatment system configuration with treatment zones that can employ any of a number of 

treatment technologies, such as in situ bioremediation or in situ chemical oxidation. Depending on which 

treatment technology is employed, the properties of MtBE and other oxygenates as they apply to that 

specific technology (as discussed earlier in this section) will affect treatment differently. 

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 Technologies for Treating MtBE and Other Fuel Oxygenates 

Application – 

Information relevant to the application of PRBs at sites contaminated with MtBE and other oxygenates is 

available in the documents: 

• Gavaskar, A., N. Gupta, B. Sass, R. Janosy, and J. Hicks. 2000. Design Guidance for 

Application of Permeable Reactive Barriers for Groundwater Remediation. Prepared for U.S. 

Air Force, Air Force Research Laboratory. March. 

• ITRC. 1999. Regulatory Guidance for Permeable Reactive Barriers Designed to Remediate 

Chlorinated Solvents. December. 

• EPA. 1998. Permeable Reactive Barrier Technologies for Contaminant Remediation. 

EPA/600/R-98/125. Office of Research and Development. September. 

• EPA. 2002. Field Applications of In Situ Remediation Technologies: Permeable Reactive 

Barriers. Office of Solid Waste and Emergency Response. January. 

• EPA. 2002. Economic Analysis of the Implementation of Permeable Reactive Barriers for 

Remediation of Contaminated Ground Water. EPA/600/R-02/034. National Risk Management 

Research Laboratory, Ada, Oklahoma. June. 

Projects – 

While no projects in the dataset were identified explicitly as using PRBs, several projects discussed under 

other technologies involved these types of components. For example, several bioremediation projects, 

such as at Port Hueneme, were performed using a PRB configuration; these are discussed further in 

Section 4.4. 

Costs – 

No total project cost data were reported for any of the projects in the dataset that employed in situ thermal 

treatment technology. However, additional information in the literature includes information about the 

application of PRBs for the treatment of other contaminants. One reference showed a range of total costs 

for 16 PRB projects ranging from $43,000 to $1,900,000 with a median total cost of $680,000 (EPA, 

2000c). 

4.8.4 How Is In Situ Thermal Treatment Used for Remediation of Oxygenates? 

Properties -- 

Thermal treatment can be used to mobilize or destroy MtBE and other oxygenates from soil either in situ 

or ex situ, similar to other petroleum contaminants. Projects in the dataset applied in situ thermal 

treatment. Volatilization from soil is affected by vapor pressure, with a higher vapor pressure making 

volatilization occur more readily. In general, alcohol-based oxygenates have lower vapor pressures than 

ether-based oxygenates, but the vapor pressures of both are comparable to or greater than other petroleum 

contaminants such as benzene. Similar to other organic contaminants, MtBE and other oxygenates may 

also be susceptible to thermal destruction at high temperatures. 

 4-60 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Application – 

Information relevant to the application of in situ thermal treatment at sites contaminated with MtBE and 

other oxygenates is available in the following document: 

• EPA. 2004. In Situ Thermal Treatment of Chlorinated Solvents: Fundamentals and Field 

Applications. EPA 542-R-04-010. Office of Solid Waste and Emergency Response. March. 

Projects – 

While no projects in the dataset were identified explicitly as using in situ thermal treatment, several 

projects discussed under other technologies involved these types of components. For example, one site in 

Texas also discussed under bioremediation (Rural Area Disposal Area, Liberty, TX) used a combination 

of technologies that included an in situ thermal treatment component. 

Costs – 

No total project cost data were reported for any of the projects in the dataset that employed in situ thermal 

treatment technology. 

4.8.5 What Factors may Affect the Performance and Cost of Phytoremediation, PRBs, or 

Thermal Treatment? 

When MtBE or other oxygenates are present and must be remediated at a site, phytoremediation, PRBs, 

or in situ thermal treatment, may be part of a suitable remediation approach. Information about the 

factors that influence the performance and cost of these systems in general is available in the references 

listed in this report. 

4.8.6 Conclusions 

Data from MtBE Treatment Profiles Reporting About Other Treatment Technologies 

• Phytoremediation, PRBs, and thermal treatment have been used to remediate groundwater 

contaminated with MtBE, but less frequently than some other technologies such as air sparging 

and bioremediation; phytoremediation has been used at 8 sites for MtBE 

• All PRB projects in the dataset have treatment zones that employed bioremediation technology 

• The thermal treatment projects in the dataset used thermal desorption in conjunction with other 

technologies, such as in situ bioremediation 

• No information on total project cost was reported for projects using phytoremediation, PRBs, or 

thermal treatment 

Treatability of MtBE and Other Oxygenates Using Other Treatment Technologies 

• Treatability during phytoremediation based on multiple contaminant properties, including 

biodegradability, solubility, partition coefficient, vapor pressure, and Henry’s Constant 

• Treatability using PRBs dependant on reactive treatment zone employed 

• Vapor pressure from soil affects volatilization during thermal treatment; generally oxygenates 

have comparable or higher (more favorable for volatilization) vapor pressures than other 

petroleum contaminants 

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 Technologies for Treating MtBE and Other Fuel Oxygenates 

Other Potential Advantages of Applying Other Treatment Technologies 

• Phytoremediation or PRBs may be a cost-effective alternative for remediating or containing 

relatively low concentration, shallow, and widespread groundwater plumes 

• Thermal treatment technologies tend to remove oxygenates along with other petroleum 

contaminants (such as petroleum hydrocarbons) that are more typically treated using this 

technology 

Other Potential Limitations to Applying Other Treatment Technologies 

• The processes that effectively treat MtBE and other oxygenates during phytoremediation are still 

being studied 

• Phytoremediation may be less applicable to higher concentration or deeper groundwater plumes 

 4-62 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

5.0 NON-TREATMENT REMEDIES

Overview 

$ Non-treatment remedies that address oxygenates include excavation, free 

product recovery, MNA, and institutional controls 

$ Non-treatment remedies may be appropriate for use either alone or in 

conjunction with one or more of the other remedies discussed in this report 

$ Containment (caps or vertical barrier walls) typically have not been used at 

sites contaminated with MtBE, and is not discussed further 

While this report focuses on treatment technologies that have been used for MtBE and other fuel 

oxygenates, many sites are being remedied using non-treatment options that include excavation, free 

product recovery, MNA, and institutional controls. In addition, these remedies sometimes are used in 

conjunction with one or more of the treatment technologies discussed in Section 4. 

5.1 Excavation 

Excavation is the removal of contaminated soil or sludge from a site by use of mechanical equipment. It 

often is used at sites where significant volumes of petroleum products are present in the soils located near 

the surface, and which are likely to be a continuing source of contaminant migration. Commonly, 

excavation is performed prior to or while implementing other remedies such as groundwater treatment 

technologies. Similar to free product recovery, excavation is used to remove/control the source of 

contamination, so that MtBE will not continue to migrate to the vadose zone and groundwater (FRTR, 

2002). 

Site-specific characteristics, such as the presence of aboveground and below ground obstructions, largely 

dictate the implementation of excavation. Locations where underground utilities or storage facilities exist 

may require extensive and time-consuming exploratory excavation and hand-digging. Excavation around 

or near buildings may require the use of underpinning or sheet piling to stabilize the structure and 

rerouting of utility lines. Shoring or sloping may be required in sandy soil to maintain trench wall 

stability. Monitoring for air quality may be required during excavation. When fugitive air emissions 

exceed air quality standards, there may be limitations imposed on the quantity of soil that can be 

excavated per day. 

Excavation equipment ranges from hand tools, such as pick axes and shovels, to backhoes, front-end 

loaders, clamshells, and draglines, depending on the amount of soil to be excavated, the total depth of the 

excavation, moisture content of the soil, and the space allowed at the site for staging of excavated 

material. Backhoes and front-end loaders are the most commonly used equipment for excavation of 

relatively shallow (less than 15 ft bgs) soils. Excavation rates for these types of units with 1 cubic yard 

bucket capacities are typically 75 cubic yards per hour. Larger bucket capacities can increase this rate to 

up to 160 cubic yards per hour (ECHOS, 2002). The maximum excavation rate using hand tools is 

approximately 1 cubic yard per hour /laborer. 

Factors that affect the costs for excavation include the depth of contamination, depth of groundwater 

(requiring dewatering), and extent of underground infrastructure and/or nearby structures that require 

shoring. The cost for excavation tends to be higher for areas with deeper contamination, shallower 

groundwater, and more infrastructure and nearby structures. 

 5-1 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

5.2 Free Product Recovery 

Free product recovery is the extraction of separate phase material (primarily petroleum liquids) that is 

located in the subsurface (in the case of petroleum liquids, at the top of the water table). It is often used at 

sites where significant volumes of petroleum products have reached the water table, and which are likely 

to be a continuing source of contaminants migrating to the vadose zone or dissolving in groundwater. 

Commonly, free product recovery is performed prior to or during implementation of remedies such as 

groundwater treatment. Similar to excavation, free product recovery is used to remove/control the source 

of contamination, so that the source will not continue to migrate to the vadose zone or the groundwater. 

Note that free product removal is a Federal regulatory requirement, under 40 CFR Section 280.64. This 

section requires owners and operators to remove free product to the maximum extent practicable, while 

continuing other remedial actions, as discussed in that section. 

Technologies typically used to recover free product include skimming equipment in wells, trenches, or 

excavation pits, and pumping of free product. These approaches have been used with and without 

depressing the water table to enhance migration of free product to a well or drain. The design of a free 

product recovery system requires an understanding of the site hydrogeology and characteristics, the types, 

extent, and distribution of free product in the subsurface, and the engineering aspects of the equipment 

and installation. Free product recovery sometimes is combined with other technologies to enhance 

removal of contaminants from the vadose zone or that are dissolved in the groundwater. 

EPA published a guide for state regulators about how to effectively recover free product at leaking USTs, 

How to Effectively Recover Free Product at Leaking Underground Storage Tank Sites; A Guide for State 

Regulators (EPA, 1996). In that guide, EPA provided scientific and engineering considerations for 

evaluating technologies for the recovery of free product from the subsurface. The guide discussed the 

behavior of hydrocarbons in the subsurface, methods for evaluating recoverability of subsurface 

hydrocarbons, and recovery systems and equipment. 

5.3 Monitored Natural Attenuation 

EPA defines MNA as “the reliance on natural processes, within the context of a carefully controlled and 

monitored site cleanup approach, to achieve site-specific remediation objectives within a time frame that 

is reasonable compared to that offered by other more active methods. The natural processes include 

biodegradation, dispersion, dilution, sorption, volatilization, stabilization, and transformation. These 

processes reduce site risk by transforming contaminants to less toxic forms, reducing contaminant 

concentrations, and reducing contaminant mobility and bioavailability”. Other terms for natural 

attenuation in the literature include “intrinsic remediation”, “intrinsic bioremediation”, “passive 

bioremediation”, “natural recovery”, and “natural assimilation” (EPA, 1999b). 

While offering the potential to cleanup sites at lower cost, MNA typically would require a longer period 

of time to achieve remediation objectives, compared to active remediation measures. In addition, it 

generally requires extensive long-term monitoring data. Other potential limitations of MNA include the 

potential that the toxicity and/or mobility of transformation products may be greater than for the parent 

compound (e.g., TBA as a degradation product of MtBE); hydrologic and geochemical conditions 

amenable to natural attenuation may change over time and could result in renewed mobility of previouslystabilized contaminants; and more extensive education and outreach efforts may be required to gain 

public acceptance of MNA. Information about research into field use of MNA is provided in Schirmer 

1999. 

 5-2 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

EPA published a guide about the steps needed to understand the rate and extent to which natural 

processes are reducing contaminant concentrations, Technical Protocol for Evaluating Natural 

Attenuation of Chlorinated Solvents in Ground Water (EPA, 1998b). While this guide is directed at sites 

contaminated by chlorinated solvents, some of the steps would also have relevance for sites contaminated 

by oxygenates like MtBE. The guide identifies parameters that are useful in the evaluation of natural 

attenuation and provides recommendations on how to analyze and interpret the data collected from the 

site characterization process. It also provides suggestions for integrating MNA into an integrated 

approach to remediation that includes an active remedy. 

Recently, EPA published a report titled "Performance Monitoring of MNA Remedies for VOCs in 

Ground Water" (EPA, 2004a) that provides guidance about types of monitoring used during MNA 

remedies. 

5.4 Institutional Controls 

ICs are non-engineered instruments such as administrative and/or legal controls that minimize the 

potential for human exposure to contamination by limiting land or resource use, and generally are used in 

conjunction with engineering measures such as treatment or containment. ICs are used during all stages 

of a cleanup and often involve multiple activities (“layered IC”) implemented in parallel or in series. 

Examples of ICs are easements, covenants, well drilling prohibitions, zoning restrictions, and special 

building permit requirements (sometimes referred to as deed restrictions) (EPA, 2000d). 

Often, ICs are considered within the context of long-term plume management and MNA. Typically, after 

the source of contamination has been addressed (such as through removal or destruction), ICs are used to 

limit the long-term use of a site and the potential for exposure of residual contaminants to human or 

environmental receptors. When deciding about appropriate types of ICs, site managers look at the lifecycle strengths, weaknesses, and costs for implementation, monitoring, and enforcement, and 

coordination with state and local governments that have responsibilities for ICs. Additional information 

about ICs is available in Institutional Controls: A Site Manager’s Guide to Identifying, Evaluating, and 

Selecting Institutional Controls at Superfund and RCRA Corrective Action Clean-ups (EPA, 2000d). 

 5-3 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

6.0 REFERENCES 

American Petroleum Institute (API). 1998. API Soil & Groundwater Research Bulletin: Ten Frequently 

Asked Questions About MtBE in Water. Technical Bulletin 3, Version 1.1. March. 

API. 1995. In Situ Air Sparging: Evaluation of Petroleum Industry Sites and Considerations for 

Applicability, Design and Operation. Product Number I46090. May. 

American Water Works Research Foundation. 2003. Occurrence of MtBE and VOCs in Drinking Water 

Sources of the U.S. 

Anderson, R.T. and Lovley, D.R. 1997. "Ecology and biogeochemistry of in situ groundwater 

bioremediation." In: (J. G. Jones, ed.) Advances in Microbial Ecology., vol. 15, pp. 289-350, Plenum 

Press, New York. 

Bauman, Bruce, API. 1999. MtBE and Gasoline Oxygenates - Legislative and Regulatory Updates, 

Developments in Groundwater Research. Presentation at SERDP/ESTCP Conference. December 2. 

Blue Ribbon Panel Oxygenates in Gasoline. 1999. Achieving Clean Air and Clean Water: The Report of 

the Blue Ribbon Panel on Oxygenates in Gasoline. EPA 420-R-99-021. 

http://www.epa.gov/oms/consumer/fuels/oxypanel/blueribb.htm. 

Bradley, Paul M., F.H. Chapelle, and J.E. Landmeyer, USGS. 2001. “Methyl t-Butyl Ether 

Mineralization in Surface-Water Sediment Microcosms under Denitrfying Conditions”. Applied and 

Environmental Microbiology. Pp. 1975-1978. April. 

Bruce, C.L., Miller, K.D., Johnson, P.C. 2001. Full Scale Bio-Barrier Demonstration for Treatment of a 

Mixed MtBE/TBA/BTEX Plume at Port Hueneme. 

California EPA, 1999. Public health goal for methyl tert butyl ether (MTBE) in drinking water. Office of 

Environmental Health Hazard Assessment. Sacramento. 

http://www.oehha.ca.gov/water/phg/allphgs.html 

California MtBE Research Partnership. 2000. Treatment Technologies for Removal of Methyl Tertiary 

Butyl Ether (MtBE) from Drinking Water, Second Edition. February. 

Chang, H.L. and T.F. Yen. 2000. An improved chemical-assisted ultrasound treatment for MTBE. 

Proceedings of the Second International Conference on Remediation of Chlorinated and Recalcitrant 

Compounds. Battelle Press. 

Chard, J., A.M. Ferro, and J. Greene. 2001. “Recent Advances in Phytoremediation of MtBE 

Groundwater Plumes”. Contaminated Soil, Sediment, and Water. Spring. 

Church, C.D. and P.G. Tratnyek. 2000. Process Level Investigations of the In Situ Degradation of 

MTBE. Presented at the MTBE Biodegradation Workshop, Cincinnati, OH, February 1-3. 

Cohen, R.M., J.W. Mercer, and R.M. Greenwald. 1998. EPA Groundwater Issue, Design Guidelines for 

Conventional Pump-and-Treat Systems. EPA 540/S-97/504. September. 

http://www.epa.gov/ada/issue.html. 

Corseuil, H.X. and F.N. Moreno. 2001. “Phytoremediation potential of willow trees for aquifers 

contaminated with ethanol-blended gasoline”. Water Research. 35(12): 1013-7. August. 

Creek, D.M., and J.M. Davidson, Alpine Environmental Inc. 1998. The performance and cost of MtBE 

remediation technologies. In Stanley, Anita, ed., Petroleum Hydrocarbons and Organic Chemicals in 

Ground Water. Published in Proceedings of Prevention, Detection, and Remediation Conference, 

National Ground Water Association and American Petroleum Institute. Houston, Texas. November. 

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 Technologies for Treating MtBE and Other Fuel Oxygenates 

Crumbling D.M., Lesnik B. 2000. Analytical Issues for MtBE and Related Oxygenate Compounds. 

L.U.S.T.Line, Bulletin 36, New England Interstate Water Pollution Control Commission. pp 16-18. 

Da Silva, M.L.B., A. Ulrich, E. Edwards, and P.J.J. Alvarez. 2003. Enhanced Anaerobic Bioremediation 

of BTEX-Ethanol Mixtures Through Bioaugmentation. Presented at the “In Situ and On-Site 

Bioremediation” Conference”, Orlando, FL. Session B.4. June 2. 

Deeb, R.A. and M. Kavanaugh. 2002. In-Situ Biological Destruction of MtBE: Field Engineering 

Solutions. Presented at the “Remediation of Chlorinated and Recalcitrant Compounds” Conference, 

Monterey, CA. May 23. 

Delta Environmental Consultants. 2004. Groundwater Oxygenate Cleanup Levels for LUST Sites. 

http://www.epa.gov/oust/mtbe/mtbetable.pdf. 

Environmental Cost Handling Options and Solutions (ECHOS). 2002. RS Means Environmental 

Remediation Cost Data - Unit Price, 8th Annual Edition. 

EPA. 2004. In Situ Thermal Treatment of Chlorinated Solvents: Fundamentals and Field Applications. 

EPA 542-R-04-010. Office of Solid Waste and Emergency Response. March. 

EPA. 2004a "Performance Monitoring of MNA Remedies for VOCs in Ground Water". EPA 600/R04/027. April. 

EPA. 2003a. Underground Storage Tanks Fact Sheet: Analytical Methodologies for Fuel Oxygenates. 

EPA=510-F-03-01. Office of Solid Waste and Emergency Response. April. 

http://www.epa.gov/OUST/mtbe/omethods.pdf. 

EPA. 2003b. In Situ Thermal Treatment of Chlorinated Solvents: Fundamentals and Field Applications. 

EPA 542-R-03-012. Office of Solid Waste and Emergency Response. July. 

EPA. 2002a. MtBE Treatment Profiles. http://clu-in.org/products/MtBE. 

EPA. 2002b. Economic Analysis of the Implementation of Permeable Reactive Barriers for Remediation 

of Contaminated Ground Water. EPA/600/R-02/034. National Risk Management Research Laboratory, 

Ada, Oklahoma. June. 

EPA. 2002c. Field Applications of In Situ Remediation Technologies: Permeable Reactive Barriers. 

Office of Solid Waste and Emergency Response. January. 

EPA. 2002d. Environmental Research Brief: Long-term Performance of Permeable Reactive Barriers 

Using Zero-valent Iron: An Evaluation at Two Sites. EPA/600/S-02/001. National Risk Management 

Research Laboratory, Ada, Oklahoma. March. 

EPA. 2002e. Field Applications of In Situ Remediation Technologies: Permeable Reactive Barriers. 

Office of Solid Waste and Emergency Response. January. 

EPA. 2001a. Summary of Workshop on Biodegradation of MtBE, February 1-2, 2000. Workshop 

Sponsored by EPA and American Petroleum Institute. EPA/625/R-01/001A. February. 

EPA. 2001b. Development of Recommendations and Methods to Support Assessment of Soil Venting 

Performance and Closure. EPA 600-R-01-070. 

EPA. 2001c. Remediation Technology Cost Compendium - Year 2000. EPA 542-R-01-009. 

September. 

EPA. 2001d. Cost Analyses for Selected Groundwater Clean-up Projects: Pump-and-treat Systems and 

Permeable Reactive Barriers. EPA 542-R-00-013. February. 

EPA. 2001e. MtBE Case Study. "Soil Vapor Extraction/Air Sparging at Eaddy Brothers, Hemingway, 

South Carolina." 

 6-2 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

EPA. 2000a. Engineered Approaches to In Situ Bioremediation of Chlorinated Solvents: Fundamentals 

and Field Applications. EPA 542-R-00-008. July. 

EPA. 2000b. MtBE Case Study. "Four Sites: Air Sparging of Groundwater." July. 

EPA. 2000c. MtBE Case Study. "Eight Service Stations in Maryland: Soil Vapor Extraction and 

Groundwater Extraction Used to Treat Soil and Groundwater." July. 

EPA. 2000d. Institutional Controls: A Site Manager’s Guide to Identifying, Evaluating, and Selecting 

Institutional Controls at Superfund and RCRA Corrective Action Clean-ups. EPA 540-F-00-005. 

September. 

EPA. 2000e. MtBE Case Study. "Sparks Solvent/Fuel Site: Multi-Phase Extraction Using Fluidized Bed 

Reactor (FBR) and Granular Activated Carbon (GAC) Media for Treatment of Groundwater." July. 

EPA. 2000f. Memorandum from Elizabeth Cotsworth, Director, Office of Solid Waste. Applicability of 

RCRA Section 3020 to In-Situ Treatment of Groundwater. www.cluin.org. December 27. 

EPA. 2000g. Introduction to Phytoremediation. Office of Research and Development. EPA 600-R-99-

107. February. 

EPA. 1999a. Multi-Phase Extraction: State of the Practice. Office of Solid Waste and Emergency 

Response. June. http://cluin.org/download/remed/mpe2.pdf. 

EPA. 1999b. Use of Monitored Natural Attenuation at Superfund, RCRA Corrective Action, and 

Underground Storage Tank Sites. April. OSWER Directive 9200-4.17P. 

http://www.epa.gov/oust/directiv/d9200417.pdf. 

EPA. 1999. Groundwater Clean-up: Overview of Operating Experience at 28 Sites. EPA 542-R-99-

006. September. 

EPA. 1998a. Oxygenates in Water: Critical Information and Research Needs. Office of Research and 

Development. EPA 600-R-98-048. December. 

EPA. 1998b. Technical Protocol for Evaluating Natural Attenuation of Chlorinated Solvents in Ground 

Water. National Risk Management Research Laboratory. October. 

EPA. 1998c. Permeable Reactive Barrier Technologies for Contaminant Remediation. EPA/600/R98/125. Office of Research and Development. September. 

EPA. 1998d. MtBE Fact Sheet #3: Use and Distribution of MtBE and Ethanol. EPA Office of 

Underground Storage Tanks. EPA 625-K-98-001. September. 

http://www.epa.gov/swerust1/MtBE/MtBEfs3.pdf. 

EPA. 1997a. Presumptive Remedy: Supplemental Bulletin, Multi-Phase Extraction Technology for 

VOCs in Soil and Groundwater. Office of Solid Waste and Emergency Response. April. http://cluin.org/download/toolkit/finalapr.pdf. 

EPA. 1997b. Rules of Thumb for Superfund Remedy Selection. EPA 540-R-97-013. August. 

EPA. 1997c. Expedited Site Assessment Tools for UST Sites. EPA 510-B-97-001. 

http://www.epa.gov/oust/pubs/sam.htm. 

EPA. 1996. How to Effectively Recover Free Product at Leaking Underground Storage Tank Sites; A 

Guide for State Regulators. EPA 510-R-96-001. September. http://www.epa.gov/oust/pubs/fprg.htm. 

EPA. 1995. How to Evaluate Alternative Cleanup Technologies for Underground Storage Tank Sites: A 

Guide for Corrective Action Plan Reviewers. Office of Underground Storage Tanks. EPA 510-B-95-007. 

http://www.epa.gov/oust/pubs/tums.htm. 

 6-3 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

EPA. Not Dated. “Case 10 - Cost and Performance Report, In-Situ Ozone Remediation of Soil & 

Groundwater: Former Retail Service Station, Bucks County, Pennsylvania”. Office of Underground 

Storage Tanks. Draft Report. 

Eremita, Pete M., Maine Dept. of Environmental Protection. 2000. E-mail to Aaron Hastings, Tetra Tech 

EM Inc. Christy’s in N. Windham. August 16. 

ESTCP. 2003. Cost and Performance Report – In-Situ Bioremediation of MTBE in Groundwater. CU0013. September. 

Federal Remediation Technology Roundtable (FRTR). 2002. Remediation Technology Screening Matrix 

and Reference Guide, 4th Edition. http://www.frtr.gov. 

FRTR. 1998. Guide to Documenting and Managing Cost and Performance Information for Remediation 

Projects (Revised Version). EPA 542-B-98-007. 

Fields, K.A., Zwick, T.C., Leeson, A., Wichramanayake, G.B., Doughty, H., and Sahagun, T. 2001. Air 

sparging life cycle design for an MtBE and BTEX site. In: Enhanced Aerobic Restoration, In Situ 

Aeration Aerobic Remediation, the Sixth International In Situ and On-Site Bioremediation Symposium, 

San Diego, California. June 4-7, 2001. Colume 6, pp. 1-8. (Leeson, A., Johnson, P.C., Hinchee, R.E., 

Semprini, L., and Magar, V.S., Eds.). Columbus, Ohio. Battelle Press. 

Finneran, K.T. and D.R. Lovely. 2003. “Anaerobic In Situ Bioremediation”. In MTBE Remediation 

Handbook. Moyer, E.E. and Kostecki, P.T., Eds. Amherst Scientific Publishers. 

GAO. 2002. Testimony Before the Subcommittee on Environment and Hazardous Materials, Committee 

on Energy and Commerce, House of Representatives, Environmental Protection, MtBE Contamination 

from Underground Storage Tanks, Statement of John Stephenson, Director, Natural Resources and 

Environment. GAO.02.753T. May 21. http://www.gao.gov/new.items/d02753t.pdf. 

Gavaskar, A., N. Gupta, B. Sass, R. Janosy, and J. Hicks. 2000. Design Guidance for Application of 

Permeable Reactive Barriers for Groundwater Remediation. Prepared for U.S. Air Force, Air Force 

Research Laboratory. March. 

Global BioSciences, Inc. Petroleum Pollutants Case Study: Sunoco Service Station/Massachusetts”. 

http://www.biobutane.com/sunoco.htm. 

Greenberg, Richard S., et al., In-Situ Oxidative Technologies, Inc. 1998. “In-Situ Fenton-Like Oxidation 

of Volatile Organics: Laboratory, Pilot, and Full-Scale Demonstrations”. Remediation. Spring. 

Ground-Water Remediation Technologies Analysis Center. 1999. Technology Evaluation Report, In Situ 

Chemical Treatment (TE-99-01). Prepared by Yin, Y. and Allen, H.E. July. 

http://www.gwrtac.org/pdf/inchem.pdf. 

“Guidelines for Investigation and Cleanup of MtBE and Other Ether-Based Oxygenates,” CalEPA, State 

Water Resources Control Board, March 2000. 

Halden, R. U., A. M. Happel, and S. R. Schoen. 2001. Evaluation of Standard Methods for the Analysis 

of Methyl tert-Butyl Ether and Related Oxygenates in Gasoline-Contaminated Groundwater. 

Environmental Science & Technology, Vol. 35, no. 7, pp.1469-1474. (Additions and Corrections, Vol. 

35, no. 7, p.1560.) 

Halden, R.U., S.R. Schoen, Y.Galperin, I.R. Kaplan, and A.M. Happel. 1998. Evaluation of EPA and 

ASTM Methods for Analysis of Oxygenates in Gasoline-Contaminated Ground Water, Eighth West Coast 

Conference on Contaminated Soil and Groundwater: Oxnard, CA. 

Hong, M. S., W. F. Farmayan, I. J. Dortch, C. Y. Chiang, S. K. McMillan and J. L. Schnoor. 2001. 

“Phytoremediation of MtBE from a Groundwater Plume”. Environ. Sci. Technol. 35(6): 1231-1239. 

 6-4 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Hyman, M. 2000. Microbial Cometabolism of MTBE. Presented at the MTBE Biodegradation 

Workshop, Cincinnati, OH, February 1-3. 

Interstate Technology and Regulatory Cooperation (ITRC). 2002. A Systematic Approach to In Situ 

Bioremediation in Groundwater. August. 

ITRC. 2001. Technical and Regulatory Guidance for In Situ Chemical Oxidation of Contaminated Soil 

and Groundwater. June. http://www.itrcweb.org/ISCO-1.pdf. 

ITRC. 1999. Regulatory Guidance for Permeable Reactive Barriers Designed to Remediate Chlorinated 

Solvents. December. 

Jansen, Ron, Remedial Operations Group, Inc., Ellen Moyer, Tighe & Bond, Inc., and Richard Sloan, 

Lyondell Chemical Company. 2002. MtBE Remediation Seminar. Winter. 

Kelly, K.L, M.C. Marley, K.L. Sperry. 2003. “In-Situ Chemical Oxidation”. In MTBE Remediation 

Handbook. Moyer, E.E. and Kostecki, P.T., Eds. Amherst Scientific Publishers. 

Kelly, K.L, M.C. Marley, K.L. Sperry. 2002. “In-Situ Chemical Oxidation of MtBE”. Contaminated 

Soil Sediment and Water. July/August. 

Kerfoot, William B., K-V Associates, Inc. 2000. “Ozone Microsparging for Rapid MtBE Removal”. 

Published in Proceedings of the Second International Conference on Remediation of Chlorinated and 

Recalcitrant Compounds, Monterey, California. Battelle. May. 

Kinner, N.E. 2001. Fate, Transport and Remediation of MtBE. Testimony before the U.S. Senate 

Committee on Environment and Public Works, Salem, NH. April 23. 

Landmeyer, J. E., D. A. Vrblosky and P. M. Bradley. 2000. “MtBE and BTEX in Trees above 

Contaminated Groundwater”. Battelle International Conference on Remediation of Chlorinated and 

Recalcitrant Compounds, Monterey, CA. 

Lawrence Livermore National Laboratory. 1998. An Evaluation of MtBE Impacts to California 

Groundwater Resources. UCRL-AR-130897. July 11. 

Leethem, John T., URS Corporation. 2001. “In Situ Chemical Oxidation of MtBE and BTEX in Soil and 

Groundwater: A Case Study”. Contaminated Soil, Sediment, and Water, Spring Special Issue. 

Levine Fricke. Not Dated. A Success Story: Ozone -Air Sparging Pilot Test at an MtBE Site in Long 

Island, New York” and “Introduction to Ozone Injection Technology. Company Literature. 

Li, Tie, U. Raaj, P.G. Patel, D.K. Ramsden, and J. Greene. 2003. “Groundwater Recovery and 

Treatment”. In MTBE Remediation Handbook. Moyer, E.E. and Kostecki, P.T., Eds. Amherst Scientific 

Publishers. 

Maryland Department of the Environment. 2001. The Task Force on the Environmental Effects of 

MtBE. Final Report. December. 

McGarry, Fred J., New Hampshire Dept. of Environmental Services. 2002. “2002 State Symposium on 

Fuel Oxygenates”. Presentation at ASTSWMO. Roslyn, VA. October 22. 

McMillan, S. and J. Schnoor. 2000. “Phytoremediation of Methyl Tert-Butyl Ether by Hybrid Poplar 

Trees”. Abstr. Pap. Am. Chem. Soc. 219(1): 195-ENVR. 

Miller, K.D. 2002. Bio-Barrier Treats Mixed MtBE Plume at Port Hueneme. Technology News and 

Trends. November. http://www.epa.gov/tio/download/newsltrs/tnandt1102.pdf. 

Moyer, E.E. and Kostecki, P.T., Eds. 2003. MtBE Remediation Handbook. Amherst Scientific 

Publishers. 

 6-5 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Moyer Ellen E., ENSR Corp., and Richard L. Sloan, Lyondell Chemical Company. 2000. MtBE 

Remediation Technology Selection, Sequencing, and Case Studies. Powerpoint Presentation. May 24. 

National Science and Technology Council. 1996. Interagency Assessment of Potential Health Risks 

Associated with Oxygenated Gasoline. Office of Science and Technology Policy. Executive Office of 

the President. 

Naval Facilities Engineering Service Center. Chemical Oxidation, In-Situ Technology Web Page. 

http://enviro.nfesc.navy.mil/erb/restoration/technologies/remed/phys_chem/phc-43.asp. 

Naval Facilities Engineering Service Center. 2001. Final Air Sparging Guidance Document. NFESC 

Technical Report TR-2193-ENV. August 31. 

New England Interstate Water Pollution Control Commission (NEIWPCC). 2000. A Survey of State 

Experience with MtBE Contamination at LUST Sites. December 15. 

Newman, L., A. Wilson, S. Strand, P. Heilman and M. Gordon. 2000. “Phytoremediation of Methyl-TButyl Ether (MtBE)”. Abstr. Pap. Am. Chem. Soc. 219: 232-ENVR. 

National Institute of Occupational Safety and Health. 1990. Pocket Guide to Chemical Hazards. 

O'Connell, Joseph E., Environmental Resolutions Inc. 2004. E-mail to Linda Fiedler, EPA, Belated 

Comments to MtBE Report. February 24. 

Prah, J., EPA, D. Ashley, B. Blount, M. Case, T. Leavens, J. Pleil, and F. Cardinali. 2004. “Dermal, 

Oral, and Inhalation Pharmacokinetics of Methyl Tertiary Butyl Ether (MTBE) in Human Volunteers”. 

Toxicological Sciences. 77, 195-205. 

Resource Control Corporation. Not Dated. “In-Situ Ozone Remediation of MtBE in Groundwater; 

Effectiveness and Efficiency”. Powerpoint Presentation, Rancocas, New Jersey. 

Rhodes, I., J. Milazzo, L. Brzuzy, L Harvey, A. Verstuyft, R.U. Halden, S.R. Schoen, Y. Galperin, I. 

Kaplan, and A.M. Happel. 1998. Analytical Methods for the Determination of Oxygenates in Gasolinecontaminated Groundwater: Modified EPA and ASTM Methods, 21st Annual EPA Conference on 

Analysis of Pollutants in the Environment: Norfolk, VA. 

Rittmann, B. E. 2003. “Monitored Natural Attenuation of MTBE”. In MTBE Remediation Handbook. 

Moyer, E.E. and Kostecki, P.T., Eds. Amherst Scientific Publishers. 

Rubin, E. and A. Ramaswami. 2001. “The Potential for Phytoremediation of MtBE”. Water Res. 35(5): 

1348-1353. 

Schirmer, M., B. Butler, J. Barker, C. Church and K. Schirmer. 1999. “Evaluation of Biodegradation and 

Dispersion as Natural Attenuation Processes of MtBE and Benzene at the Borden Field Site”. Phys. 

Chem. Earth Pt B-Hydrol. Oceans Atmos. 24(6): 557- 560. 

Schmidt, T.C., M. Schirmerb, H. Wei, and S. B. Haderleina. 2004. Microbial degradation of methyl tertbutyl ether and tert-butyl alcohol in the subsurface. Journal of Contaminant Hydrology. Volume 70, 

Issues 3-4. June. Pages 173-203. 

SERDP. 2003. In Situ Chemical Oxidation Initiative. http://www.serdp-estcp.org/ISCO.cfm. 

Speth, T.F. and G.R. Swanson 2002. Demonstration of the HiPOx Advanced Oxidation Technology for 

the Treatment of MTBE-Contaminated Groundwater. Report No. EPA/600/R-02/098. USEPA National 

Risk Management Research Laboratory, Cincinnati, OH. September. 

Steffan, R.J., H.H. Farhan, and C.W. Condee, 2003. “Bioremediation at a New Jersey Site Using 

Propane-Oxidizing Bacteria”. MTBE Remediation Handbook. Moyer, E.E. and Kostecki, P.T., Eds. 

Amherst Scientific Publishers. 

 6-6 
 Technologies for Treating MtBE and Other Fuel Oxygenates 

Stocking, A.J., R.A. Deeb, A.E. Flores, W. Stringfellow, J. Talley, R. Brownell, and M.C. Kavanaugh. 

2000. “Bioremediation of MTBE: a review from a practical perspective”. Biodegradation. 11, 187-201. 

Symons, Brian D., and J. Greene. 2003. “Soil Vapor Extraction, Bioventing, and Air Sparging”. In 

MTBE Remediation Handbook. Moyer, E.E. and Kostecki, P.T., Eds. Amherst Scientific Publishers. 

U.S. Geological Survey (USGS). 2003. A National Assessment of Volatile Organic Compounds (VOCs) 

in Water Resources of the U.S. Summer 2003. http://sd.water.usgs.gov/nawqa/vocns/. 

U.S. Army Corps of Engineers (USACE). 1999. Engineering and Design: Multi-Phase Extraction (EM 

1110-1-4010). June 1. http://www.usace.army.mil/inet/usace-docs/eng-manuals/em1110-1-4010/. 

USACE. 1997. USACE Engineering Manual: In Situ Air Sparging. EM 1110-1-4005. September 15. 

USACE. 1995. USACE Engineering Manual: SVE and Bioventing. EM 1110-1-4001. 

Vance, David B. (ARCADIS G&M), M. Lupo, and N. McHugh. 2003. “Anaerobic Bio-Oxidation of 

MTBE and 1,2-DCA. Proceedings of the 10th Annual International Petroleum Environmental 

Conference. Houston, TX. November. 

Venosa, A.D. and M.T. Suidan 2003. Biomass Concentrator Reactor: The Answer to the MtBE Problem 

in Groundwater. Presented at the EPA Science Forum 2003: Partnering to Protect Human Health and the 

Environment. Washington, DC. 5-7 May. 

Venosa, A.D. and G.R. Swanson 2002. Innovative Technology Evaluation Report for the High Energy 

Electron Injection (E-Beam) Technology. EPA Report No. EPA 600-R-02-066. 

White H., B. Lesnik, and J.T. Wilson. 2002. Analytical Methods for Oxygenates. L.U.S.T.Line, Bulletin 

42, New England Interstate Water Pollution Control Commission. pp 1-8. October. 

Wilson, J. T. 2003a. “Fate and Transport of MTBE and Other Gasoline Components”. In MTBE 

Remediation Handbook. Moyer, E.E. and Kostecki, P.T., Eds. Amherst Scientific Publishers. 

Wilson, J. T. 2003b. “Aerobic In Situ Bioremediation”. In MTBE Remediation Handbook. Moyer, E.E. 

and Kostecki, P.T., Eds. Amherst Scientific Publishers. 

Zhang, Q., L. C. Davis and L. E. Erickson. 2000. “An Experimental Study of Phytoremediation of 

Methyl-Tert-Butyl Ether (MtBE) in Groundwater”. J. Hazardous Substance Research 2. 

Zhang, Q., L. C. Davis and L. E. Erickson. 2000. “Plant Uptake of Methyl Tert-Butyl Ether (MtBE) 

from Groundwater”. ASCE national Conf on Environmental and pipeline engineering, Kansas City, MO, 

ASCE. 

Zogorski, J.S., Morduchowitz, A.M., Baehr, A.L, Bauman, B.J., Conrad, D.L., Drew, R.T., Korte, N.E., 

Lapham, W.W., Pankow, J.F., and Washington, E.R. 1996. Fuel oxygenates and water quality--Current 

understanding of sources, occurrence in natural waters, environmental behavior, fate, and significance--

Final Report: Office of Science and Technology Policy, Executive Office of the President. [Also 

published by National Science and Technology Council, 1997, Interagency assessment of oxygenated 

fuels, Chap. 2, Fuel oxygenates and water quality: Washington, DC, Office of Science and Technology 

Policy, The Executive Office of the President.] 

 6-7 
APPENDIX A 

MtBE TREATMENT PROFILE DATA 

(see www.cluin.org/mtbe)