### EPA-600/R-0 8 /0 77

Jul y 200 8 

# Characterization of

Coal Combustion

Residues from Electric Utilities Using Wet

Scrubbers for Multi-Pollutant

ControlEPA/600/R-08/077 July 2008



# Characterization of Coal Combustion Residues from Electric Utilities Using Wet Scrubbers for

Multi-Pollutant Control

F. Sanchez 1 

### , D. Kosson 1



### , R. Keeney 2 

### , R. Delapp 1 

### , L. Turner 3 

### , and P. Kariher 2

1 

### Vanderbilt University Department of Civil and Environmental Engineering

Nashville, TN 37235

2 

### ARCADIS 4915 Prospectus Drive, Suite F
Durham, NC 27713

3 

### Turner Technology
Nashville, TN 37235

Category III / Applied Research

Contract No. EP-C-04-023 Work Assignment No. 4-26 Project No. RN990234.0026



### U.S. Environmental Protection Agency Office of Research and Development National Risk Management Research Laboratory

Air Pollution Prevention and Control Division

Cincinnati, Ohio

### Notice

The U.S. Environmental Protection Agency (EPA) thro ugh its Office of Research and Development funded the research described here under Work Assig nment No. 4-26 of Contract Number EP-C-04-023 to Vanderbilt University. It has been subjected to the Agency’s peer and administrative review and has been cleared for publicationas an EPA document. Referen ce herein to any specific commercial product, proce ss, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or im ply its endorsement or recommendation. The views and opini ons of authors expressed herein do not necessarily state or reflect those of EPA or any agency thereof.

ii

### Foreword

The U.S. Environmental Protection Agency (EPA) is c harged by Congress with protecting the Nation's land, air, and water resources. Under a mandate of national environmental laws, the Agency strives to formulate and implement actions leading to a compat ible balance between human activities and the abili ty of natural systems to support and nurture life. To meet this mandate, EPA's research program is providing data and technical support for solving en vironmental problems today and building a science knowledge base necessary to manage our ecological r esources wisely, understand how pollutants affect our health, and prevent or reduce environmental ris ks in the future.

The National Risk Management Research Laboratory (N RMRL) is the Agency's center for investigation of technological and management approaches for prev enting and reducing risks from pollution that

threaten human health and the environment. The foc us of the Laboratory's research program is on methods and their cost-effectiveness for prevention and control of pollution to air, land, water, and subsurface resources; protection of water quality i n public water systems; remediation of contaminated sites, sediments and ground water; prevention and c ontrol of indoor air pollution; and restoration of ecosystems. NRMRL collaborates with both public an d private sector partners to foster technologies th at reduce the cost of compliance and to anticipate eme rging problems. NRMRL's research provides solutions to environmental problems by: developing and promoting technologies that protect and improve the environment; advancing scientific and engineeri ng information to support regulatory and policy decisions; and providing the technical support and information transfer to ensure implementation of environmental regulations and strategies at the nat ional, state, and community levels.

This publication has been produced as part of the L aboratory's strategic long-term research plan. It is published and made available by EPA's Office of Res earch and Development to assist the user community and to link researchers with their client s.

Sally Gutierrez, Director National Risk Management Research Laboratory

iii

### Characterization of Coal Combustion Residues II



## ACKNOWLEDGMENTS

Extensive input on the research program design was provided by G. Helms, U.S. EPA, Office of Solid Waste (Washington, D.C.).

Laboratory testing described herein was carried out by ARCADIS with technical support from Vanderbilt University. R. Delapp was responsible fo r the chemical analyses carried out at Vanderbilt University. Technical assistance also was p rovided by A. Garrabrants.

K. Ladwig and the Electric Power Research Institute (EPRI) are gratefully acknowledged for assistance in obtaining coal combustion residue samp les and providing information from the

EPRI database on coal combustion residues.

S. Thorneloe is the U.S. EPA project officer for this researc h.

Note: R. Keeney substantially participated in the work reported here and the preparation of this report but left employment of ARCADIS prior to the comple tion of this study and report.

iv

### Characterization of Coal Combustion Residues II



## TABLE OF CONTENTS

Acknowledgments.......................................................................................................................... iv

Abstract...........................................

................................................... ............................................. v

Glossary of terms ...................................

................................................... ..................................... vi

Executive Summary....................................................................................................................... ix

Table of Contents....................................

................................................... ................................... xii

List of Tables ................................................................................................................................ xv

List of Figures.............................................................................................................................. xvi

1. Introduction................................................................................................................................. 1

1.1. Regulatory Context ...............................................................................................................6

1.1.1. Waste Management............................

................................................... ........................ 6

1.1.2. Air Pollution Control .........................

................................................... ........................ 6

1.2. Configurations of U.S. Coal Fired Power Plants and Mult i-pollutant Control Technologies................................................................................................................................7

1.2.1. Current Air Pollution Control Technologies.....

................................................... ......... 8

1.2.2. Wet Scrubbers, NOx Controls and Multi-pollut ant Controls ..................................... 1 1

1.3. Coal Combustion Residues.................................................................................................12

1.4. Residue Management Practices ..........................................................................................13

1.4.1. Beneficial Use............................................................................................................. 13

1.4.2. Land Disposal ............................................................................................................. 14

1.5. Leaching Protocol ..............................

................................................... ..............................16

2. Materials and Methods.............................................................................................................. 20

2.1. CCR Materials for Evaluation ............................................................................................20

2.1.1. Facilities Using Inhibited or Natural Oxidation of Scrubber Residues (P roducing Scrubber Sludge or Fixated Scrubber Sludge)...................................................................... 24

2.1.1.1. Facility A (Natural Oxidation and SNCR)........................................................... 24

2.1.1.2. Facility B (Natural Oxidation and SCR)..........

................................................... . 24

2.1.1.3. Facility K (Natural Oxidation and SCR) ............................................................. 25

2.1.1.4. Facility M (Inhibited Oxidation and SCR) .

................................................... ...... 25

2.1.2. Facilities Using Forced Oxidation of Scrubber Res idues (Producing FGD Gypsum) 26

2.1.2.1. Facility N (Forced Oxidation).............................................................................. 26

2.1.2.2. Facility O (Forced Oxidation and SCR) .............................................................. 26

2.1.2.3. Facility P (Forced Oxidation and SCR and SNCR)............................................. 26

2.1.2.4. Facility Q (Forced Oxidation and SCR) .............................................................. 27

v

### Characterization of Coal Cumbustion Residues II



### 2.2. Leaching Assessment Protocols....................

................................................... ...................27

2.2.1. Alkalinity, Solubility and Release as a Function of pH (SR002.1) ............................ 27

2.2.2. Solubility and Release as a Function of LS R atio (SR003.1)..................................... 28

2.3. Analytical Methods.............................................................................................................28

2.3.1. Surface Area and Pore Size Distribution ....

................................................... ............. 28

2.3.2. pH and Conductivity................................................................................................... 28

2.3.3. Moisture Content ........................................................................................................ 28

2.3.4. Carbon Content Organic Carbon/Elemental Carbon Ana lyzer................................... 28

2.3.5. Dissolved Inorganic Carbon (DIC) and Dissolved Orga nic Carbon (DOC) .............. 29

2.3.6. Mercury (CVAA, Method 3052, and Method 7473) .................................................. 29

2.3.7. Other Metals (ICP-MS, Method 3052, and Metho d 6020)......................................... 30

2.3.7.1. ICP-MS Analysis ................................................................................................. 30

2.3.8. X-Ray Fluorescence (XRF) ........................................................................................ 32

2.3.9. MDL and ML for Analytical Results.................

................................................... ..... 32

2.4. Quality Assurance ASSESSMENT .................

................................................... ................33

2.4.1. Homogenization of Individual CCR Samples and A liquots for Analyses.................. 33

2.4.2. Leaching Test Methods and Analytical QA/QC......................................................... 33

2.4.3. Improving QA/QC efficiency ....................

................................................... .............. 34

2.5. Interpretation and Presentation of Laboratory Leachi ng Data............................................3 5

2.5.1. Interpretation of Mechanisms Controlling Con stituent Leaching .............................. 36

2.6. Field pH probability distribution ........................................................................................38

2.7. Estimated leachate concentration as a function of pH............................................. ...........41

3. Results and Discussion ............................................................................................................. 43

3.1. Total elemental content by digestion ..............

................................................... .................43

3.2. total elemental content by xrf ....................

................................................... ......................51

3.3. Laboratory Leaching Test Results .................

................................................... ..................57

3.3.1. Typical Characteristic Leaching Behavior as a Fu nction of pH and LS..................... 58

3.3.2. Comparisons of the Ranges of Constituent Concentra tions from Laboratory Testing with Measurements of Field Samples and the EPA Risk Report Da tabase.......................... 77

4. Summary of Results, Conclusions and Recommendations...

................................................... . 87

5. References................................................................................................................................. 94

Appendices.................................................................................................................................... 97

A. Quality Assurance Project Plan .....................

................................................... ............. A-1

B. Total Elemental Content by Digestion.................

................................................... .........B-1

vi

### Characterization of Coal Combustion Residues II



### C. Elemental Total Content (by XRF), Carbon, Loss on Ignition and Specific Surface Area ......................................................................................................C-1 D. pH Titration and Constituent Leaching as a Function of pH (SR002 test results) ......... D-1 E. pH and Constituent Leaching as a Function of LS (SR003 tes t results)..........................E-1

F. Curve Fits.......................................

................................................... ...............................F-1 G. Additional Facility Information ..................

................................................... ................ G-1

vii

### Characterization of Coal Cumbustion Residues II



## LIST OF TABLES

Table 1. Summary of facility configurations and sample identification contained in this report. Facilities are identified by code letter only (e.g. , “Facility A”) to preserve the confidentiality of the CCR source. All fly ash samples are ASTM Cla ss F. ............................................. ....... 5

(EPA, 2005). CCR samples evaluated in this report a re from configurations indicated by shaded (light gray) rows. Current capacity reflect s date of data collection for EPA report

Table 4. Beneficial uses of CCRs (ACAA, 2007). Total production of CCRs during 2006 wa s

Table 6. Method detection limits (MDLs) and minimum level of quantification (ML) for ICPTable 7. Comparison of summary statistics for field pH data and pH probability distributions Table 2. General Characteristics of Coals Burned in U. S . Power Plants (EPA, 2005). ............... 7

Table 3. Projected Coal-Fired Capacity by APC Configurati on as per data collection in 1999

(EPA, 2005). ........................................................................................................................... 10

124,795,124 short tons............................................................................................................ 15

Table 5. MDL and ML of analysis of DIC and DOC. ............

................................................... .. 29

MS analysis on liquid samples................................................................................................ 31

used in Report 1 and this report. .................

................................................... ......................... 41

Table 8. Fly Ash. Summary of results. .................

................................................... ................... 90

Table 9. FGD Gypsum. Summary of results................

................................................... ............ 91

Table 10. Scrubber Sludge. Summary of results......................................................................... 92

Table 11. Fixated Scrubber Sludge. Summary of results............................................................ 93

viii

### Characterization of Coal Combustion Residues II



## LIST OF FIGURES

Figure 1. Flow diagram describing processing and nomen clature of FGD scrubber residues and samples included in this study. ...................

................................................... ........................... 2

Figure 5. Fly ash (FA) comparisons (CFA, AFA, DFA, etc refer to sample identification codes;

Figure 6. Gypsum (Gyp-U, Gyp-W) comparisons (NAU, NAW, OAU , etc. are sample

Figure 7. Scrubber sludge (ScS) comparisons (CGD, AGD, DGD, etc. are sample identification

Figure 8. Fixated scrubber sludge (FSS) and fixated scrubber sludge with lime (FSSL)

Figure 9. Coefficient of variation (C.V.) from XRF elemental analysis of 10 subsamples of Figure 2. Multi-pollutant control systems in coal fire d power plants..................................... ..... 12

Figure 3. Life-cycle evaluation of coal combustion residu es (EPA, 2002)................................. 13

Figure 4. Uses of CCRs based on 2006 Industry Statistics (ACAA, 2007)................................. 16

see Table 1). Shorthand is used for when SCR is in use (“on”) or not in use (“off”)............ 20

identification codes; see Table 1). ...............

................................................... ........................ 21

codes; see Table 1). Shorthand is used for when SCR is in use (“on”) or not in (“off”)....... 22

comparisons (DCC, BCC, KCC, etc. are sample identificatio n codes; see Table 1).............. 23

FSSL sample MAD after mixing by coning and quartering................................................... 33

Figure 10. An example of extract concentrations as a f unction of pH from SR002.1................. 38

Figure 11. Probability distributions for field pH used i n Report 1 (LogLogistic) and this report (BetaGeneral). Summary statistics for the field data and the probability distribution used in this report (BetaGeneral) are provided to the right of the graph.......................................... ... 40

Figure 12. Example of regression fit and corresponding coefficients for a 5 th 

### order polynomial equation used to represent solubility and release as a function of pH (antimony for fly a sh from Facility B with SCR bypassed (DFA)). ...............

................................................... ....... 42

Figure 13 and Figure 14. Mercury and Aluminum. Compari son of total elemental content by digestion.................................................................................................................................. 45

Figure 15 and Figure 16. Antimony and Arsenic. Comp arison of total elemental content by

Figure 17 and Figure 18. Barium and Cadmium. Compari son of total elemental content by

Figure 19 and Figure 20. Chromium and Cobalt. Comparison of total elemental content by

Figure 21 and Figure 22. Lead and Molybdenum. Compa rison of total elemental content by

Figure 23 and Figure 24. Selenium and Thallium. C omparison of total elemental content by digestion.................................................................................................................................. 46

digestion.................................................................................................................................. 47

digestion.................................................................................................................................. 48

digestion.................................................................................................................................. 49

digestion.................................................................................................................................. 50

Figure 25. Fly Ash - Total content by XRF..........

................................................... .................... 52

Figure 26. Gypsum – Total content by XRF...........

................................................... .................. 53

Figure 27. Scrubber Sludge – Total content by XRF..

................................................... .............. 54

ix

### Characterization of Coal Cumbustion Residues II



### Figure 28. Fixated Scrubber Sludge – Total content by XRF............................................. ......... 55

Figure 30. Mercury - Examples of characteristic lea ching behavior as a function of pH (SR002.1

Figure 47 and Figure 48. Mercury and Aluminum. Com parison of maximum, minimum and natural pH concentrations observed in SR02 and SR03 extracts over the pH domain 5.4 !

Figure 49 and Figure 50. Antimony and Arsenic. Com parison of maximum, minimum and natural pH concentrations observed in SR02 and SR03 extracts over the pH domain 5.4 !

Figure 51 and Figure 52. Barium and Boron. Comparis on of maximum, minimum and natural pH concentrations observed in SR02 and SR03 extracts ove r the pH domain 5.4 ! pH ! 12.4.

Figure 53 and Figure 54. Cadmium and Chromium. Com parison of maximum, minimum and natural pH concentrations observed in SR02 and SR03 extracts over the pH domain 5.4 !

Figure 55 and Figure 56. Cobalt and Lead. Comparis on of maximum, minimum and natural pH

Figure 57 and Figure 58. Molybdenum and Selenium. Comparison of maximum, minimum and natural pH concentrations observed in SR02 and SR03 extracts over the pH domain 5.4 ! Figure 29. Fixated Scrubber Sludge with Lime – Total co ntent by XRF.................................... 56

results)..................................................................................................................................... 61

Figure 31. Aluminum. Examples of characteristic leachin g behavior as a function of pH. ....... 62

Figure 32. Antimony. Examples of characteristic leaching behavior as a function of pH. ........ 63

Figure 33. Arsenic. Examples of characteristic leachi ng behavior as a function of pH............. 64

Figure 34. Barium. Examples of characteristic leachi ng behavior as a function of pH. ............ 65

Figure 35. Boron. Examples of characteristic leaching behavior as a function of pH. .............. 66

Figure 36. Cadmium. Examples of characteristic leaching behavior as a function of pH.......... 67

Figure 37. Chromium. Examples of characteristic leachin g behavior as a function of pH. ....... 68

Figure 38. Chromium. Examples of characteristic leachin g behavior as a function of pH. ....... 69

Figure 39. Cobalt. Examples of characteristic leachi ng behavior as a function of pH............... 70

Figure 40. Lead. Examples of characteristic leaching behavior as a function of pH. ................ 71

Figure 41. Molybdenum. Examples of characteristic leaching behavior as a function of pH.... 72

Figure 42. Molybdenum. Examples of characteristic leaching behavior as a function of pH.... 73

Figure 43. Selenium. Examples of characteristic le aching behavior as a function of pH. ......... 74

Figure 44. Selenium. Examples of characteristic le aching behavior as a function of pH. ......... 75

Figure 45. Thallium. Examples of characteristic le aching behavior as a function of pH........... 76

Figure 46. Natural pH (pH in distilled water at LS= 10) observed in SR02 extracts. .................. 79

pH ! 12.4.. ............................................................................................................................... 80

pH ! 12.4.. ............................................................................................................................... 81

................................................................................................................................................. 82

pH ! 12.4.. ............................................................................................................................... 83

concentrations observed in SR02 and SR03 extracts o ver the pH domain 5.4 ! pH ! 12.4. . 84

pH ! 12.4.. ............................................................................................................................... 85

x

### Characterization of Coal Combustion Residues II



### Figure 59. Thallium. Comparison of maximum, minimum and natural pH concentrations observed in SR02 and SR03 extracts over the pH doma in 5.4 ! pH ! 12.4............................. 86

xi

### Characterization of Coal Cumbustion Residues II



## ABSTRACT

This report evaluates leaching characteristics of a ir pollution control residues from coal-fired power plants that use acid gas scrubbers, which may also reduce air emissions of mercury and other pollutants. Leaching of mercury and other con stituents of potential concern (COPCs) during land disposal of coal combustion residues (CCRs) 1 

### is evaluated in this report. The data presented in this report will be used in a future r eport to evaluate the fate of mercury and other COPCs from the management of CCRs resulting from th e use of multi-pollutant control technologies. This research is part of an on-going effort by U.S. Envir onmental Protection Agency (EPA) to use a holistic approach to account for the fate of mercury and other metals in coal throughout the life-cycle stages of CCR manage ment including disposal and beneficial use.

The specific objectives of the research reported here are to :

1. Evaluate the potential for leaching to groundwater of mercury and other COPCs (i.e., aluminum, antimony, arsenic, barium, boron, cadmium , chromium, cobalt, lead, molybdenum, selenium, and thallium) removed from th e flue gas of coal-fired power plants by facilities that use wet scrubbers as part of a m ulti-pollutant control strategy to reduce air

emissions.

2. Provide the foundation for assessing the impact of enhanced mercury and multi-pollutant control technology on leaching of mercury and other COPCs from CCR management including storage, beneficial use, and disposal; and,

3. Perform these assessments using the most appropria te evaluation methods currently available. The laboratory leach testing followed th e approach developed by Kosson, et al. (2002), which considers the effects of varying envi ronmental conditions on waste constituent leaching.

Air pollution control residues (fly ash, gypsum, an d scrubber sludge samples) were obtained from coal combustion electric utility facilities us ing wet scrubbers. A range of facility configurations was selected representing difference s in air pollution control technology configurations and coal rank. Each of the residues sampled has been analyzed for selected physical properties, and for total content and leaching characteristics of select ed COPCs. Results of laboratory leaching tests were used to develop e stimates of constituent release under field management scenarios. Laboratory leaching test resu lts also were compared to field observations of leaching.

This report includes results for 23 CCRs (5 fly ash es, 6 gypsum samples, 5 scrubber sludges, 7 fixated scrubber sludges) sampled from eight facili ties. Each CCR sampled was evaluated in the laboratory for leaching as a function of pH and liq uid-to-solid ratio. Results are presented for mercury, aluminum, antimony, arsenic, barium, boron , cadmium, chromium, cobalt, lead, molybdenum, selenium and thallium.

1 

### Coal combustion residues (CCRs) refer collectively to fly ash, scrubber residues and other air pollut ion control solid residues generated during the combust ion of coal collected through the associated air pollution control system. Resultant CCRs may be ma naged as separate or combined residue streams, depending on individual facility configuration.



### xii

### Characterization of Coal Combustion Residues II



## GLOSSARY OF TERMS

ACI Activated Carbon Injection

Al Aluminum

APC Air Pollution Control

APPCD Air Pollution Prevention and Control Division

As Arsenic

ASTM American Society for Testing and Materials

B Boron

Ba Barium

BET Brunauer, Emmett and Teller (method for quantificatio n of surface area)

BML Below Method Limit

CAIR Clean Air Interstate Rule

CAMR Clean Air Mercury Rule

Cd Cadmium

CCRs Coal Combustion Residues

CCV Continuing Calibration Verification

Co Cobalt

COPCs Constituents of Potential Concern

Cr Chromium

C.V. Coefficient of Variation

CVAA Cold Vapor Atomic Adsorption

DIC Dissolved Inorganic Carbon

DOC Dissolved Organic Carbon

DOE United States Department of Energy

DI Deionized (i.e., deionized water)

DRC Dynamic Reaction Chamber

dw dry weight basis

DWEL Drinking Water Equivalent Level

EPA United States Environmental Protection Agency

EPRI Electric Power Research Institute

ESP Electrostatic Precipitator

ESP-CS Cold-side Electrostatic Precipitator

ESP-HS Hot-side Electrostatic Precipitator

xiii

### Characterization of Coal Cumbustion Residues II



### FF Fabric Filter (bag house)

FGD Flue Gas Desulfurization

FID Flame Ionization Detector

FO Forced Oxidation

FSS Fixated Scrubber Sludge

FSSL Fixated Scrubber Sludge with Lime

Gyp-U Unwashed Gypsum

Gyp-W Washed Gypsum

Hg Mercury

HHV Higher Heating Value

Ho Holmium

ICP-MS Inductively Coupled Plasma-Mass Spectrometry

ICV Initial Calibration Verification

In Indium

IO Inhibited Oxidation

I.Ox. Inhibited Oxidation (this abbreviation used in some figures to improve

clarity)

LOI Loss On Ignition

LS Liquid-to-Solid Ratio (LS ratio)

M Molar

Max Maximum

MCL Maximum Contaminant Level (for drinking water)

MDL Method Detection Limit

Mg Lime Magnesium Enriched Lime (often also referred to as “mag-lime”)

Min Minimum

ML Minimum Level of Quantification

Mo Molybdenum

NETL National Energy Technology Laboratory (DOE)

NIOSH National Institute of Occupational Safety and Health

NO Natural Oxidation

NOx Nitrogen Oxides

NSPS New Source Performance Standards

OC/EC Organic Carbon/Elemental Carbon

ORD Office of Research and Development (EPA)

xiv

### Characterization of Coal Combustion Residues II



### OSWER Office of Solid Waste and Emergency Response

PAC Powdered Activated Carbon

Pb Lead

PM Particulate Matter

PRB Sub-bituminous coal mined in Wyoming’s Powder River Bas in

PS Particulate Scrubber

QA/QC Quality Assurance/Quality Control

RCRA Resource Conservation and Recovery Act

RFA Reference Fly Ash

SAB U.S. EPA Science Advisory Board

SCA Specific Collection Area

Sb Antimony

ScS Scrubber Sludge

SCR Selective Catalytic Reduction

SNCR Selective Non-Catalytic Reduction

SDA Spray Dryer Absorber

Se Selenium

SO 2 

### Sulfur Dioxide

SPLP Synthetic Precipitation Leaching Procedure

SRM Standard Reference Material

S/S Stabilization/Solidification

SWDA Solid Waste Disposal Act

TC Toxicity Characteristic

TCLP Toxicity Characteristic Leaching Procedure

Tl Thallium

XRF X-Ray Fluorescence

xv

### Characterization of Coal Cumbustion Residues II



## EXECUTIVE SUMMARY

This report evaluates changes that may occur to coa l combustion residues (CCRs) 2 

### in response to changes in air pollution control technology at coal -fired power plants, which will reduce emissions from the flue gas stack by transferring p ollutants to fly ash and other air pollution control residues. Congress has directed EPA to document that the Clean Air Act regulations do not have the net effect of trading one environmenta l burden for another. The Air Pollution Prevention and Control Division (APPCD) of EPA’s Of fice of Research and Development (ORD) is conducting research to evaluate potential leaching and cross media transfers of mercury and other constituents of potential concern (COPCs) resulting from land disposal or beneficial use of CCRs. The focus of this report is to present data that will be used to evaluate the fate of mercury and other metals from the use o f wet scrubbers at coal-fired power plants. Leaching tests are being conducted on the residues to determine the potential transfer of pollutants from the residues to water resources or other environmental systems (e.g., soils, sediments).

The specific objectives of the research reported here are to :

1. Evaluate the potential for leaching to groundwater of mercury and other COPCs (i.e., aluminum, antimony, arsenic, barium, boron, cadmium , chromium, cobalt, lead, molybdenum, selenium, and thallium) removed from th e flue gas of coal-fired power plants by facilities that use wet scrubbers as part of a multi-pollutant control strategy to

reduce air emissions.

2. Provide the foundation for assessing the impact of enhanced mercury and multi-pollutant control technology on leaching of mercury and other COPCs from CCR management including storage, beneficial use, and disposal; and,

3. Perform these assessments using the most appropria te evaluation methods currently available. The laboratory leach testing followed th e approach developed by Kosson, et al. (2002), which considers the effects of varying envi ronmental conditions on waste constituent leaching.

Air pollution control residues were obtained from coal combustion electric utility facilities using wet scrubbers. A range of facility configurations w as selected representing differences in air pollution control technology configurations and coa l rank. Each of the residues sampled has been analyzed for selected physical properties, and for total content and leaching characteristics. Results of laboratory leaching tests were used to d evelop estimates of constituent release under field management scenarios. Laboratory leaching tes t results also were compared to field observations of leaching.

2 

### Coal combustion residues (CCRs) refer collectively to fly ash and other air pollution control solid residues generated during the combustion of coal co llected through the associated air pollution contro l system. Resultant CCRs may be managed as separate or combined residue streams, depending on individual facility configuration.



### xvi

### Characterization of Coal Combustion Residues II



### This report includes results for 23 CCRs (5 fly ash es, 6 gypsum samples, 5 scrubber sludges, 7 fixated scrubber sludges) sampled from eight facili ties. 3 

### The samples are considered to be representative of likely facility configurations in dicative of 84 and 74 percent, respectively, of the current and future facility configuration types with acid gas scrubbers based on generating capacity; however, only a limited number of facilit ies representing each configuration type have been sampled. A range of coal ranks typically combu sted is also represented. Each CCR sampled was evaluated in the laboratory for leaching as a f unction of pH and liquid-to-solid ratio. Results are presented for mercury, aluminum, antimony, arse nic, barium, boron, cadmium, chromium, cobalt, lead, molybdenum, selenium and thallium.

The selected testing approach was chosen for use be cause it evaluates leaching over a range of values for two key variables [pH and liquid-to-soli d ratio (LS)] that both vary in the environment

and affect the rate of constituent release from was te. The range of values used in the laboratory testing encompasses the range of values expected to be found in the environment for these parameters. Because the effect of these variables o n leaching is evaluated in the laboratory, prediction of leaching from the waste in the field is expected to be done with much greater reliability.

In addition, results from laboratory leaching evalu ation were compared to field leachate concentrations from CCR management facilities avail able from a U.S. EPA database and an Electric Power Research Institute (EPRI) database t o determine if laboratory testing results reasonably represented field observations.

Summary of Conclusions

The data presented in this report will be used in a future report that provides a probabilistic assessment of plausible management practices to eva luate the fate of mercury and other COPCs. Leach results contained in this report are compared to health-based values to identify where there may be potential concerns. The intended use of thes e results is to suggest that for values less than MCLs or DWELs there is unlikely a potential for envi ronmental concern. The thresholds used here for preliminary screening do not account for a dditional dilution and attenuation processes that may occur under field management scenarios 4 

### . Therefore the results are considered environmentally conservative and actual release rat es would be less. For values greater than MCLs or DWELs, additional research is needed to det ermine potential release rates.

Based on the results of testing and evaluations in this study, the following conc lusions are drawn:

1. For each CCR type, the following constituents exce eded either the maximum contaminant level (MCL) or drinking water equivalen t level (DWEL) in at least one laboratory leaching test condition over the range o f pH and LS ratios considered, and therefore potentially may present unacceptable environmental risks under some management scenarios. These cases warrant more deta iled evaluation, including consideration of site-specific conditions.

3 

### Fly ash is collected by the particulate collection device, such as an electrostatic precipitator; gyp sum is

dewatered material collected from forced oxidation flue gas desulfurization; scrubber sludge is collec ted from natural or inhibited oxidation flue gas desulf urization; and fixated scrubber sludge is a mixture of scrubber sludge, fly ash and often with additional lime added.

4 

### Dilution and attenuation factors are specific to i ndividual sites and management scenarios and may range from less than 10 to greater than 100.



### xvii

### Characterization of Coal Cumbustion Residues II



### (i) Fly ash – antimony, arsenic, boron, cadmium, ch romium, molybdenum,

selenium and thallium.

(ii) FGD gypsum – boron, cadmium, molybdenum, selen ium and thallium.

(iii) Scrubber sludge – mercury, antimony, arsenic, boron, chromium, lead, molybdenum, selenium and thallium.

(iv) Fixated scrubber sludge – mercury, antimony, a rsenic barium, boron, cadmium, chromium, lead, molybdenum, selenium and thallium.

However, (i) typically, evaluation results from onl y a subset of samples of a given material type exceeded the indicated criteria, and (ii) never did the full range reported

exceed the indicated threshold.

2. Leaching of individual constituents may vary over several orders of magnitude, depending on the conditions of the management scenario. Thus, these re sults can be used to suggest design conditions that would reduce or m inimize constituent release (e.g., pH, and other conditions).

3. Leaching concentrations do not correlate with tota l content except for specific

constituents in selected materials where the consti tuent (i) is weakly retained, and (ii) leaching concentrations have a low variability rela tive to pH. Thus, total content is not a good indicator of leaching.

4. Results of this study suggest that it appears that Cr leachability is associated with the use of post-combustion NOx controls. This is based on a limited set of paired samples from the same facility operating with and with SCR or SN CR in use. This finding will be

further evaluated as additional data are collected.

5. The systematic leaching behavior of COPCs observed in the range of samples evaluated suggests that the geochemical mechanisms controllin g leaching can be discerned and quantified using geochemical speciation modeling, w hich in turn, can serve as the basis for evaluating and improving design of CCR manageme nt scenarios. Development of generalized geochemical speciation models for the C CR materials evaluated in this study

is recommended.

The new information reported here provides an expan ded basis for future assessments and may impact risk evaluations. Ranges of concentrations o f some constituents in laboratory leaching test extracts and field data included in this study suggest different applicable concentration ranges for risk evaluation other than used in the r ecent risk assessment on coal combustion waste found in docket # EPA-HQ-RCRA-2006-0796

( 

### http://www.regulations.gov/fdmspublic/component/mai n ).

This is the second of a series of reports that will evaluate the potential for leaching of COPCs from CCRs from coal-fired power plants that use wet scrubbers. The first report focused on the use of sorbents for enhancing mercury capture at coal-fired power plants. (Sanchez et al., 2006) The third report will evaluate CCRs from facilities with different air pollution control configurations and coal ranks that were not previously covered in the first two reports. The fourth and final report will provide a probabilisti c assessment of the leaching potential of mercury and other COPCs based on plausible management strat egies. The data will be used to correlate leaching characteristics to coal rank, air pollution control configurations, and combustion facility characteristics.

xviii

### Characterization of Coal Cumbustion Residues II



## 1. INTRODUCTION

Changes are occurring to air pollution control technology at coal-fired power plants which will reduce emissions from the flue gas stack by transfe rring pollutants to fly ash and other air pollution control residues. Congress has directed E PA to document that the Clean Air Act regulations do not have the net effect of trading o ne environmental burden for another. The Air Pollution Prevention and Control Division (APPCD) o f EPA’s Office of Research and Development (ORD) is conducting research to evaluat e potential leaching and cross media transfers of Constituents of Potential Concern (COP Cs) resulting from land disposal or beneficial use of coal combustion residues (CCRs). This report is part of a series of reports being prepared to document the fate of mercury and other metals found in coal that are being controlled at the power plant stack through implementation of multi-pol lutant control technology.

The focus of this report is to present an evaluatio n of air pollution control residues that may

result from the use of SO 2 

### scrubbers as mercury control technology at coal-fired power plants, and the potential for transfer of pollutants from t he resulting residues to water resources or other environmental systems (e.g., soils, sediments). The residues studied for this report were unwashed and washed flue gas desulfurization (FGD) gypsum, scrubber sludge, fixated scrubber sludge, and fly ashes generated from power plants t hat have SO 2 

### scrubbers. This report compares the impact of NOx control technology [selective cat alytic reduction (SCR) and selective noncatalytic reduction (SNCR)] on characteristics of C CRs obtained from the same facilities during periods when the NOx control was and was not in use.

The potential for leaching of mercury and other COP Cs during land disposal or beneficial use of

the CCRs is the more narrow focus of this assessmen t. This research is part of an on-going effort by EPA to use an integrated, comprehensive approach to account for the fate of mercury and other metals in coal throughout the life-cycle stag es of CCR management (Thorneloe et al., 2008; Sanchez et al., 2006). Related research and a ssessment on environmental fate of constituents during CCR management includes conduct ing thermal stability studies, leach testing, and probabilistic assessment modeling to d etermine fate of mercury and other metals that are in coal combustion residues resulting from impl ementation of multi-pollutant control technology (Kilgroe et al., 2001; EPA, 2002).

CCRs include bottom ash, boiler slag, fly ash, scrubber residues and other miscellaneous solids generated during the combustion of coal. Air pollution con trol can concentrate or partition metals to fly ash and scrubber residues. The boiler slag a nd bottom ash are not of interest in this study because enhanced mercury emission controls are not e xpected to change their composition. Use of multi-pollutant controls minimizes air emissions o f mercury and other metals by the transfer of the metals to the fly ash and other CCRs. This research will help determine the fate of mercury and other COPCs from the management of CCRs through either disposal or reuse. Fly ash may include unburned carbonaceous materials and inorganic materials in coal that do not burn, such as oxides of silicon, aluminum, iron, an d calcium. Fly ash is light enough to be entrained in the flue gas stream and captured in th e air pollution control equipment.

The type and characteristics of FGD scrubber residu e produced is primarily a function of (i) the scrubber sorbent used (i.e., limestone, lime, magne sium enriched lime referred to as Mg lime, or alkaline fly ash), (ii) the extent of oxidation during scrubbing (i.e., forced ox idation, natural oxidation, or inhibited oxidation), (iii) post-scrubber processing, including po ssibly dewatering or thickening, drying, water rinsing, or blending w ith other materials, and (iv) coal rank

1

### Characterization of Coal Combustion Residues II



### combusted. The presence and leaching characteristic s of the constituents of potential concern in scrubber residues is a consequence of the coal comb usted, process sequence employed, process conditions, process additives and use or disposal scenario. Figure 1 illustrates t he processes used in the production of materials that were sampled fo r this study, sample nomenclature, and the typical management pathways for each material. FGD gypsum is defined here as the by-product

of the SO 2 

### wet scrubbing process when the scrubber residue is subjected to forced oxidation. In forced oxidation systems, nearly all of the by-product is calcium sulf ate dihydrate (CaSO 4 

### •H 2 

### O). The resulting wet gypsum is partially dewatered and then either disposed in a landfill ( unwashed

gypsum ; Gyp-U

) or water rinsed (in some cases) and dried to prod uce washed gypsum ( washed gypsum; Gyp-W

) that then potentially can be used in wallboard ma nufacturing or agricultural applications. Scrubber sludge ( ScS ) is the by-product of the SO 2 

### wet scrubbing process resulting from neutralization of acid gases at facilities tha t use either inhibited oxidation or natural

oxidation of scrubber residue. In inhibited oxidati on systems, nearly all of the by-product is calcium sulfite hemihydrates (CaSO 3 

### •1⁄2H 2 

### O). In natural oxidation systems, the by-product is a mixture of CaSO 3 

### •1⁄2H 2 

### O and CaSO 4 

### •H 2 

### O. Scrubber sludge typically will be either partial ly dewatered in a thickener and then disposed in a surf ace impoundment, or after thickening, further dewatered and mixed with fly ash to form fixated scrubber sludge (FSS ). In most cases,

additional lime is also blended with the scrubber s ludge and fly ash to form fixated scrubber sludge with lime ( FSSL ). The blend of fly ash and scrubber sludge is typi cally between 0.5 to 1.5 parts fly ash to 1 part scrubber sludge on a dry weight basis, with 0 or 2-4 % additional lime added (FSS or FSSL, respectively). Fixated scrubber sludge typically is either disposed in a landfill or supplied to a beneficial use (e.g., fil l in mining applications). This report evaluates the characteristics of fly ash, FGD gypsum, scrubber sl udge, and fixated scrubber sludge (as produced with or without lime) from several coal combust ion facilities.

Absorber (Forced Oxidation) Facilities N, O, P, Q Facilities A, B, K, M

Wet Gypsum 

### Absorber (Inhibited Oxidation
or Natural Oxidation)

Thickener Impoundment Dewatering (Scrubber Sludge; ScS)



### Landfill (Agriculture?)

(Unwashed Gypsum; Gyp

! U) 

### Drying

Rinsing Mixing of Scrubber Sludge

& Drying Fly Ash and Lime

(Fixated Scrubber Sludge) (Washed Gypsum; Gyp

! W) (FA+ScS; FSS) (FA+ScS+lime; FSSL)



### Wallboard Landfill or

Beneficial Use



### Figure 1. Flow diagram describing processing and no menclature of FGD scrubber residues and samples included in this study.

2

### Characterization of Coal Cumbustion Residues II



### When coal is burned in an electric utility boiler, t he resulting high combustion temperatures vaporize the Hg in the coal to form gaseous elementa l mercury (Hg 0 

### ). Subsequent cooling of the combustion gases and interaction of the gaseous Hg 0 

### with other combustion products result in a portion of the Hg being converted to gaseous oxidiz ed forms of mercury (Hg 2+ 

### ) and particlebound mercury. The specific chemical form — known a s the speciation — has a strong impact on the capture of mercury and other metals by boile r air pollution control (APC) equipment. (EPA, 2001)

Mercury and other elements partition between the co mbustion gas, fly ash and scrubber residues. Depending upon the gas conditioning, presence or ab sence of NOx control and other air pollution control technology in use, there may be c hanges occurring to the fly ash that may affect the stability and mobility of mercury and other met als in the CCRs. Similarly, NOx control and

SO 2 

### scrubber technology may affect the content, stabil ity and mobility of mercury and other

metals in scrubber residues.

In response to wider use of multi-pollutant control , changes are occurring in air pollution control at coal-fired power plants to reduce emissions of n itrogen oxides, sulfur oxides, and mercury. How these changes in air pollution control is the f ocus of this research. The fate of mercury and other COPCs in fly ash and scrubber residues is of interest as part of the overall lifecycle evaluation of impact of air pollution control techn ology and the management of CCRs either through disposal or beneficial use. This research is evaluating changes to ai r pollution control residues as a result of more widespread implementat ion of these multi-pollutant technologies, and the impacts of land disposal or commercial use of t he residues.

The specific objectives of the research reported here are to :

1. Evaluate the potential for leaching of mercury andother COPCs removed from coalfired power plant air emissions by different types of air pollution control technology that includes acid gas scrubbers, particulate, and sorbents;

2. Provide information to be used in separate reports to assess the fate of mercury and other COPCs from enhanced or expanded use multi-pol lutant control technologies. This will include consideration of potential leachi ng of mercury and other COPCs during the life-cycle management of CCRs during storage, beneficial use and disposal; and

3. Perform these assessments using the most appropria te evaluation methods currently available. The laboratory leach testing followed th e approach developed by Kosson, et al. (2002), which considers the effects of varyi ng environmental conditions on waste constituent leaching.

This is the second of a series of reports that will address the potential for cr oss-media transfer of COPCs from CCRs. The first report focused on the use of sorbent injection (activated car bon and brominated activated carbon) for enhanced mercu ry control (Sanchez et al., 2006). Subsequent reports will address:

! 

### CCRs from coal-fired power plants that use air poll ution control technologies other than evaluated in earlier reports necessary to span the range of coal-types and air pollution control technology configurations (report 3);

! 

### Assessment of leaching for COPCs under additional m anagement scenarios, including impoundments and beneficial use on the land (report 4); and,

3

### Characterization of Coal Combustion Residues II

! 

### Broader correlation of CCR leaching characteristics to coal rank, combustion facility characteristics and geochemical speciation within C CRs supported by information and analysis on additional trace elements and primary con stituents (report 4).

Table 1 provides a summary of facility configuratio ns, including samples and sample identification for testing, described in this report. For simplicity in presentati on, the use of NOx controls is indicated as either “off” or “on” (i.e. , SNCR Off, SNCR On, SCR Off, SCR On), recognizing that SCR not in use (SCR Off) reflects that either the system was bypassed or ammonia was not added, and SNCR not in use (SNCR Off) indica tes that urea was not added.

Sampled CCRs were subjected to multiple leaching co nditions according to the designated leaching assessment approach. Leaching conditions i ncluded batch equilibrium 5 

### extractions at acidic, neutral and alkaline conditions at an LS of 10 mL/g, and LS from 0.5 to 10 mL/g using distilled water as the leachant. The leach testing results are used to evaluate the likely range of leaching characteristics during land disposal (i.e. , landfill or surface impoundment). Results of the laboratory leaching tests carried out in this s tudy were compared to the range of observed constituent concentrations in field leachates reported in a U.S. EPA database (EPA, 2007) and an Electric Power Research Institute (EPRI) database (EPRI, 2006). The testing results presente d here will be used for evaluating disposal and beneficial use scenarios in subsequent reports.

As part of this research program, a QA/QC plan cons istent with EPA requirements was developed for the leaching assessment approach and reported earlier (Sanchez et al., 2006). The QA/QC methodology included initial verification of acceptable mercury retention during laboratory testing through evaluation of a mass bal ance around testing procedures (Sanchez et al., 2006). Modifications to the QA/QC program to r educe the experimental and analytical burden while maintaining confidence in the resultin g data, based on program results to date, are presented in this report.

Laboratory testing for leaching assessment was carr ied out at the EPA National Risk Management Research Laboratory (Research Triangle P ark, North Carolina) with technical assistance from Vanderbilt University and ARCADIS.

5 

### In the context of leaching tests, the term “equili brium” is used to indicate that the test method res ult is a reasonable approximation of chemical equilibrium co nditions even though thermodynamic equilibrium may not be approached for all constituents.



### 4Characterization of Coal Cumbustion Residues II5Table 1. Summary of facility configurations and sample identification contained in this report. Facilities are identified by code letteronly (e.g., “Facility A”) to preserve the confidentiality of the CCR source. All fly ash samples are ASTM Class F.1Bit – bituminous; Sub-Bit – sub-bituminous2SNCR – selective non-catalytic reduction; SNCR-BP – SNCR by-passed during winter months; SCR & SNCR – residues combinedfrom facility with both SCR and SNCR3ESP-CS – cold-side electrostatic precipitator; ESP-HS – hot-side electrostatic precipitator.4FA – fly ash; Gyp-U – unwashed gypsum; Gyp-W – washed gypsum; ScS – scrubber sludge; FSS – fixated scrubber sludge (amixture of fly ash and scrubber sludge); FSSL – fixated scrubber sludge with lime (a mixture of fly ash and scrubber sludge withadditional lime added). The three-letter identification codes are shown for each facility and sample type (e.g., CFA, CGD).FGD Scrubber Type Sample Types and Identification4FacilityCodeCoalRank1PostCombustionNOx Control2ParticulateControl3LimeorMg Lime Oxidation FA Gyp-U Gyp-WScS FSS FSSLA Bit SNCR-BP (off) Fabric Filter Limestone Natural CFA CGD CCCA Bit SNCR (on) Fabric Filter Limestone Natural AFA AGDACCB Bit SCR-BP (off) ESP-CS Mg Lime Natural DFA DGD DCCB Bit SCR (on) ESP-CS Mg Lime Natural BFA BGD BCCK Sub-Bit SCR (on) ESP-CS Mg Lime Natural KFA KGD KCCM Bit SCR-BP (off) ESP-CS Limestone Inhibited MADM Bit SCR (on) ESP-CS Limestone Inhibited MASN Bit None ESP-CS Limestone Forced NAU NAWO Bit SCR (on) ESP-CS Limestone Forced OAU OAWP Bit SCR & SNCR ESP-CS Limestone Forced PADQ Sub-Bit none ESP-HS Limestone Forced QAU

### Characterization of Coal Combustion Residues II



## 1.1. REGULATORY CONTEXT

1.1.1. Waste Management
The management of coal combustion residues is subje ct to the Resource Conservation and Recovery Act (RCRA), which is the federal law regul ating both solid and hazardous wastes, as well as state regulatory requirements. Subtitle C o f RCRA pertains to hazardous waste; other solid, non-hazardous wastes fall under RCRA Subtitl e D. Subtitle C wastes are federally regulated while Subtitle D wastes are regulated pri marily at the state level. The original version of RCRA did not specify whether CCRs were Subtitle C or D wastes. In 1980, the Solid Waste Disposal Act (SWDA) amendments to RCRA conditionally excluded CCRs from Subtitle C regulation pending completion of a study of CCR hazards. Since that time, CCRs have been regulated at the state level under Subtitle D.

The SWDA amendments to RCRA required EPA to prepare a report to Congress identifying CCR hazards and recommending a regulatory approach for CCRs. In this report (EPA, 1988) and the subsequent regulatory determination, EPA recomm ended that CCRs generated by electric utilities continue to be regulated under RCRA Subtitle D (See 58 FR 42466, August 9, 1993).

Other residues generated at coal-fired electric uti lities were not included in this 1993 decision. EPA conducted a follow-up study specifically aimed at low-volume, co-managed wastes 6 

### and issued another Report to Congress (EPA, 1999) with a similar recommendation. In April 2000, EPA issued a regulatory determination exempting the se wastes from hazardous waste regulations (see 65 FR 32214, May 22, 2000). However, concern w as expressed over the use of CCRs as backfill for mine reclamation operations, and it wa s determined that this practice should be regulated under a federal Subtitle D rule. It was a lso decided by EPA that federal regulations under Subtitle D are needed for CCR when they are d isposed in surface impoundments and landfills. Currently, the agency is in the process of developing these regulations ( http://www.epa.gov/epaoswer/other/fossil/noda07.htm ). The results presented in this report, and subsequent reports, will help provide the informati on needed to identify the release potential of mercury and other metals that have been removed fro m stack gases into air pollution control residues, over a range of plausible management opti ons. These data will help identify those

conditions that will either reduce or enhance relea ses to the land so that the effects of different management conditions can be factored into any controls developed under the regulations.

1.1.2. Air Pollution Control
On March 10, 2005, EPA announced the CAIR (FR 25612 , May 2005) which is expected to

increase the use of wet scrubbers and selective cat alytic reduction (SCR) units to help reduce sulfur dioxide and nitrogen oxides emissions from c oal-fired power plants. On March 15, 2005, EPA announced the CAMR (FR 28606, May 2005) for red ucing mercury emissions through the use of a cap and trade program. Power plants are th e largest remaining source of anthropogenic mercury emissions in the county. The CAMR established “standards of performa nce” that limit mercury emissions from new [through new source perf ormance standards (NSPSs)] and existing (through emission guidelines) coal-fired power plan ts through the creation of a market-based cap-and-trade program that will reduce mercury emis sions in two phases. The first phase caps

6 

### Co-managed wastes are low-volume wastes that are c o-managed with the high-volume CCRs.



### 6

### Characterization of Coal Cumbustion Residues II



### national annual mercury emissions at 38 tons throug h co-benefit reductions achieved through controlling sulfur dioxide (SO 2 

### ) and nitrogen oxides (NOx) emissions under CAIR. I n the second phase, due in 2018, coal-fired power plants will be subject to a second cap, which will reduce mercury emissions to 15 tons per year upon full imp lementation. On February 8, 2008, the D.C. Circuit vacated EPA's rule removing power plants from the Clean Air Act list of sources of hazardous air pollutants. At the same time, the court vacated the CAMR. EPA is reviewing the court's decisions and evaluating its impacts. ( http://www.epa.gov/mercuryrule/ ) On July 11, 2008, the D.C. Circuit vacated EPA’s Clean Air Int erstate Rule. EPA is reviewing the court’s decisions and evaluating its impacts.

Congress has directed EPA to document that the Clean Air Act regulations are not trading one

environmental burden for another. The Air Pollution Prevention and Control Division (APPCD) of EPA’s Office of Research and Development (ORD) i s conducting the current research to help identify any potential pollutant transfers resultin g from land disposal or beneficial use of mercury-enriched CCRs. The research results present ed in this report are part of that effort.

In response to the evolving implementation of advan ced air pollution control technology for coal-fired power plants, this research is directed towards understanding changes in CCR characteristics that may increase environmental burdens from land disposal of CCRs or impact CCR usage in commercial applications.



## 1.2. CONFIGURATIONS OF U.S. COAL FIRED POWER PLANTS AND

MULTI-POLLUTANT CONTROL TECHNOLOGIES

In the U.S., there are approximately 1,100 units at approximately 500 coal-fired electricity generating facilities. These facilities represent a range of coal ranks, boiler types, and air pollution control technologies. The current combined capacity of U.S. coal-fired po wer plants is 307 GW (DOE-EIA, 2007). The coal rank burned and fa cility design characteristics affect the effectiveness of multi-pollutant control technologies that are or could be used at these plants. The U.S. coal-fired power plants typically burn one of three types of fuel: (1) bituminous coal (also referred to as “high rank” coal), (2) sub-bituminou s coal, and (3) and lignite (sub-bituminous coal and lignite are referred to as “low rank” coal s). Some of the characteristics of interest related to the possible environmental impacts of bu rning these different coal ranks are given in Table 2 (EPA, 2005).

Table 2. General Characteristics of Coals Burned in U. S. Power Plants (EPA, 2005).

Mercury Chlorine Sulfur Ash HHV a


### ppm (dry) ppm (dry) % (dry) % (dry) BTU/lb (dry) Coal Range Avg Range Avg Range Avg Range Avg Range Avg

Bitu- 0.036 - 0.113 48 - 1033 0.55 - 1.69 5.4 - 11.1 8646 - 13203

minous 0.279 2730 4.10 27.3 14014

Sub- 0.025 - 0.071 51 - 158 0.22 - 0.50 4.7 - 8.0 8606 - 12005

bitu- 0.136 1143 1.16 26.7 13168

minous Lignite 0.080 -

0.127 0.107 133 -

233 188 0.8 -

1.42 1.30 12.2 -

24.6 19.4 9487 -

10702 10028

a 

### Higher Heating Value.

7

### Characterization of Coal Combustion Residues II



### 1.2.1. Current Air Pollution Control Technologies
The key air pollutants of concern released by coal fired power plants include particulates, SO 2 

### , NOx, mercury and other metals 7 

### . A range of pollution control technologies is used to reduce particulate, SO 2 

### , and NOx and these technologies also impact the em ission of mercury and other metals. The pollution control technology type and configurations vary ac ross facilities.

7 

### Concerns regarding carbon dioxide emissions from c oal fired power plants are beyond the scope of this

report.



### 8

### Characterization of Coal Cumbustion Residues II



### Table 3 shows the current and projected coal-fired capacity by air pollution control technology configuration. This report emphasizes wet scrubbers since their use is expected to double or triple in response to implementation of CAIR. Post- combustion particulate matter controls used at coal-fired utility boilers in the United States can include electrostatic precipitators (ESPs), fabric filters (FFs), particulate scrubbers (PSs), or mechanical collectors (MCs). Post-combustion

SO 2 

### controls can consist of a wet scrubber (WS), spray dryer adsorber (SDA), or duct injection.

Post-combustion NOx controls can involve selective catalytic reduction (SCR) or selective noncatalytic reduction (SNCR).

In response to current and proposed NOx and SO 2 

### control requirements, additional NOx control and flue gas desulfurization (FGD) systems for SO 2 

### control are expected to be installed and more widely used in the future. Some estimates project a doubling or tripling of the number of wet scrubbers as a result of CAIR implementation. Over half of the U.S. coal-fired capacity is projected to be equipped with SCR and, or, FGD technolo gy by 2020.

The mercury capture efficiency of existing ESPs and FFs app ears to be heavily dependent on the partitioning of mercury between the particulate and vap or phases and the distribution of mercury species (e.g., elemental or oxidized) in the vapor phase. In general, ESPs and FFs which are designed for particulate control are quite efficien t at removing mercury in the particulate phase; however, the overall mercury removal efficiency in these devices may be low if most of the mercury entering the device is in the vapor phase (M TI, 2001). Many factors contribute to the observed differences in mercury removal efficiency, such as the mercury oxidation state. Differences in mercury contents of U.S. coals also result in a range of mercury concentrations in the flue gas from the boiler. In general, it is eas ier to achieve higher mercury percent removal with higher mercury inlet concentrations (MTI, 2001). Further, the chlorine content of the c oal may have an impact on mercury removal because the oxidation s tate of mercury is strongly affected by the presence of halides in the flue gas . In general, the higher the chlorine content of the coal, the more likely the mercury will be prese nt in its oxidized state, enhancing the likelihood of its removal from the gas stream. The addi tion of NO

x 

### controls may improve the mercury capture efficiency of particulate collection dev ices for some cases. (EPA, 2001)

9

### Characterization of Coal Combustion Residues II



### Table 3. Projected Coal-Fired Capacity by APC Confi guration as per data collection in 1999 (EPA, 2005). CCR samples evaluated in this report are from configurations indicated by shaded (light gray) rows. Current capacity reflects date o f data collection for EPA report (EPA, 2005).

Air Pollution Control Configuration Current Capacity, MW 2010 Capacity,

MW 2020 Capacity,

MW Cold-side ESP 111,616 75,732 48,915 Cold-side ESP + Wet Scrubber 41,745 34,570 33,117

Cold-side ESP + Wet Scrubber + ACI - 379 379 Cold-side ESP + Dry Scrubber 2,515 3,161 5,403 Cold-side ESP + SCR 45,984 35,312 22,528 Cold-side ESP + SCR + Wet Scrubber 27,775 62,663 98,138 Cold-side ESP + SCR + Dry Scrubber - 11,979 13,153 Cold-side ESP + SNCR 7,019 4,576 2,534 Cold-side ESP + SNCR + Wet Scrubber 317 2,830 6,088 Fabric Filter 11,969 10,885 7,646 Fabric Filter + Dry Scrubber 8,832 8,037 9,163 Fabric Filter + Wet Scrubber 4,960 4,960 4,960 Fabric Filter + Dry Scrubber + ACI - 195 195 Fabric Filter + SCR 2,210 2,950 1,330 Fabric Filter + SCR + Dry Scrubber 2,002 2,601 4,422 Fabric Filter + SCR + Wet Scrubber 805 805 2,363

Fabric Filter + SNCR 267 267 345 Fabric Filter + SNCR + Dry Scrubber 559 557 557 Fabric Filter + SNCR + Wet Scrubber 932 932 1,108 Hot-side ESP 18,929 11,763 10,160 Hot-side ESP + Wet Scrubber 8,724 10,509 10,398 Hot-side ESP + Dry Scrubber - 538 538 Hot-side ESP + SCR 5,952 3,233 1,847 Hot-side ESP + SCR + Wet Scrubber 688 6,864 9,912 Hot-side ESP + SNCR 684 1,490 1,334

Hot-side ESP + SNCR + Wet Scrubber 474 474 627 Existing or Planned Retrofit Units 304,955 298,263 297 ,161

New Builds of Coal Steam Units Current Capacity, MW 2010 Capacity,

MW 2020 Capacity,

MW Fabric Filter + SCR + Wet Scrubber - 221 17,292

Total All Units 304,955 298,484 314,453
Note: IGCC units are not included as part of this l ist. Note: Current capacity includes some SCR and FGD pr ojected to be built in 2005 and 2006. Note: 2010 and 2020 is capacity projected for final CAIR rule. Note: IPM projects some coal retirements and new co al in 2010 and 2020.



### 10

### Characterization of Coal Cumbustion Residues II



### 1.2.2. Wet Scrubbers, NOx Controls and Multi-pollutant Controls
Wet FGD scrubbers are the most widely used technolo gy for SO 2 

### control. Scrubbers are typically installed downstream of particulate control (i.e., ESP or FF). Removal of PM from the flue gas

before it enters the wet scrubber reduces solids in the scrubbing solution and minimizes impacts to the fly ash that might affect its beneficial use.

FGD technology uses sorbents and chemical reactants such as limestone (calcium carbonate) or lime (hydrated to form calcium hydroxide) to remove sulfur dioxide from the flue gas created from coal combustion. Limestone is ground into a fi ne powder and then combined with water to spray the slurry into combustion gases as they pass through a scrubber vessel. The residues are collected primarily as calcium sulfite (a chemicall y reduced material produced in natural oxidation or inhibited oxidation scrubbers), or can be oxidized to form calcium sulfate or FGD gypsum (using forced oxidation). The most widely used FGD systems use either forced oxidation scrubbers with limestone addition, or natural/inhib ited oxidation scrubbers with lime or Mg-lime

addition 8 

### . Wet scrubbers that use forced oxidation produce c alcium sulfate (gypsum) and are expected to be the most prevalent technology because of the potential beneficial use of gypsum and easier management and handling of the residues. There are also dry FGD systems that include spray dryer absorbers, usually in combinati on with a FF (EPA, 2001; Srivastava et al., 2001).

NOx emissions are controlled through the use of low NOx producing burners and use of a selective catalytic reduction (SCR) system in the f lue gas that is capable of a 90% reduction of flue gas NOx emissions. SCR is typically installed upstream of the PM control device. Sometimes selective non-catalytic reduction (SNCR) is used for NOx control, although use of SNCR is less frequent.

Figure 2 illustrates options for multi-pollutant control a t power plants.

8 As of 1999: Total FGD units – 151; limestone force d oxidation (FO) - 38 units (25%); limestone natura l/inhibited oxidation - 65 (43%); lime FO (all forms other than Mg-Lime) - 1 (<1%); lime natural/inhibited oxidati on (all forms other than Mg-lime) - 23 (15%); Mg-lime FO - 0 (0%) ; Mg-lime natural/inhibited oxidation - 25 (17%)

It is estimated that the numbers of natural/inhibit ed systems has remained nearly the same since 1999, and the limestone FO units have increased significantly. In the future, limestone FO units will increase signi ficantly, and all types of natural/inhibited units will likely decrea se (Ladwig, 2007).



### 11

### Characterization of Coal Combustion Residues II



### Oxidizing Wet Scrubber Stack Wet Scrubber Stack

Coal & Air

Oxidizing

Chemicals SCR Catalysts

Residue

Ash PM Control

Coal & Air

Oxidizing

Chemicals SCR Catalysts

Residue

Ash PM Control

Figure 2. Multi-pollutant control systems in coal fire d power plants.

Improvements in wet scrubber performance to enhance mercury capture depend on oxidizing elemental mercury (Hg 0 

### ) to Hg 2+ 

### by using additives to the flue gas or scrubber. A DOE-funded study found that wet scrubbers remove about 90% of the oxidized gaseous mercury (Hg 2+ 

### ) in the flue gas but none of the elemental mercury (Pavlish et al., 2003). The percentage of total Hg removed by multi-pollutant controls (particulate an d scrubber devices) is influenced by coal chlorine content, which determines the Hg oxidation status exiting the particulate control and entering the scrubber. Mercury removal efficiency b y wet scrubbers ranges from 30 to 60% for

cold-side ESPs as coal chlorine content is increase d from 50 to 1000 mg kg -1 

### . Mercury removal efficiency for hot-side ESPs is less effective rang ing from 20 to 50% as coal chlorine content is increased from 200 to 1000 mg kg -1 

### (Pavlish et al., 2003). Other factors that influen ce mercury capture are the amount of carbon and chlorine in the fly ash. Fuel blending, addition of o xidizing chemicals, controlling unburned carbon content in t he fly ash, and addition of a mercury-specific oxidizing catalyst downstream of the particulate ma tter control can help improve mercury capture (Thorneloe, 2006; EPA, 2005).



## 1.3. COAL COMBUSTION RESIDUES

The range of air pollution control technologies and configurations determines the characteristics of the coal combustion residues. In 2006, 125 milli on tons of coal combustion residues were produced with ~53 million tons being used in commer cial, engineering, and agricultural applications. (ACAA, 2007). CCRs result from unburned carbon and inorg anic materials in coals that do not burn, such as oxides of silicon, aluminum, iron, and calcium. Fly ash is the unburned material from coal combustion that is ligh t enough to be entrained in the flue gas stream, carried out of the process, and collected a s a dry material in the APC equipment. APC can concentrate or partition metals in fly ash and scrubber sludge. Bottom ash and boiler slag are not affected by APC technology and, therefore, thes e materials are not being evaluated as part of this study. Bottom ash is the unburned material tha t is too heavy to be entrained in the flue gas

12

### Characterization of Coal Cumbustion Residues II



### stream and drops out in the furnace. Boiler slag, u nburned carbon or inorganic material in coal that does not burn, falls to the bottom of the furn ace and melts.

Changes in multi-pollutant control in response to C AIR implementation, voluntary improvements by facilities, and changes in state re quirements, will reduce air emissions of mercury and other pollutants that will be transferr ed from the flue gas to the APC residues. The purpose of this research is to evaluate the impact of these changes on CCRs, with a focus on changes in metals concentrations in CCRs, and the p otential for subsequent release of these metals to the environment under different plausible management (disposal or reuse) conditions (Figure 3). The properties of fly ash and scrubber residues are likely to change as a result of changes in air pollution control to reduce emission s of concern from coal-fired power plants. Changes in CCRs that may occur include increased co ntent of mercury and other metals (e.g., arsenic, selenium, chromium) The chemical and phys ical properties may also change as a results of sorbents and other additives being used to impro ve air pollution control.

Figure 3. Life-cycle evaluation of coal combustion residues (EPA, 2002).



## 1.4. RESIDUE MANAGEMENT PRACTICES

CCRs can be disposed in landfills or surface impoun dments or used in commercial applications to produce concrete and gypsum wallboard, among oth er products. The major pathway of concern for release from land disposal and some ben eficial use applications is leaching to groundwater. Research on the impact of CCR disposal on the environment has been conducted by many researchers and has been summarized by the EPA (1988, 1999). However, most of the existing CCR data are for CCRs prior to implementation of mer cury or multi-pollutant controls.

1.4.1. Beneficial Use
In the United States, approximately 40% percent (49 .6 million tons) of all CCRs produced are reused in commercial applications or other uses tha t are considered beneficial and avoid

13

### Characterization of Coal Combustion Residues II



### landfilling. Forty-eight percent (23.8 million tons ) of CCRs is fly ash which is used in commercial applications such as making concrete/gro ut, cement, structural fill, and highway construction (ACAA, 2005; Thorneloe, 2003). Eight m illion tons of the FGD gypsum that was produced (or 68%) was used in making wall board (AC AA, 2005). Table 4 and Figure 4 present the primary commercial uses of CCRs, and a breakdow n of U.S. production and usage by CCR

type.

Some of the beneficial uses may have the potential to release mercury from the CCRs by several pathways. Of particular concern are high-temperatur e processes. In cement manufacturing, for example, CCRs are inputs to the cement kiln. Virtua lly all mercury will be volatilized from

CCRs when CCRs are used as feedstock to cement kiln s. Even where mercury can be captured by the controls on cement kilns, approximately two- thirds of cement kiln dust captured by the

control devices is reintroduced into the kiln. Ther efore, a significant fraction of the mercury in CCRs introduced into cement kilns may be emitted to the air at the cement plant. Some mercury may also be revolatilized when CCRs are used as fil ler for asphalt, or when FGD material is used in wallboard manufacturing. A separate report is be ing prepared to document the finding on the thermal stability of Hg and other metals when used in high-temperature processes.

The fate of mercury and other metals is also a pote ntial concern when CCRs are used on the land (mine reclamation, building highways, soil amendmen ts, agriculture and in making concrete, cement) or to make products that are subsequently d isposed (e.g., disposal of wallboard in unlined landfill).

For several commercial uses, it appears less likely that mercury in CCRs will be reintroduced into the environment, at least during the lifetime of the product. However, the impact of advanced mercury emissions control technology (e.g. , activated carbon injection) on beneficial use applications is uncertain. There is concern tha t the presence of increased concentrations of mercury, certain other metals, or high carbon content may reduce the suitability of CCRs for use in some applications (e.g., carbon content can limit use in P ortland cement concrete).

1.4.2. Land Disposal
There are approximately 600 land-based CCR waste di sposal units (landfills or surface impoundments) being used by the approximately 500 c oal-fired power plants in the United States (EPA, 1999). About 60% of the 122 million tons of C CRs generated annually are land disposed. Landfills may be located either on-site or off-site while surface impoundments are almost always located on-site with the combustion operations. Alt hough the distribution of units is about equal between landfills and surface impoundments, there i s a trend toward increased use of landfills as the primary disposal method.

14Characterization of CoalCumbustion ResiduesReportTable 4. Beneficial uses of CCRs (ACAA, 2007). Total production of CCRs during 2006 was 124,795,124 short tons.CCR Categories (Short Tons)FlyAshBottomAshFGDGypsumFGD WetScrubbersBoilerSlag1FGD DryScrubbers1FGDOtherCCR Production Category Totals272,400,000 18,600,000 12,100,000 16,300,000 2,026,066 1,488,951 299,195CCR Used Category Totals332,423,569 8,378,494 9,561,489 904,348 1,690,999 136,639 29,341CCR Use By Application4FlyAshBottomAshFGDGypsumFGD WetScrubbersBoilerSlag1FGD DryScrubbers1FGDOther1. Concrete/Concrete Products/Grout 15,041,335 597,387 1,541,930 0 0 9,660 02. Cement/Raw Feed for Clinker 4,150,228 925,888 264,568 0 17,773 0 03. Flowable Fill 109,357 0 0 0 0 9,843 04. Structural Fills/Embankments 7,175,784 3,908,5610 131,821 126,280 0 05. Road Base/Sub-base/Pavement 379,020 815,520 0 0 60 249 06. Soil Modification/Stabilization 648,551 189,5870 0 0 2991,5037. Mineral Filler in Asphalt 26,720 19,250 0 0 45,0000 08. Snow and Ice Control 0 331,107 0 0 41,549 0 09. Blasting Grit/Roofing Granules 0 81,242 0 232,7651,445,933 0 010. Mining Applications 942,048 79,636 0 201,011 0 115,696 011. Wallboard 0 0 7,579,187 0 0 0 012. Waste Stabilization/Solidification 2,582,125 105,052 0 0 0 0 27,83813. Agriculture 81,212 1,527 168,190 0 0 846 84614. Aggregate 271,098 647,274 0 0 416 0 015. Miscellaneous/Other 1,016,091676,463 7,614 338,751 13,988 46 46CCR Category Use Tools 32,423,569 8,378,494 9,561,489 904,348 1,690,999 136,639 29,341Application Use to Production Rate44.8% 45.0% 79.0% 5.5% 83.5% 9.2% 9.8%1As submitted based on 54 percent coal burn.2CCR Production totals for Fly Ash, Bottom Ash, FGDGypsum, and Wet FGD are extrapolated estimates rounded off to nearest 50,000 tons.3CCR Used totals for Fly Ash, Bottom Ash, FGD Gypsum, and Wet FGD are per extrapolation calculations (not rounded off).4CCR Uses by application for Fly Ash, Bottom Ash, FGD Gypsum, and Wet FGD are calculated per proportioning the CCR Used CategoryTotals by the same percentage as each of the individual application types' raw data contributions to the as-submitted raw data submittal total(not rounded off).15

### Characterization of Coal Combustion Residues II

0 2 4 6 8 10 12 14 16 18

Con c ret e / G r o ut Structu r al Fill
Wa ll b oar d Cement Waste Stabiliz

at ion/Sol i dif i cat i o n

Mi s cellan e o u s /O t h er

B lastin g Grit/Roofing G ra n ules Road Base/Pavem

e nt Mining Applications Soil Modification/Stabilization

A g gregate

Snow an d Ice Con t rol Agricult u r e

Mi ner al Filler i n A s p ha lt Flow abl e F i l lQuantity of CCRs (million tons)

FGD Dry Scrubbers

Boiler Slag

FGD Wet Scrubbers

FGD Gypsum

Bottom Ash

Fly Ash



### Figure 4. Uses of CCRs based on 2006 Industry Statistics (ACAA, 2007).



## 1.5. LEACHING PROTOCOL

One of the major challenges initially facing this r esearch was identification of an appropriate test protocol for evaluating the leaching potential of C CRs that may have increased levels of several metals, particularly mercury. The goal of this rese arch is to develop the most accurate estimates of likely constituent leaching when CCRs are land d isposed. These estimates of leaching need to be appropriate for assessing at a national level th e likely impacts through leaching of pollutants from CCRs that is a consequence of installation of enhanced mercury and, or, multi-pollutant controls. To achieve this goal requires that U.S. E PA evaluate leaching potential for CCRs as managed (to the degree this is known), and that the leach testing results can be appropriately extrapolated to a national assessment. A large part of the approach to achieving this goal has been to identify and evaluate CCR samples collected from the most prevalent combinations of power plant design (with a focus on air pollution control technology configurations) and coal rank used. In addition, the resulting data set is expected to serve as foundatio n for evaluation of CCR management options for different types of CCRs at s pecific sites.

Data have been collected on the disposal conditions for CCRs. The conditions will vary over time which need to be considered when evaluating le aching. (EPA, 1999, 202, 2007). When

16

### Characterization of Coal Cumbustion Residues II



### disposed, CCRs are typically monofilled or disposed with other CCRs. However, CCR composition can change over time, due to reactions with the atmosphere ( e.g., carbonation and oxidation), changes in the source of coal or coal r ank burned, or due to installation of additional pollution control equipment.

Many leaching tests have been developed by regulato ry agencies, researchers, or third-party technical standards organizations, and are describe d in the published literature. States and others have expressed concern with the variety of leaching protocols in use, the lack of correlation of

test results with field conditions and actual leach ing, and lack of comparability of available data because of incomplete reporting of test conditions. There is also limited or no quality assurance (QA) information for many of these tests. Leaching te sts such as the Toxicity Characterization Leaching Procedure (TCLP) 9 

### (which reflects municipal solid waste co-disposal conditions) or the synthetic precipitation leaching procedure (SPL P), or any number of deionized water based tests may be inappropriate, or are at least not opt imal for evaluating the leaching potential of CCRs as they are actually managed (i.e., monofilled or codisposed with other CCRs). These tests either presume a set of prevailing landfill conditi ons (which may or may not exist at CCR disposal sites; e.g., TCLP), try to account for an environmental factor considered to be important in leaching (e.g., SPLP), or presume that the waste as tested in the laboratory will define the disposal conditions (such as deionized (DI) water t ests). Most existing leaching tests are empirical, in that results are presented simply as the contaminant concentrations leached when using the test, and without measuring or reporting values for factors that may affect waste leaching, or that provide insight into the chemistr y that is occurring in leaching. Most tests are performed as a single batch test, and so do not consider the effect of variations in conditions on waste constituent leaching 10



### . In searching for a reliable procedure to characteri ze the leaching potential of metals from the management of CCRs, EPA sought an approach that (i) considers key aspects of the range of known CCR chemistry and management conditions (incl uding re-use); and (ii) permits development of data that are comparable across U.S. coal and CCR types. Because the data resulting from this research will be used to suppor t regulations, scrutiny of the data is expected.

9 

### The Toxicity Characterization Leaching Procedure (T CLP) was not included as part of this study for two reasons. First, EPA previously made a waste sta tus determination under RCRA that coal combustion residues are non-hazardous (65 FR 32214, May 22, 20 00). Therefore, use of TCLP was not required as indicated under the RCRA toxicity characteristic re gulation for determination of whether or not CCRs were hazardous. Second, TCLP was developed to simul ate co-disposal of industrial waste with municipal solid waste as a mismanagement scenario, and to ref lect conditions specific to this scenario. However, the vast majority of CCRs are not being managed through co-disposal with municipal solid waste, and the te st
conditions for TCLP are different from the actual m anagement practices for most CCRs. In seeking a tailored, “best-estimate” of CCR leaching, the leac hing framework provides the flexibility to consider the effects of actual management conditions on these wa stes, and so will be more accurate in this case.

10 

### Many factors are known or may reasonably be expect ed to affect waste constituent leaching. The solubility of many metal salts is well known to var y with pH; adsorption of metals to the waste matrix varies with pH; redox conditions may determine whic h metal salts are present in wastes; temperature ma y affect reaction rates; water infiltration can affec t the leaching rate, and also affect leaching chemi stry and equilibrium.



### 17

### Characterization of Coal Combustion Residues II



### Therefore, the use of a published, peer-reviewed pr otocol is also considered to be an essential

element of this work.

EPA ORD has worked closely with EPA’s Office of Solid Waste and Emergenc y Response (OSWER) to identify an appropriate leaching protoco l for evaluating CCRs. The protocol that has been adopted is the “Integrated Framework for E valuating Leaching in Waste Management and Utilization of Secondary Materials” (Kosson et al., 2002) and referred to here as the “leaching framework.” The leaching framework consis ts of a tiered approach to leaching assessment. The general approach under the leaching framework is to use laboratory testing to measure intrinsic leaching characteristics of a mat erial (i.e., liquid-solid equilibrium partitioning as a function of pH and LS ratio, mass transfer rat es) and then use this information in conjunction with mass transfer models to estimate c onstituent release by leaching under specific management scenarios (e.g., landfilling). Unlike ot her laboratory leaching tests, under this approach, laboratory testing is not intended to dir ectly simulate or mimic field conditions. Development work to-date on the leaching framework has focused on assessing metals leaching, and this work includes equilibrium batch testing (o ver a range of pH and LS ratio values), diffusion-controlled mass transfer, and percolation -controlled (column) laboratory test methods in conjunction with mass transfer models, to estimate release for specific management scenarios based on testing results from a common set of leach ing conditions. EPA OSWER and ORD believe that this approach successfully addresses the concerns identified above, in that it seeks to consider the effect of key disposal conditions on c onstituent leaching, and to understand the leaching chemistry of wastes tested.

The following attributes of the leaching framework were considered as part of the selection

process:

! 

### The leaching framework will permit development of d ata that are comparable across U.S. coal and CCR types;

! 

### The leaching framework will permit comparison with existing laboratory and field leaching data on CCRs;

! 

### The leaching framework was published in the peer-re viewed scientific literature (Kosson et al., 2002);

! 

### On consultation with EPA’s OSWER, it was recommende d as the appropriate protocol based on review of the range of available test methods and ass essment approaches; and

! 

### On consultation with the Environmental Engineering Committee of the Science Advisory Board (June 2003), the committee considered the lea ching framework responsive to earlier SAB criticisms of EPA’s approach to leaching evalua tion, and also was considered broadly applicable and appropriate for this study

For this study, the primary leaching tests used fro m the leaching framework were Solubility and Release as a Function of pH (SR002.1) and Solubilit y and Release as a Function of the LiquidSolid Ratio (LS) (SR003.1) 11 

### . These tests represent equilibrium-based leaching c haracterization

11 

### LS refers to liquid to solid ratio (mL water/g CCR or L water/kg CCR) occurring during laboratory leaching tests or under field conditions. SR002.1 i s carried out at LS=10 with several parallel batch extractions over a range of pH, while SR003.1 is ca rried out using several parallel batch extractions with



### 18

### Characterization of Coal Cumbustion Residues II



### (Kosson et al., 2002). The range of pH and LS ratio used in the leaching tests includes the range of conditions (pH and LS ratio) observed for current CCR ma nagement practices. Results of these tests provide insights into the physical-chem ical mechanisms controlling constituent leaching. When used in conjunction with mass transf er and geochemical speciation modeling, the results can provide conservative 12 

### but realistic estimates of constituent leaching un der a variety of environmental conditions (pH, redox, salinity, c arbonation) and management scenarios.

Laboratory testing for leaching assessment was carr ied out at the U.S. EPA National Risk Management Research Laboratory (Research Triangle P ark, NC) with technical assistance from Vanderbilt University.

deionized water at LS= 0.5, 1, 2, 5 and 10. Under f ield conditions, LS refers to the cumulative amount of water passing through the total mass of CCR subject to leaching.

12 

### In this report, “conservative” implies that the co nstituent release estimates are equal to or greater than actual expected release under field conditions.



### 19

### Characterization of Coal Combustion Residues II



## 2. MATERIALS AND METHODS

2.1. CCR MATERIALS FOR EVALUATION

The 23 CCR materials tested in this study include f ive fly ash, four unwashed gypsum, two washed gypsum, five scrubber sludges, two fixated s crubber sludges and five fixated scrubber sludges with lime obtained from eight coal fired po wer plants (Table 1). The facilities and CCRs that were sampled were selected to allow comparison s

(i) between different CCR types from a given facili ty (Facilities A, B and K),

(ii) between CCRs of the same type from the same fa cility without and with postcombustion NOx control, either by SNCR (Facility A) or S CR (Facility B),

(iii) the impact of different FGD scrubber types on scrubbe r sludge and “as managed” FSS or FSSL (Facilities A, B, K and M),

(iv) the influence of coal rank (bituminous vs. sub- bituminous) being combusted in facilities with similar APC technology configurations (Facility B and K with SCR on),

(v) unwashed and washed gypsum from the same facility (Facilities N and O), and

(vi) unwashed gypsum from four facilities (Facilitie s N, O, P and Q). This set of 23 CCRs reflects 84 and 74 percent, respectively, of the current and expected future facility configuration types with acid gas scrubbers based on generating capacity, but only a limited number of facilities within each configuration type. Figure 5, Figure 6,

(vii) Figure 7, and Figure 8 diagram the layout of comparison s that will be used in presentation of data for fly ash, gypsum, scrubber sludge, fixated scrubber sludge and fixated scrubber sludge with lime, respectively.



## Facility A

Coal: low sulfur bituminous

APC: NO+SNCR+FF

Facility B
Coal: low sulfur bituminous APC: NO+SCR+ESP(CS) [Mg lime]

Facility K
Coal: sub

- bituminous APC: NO+SCR+ESP(CS) [Mg lime] 

# BFA
(SCR On) 

# DFA
(SCR Off) 

# AFA

(SNCR On) 

# CFA
(SNCR Off)



# KFA

(SCR On)

Figure 5. Fly ash (FA) comparisons (CFA, AFA, DFA, etc refer to sample identification codes; see Table 1). Shorthand is used for when SCR is in use (“on”) or not in use (“off”).

20

## Facility N

Coal: bituminous APC: FO+ESP(CS)

Facility O

Coal: bituminous APC: FO+SCR+ESP(CS) 

# Gyp-U

OAU

(unwashed) 

# NAU

(unwashed) 

# Gyp-W

OAW

(washed) 

# NAW

(washed)



## Facility P

Coal: bituminous APC: FO+ SCR & SNCR +ESP(CS) 

# PAD (U)

(unwashed) 

# QAU

(unwashed)



## Facility Q

Coal: sub-bituminous APC: FO+SCR+ESP(CS) Characterization of Coal Cumbustion Residues II



### Figure 6. Gypsum (Gyp-U, Gyp-W) comparisons (NAU, N AW, OAU, etc. are sample identification codes; see Table 1).

Errata: Subsequent tables and figures indicate the Facilit y N has SCR in use. That is not correct. This will be corrected in Report 4 and does not cha nge the leach testing results.

21

## Facility A

Coal: low sulfur bituminous

APC: NO+SNCR+FF

Facility B

Coal: low sulfur bituminous APC: NO+SCR+ESP(CS) [Mg lime] 

# BGD

(SCR On) 

# DGD

(SCR Off) 

# AGD

(SNCR On) 

# CGD

(SNCR Off)



# KGD

(SCR On) 

## Facility K

Coal: sub- bituminous APC: NO+SCR+ESP(CS) [Mg lime] Characterization of Coal Combustion Residues II



### Figure 7. Scrubber sludge (ScS) comparisons (CGD, AGD, DGD, etc. are sampl e identification codes; see Table 1). Shorthand is used for when SCR is in use (“on”) or not in (“off”).

22

## FSS: Fly Ash + Scrubber Sludge (FA+ScS)

Facility A ( FSS )

Coal: low sulfur bituminous

APC: NO+SNCR+FF 

# ACC

(SNCR On) 

# CCC

(SNCR Off)



## FSSL: Fly Ash + Scrubber Sludge + Lime (FA+ScS+lime )

Facility B ( FSSL )

Coal: low sulfur bituminous APC: NO+SCR+ESP(CS) [Mg lime]

Facility K ( FSSL )

Coal: sub-bituminous APC: NO+SCR+ESP(CS) [Mg lime]

Facility M ( FSSL )

Coal: bituminous 

# MAD MAS
APC: IO+SCR+ESP(CS) (SCR Off) (SCR On) 

# BCC

(SCR On) 

# DCC

(SCR Off)



# KCC

(SCR On) Characterization of Coal Cumbustion Residues II



### Figure 8. Fixated scrubber sludge (FSS) and fixated scrubber sludge with lime (FSSL) comparisons (DCC, BCC, KCC, etc. are sample identificatio n codes; see Table 1).

23

### Characterization of Coal Combustion Residues II



### 2.1.1. Facilities Using Inhibited or Natural Oxidation of Scrubber Residues (Producing Scrubber Sludge or Fixated Scrubber Sludge)

2.1.1.1. Facility A (Natural Oxidation and SNCR)

Facility A is a 440-MW coal-fired power plant with a reverse-air fabric filter followed by a wet FGD system. The unit burns ~1 percent sulfur easter n bituminous coal. The unit operated at nominally full load for the duration of the test pr ogram. The unit is equipped with a pulverizedcoal boiler and in-furnace selective SNCR; urea was injected into the boiler during the course of operations within the duration of the initial part of this test program. However, urea was not injected into the boiler for the final comparison t est (“SNCR off”). Gas exiting the furnace is split between two flues equipped with comparable co ntrol equipment. Particulate is removed with a reverse-air fabric filter. Flue gas is then scrubbed through a multiple tower wet FGD unit; FGD is a limestone natural-oxidation design. The tw o flues are joined prior to exhausting to a

common stack. The annular stack rises 308 feet abov e the top of the incoming flue. The stack is operated in a saturated condition with no reheat. T he fly ash and FGD waste are combined and then dewatered before landfill disposal.

Facility A was sampled in September 2003. Three sa mples were collected in September 2003 when the SCR was operating: one fresh fly ash sampl e collected from the ash hopper (sample AFA), one scrubber sludge filter cake sample collec ted after the centrifuge but before mixing with other materials in the pug mill (sample AGD), and one fixated scrubber sludge sample collected after mixing the scrubber sludge with fly ash and magnesium-enhanced lime in the pug mill (sample ACC). Three additional samples were co llected from the same locations in February 2004 when the SCR was not in use (samples CFA, CGD and CCC, respectively). Each sample consisted of two 5-gallon pails of the material, an d all were collected by plant personnel.

2.1.1.2. Facility B (Natural Oxidation and SCR)

Facility B is a 640 MW coal-fired power plant with cold side ESP followed by a wet FGD system with Mg-lime. The unit burns medium to high s ulfur eastern bituminous coals. The unit is equipped with a pulverized coal boiler and selectiv e catalytic reduction composed of vanadium pentoxide (V 2 

### O 5 

### ) and tungsten trioxide (WO 3 

### ), on titanium dioxide (TiO 2 

### ) supporting matrix. One set of samples was collected during the season of elevated ozone, when ammonia is injected into the ductwork in front of the SCR catalyst, res ulting in a flue gas mixture with a concentration of 320 ppm ammonia as it enters the catalyst. Samples were also collected during the winter when ammonia was not being injected (“SC R off”). Particulate is removed with a cold-side ESP. Flue gas is then scrubbed through a wet FGD unit; FGD is an inhibited mag-lime design. The FGD sludge is thickened and then mixed with fly ash and magnesium-enhanced lime before landfill disposal in a clay-lined site. Ref er to appendix G for a process flow-diagram for facility A.

Three samples were collected in September, 2003 whe n the SCR was operating: one give gallon bucket of the fly ash (BFA) from the hoppers, parti ally dewatered scrubber sludge by centrifuging (BGD), and centrate cake (BCC) or scru bber sludge fixated with fly ash and Mg lime (MgO). Three additional samples were collecte d from the same locations in February, 2004 when the SCR was not in use (samples DFA, DGD, and DCC, respectively). Each sample consisted of one 5-gallon bucket of the material, a nd all were collected a Natural Resource Technology contractor to EPRI.

24

### Characterization of Coal Cumbustion Residues II



### Coal analysis information for facility B was provid ed by EPRI. Results of the analysis on the medium to high sulfur bituminous coal for sulfur wa s 3.24% by weight, ash was 12.4%, moisture was 6.1%, heat of combustion was 12,000 BTU/lb, chloride was 615 ug/g, and mercury was 0.08 ug/g.

2.1.1.3. Facility K (Natural Oxidation and SCR)

Facility K is two tangentially fired 400 MW coal-fi red boilers with cold side ESP followed by a wet flue gas desulfurization system with wet Mg-lim e natural oxidation. These units burn medium sulfur eastern bituminous coals from Ohio, P ennsylvania and West Virginia. Flue gas is scrubbed through a common wet FGD unit; FGD is a we t Mg-lime natural oxidation design. FGD sludge is mixed with fly ash and quicklime for stabilizat ion prior to disposal.

Two samples were collected on November 29, 2004: on e scrubber sludge filter cake before mixing in the pug mill (sample KGD), and one fixate d scrubber sludge collected after mixing the scrubber sludge with fly ash and 2-3% lime in the p ugmill (sample KCC). On January 12, 2005, one fly ash sample was collected directly from the ESP before the ash storage silo (sample KFA). Each sample consisted of four 5-gallon pails of the material, and all were collected by plant personnel.

2.1.1.4. Facility M (Inhibited Oxidation and SCR)

Facility M is a 1,000+ MW power plant. The plant burns bituminous coal in a dry-bottom pulverizer boiler. Cold-side ESPs are used on all u nits for particulate control, and wet FGD systems are used to reduce SO 2 

### emissions on two units. The wet FGD systems utiliz e limestone slurry and an inhibited oxidation process. The FGD sludge, consisting primar ily of calcium sulfite, is pumped from the absorber to a thickener. Liquid overflow from the thickener is recycled back into the FGD system, and the thickene d sludge is pumped to a series of drum vacuum filters for further dewatering. Water remove d by the drum vacuum filters is recycled back into the FGD system, and the filter cake is ta ken by conveyor belt to a pug mill, where it is mixed with dry fly ash and dry quicklime for stabil ization. The resulting scrubber FGD solids are taken by conveyor to a temporary outdoor stockpile, and then transported by truck either to a

utilization site or to an on-site landfill. The cur rently active portion of the landfill is lined and includes leachate collection. An older inactive portion of the landfill is clay- lined but does not

have leachate collection.

Three samples were obtained from the Pug Mill Area by the EPRI contractor during the week of March 6, 2006 when the SCR was not operating: fly a sh, vacuum drum filter cake, and fixated scrubber sludge with lime (only FSSL was evaluated as part of this study, sample MAD). In each case, the samples were collected daily during the four day sample collection (four daily samples of each), for compositing in the laboratory. All of the samples were collected into clean 5 gallon plastic pails. Excess sample was container ized and discharged back into the appropriate system. The drum filter cake was sampled daily from the conveyor belt leading into the pug mill. Two of the three drum filters were running simultane ously; both were feeding the conveyor belt. The same drums were running each day of sampling. E ach 5 gallon bucket was sealed immediately after collection and the lid secured wi th duct tape. The dry fly ash sample was obtained directly from the day tank via a hose connected to a sampling port. Each 5 gallon bucket was sealed immediately after collection and the lid secured with duct tape. FSS was

25

### Characterization of Coal Combustion Residues II



### sampled from the conveyor belt on the outlet side o f the pug mill on the first, third and fourth days. A clean, short handled spade was used to coll ect sample from the conveyor belt into a 2 gallon bucket. The sample in the bucket was placed on a clean piece of 3 mm plastic sheeting; then more sample was collected from the conveyor be lt into the bucket and added to the sheet until at least 6 gallons of sample was collected. E ach sample was homogenized on the sheet using the spade and placed into a 5 gallon bucket, sealed immediately, and the lid secured with duct tape. A similar process was used to collect th ree more samples the week of May 9 when the SCR was in use (FSSL sample MAS).

2.1.2. Facilities Using Forced Oxidation of Scrubber Residu es (Producing FGD Gypsum)

2.1.2.1. Facility N (Forced Oxidation)

Facility N is a wall fired 715 MW coal-fired power plant with cold side ESP followed b y a wet FGD system with wet limestone forced oxidation. Th e unit burns medium to high sulfur eastern bituminous coals approximately 3% sulfur. The gypsu m is washed, dried and then sold to the wallboard industry.

Facility N was sampled on June 1, 2006. Five gallo n buckets of the washed and unwashed gypsum were collected by RMB Consulting & Research Inc. (Raleigh, NC) personnel and provided for analysis.

2.1.2.2. Facility O (Forced Oxidation and SCR)

Facility O is a tangentially fired 500 MW coal-fired plant with cold side ESP followed by a wet FGD system with wet limestone forced oxidation. The unit is equipped with a pulverized coal boiler and ammonia based SCR. This unit burns high sulfur eastern bituminous coals. Slurry from the absorber goes to a primary hydrocyclone fo r initial dewatering. The gypsum (hydrocyclone underflow) is dried on a vacuum belt and washed to remove chlorides, before use

in wallboard.

Two samples were collected from the FGD gypsum dryi ng facility by compositing samples collected on June 10, 11, and 12, 2006 when the SCR was operating. On each day, two gallon pails of unwashed gypsum and washed/dried gypsum were collected. The unwashed gypsum was collected from the vacuum belt prior to the chlorid e spray wash. The washed/dried gypsum was

collected from the end of the vacuum belt. The thre e daily samples were sent to Arcadis for compositing to form sample OAU (unwashed gypsum) an d sample OAW (washed gypsum). All samples were collected by plant personnel.

2.1.2.3. Facility P (Forced Oxidation and SCR and SNCR)

Facility P is two wall fired 200 MW coal-fired boil ers with cold side ESP followed by a wet FGD system with wet limestone forced oxidation. Uni t 1 is equipped with SNCR and Unit 2 is equipped with SCR. These units burn medium sulfur e astern bituminous coals. Particulate is removed with a cold-side ESP. Flue gas is then scru bbed through a common wet FGD unit; FGD is a wet limestone forced oxidation design. The gypsum provided was not washed.

Facility P was sampled in October 2006 when both SCR and SNCR were operating and the residues from Unit 1 and Unit 2 were commingled dur ing collection. A five gallon bucket of the washed gypsum was collected by plant personnel.

26

### Characterization of Coal Cumbustion Residues II



### 2.1.2.4. Facility Q (Forced Oxidation and SCR)

Facility Q is a 1800 MW coal fired plant with hot s ide ESP followed by a wet flue gas desulfurization system with wet limestone forced ox idation. This unit burns sub-bituminous

coals. Particulate is removed with a hot-side ESP. Flue gas is then scrubbed through a wet FGD unit; FGD is a wet limestone forced oxidation desig n that includes the addition of dibasic acid to

the absorber 13 

### . The gypsum provided was not washed and was sample d on Oct. 30, 2006 by an EPRI contractor (Natural Resource Technology). A five gall bucket of the unwashed gypsum was shipped to ARCADIS for analysis on May 4, 2007.



## 2.2. LEACHING ASSESSMENT PROTOCOLS

Laboratory testing for this study focused on leachi ng as a function of pH and LS ratio as defined by the leaching framework. This test set is conside red Tier 2 testing (equilibrium-based) for detailed characterization, which was selected to de velop a comprehensive data set of CCR characteristics. Mass transfer rate testing (Tier 3 , detailed characterization) may be carried out in the future for specific cases where results from equi librium-based characterization indicate a

need for detailed assessment.

2.2.1. Alkalinity, Solubility and Release as a Function of pH (SR002.1)
Alkalinity, solubility and release as a function of pH were determined according to method SR002.1 (Kosson et al., 2002). This protocol consis ts of 11 parallel extractions of particle size reduced material, at a LS ratio of 10 mL extractant/g dry sample. In this method, particle-size reduction is used to prepare large-grained samples for extraction so that the approach toward liquid-solid equilibrium is enhanced and mass trans port through large particles is minimized. For the samples evaluated in this study, minimal si ze reduction was required. Each extraction condition was carried out in triplicate using 40 g of material for each material evaluated. In addition, three method blanks were included, consis ting of the DI water, nitric acid and potassium hydroxide used for extractions. Typical p article size of the tested materials was less than 300 μm using standard sieves according to ASTM E-11-70(1995). An acid or base addition schedule is formulated based on initial screening f or eleven extracts with final solution pH values between 3 and 12, through addition of aliquots of n itric acid or potassium hydroxide as needed. The exact schedule is adjusted based on the nature of the material; however, the range of pH values includes the natural pH of the matrix that may extend the pH domain (e.g., for very alkaline or acidic materials). The final LS ratio i s 10 mL extractant/g dry sample which includes DI water, the added acid or base, and the amount of moisture that is inh erent to the waste matrix as determined by moisture content analysis. The ele ven extractions were tumbled in an end-overend fashion at 28 ± 2 rpm for 24 hours followed by filtration separation of the solid phase from the extract using a 0.45 μm polypropylene filter. E ach extract then was analyzed for constituents

of interest. The acid and base neutralization behav ior of the materials is evaluated by plotting the pH of each extract as a function of equivalents of acid or base added per gram of dry solid.

Concentration of constituents of interest for each extract is plotted as a function of extract final pH to provide liquid-solid partitioning equilibrium as a function of pH. Initially, the SR002.1 test was carried out in triplicate; however, replication was reduced to two replicates of the test

13 

### Dibasic acid (DBA) is a commercial mixture of glut aric, succinic, and adipic acids: HOOC(CH 2 

### ) 2-4 

### COOH.



### 27

### Characterization of Coal Combustion Residues II



### method for later samples based on good replication and consistency amongst the early results (Sanchez et al., 2006).

2.2.2. Solubility and Release as a Function of LS Ratio (SR003.1)
Solubility and release as a function of LS ratio wa s determined according to method SR003.1 (Kosson et al., 2002). This protocol consists of five parallel batch extractions over a range of LS ratios (i.e., 10, 5, 2, 1, and 0.5 mL/g dry materia l), using DI water as the extractant with aliquots of material that has been particle size reduced. Ty pical particle size of the material tested was less than 300 μm. Between 40 and 200 g of material were used for each extraction, based on the

desired LS ratio. All extractions are conducted at room temperature (20 ± 2 ! C) in leak-proof

vessels that are tumbled in an end-over-end fashion at 28 ± 2 rpm for 24 hours. Following gross separation of the solid and liquid phases by centri fuge or settling, leachate pH and conductivity measurements are taken and the phases are separated by pressure filtration using 0.45-μm polypropylene filter membrane. The five leachates a re collected, and preserved as appropriate for chemical analysis. Initially, the SR003.1 test was carried out in triplicate; however, replication was reduced to two replicates of the test method fo r later samples based on good replication and consistency amongst the early results.



## 2.3. ANALYTICAL METHODS

2.3.1. Surface Area and Pore Size Distribution
A Quantachrome Autosorb-1 C-MS chemisorption mass s pectrometer was used to perform 5- point Brunauer, Emmett, and Teller (BET) method sur face area, pore volume, and pore size distribution analysis on each as-received and size- reduced CCR. A 200 mg sample was degassed

under vacuum at 200 oC for at least one hour in the sample preparation manifold prior to analysis

with N 2 

### as the analysis gas. Standard materials with known surface area were routinely run as a QC check.

2.3.2. pH and Conductivity
pH and conductivity were measured for all aqueous e xtracts using an Accumet 925 pH/ion meter. The pH of the leachates was measured using a combined pH electrode accurate to 0.1 pH units. A 3-point calibration was performed daily using pH buffer solutions at pH 4.0, 7.0 and 10.0. Conductivity of the leachates was measured us ing a standard conductivity probe. The conductivity probe was calibrated using appropriate standard conductivity solutions for the conductivity range of concern. Conductivity meters typically are accurate to " 1% and have a precision of " 1%.

2.3.3. Moisture Content

Moisture content of the “as received” CCRs was dete rmined using American Society for Testing and Materials (ASTM) D 2216-92. This procedure supersedes the method indic ated in the version of the leaching procedure published by Kosson et al. (2002).

2.3.4. Carbon Content Organic Carbon/Elemental Carbon Analyz er Organic carbon (OC) and elemental carbon (EC) content of eac h CCR tested was measured using a Sunset Lab thermal-optical EC/OC analyzer using t he thermal/optical method (NIOSH Method 5040). The sample collected on quartz fiber filters is heated under a completely oxygen-free

28

### Characterization of Coal Cumbustion Residues II



### helium atmosphere in a quartz oven in four increasi ng temperature steps (375 °C, 540 °C, 670 °C and 870 °C) at 60 second ramp times for the first t hree temperatures and a ramp time of 90 seconds for the final temperature. The heating proc ess removes all organic carbon on the filter. As the organic compounds are vaporized, they are im mediately oxidized to carbon dioxide in an oxidizer oven which follows the sample oven. The fl ow of helium containing the produced carbon dioxide then flows to a quartz methanator ov en where the carbon dioxide is reduced to methane. The methane is then detected by a flame io nization detector (FID). After the sample oven is cooled to 525 oC, the pure helium eluent is switched to an oxygen/helium mixture in the sample oven. At that time, the sample oven temperat ure is stepped up to 850 oC. During this phase, both the original elemental carbon and the r esidual carbon produced by the pyrolysis of organic compounds during the first phase are oxidiz ed to carbon dioxide due to the presence of oxygen in the eluent. The carbon dioxide is then co nverted to methane and detected by the FID. After all carbon has been oxidized from the sample, a known volume and concentration of methane is injected into the sample oven. Thus, eac h sample is calibrated to a known quantity of carbon as a means of checking the operation of the instrument.

The calibration range for these analyses was from 1 0 to 200 μg/cm 2 

### of carbon using a sucrose

solution as the standard. The detection limit of th is instrument is approximately 100 ng/cm 2 

### with a linear dynamic range from 100 ng/cm 2 

### to 1 g/cm 2



### .

2.3.5. Dissolved Inorganic Carbon (DIC) and Dissolved Organic Carbon (DOC)
Analyses of total organic carbon and inorganic carb on were performed on a Shimadzu model TOC-V CPH/CPN. Five-point calibration curves, for b oth dissolved inorganic carbon (DIC) and non-purgeable dissolved organic carbon (DOC) analys es, were generated for an analytical range between 5 ppm and 100 ppm and are accepted with a c orrelation coefficient of at least 0.995. An analytical blank and check standard at approximatel y 10 ppm were run every 10 samples. The standard was required to be within 15% of the speci fied value. A volume of approximately 16 mL of undiluted sample is loaded for analysis. DIC analysis is performed first for the analytical blank and standard and then the samples. DOC analys is is carried out separately after completion of DIC analysis. DOC analysis begins with addition of 2 M (mole/L) of hydrochloric acid to achieve a pH of 2 along with a sparge gas flow rate of 50 mL/min to purge inorganic carbon prior to analysis. Method detection limit (MDL) and minimum level of quantification (ML) are

shown in Table 5.

Table 5. MDL and ML of analysis of DIC and DOC.

MDL (μg/L) ML (μg/L)

DIC 70 200

DOC 90 200

2.3.6. Mercury (CVAA, Method 3052, and Method 7473)
Liquid samples were preserved for mercury analysis by additions of nitric aci d and potassium permanganate and then prepared prior to analysis ac cording to the following method. For each 87 mL of sample, 3 mL of concentrated nitric acid a nd 5 mL of 5 wt% aqueous potassium permanganate solution were added prior to storage. Immediately before cold vapor atomic absorption (CVAA) analysis, 5 mL of hydroxylamine w ere added to clear the sample and then the sample was digested according to ASTM Method D6 784-02 (Ontario Hydro) as described for

29

### Characterization of Coal Combustion Residues II



### the permanganate fraction (ASTM, 2002). On completi on of the digestion, the sample was analyzed for mercury by CVAA. Samples with known ad ditions of mercury for matrix analytical spikes also were digested as described above prior to C VAA analysis.

Sample preparation of the solids and filters was ca rried out by HF/HNO 3 

### microwave digestion according to Method 3052 (EPA, 1996) followed by CV AA analysis as indicated above. No additional preservation or digestion was carried out prior to CVAA analysis.

Mercury analysis of each digest, extract and leacha te was carried out by CVAA according to EPA SW846 Method 7470A “Mercury in Liquid Waste (Ma nual Cold Vapor Technique)” (EPA, 1998a). A Perkin Elmer FIMS 100 Flow Injection Mercury System was used for this analysis

. The instrument was calibrated with known standards ranging from 0.025 to 1 # g/L mercury.

Solids also were analyzed by Method 7473 “Mercury i n Solids and Solutions by Thermal Decomposition, Amalgamation, and Atomic Absorption Spectrophotometry” (EPA, 1998b). A Nippon MD-1 mercury system was used for this analys is. The instrument was calibrated with known standards ranging from 1 to 20 ng of mercury. The method detection limit for mercury in solids is 0.145 μg/kg.

2.3.7. Other Metals (ICP-MS, Method 3052, and Method 6020)
Liquid samples for ICP-MS analysis were preserved t hrough addition of 3 mL of concentrated nitric acid (trace metal grade) per 97 mL of sample . Known quantities of each analyte were also added to sample aliquots for analytical matrix spik es. Solid samples were digested by EPA Method 3052 (EPA, 1996) prior to ICP-MS analysis.

2.3.7.1. ICP-MS Analysis

ICP-MS analyses of aqueous samples from laboratory leaching tests were carried out at Vanderbilt University (Department of Civil and Envi ronmental Engineering) using a Perkin Elmer model ELAN DRC II in both standard and dynami c reaction chamber (DRC) modes. Standard analysis mode was used for all analytes ex cept for As and Se, which were run in DRC mode with 0.5 mL/min of oxygen as the reaction gas. Seven-point standard curve s were used for an analytical range between approximately 0.5 μg/L and 500 μg/L and completed before each analysis. Analytical blanks and analytical check st andards at approximately 50 μg/L were run every 10 samples and required to be within 15% of t he specified value. Samples for analysis were diluted gravimetrically to within the targeted analytical range using 1% v/v Optima grade nitric acid (Fisher Scientific). Initially, analyse s for 10:1 dilutions were performed to minimize total dissolved loading to the instrument. Addition al dilutions at 100:1 and 1000:1 were analyzed if the calibration range was exceeded with the 10:1 dilution. 50 μL of a 10 mg/L intern al standard consisting of indium (In) (for mass range below 150) and holmium (Ho) (for mass range over 150) was added to 10 mL of sample aliquo t prior to analysis. Analytical matrix spikes were completed for one of each of the replicate ext racts from SR002.1. For each analytical matrix spike, a volume between 10 μL and 100 μL of a 10 mg/L standard solution was added to 10 mL of sample aliquot. Table 6 provides the eleme nt analyzed, method detection limit (MDL) and minimum level of quantification (ML). Analyte concentrations measured that are less than the ML and greater than the MDL are reported as est imated value using the instrument response.

The values reflect the initial 10:1 dilution used f or samples from laboratory leaching tests.

30

### Characterization of Coal Cumbustion Residues II



### Table 6. Method detection limits (MDLs) and minimum level of quantification (ML) for ICPMS analysis on liquid samples.*

Symbol Units MDL ML

Al μg/L 1.25 2.00

Sb μg/L 0.60 2.00

As μg/L 1.09 2.00

Ba μg/L 0.75 2.00 Be μg/L 0.85 2.00

B μg/L 0.63 2.00

Cd μg/L 0.40 1.00 Ca μg/L 1.86 5.00 Cs μg/L 0.60 2.00

Cr μg/L 0.47 1.00

Co μg/L 0.51 2.00 Cu μg/L 0.87 2.00 Fe μg/L 1.55 5.00

Pb μg/L 0.28 1.00 Li μg/L 0.80 2.00

Mg μg/L 1.17 2.00 Mn μg/L 0.47 1.00

Mo μg/L 0.75 2.00 Ni μg/L 0.90 2.00 K μg/L 1.86 5.00

Re μg/L 0.30 1.00 Rb μg/L 0.70 2.00

Se μg/L 0.78 2.00 Si μg/L 1.85 5.00 Ag μg/L 2.10 5.00

Na μg/L 1.12 2.00 Sr μg/L 0.47 1.00

Tl μg/L 0.63 2.00 Sn μg/L 0.87 2.00 Ti μg/L 0.61 2.00

U μg/L 0.36 1.00 V μg/L 0.79 2.00 Zn μg/L 1.15 2.00 Zr μg/L 0.60 2.00 

### * All elements indicated in Table 6 have been analy zed, however, only elements indicated in bold are reported as part of the leaching studies. The elements that were included in the leaching studies were selected based on input from EPA program offices due to potential concern for

human health and the environment.

31

### Characterization of Coal Combustion Residues II



### 2.3.8. X-Ray Fluorescence (XRF)
XRF analysis was performed on each CCR to provide a dditional information on each CCR total elemental composition. For each CCR two pellets wer e prepared as follows. 3000 mg of material was weighed and mixed with 1.5 mL (100 mg dry solids) of liquid binder to give a 32 mm diameter pellet weighing 3150 mg with a material-to -diluent ratio of 0.05. For high carbon content samples 3.0 ml (100 mg dry solids) of liqui d binder was used to give a 32 mm diameter pellet weighing 3300 mg with a material to diluent ratio of 0. 1. XRF intensities were collected on each side of each pellet using Philips SuperQ data collection software and evaluated using Omega Data System’s UniQuant 4 XRF “standardless” d ata analysis software. The UQ/Fly ash calibration was used to analyze the samples. The pe llets were evaluated as oxides. Known fly ash Standard Reference Materials (SRMs) were also run t o assess the accuracy of the analysis. This information is useful in supplementing CVAA and ICP results

.

2.3.9. MDL and ML for Analytical Results
The MDL is defined by 40 CFR Part 136, Appendix B, July 1, 1995, Revision 1.11 as “the

minimum concentration of a substance that can be me asured and reported with 99% confidence that the analyte concentration is greater than zero and is determined from analysis of a sample in a given matrix containing the analyte.”

The MDL was determined statistically from data generated by the analysis of seven or more aliquots of a spiked reagent matrix 14 

### and verified by the analysis of calibration standa rds near the calculated MDL according to EPA (2003). The MDL the n was determined by multiplying the standard deviation of the replicate measurements by the appropriate Students t value for a 99% confidence level (two tailed) and n-1 (six) degrees of freedom and also multiplying by the minimum dilution factor required for matrix preservation and analysis.

The ML is defined by 40 CFR Part 136, 1994 as “the lowest level at which the entire analytical system must give a recognizable signal and acceptab le calibration point for the analyte.” According to EPA (2003), the ML is intended to be t he nearest integer value (i.e., 1, 2 or 5x10 n



### , where n is an integer) to 10 times the standard dev iation observed for determination of the MDL. This value is also multiplied by the minimum diluti on factor required for preservation and analysis of the sample matrix to obtain the ML reported here.

Mercury, as measured by CVAA, required modification of the calculation of the MDL and M L because very consistent replication resulted in cal culation of a MDL lower than the instrument detection limit. For this case, the standard deviat ion of seven replicate analyses of 0.025 μg/L was 0.00069. Therefore, the MDL was set equal to th e instrument detection limit of 0.001 μg/L times the minimum dilution factor from sample prepar ation (3.59) to result in an MDL of 0.0036 μg/L. The ML was set to 10 times the instrument det ection limit and rounded to the nearest integer value as above. The resulting ML was 0.01 μg/L.

14 

### Establishing spikes in an actual leaching extract matrix is not possible because the sample being extracted dictates the matrix composition by virtue of the constituents that partition into the result ing aqueous extract, which varies by test position and material being tested. However, the extract aliquo ts are diluted at least 10:1 with 1% nitric acid (prepared from Optima grade nitric acid, Fisher Scientific), and the COPCs are dilute in the resulting analytical sa mple. Therefore, the 1% nitric acid solution was u sed

as the matrix for MDL and ML determinations.



### 32

### Characterization of Coal Cumbustion Residues II



## 2.4. QUALITY ASSURANCE ASSESSMENT

2.4.1. Homogenization of Individual CCR Samples and Aliquots for Analyses
To ensure sample homogeneity the fly ashes were mix ed using a Morse single can tumbler model 1-305 as described in Sanchez et al. (2006). Scrubber sludges that were flowable slurries were mixed using a paddle mixer. Gypsum and fixated scrubber sludge samples were mixed by repetitively coning 15 

### and quartering while passing through a mesh screen . After mixing, ten Subsamples were taken from FSSL sample MAD and anal yzed by XRF to evaluate the homogeneity of the resultant material; Figure 9 pre sents the coefficient of variation for the XRF

results. These results indicate that total content variability for primary and most trace constituents is less than 20% for this set of sampl es.

0 5 10 15 20 25 30 35 40

C.V. (%)

K P S V Y

F Si Ti

Al Cl Ni Sr Zr

As Br Cr Fe La Sc Se W Zn

Ba Ca Cd Ce Co Cu Ga Ge Na Nb Pb Rb

Mg

Mn Mo 

### Fac. M, SCR off, FSSL (MAD)

Figure 9. Coefficient of variation (C.V.) from XRF elemental analysis of 10 subsamples of FSSL sample MAD after mixing by coning and quartering.

2.4.2. Leaching Test Methods and Analytical QA/QC
One of the requirements of this project was to esta blish a QA/QC framework for the leaching assessment approach developed by Kosson et al. (200 2). The developed QA/QC framework incorporates the use of blanks, spiked samples, and replicates. Appendix A provides the complete Quality Assurance Project Plan, as updated for this phase of the study. For each designated leaching test condition (i.e., acid or b ase addition to establish end-point pH values and LS value), triplicate leaching test extractions were completed (i.e., three separate aliquots of CCR were each extracted at the designated test cond ition) for early samples, while duplicate

extractions were used after evaluation of initial r esults. The three types of method blanks were the deionized water case, the most concentrated nitric acid addition case, and the most

15 

### "Coning and quartering" is a term used to describe how the material is mixed. The approach is to pas s the material through a screen so that a "cone" form s in the collection container. Then the cone is bis ected twice into quarters (quarter sections of the cone) and each section then is passed sequentially throug h the screen again to form a new cone. This sequence is repeated several times to achieve desired mixing.



### 33

### Characterization of Coal Combustion Residues II



### concentrated potassium hydroxide addition case. Eac h method blank was carried through the entire protocol, including tumbling and filtration, except an aliquot of CCR was not added.

During analysis for mercury and elemental species b y ICP-MS, analytical spikes for the

constituents of interest were carried out for one r eplicate of each test case to assess analytical recoveries over the complete range of pH and liquid matrix conditions. Multipoint calibration curves using at least seven standards and an initia l calibration verification (ICV) using a standard

obtained from a different source than the calibrati on standards were completed daily or after every 50 samples, whichever was more frequent. In a ddition, instrument blanks and continuing calibration verification (CCV) standards were analy zed after every 10 analytical samples and required to be within 10 percent of the expected value. Samples are rerun if they are not within 10 percent of the expected value. CCV standards an d instrument blanks also were run at the end of each batch of samples.

For both ICP-MS and CVAA analyses, each sample was analyzed along with a matrix spike, which is an aliquot of the sample plus a known spik e concentration of the element of interest. The “spike recovery” was required to be within 80 – 120% of the expected value for an acceptable analytical result.

2.4.3. Improving QA/QC efficiency
Throughout the study, the approach to QA/QC was reg ularly reviewed to seek out opportunities for increased evaluation efficiency without unaccep table degradation of precision or accuracy in

results. Based on evaluation of results from the fi rst several facilities (Sanchez et al, 2006), the number of replicates for Method SR002.1 (solubility as a function of pH) and Method SR003.1 (solubility as a function of liquid/solid ratio) wa s reduced from three to two. Results from this study (Sanchez et al., 2006 and this report) show t hat the precision between duplicate analyses is acceptable and that the triplicate set does not sig nificantly increase the quality of the data set. This finding follows from recognition that (i) the data sets generated by Method SR002.1 and SR003.1 must provide both consistency between repli cate extractions and analyses, and internal consistency between results at different pH and LS ratio, and (ii) precision is controlled primarily by the degree of homogeneity of the CCR under evaluation and representative sub-sa mpling, rather than by the intrinsic variability of the lea ching test methods. There were a total of 11,743 observations for the 14 parameters evaluated in det ail in this report (pH and 13 constituents of interest). Review of the resulting data sets indica ted 15 outlier pH values of 846 measurements 16



### and an additional 19 outliers out of 10,897 measure ments of specific constituents. Thus, the overall error rate was less than 2%. Implementation of a reduction in the number of replicates has greatly improved laboratory efficiency without co mpromising data quality.

Data were screened for outliers based on comparison of individual data points (i) relative to replicate extractions (i.e., parallel extractions o f aliquots of the same material under the same extraction conditions), and (ii) relative to the ot her data points in the extraction series (i.e., parallel extractions of aliquots of the same materi al at different pH (SR02) and LS conditions

16 

### When a pH measurement is determined to be an outli er, then all constituent measurements associated with the particular extract sample are also conside red outliers because they would be incorrectly eval uated as release as a function of pH. This resulted in e xcluding (15) $ (13)=195 individual constituent

measurements.



### 34

### Characterization of Coal Cumbustion Residues II



### (SR03)) because of the expected systematic response behavior. The pH was considered an outlier when the final pH of the extract deviated f rom the other replicates by more than 0.5 pH units and corresponding constituent analyses did no t follow systematic behavior indicated by other extracts across multiple constituents. Indivi dual constituents were considered outliers when results of constituent analyses deviated from the s ystematic behavior indicated by results in the extraction series (as a function of pH or as a func tion of LS) by more than one-half to one order of magnitude. Results were screened through inspect ion of the appropriately plotted results.

Data quality indicators (DQIs) were measured for al l parameters continuously during the leaching experiments and during analytical tasks. C hemical (ICP, CVAA, XRF, IC, EC/OC) and physical (surface area, pore size distribution and density) characterization data were reduced and reports were generated automatically by the instrume nt software. The primary analyst reviewed 100% of the report data for completeness to ensure that quality control checks met established criteria. Sample analysis was repeated for any resu lts not meeting acceptance criteria. A secondary review was performed by the Inorganic Laboratory Manager to validate the analyti cal report. A data quality report for the CCR leach tes ting results will be provided in the fourth and final report of this research. The data quality report will cover the leach te st results documented in Report 1 (Sanchez et al., 2006), Report 2 (this report), and a third report (in preparation). The fourth report summarizes the data from the first th ree reports and provides probabilistic assessment of the potential release rates of mercur y and other metals based on plausible management practices.



## 2.5. INTERPRETATION AND PRESENTATION OF LABORATORY

LEACHING DATA

Complete laboratory leaching results for each CCR type and test method are presented in Appendices D and E. Appendix D presents results for Solubility and Release as a Function of pH (SR002.1). Appendix E presents results for Solubili ty and Release as a Function of LS ratio (SR003.1). Results are organized by CCR type (fly a sh, gypsum, scrubber sludge, fixated scrubber sludge), with pH results followed by mercu ry and then other constituents of interest (aluminum, antimony, arsenic, barium, boron, cadmiu m, chromium, cobalt, lead, molybdenum, selenium and thallium). For SR002.1, pH results are a titration curve of pH as a function of milliequivalents of acid or base, with acid additio ns considered positive (+) and base additions considered negative (-). For SR003.1, pH results are a curve of pH as a function of LS ratio.

For Solubility and Release as a Function of pH (SR002.1), results for each CCR type are grouped as described in Figure 5 through Figure 8. Results are presented as extract concentrations as a function of pH. The “natural” pH 17 

### of the system is indicated as a vertical line to t he average pH and a horizontal line to the y-axis indicating the corresponding extract concentration. Included with each figure are horizontal lines at the drinki ng water maximum concentration level (MCL) or drinking water equivalent level (DWEL) 18 

### , and analytical limits (ML and MDL) to provide a

frame of reference for the results. Also included w ith each figure are the 5 and 95 percentile for pH (vertical lines) from field observations of leac hate from landfills and surface impoundments

17 

### “Natural pH” or “own pH” of a material refers to t he equilibrium pH when the material is placed in deionized water at a ratio of 10 g CCR per 100 mL o f water.

18 

### MCL and DWEL values used are as reported in (EPA, 2006).



### 35

### Characterization of Coal Combustion Residues II



### for combustion residues (see Section 2.5.1). An ann otated example of the results is provided as Figure 10.

For Solubility and Release as a Function of LS ratio (SR003.1), results ar e presented as extract

concentrations as a function of LS ratio. Also indi cated are the relevant MCL, ML and MDL or

DWEL.

2.5.1. Interpretation of Mechanisms Controlling Constituent Le aching
Constituent (e.g., mercury, arsenic, and selenium) concentrations observed in laboratory leach test extracts and in field leachate samples may be the result of several mechanisms and factors. The discussion presented here focuses on constituen t leaching and source term modeling approaches. Source term is defined here as the flux or amount of constituent released from the waste or secondary material (e.g., CCRs). Factors c ontrolling constituent release and transport in

and within the near field of the CCRs are often dis tinctly different from the factors and mechanisms which are important for subsequent vados e zone or groundwater transport outside of

the near field area.

In general, constituents are present in the waste o r secondary material either as adsorbed species, co-precipitated as amorphous or crystalline solid p hases, or incorporated as trace components in solid phases. If chemical equilibrium conditions ar e approached (as is the approximate case for the laboratory and field sample conditions discussed in this report), th en the functional behavior of the aqueous solution concentration reflects the nature of the constituent species in the waste or secondary material, the presence of any co-constituents in the aqueous phas e influencing aqueous solution speciation (e.g., effects of high ionic strength, chelating or complexing constituents), and the presence of species in the s olution that may compete for adsorption sites if adsorption is the controlling solid phase mechanism . If the constituent is present in the waste or secondary material as an adsorbed species, many dif ferent adsorption/desorption characteristic patterns are possible (Ruthven, 1984; Duong, 1998).

The simplest case is when the constituent of intere st is present at very low concentration in the waste or secondary material, relatively weakly adsorbed, and the presence of c omplexing and, or, competing species in solution is at a constant conc entration. For this case, leaching test results

will indicate a constant concentration as a functio n of pH at a fixed LS ratio, and linearly increasing concentration as LS ratio decreases at c onstant pH. This case is represented mathematically as a linear equilibrium partitioning function, where the critical constant of proportionality is the partitioning coefficient, co mmonly known as K d 

### . Linear partitioning and

use of K d 

### values is a common approach for mathematically mod eling contaminant transport at low contaminant concentrations in soils. Assumption of linear partitioning is a valid and useful approach when the necessary conditions (discussed a bove) are fulfilled 19



### . For mercury adsorbed on activated carbon or char pa rticles in fly ash, a complex combination of adsorption mechanisms is indicated. During laborato ry leaching tests, mercury concentrations in the leaching test extracts are relatively constant over the pH range and LS ratio of interest, and

19 

### Often specific K d 

### values are a function of pH because of competition for adsorption sites by hydrogen ions. However, often a single K d 

### or range of K d 

### values are used in contaminant fate and transport models, without specific relationship between pH and K d 

### which can result in misrepresentation of actual

contaminant behavior.



### 36

### Characterization of Coal Cumbustion Residues II



### independent of total mercury content in the CCR. In addition, the total mercury content in the CCR is very low. These results are indicative of adsorption phenomena where, in the adsorb ed state, interactions between adsorbed mercury specie s are stronger (thermodynamically) than the interactions between the adsorbed mercury species a nd carbon surface 20 

### . This observation has been supported by the observation of mercury dimer formation during sorption (Munro et al, 2001) and the occurrence of chemisorption as the do minant adsorption mechanism at temperatures above 75 oC (consistent with condition s in air pollution control devices; Vidic, 2002). In other studies, this phenomenon has been observed as the formation o f molecular clusters on the adsorbent surface (Ruthven, 1984; D uong, 1998; Rudzinski et al., 1997). For this case, use of a K d 

### approach would underestimate release because desor ption is best represented as a constant aqueous concentration until depletion occur s.

A third case is encountered when the constituent of interest is present in the waste or secondary material (e.g., CCR) as a primary or trace constitu ent in either an amorphous or crystalline solid phase and there may be complexing or chelating co-c onstituents in the aqueous phase. Observed aqueous concentrations are a non-linear function of pH and LS ratio, and reflect aqueous saturation with respect to the species of interest under the given conditions (pH, co-constituents). For these cases, an approximation of field conditions can be made empirically based o n laboratory testing and observed saturation over the relevant domain (as applied in this report) or geochemical speciation modeling coupled with mass transfer modeling can be used to assess release under specific field scenarios (the subject of a future report). Use of a K d 

### approach would not be appropriate for these cases because constitu ent concentrations will remain relatively constant at a given pH until the controlling solid phase is depleted and control is shifted to a new solid phase or mechanism.

- - 

### 95 th 

### %tile for field pH 5 th 

### %tile for field pH

Own pH Concentration
at own pH MCL

MDL ML

20 

### For this case, the first mercury molecule is adsor bed more weakly than subsequent mercury molecules because the adsorbed mercury-mercury interaction is stronger than the adsorbed mercury-carbon surface interaction [see Sanchez et al. (2006) for further discussion].



### 37 Figure 10. An example of extract concentrations as a f unction of pH from SR002.1.

### Characterization of Coal Combustion Residues II



### 38 

## 2.6. FIELD pH PROBABILITY DISTRIBUTION

A probability distribution of field leachate pH val ues from coal combustion waste landfills was derived, as described below, from the set of field pH observations included in the EPA Risk Report (EPA, 2007). The pH probability distribution used in this report considers additional data beyond the pH probability distribution used in Report 1 (Sanchez et al, 2006), which was based solely on relevant data from the EPA Office of Solid Waste database (EPA , 2000) and included 158 observations from six CCR disposal facilities. The data set developed for the EPA Risk Report included (i) observations from the comprehen sive database of landfill leachate characteristics developed by the EPA’s Office of So lid Waste (EPA, 2000), (ii) field observations from literature, primarily from EPRI r eports, (iii) additional data reported to EPA, and (vi) pH observations from laboratory leaching tests. Only pH measurements from field samples (i.e., leachate, pore water) were selected for use in development of the resulting pH probability distribution. The resulting data set in cluded 580 observations from 42 CCR landfill disposal facilities and was highly unbalanced, with some sites having only a few (e.g., less than five) observations and some sites having many obser vations (e.g., greater than 20). To prevent the unbalanced data from skewing the resulting prob ability distribution, the minimum, 25 th 

### , 50 th



### , 75 th 

### percentile, and maximum values of observations for each individual facility were compiled into a single data set. For facilities with fewer t han five observations, all observations for that facility were included. This data set then served a s the basis for fitting a statistical distribution function. For each data set, different distribution functions were used to fit the data and the one providing the best data fit based on the chi-square test was selected. The resulting field pH probability distribution was truncated and normaliz ed to the pH range of the field data.

The resulting pH probability distribution developed in this report is compared in Figure 11 and Table 7 to the pH probability distribution used in Report 1. The new pH probability distribution reflects a similar range of pH, but has a more alka line median value, and in general, has greater weighting in the pH range between 8 and 12. The pr obability distribution used in this report is considered more representative than what was used i n Report 1 because of a larger dataset using results from recent studies by EPA and EPRI. (EPA, 2006 ; EPRI, 2006)

Field pH observations were also evaluated for surfa ce impoundments receiving CCRs from coal

combustion facilities with FGD scrubbers in use. Po re water pH values measured in samples

obtained from within the settled CCRs were selected from the EPRI database. Resulting pH observations were across the same range as the land fill field pH observations, but were insufficient to develop an independent pH probabili ty distribution. Therefore, the same pH probability distribution was used for landfill and surface impoundment facilities in this report.

### Characterization of Coal Cumbustion Residues II



### 39 0 0.2 0.4 0.6 0.8 1

2 3 4 5 6 7 8 9 10 11 12 13

pHProbability

EPA leach 2000 Fitted distribution (LogLogistic, (1))

EPA Risk database & EPA leach 2000 Fitted distribution (BetaGeneral, (2))

(1)

(2)

Distributions LogLogistic(4.7386, 2.9538, 3.4815) BetaGeneral(9.0369, 1.5076, -7.4214, 12.814) pH Field data Fitted

distribution Simulated

Min 2.75 -7.42 2.76 5th percentile 5.40 5.84 5.85 50th percentile 10.53 10.38 10.24 90th percentile 12.20 12.18 11.94 95th percentile 12.40 12.43 12.43

Max 12.80 12.81 12.43



### Figure 11. Probability distributions for field pH used in Report 1 (LogLogistic) and this report (BetaGeneral). Summary statistics for the field da ta and the probability distribution used in this report (BetaGeneral) are provided to the right of t he graph..

Table 7. Comparison of summary statistics for fiel d pH data and pH probability distributions used in Report 1 and this report.

Field Data Distribution

Estimates Used in Release

Report 1 This Report Report 1 This Report

Minimum 5.40 2.75 4.92 2.76

5 th 

### percentile 5.80 5.40 5.97 5.85

50 th 

### percentile 7.70 10.53 7.63 10.24

90 th 

### percentile NR 12.20 NR 11.94

95 th 

### percentile 12.09 12.40 10.63 12.43

Maximum 12.80 12.80 12.50 12.43

NR=not reported.



## 2.7. ESTIMATED LEACHATE CONCENTRATION AS A FUNCTION OF pH

For each CCR tested, results from SR002.1 (Alkalini ty, Solubility and Release as a Function of pH) were used to develop an empirical functional re lationship between solution pH and expected

concentration for each constituent of interest. For each constituent within each CCR case, a polynomial function was regressed to the results fr om SR002.1 (Alkalinity, Solubility and

### Characterization of Coal Combustion Residues II



### 40 Release as a Function of pH) to provide the expecte d leachate concentration as a function of solution pH. Up to a fifth order polynomial was use d for the regression. An example of a regression fit and corresponding equation for solub ility and release as a function of pH is presented in Figure 12. The coefficients provided i n the table reflect the order of the polynomial used. For all cases, the lowest order polynomial po ssible based on the R-square (no further increase for higher order) was used. Also included with each figure of regression fit is the 5 th



### and 95 th 

### percentile for pH (vertical line) from field obser vations of leachate from landfills and surface impoundments for combustion residues. Regre ssion fit results are provided in Appendix F for each case examined (i.e., for each constituent in each C CR tested).

Antimony

log (μg/L) Number

of points pH range of

validity

0.0000 pH 5 33 2.2-12.4

0.0008 pH 4

-0.0399 pH 3

0.5519 pH 2

-2.7978 pH

6.031866 pH 0

0.97 R 2

5% 95% 0.001 0.01 0.1 1 10 100 1000 10000 100000

2 4 6 8 10 12 14 pHSb [μg/L]

SR2-DFA - A SR2-DFA - B

SR2-DFA - C Fit curve



### Figure 12. Example of regression fit and correspon ding coefficients for a 5 th 

### order polynomial equation used to represent solubility and release a s a function of pH (antimony for fly ash from Facility B with SCR bypassed (DFA)).

### Characterization of Coal Cumbustion Residues II



## 3. RESULTS AND DISCUSSION

The EPA Risk Report (EPA, 2007) identified the foll owing COPCs based on the potential for either human health or ecological impacts using a s creening risk assessment: aluminum (Al), arsenic (As), antimony (Sb), barium (Ba), boron (B), cadmiu m (Cd), cobalt (Co), chromium (Cr), lead (Pb), mercury (Hg), molybdenum (Mo), selenium ( Se), and thallium (Tl). 21 

### Thus, the evaluation provided here focuses on the same thirte en constituents and can be used in future risk

and environmental assessments.



## 3.1. TOTAL ELEMENTAL CONTENT BY DIGESTION

Total elemental compositions using digestion 22 

### , on a dry weight basis, for COPCs for the CCRs evaluated are compared by constituent in Figures 13 through 24; tabular results are provided in Appendix B. Boron was not analyzed because it is us ed in the digestion process and therefore analysis would not yield meaningful results.

Mercury. Mercury content exhibited a similar range (0.01 t o 1.0 " g/g) for all CCR types. Use of SNCR (Facility A) resulted in increased mercury con tent in the fly ash and decreased mercury content in the scrubber sludge, compared to when the SNCR was not in use. In contrast, use of SCR (Facility B) resulted in decreased mercury cont ent in the fly ash and increased mercury content in the scrubber sludge, compared to when the SCR was bypassed. For all three comparative cases (Facilities A, B and M) use of th e NOx control increased the total mercury content in the fixated scrubber sludge. Mercury con tent in gypsum was significantly lower in the washed gypsum than in the unwashed gypsum for comparative c ases (Facilities N and O).

Aluminum. Aluminum content was approximately an order of ma gnitude greater in the fly ash samples than in the scrubber sludge samples from fa cilities without SCR and than in gypsum samples with and without SCR. Facilities with SCR operating (samples BGD, KGD) had greater aluminum content in scrubber sludge than the other scrubber sludges, like ly because of the addition of aluminum with the SCR catalyst. Fixated scrubber sludge samples had intermediate Al content, reflective of the blending of fly ash w ith scrubber sludge.

Antimony. Antimony content ranged over similar levels for f ly ash, scrubber sludge and fixated scrubber sludge; gypsum had lower antimony content except for the sample from Facility Q. Samples from both Facilities K and Q had greater an timony content than comparative FGD residues from other facilities (scrubber sludges an d fixated scrubber sludges for Facility K, gypsum for Facility Q) perhaps as a consequence of greater antimony content in sub-bituminous coal burned by these facilities than bituminous coa l burned by the other facilities. The SNCR samples had higher antimony contents in the fly ash , scrubber sludge and fixated scrubber sludge for Facility A than the samples collected with SNCR off. The SCR samples had higher antimony contents in the fly ash from Facility B and the fix ated scrubber sludges from Facilities A, B and

21 

### The database used in the EPA Risk Report (EPA, 200 7) for the assessment was based on both measurements of field samples (e.g., leachate, pore water) and single point laboratory leaching tests (e.g., TCLP, SPLP). The database was sparse with respect t o measurements of field samples for many

constituents.

22 

### Digestion Method 3052 and ICP-MS analysis by Metho d 6020; see Section 2.3.7.



### 41

### Characterization of Coal Combustion Residues II



### M, although the reason for the high level of antimo ny in sample BCC cannot be explained by the relative antimony content in samples BFA and BGD.

Arsenic. Gypsum had very low arsenic content (<5 μg/g) com pared to the other residue types. Arsenic content in scrubber sludge was significantl y less than in fly ash for residue from the same facility. Use of NOx controls resulted in decr eased arsenic content in the fly ash, increased content in the scrubber sludge (Facilities A and B) and decreased content in the fixated scrubber sludge (Facilities A, B and M; reflecting the relat ive contributions of fly ash and scrubber sludge in fixated scrubber sludge) for comparative samples.

Barium. Barium content was similar in scrubber sludge and gypsum for all facilities except for sample BGD (unexplained), and lower than barium con tent in fly ash by approximately an order of magnitude. The relatively low barium content in unwashed gypsum from Facility O is also unexplained.

Cadmium. Cadmium content was low in the gypsum (<0.69 ng/g ) and scrubber sludges (<1.72 ug/g) and generally total content of the gypsum was half that in fly ash (<1.51 ng/g). The greater cadmium content in sample BGD relative to sample DG D may be a consequence of the use of post-combustion NOx control using SCR.

Chromium. Chromium content in gypsum (< 19.3 ng/g) and scru bber sludges (< 139 ng/g) was low and approximately an order of magnitude less th an in fly ash samples (<194). Scrubber sludge samples without SCR in operation also had ch romium content similar to that of gypsum. Scrubber sludge samples without SCR in use also had chromium content similar to that of gypsum. Elevated chromium content in scrubber sludge samples BGD and KGD may be associated with the use of post-combustion NOx control usin g SCR.

Cobalt. Cobalt content in gypsum was low and approximatel y an order of magnitude less than in fly ash samples. Scrubber sludge samples without SCR in operation also had cobalt content similar to that of gypsum. Elevated cobalt content in scrubber sludge samples BGD and KGD may be associated with SCR catalyst addition. The r elatively low cobalt content in fixated scrubber sludge samples BCC and KCC relative to corresponding fly ash and scrubber sludg e samples is unexplained.

Lead. Lead content in gypsum was low and less than one third of the lead content in fly ash samples. Scrubber sludge samples without SCR in ope ration also had lead content similar to that of gypsum. The relatively low lead content in fixated scrubber sludge samp les BCC and KCC in relationship to corresponding fly ash and scrubber s ludge samples is unexplained.

Molybdenum. A similar range in molybdenum content was found i n fly ash, scrubber sludge and fixated scrubber sludge samples, with lower con tent by approximately one third in gypsum samples, with the exception of gypsum sample QAU.

Selenium . All samples were less than 5 μg/g, except for samp les for fly ash and fixated scrubber sludge from Facility A and unwashed gypsum from Fac ilities P and Q. The upper bound for these samples was less than 30 μg/g.

Thallium . All gypsum samples had thallium content less than 3 μg/g. Fly ash, scrubber sludge, and fixated scrubber sludge samples all had a simil ar range of thallium content between 2 and 5 μg/g, except scrubber sludge and fixated scrubber s ludge from Facility B with SCR and fly ash and fixated scrubber sludge from Facility K. Both o f these observations of greater thallium content (between 5 and 13 μg/g) may result from the SC R catalyst addition.

42

### Characterization of Coal Cumbustion Residues II



### 43 0.001 0.01 0.1 1Fac.A(CFA)!"Fac.A(AFA)+Fac.B(DFA)!"Fac.B(BFA)+Fac.K(KFA)+Fac.A(CGD)! "Fac.A(AGD)+Fac.B(DGD)! "Fac.B(BGD)+Fac.K(KGD)+Fac.N(NAU)+UFac.N(NAW)+WFac.O(OAU)+UFac.O(OAW)+WFac.P(PAD)+UFac.Q(QAU)+UFac.A(CCC)! "Fac.A(ACC)+Fac.B(DCC)!"Fac.B(BCC)+Fac.K(KCC)+Fac.M(MAD)!"Fac.M(MAS)+μg/g 

## Mercury **(Hg)**

I. Ox. Nat. Ox. Forced Ox. Nat. Ox. Nat. Ox.

Fly Ash!!!!!!!!!!!! |!! Scrubber Sludge!! |!!!!!!!!! Gypsum | Fixated Scrubber Sludge

100 1,000 10,000 100,000 1,000,000Fac.A(CFA)!"Fac.A(AFA)+Fac.B(DFA)!"Fac.B(BFA)+Fac.K(KFA)+Fac.A(CGD)! "Fac.A(AGD)+Fac.B(DGD)! "Fac.B(BGD)+Fac.K(KGD)+Fac.N(NAU)+UFac.N(NAW)+WFac.O(OAU)+UFac.O(OAW)+WFac.P(PAD)+UFac.Q(QAU)+UFac.A(CCC)! "Fac.A(ACC)+Fac.B(DCC)!"Fac.B(BCC)+Fac.K(KCC)+Fac.M(MAD)!"Fac.M(MAS)+μg/g 

## Aluminum **(Al)**

I. Ox. Nat. Ox. Forced Ox. Nat. Ox. Nat. Ox.

Fly Ash!!!!!!!!!!!! |!! Scrubber Sludge!! |!!!!!!!!! Gypsum | Fixated Scrubber Sludge



### Figure 13 and Figure 14. Mercury and Aluminum. Co mparison of total elemental content by digestion (key: - = NOx control off; + = NOx contro l on; U = unwashed gypsum; W = washed gypsum; Nat. Ox. = natural oxidation; Forced Ox. = forced oxidation; I.Ox. = inhibited oxidation).

### Characterization of Coal Combustion Residues II

0 5 10 15 20Fac.A(CFA)!"Fac.A(AFA)+Fac.B(DFA)!"Fac.B(BFA)+Fac.K(KFA)+Fac.A(CGD)! "Fac.A(AGD)+Fac.B(DGD)! "Fac.B(BGD)+Fac.K(KGD)+Fac.N(NAU)+UFac.N(NAW)+WFac.O(OAU)+UFac.O(OAW)+WFac.P(PAD)+UFac.Q(QAU)+UFac.A(CCC)! "Fac.A(ACC)+Fac.B(DCC)!"Fac.B(BCC)+Fac.K(KCC)+Fac.M(MAD)!"Fac.M(MAS)+μg/g 

## Antimony **(Sb)**

Fly Ash!!!!!!!!!!!! |!! Scrubber Sludge |!!!!!!!!! Gypsum | Fixated Scrubber Sludge I. Ox. Nat. Ox. Forced Ox. Nat. Ox. Nat. Ox.

0 20 40 60 80 100Fac.A(CFA)!"Fac.A(AFA)+Fac.B(DFA)!"Fac.B(BFA)+Fac.K(KFA)+Fac.A(CGD)! "Fac.A(AGD)+Fac.B(DGD)! "Fac.B(BGD)+Fac.K(KGD)+Fac.N(NAU)+UFac.N(NAW)+WFac.O(OAU)+UFac.O(OAW)+WFac.P(PAD)+UFac.Q(QAU)+UFac.A(CCC)! "Fac.A(ACC)+Fac.B(DCC)!"Fac.B(BCC)+Fac.K(KCC)+Fac.M(MAD)!"Fac.M(MAS)+μg/g 

## Arsenic **(As)**

Fly Ash!!!!!!!!!!!! |!! Scrubber Sludge!! |!!!!!!!!! Gypsum | Fixated Scrubber Sludge I. Ox. Nat. Ox. Forced Ox. Nat. Ox. Nat. Ox.



### 44 Figure 15 and Figure 16. Antimony and Arsenic. Co mparison of total elemental content by digestion (key: - = NOx control off; + = NOx contro l on; U = unwashed gypsum; W = washed gypsum; Nat. Ox. = natural oxidation; Forced Ox. = forced oxidation; I.Ox. = inhibited oxidation).

### Characterization of Coal Cumbustion Residues II



### 45 1 10 100 1,000 10,000Fac.A(CFA)!"Fac.A(AFA)+Fac.B(DFA)!"Fac.B(BFA)+Fac.K(KFA)+Fac.A(CGD)! "Fac.A(AGD)+Fac.B(DGD)! "Fac.B(BGD)+Fac.K(KGD)+Fac.N(NAU)+UFac.N(NAW)+WFac.O(OAU)+UFac.O(OAW)+WFac.P(PAD)+UFac.Q(QAU)+UFac.A(CCC)! "Fac.A(ACC)+Fac.B(DCC)!"Fac.B(BCC)+Fac.K(KCC)+Fac.M(MAD)!"Fac.M(MAS)+μg/g 

## Barium **(Ba)**

I. Ox. Nat. Ox. Forced Ox. Nat. Ox. Nat. Ox.

Fly Ash!!!!!!!!!!!! |!! Scrubber Sludge!! |!!!!!!!!! Gypsum | Fixated Scrubber Sludge

0.0 0.5 1.0 1.5 2.0Fac.A(CFA)!"Fac.A(AFA)+Fac.B(DFA)!"Fac.B(BFA)+Fac.K(KFA)+Fac.A(CGD)! "Fac.A(AGD)+Fac.B(DGD)! "Fac.B(BGD)+Fac.K(KGD)+Fac.N(NAU)+UFac.N(NAW)+WFac.O(OAU)+UFac.O(OAW)+WFac.P(PAD)+UFac.Q(QAU)+UFac.A(CCC)! "Fac.A(ACC)+Fac.B(DCC)!"Fac.B(BCC)+Fac.K(KCC)+Fac.M(MAD)!"Fac.M(MAS)+μg/g 

## Cadmium **(Cd)**

Fly Ash!!!!!!!!!!!! |!! Scrubber Sludge!! |!!!!!!!!! Gypsum | Fixated Scrubber Sludge I. Ox. Nat. Ox. Forced Ox. Nat. Ox. Nat. Ox.



### Figure 17 and Figure 18. Barium and Cadmium. Comp arison of total elemental content by digestion (key: - = NOx control off; + = NOx contro l on; U = unwashed gypsum; W = washed gypsum; Nat. Ox. = natural oxidation; Forced Ox. = forced oxidation; I.Ox. = inhibited oxidation).

### Characterization of Coal Combustion Residues II



### 46 0 100 200 300 400Fac.A(CFA)!"Fac.A(AFA)+Fac.B(DFA)!"Fac.B(BFA)+Fac.K(KFA)+Fac.A(CGD)! "Fac.A(AGD)+Fac.B(DGD)! "Fac.B(BGD)+Fac.K(KGD)+Fac.N(NAU)+UFac.N(NAW)+WFac.O(OAU)+UFac.O(OAW)+WFac.P(PAD)+UFac.Q(QAU)+UFac.A(CCC)! "Fac.A(ACC)+Fac.B(DCC)!"Fac.B(BCC)+Fac.K(KCC)+Fac.M(MAD)!"Fac.M(MAS)+μg/g 

## Chromium **(Cr)**

Fly Ash!!!!!!!!!!!! |!! Scrubber Sludge!! |!!!!!!!!! Gypsum | Fixated Scrubber Sludge I. Ox. Nat. Ox. Forced Ox. Nat. Ox. Nat. Ox.

0 20 40 60 80Fac.A(CFA)!"Fac.A(AFA)+Fac.B(DFA)!"Fac.B(BFA)+Fac.K(KFA)+Fac.A(CGD)! "Fac.A(AGD)+Fac.B(DGD)! "Fac.B(BGD)+Fac.K(KGD)+Fac.N(NAU)+UFac.N(NAW)+WFac.O(OAU)+UFac.O(OAW)+WFac.P(PAD)+UFac.Q(QAU)+UFac.A(CCC)! "Fac.A(ACC)+Fac.B(DCC)!"Fac.B(BCC)+Fac.K(KCC)+Fac.M(MAD)!"Fac.M(MAS)+μg/g 

## Cobalt **(Co)**

Fly Ash!!!!!!!!!!!! |!! Scrubber Sludge!! |!!!!!!!!! Gypsum | Fixated Scrubber Sludge I. Ox. Nat. Ox. Forced Ox. Nat. Ox. Nat. Ox.



### Figure 19 and Figure 20. Chromium and Cobalt. Com parison of total elemental content by digestion (key: - = NOx control off; + = NOx contro l on; U = unwashed gypsum; W = washed gypsum; Nat. Ox. = natural oxidation; Forced Ox. = forced oxidation; I.Ox. = inhibited oxidation).

### Characterization of Coal Cumbustion Residues II



### 47 0 20 40 60 80 100 120Fac.A(CFA)!"Fac.A(AFA)+Fac.B(DFA)!"Fac.B(BFA)+Fac.K(KFA)+Fac.A(CGD)! "Fac.A(AGD)+Fac.B(DGD)! "Fac.B(BGD)+Fac.K(KGD)+Fac.N(NAU)+UFac.N(NAW)+WFac.O(OAU)+UFac.O(OAW)+WFac.P(PAD)+UFac.Q(QAU)+UFac.A(CCC)! "Fac.A(ACC)+Fac.B(DCC)!"Fac.B(BCC)+Fac.K(KCC)+Fac.M(MAD)!"Fac.M(MAS)+μg/g 

## Lead **(Pb)**

Fly Ash!!!!!!!!!!!! | Scrubber Sludge!! |!!!!!!!!! Gypsum | Fixated Scrubber Sludge I. Ox. Nat. Ox. Forced Ox. Nat. Ox. Nat. Ox.

0 10 20 30 40Fac.A(CFA)!"Fac.A(AFA)+Fac.B(DFA)!"Fac.B(BFA)+Fac.K(KFA)+Fac.A(CGD)! "Fac.A(AGD)+Fac.B(DGD)! "Fac.B(BGD)+Fac.K(KGD)+Fac.N(NAU)+UFac.N(NAW)+WFac.O(OAU)+UFac.O(OAW)+WFac.P(PAD)+UFac.Q(QAU)+UFac.A(CCC)! "Fac.A(ACC)+Fac.B(DCC)!"Fac.B(BCC)+Fac.K(KCC)+Fac.M(MAD)!"Fac.M(MAS)+μg/g 

## Molybdenum **(Mo)**

Fly Ash!!!!!!!!!!!! |!! Scrubber Sludge!! |!!!!!!!!! Gypsum | Fixated Scrubber Sludge I. Ox. Nat. Ox. Forced Ox. Nat. Ox. Nat. Ox.



### Figure 21 and Figure 22. Lead and Molybdenum. Com parison of total elemental content by digestion (key: - = NOx control off; + = NOx contro l on; U = unwashed gypsum; W = washed gypsum; Nat. Ox. = natural oxidation; Forced Ox. = forced oxidation; I.Ox. = inhibited oxidation).

### Characterization of Coal Combustion Residues II



### 48 0 5 10 15 20 25 30Fac.A(CFA)!"Fac.A(AFA)+Fac.B(DFA)!"Fac.B(BFA)+Fac.K(KFA)+Fac.A(CGD)! "Fac.A(AGD)+Fac.B(DGD)! "Fac.B(BGD)+Fac.K(KGD)+Fac.N(NAU)+UFac.N(NAW)+WFac.O(OAU)+UFac.O(OAW)+WFac.P(PAD)+UFac.Q(QAU)+UFac.A(CCC)! "Fac.A(ACC)+Fac.B(DCC)!"Fac.B(BCC)+Fac.K(KCC)+Fac.M(MAD)!"Fac.M(MAS)+μg/g 

## Selenium **(Se)**

I. Ox. Nat. Ox. Forced Ox. Nat. Ox. Nat. Ox.

Fly Ash!!!!!!!!!!!! |!! Scrubber Sludge!! |!!!!!!!!! Gypsum | Fixated Scrubber Sludge

0 5 10 15Fac.A(CFA)!"Fac.A(AFA)+Fac.B(DFA)!"Fac.B(BFA)+Fac.K(KFA)+Fac.A(CGD)! "Fac.A(AGD)+Fac.B(DGD)! "Fac.B(BGD)+Fac.K(KGD)+Fac.N(NAU)+UFac.N(NAW)+WFac.O(OAU)+UFac.O(OAW)+WFac.P(PAD)+UFac.Q(QAU)+UFac.A(CCC)! "Fac.A(ACC)+Fac.B(DCC)!"Fac.B(BCC)+Fac.K(KCC)+Fac.M(MAD)!"Fac.M(MAS)+μg/g 

## Thallium **(Tl)**

I. Ox. Nat. Ox. Forced Ox. Nat. Ox. Nat. Ox.

Fly Ash!!!!!!!!!!!! |!! Scrubber Sludge!! |!!!!!!!!! Gypsum | Fixated Scrubber Sludge



### Figure 23 and Figure 24. Selenium and Thallium. C omparison of total elemental content by digestion (key: - = NOx control off; + = NOx contro l on; U = unwashed gypsum; W = washed gypsum; Nat. Ox. = natural oxidation; Forced Ox. = forced oxidation; I.Ox. = inhibited oxidation).

### Characterization of Coal Cumbustion Residues II



## 3.2. TOTAL ELEMENTAL CONTENT BY XRF

Total elemental compositions, on a dry weight basis , for major and some trace constituents in each of the CCRs evaluated are compared in grouping by CCR type (i.e., fly ash, gypsum, scrubber sludge, fixated scrubber sludge) in Figure 25 through Figure 29; tabular results are provided in Appendix C. Major elemental constituent s present in CCRs but not detected by XRF analysis include oxygen and carbon. Elements that m ay be analyzed by XRF but were below the detection limit are indicated in the figures on the x-axis but without any reported value represented. Separate analyses were carried out for carbon and are also included in Appendix C.

Fly Ash. Elemental constituents typically present in fly a sh at concentrations greater than 1 percent (10,000 mg/kg) are aluminum, calcium, iron, potassium, and silicon. Elemental constituents typically present at concentrations be tween 0.1 and 1 percent are barium, chloride, magnesium, sodium, phosphorus, strontium, sulfur, and titanium.

Gypsum. Elemental constituents typically present in gypsu m at concentrations greater than 1 percent (10,000 mg/kg) are calcium and sulfur. Elem ental constituents typically present at concentrations between 0.1 and 1 percent are chlori de (unwashed gypsum), fluoride (unwashed gypsum), iron, magnesium, sodium (unwashed gypsum) and silicon.

Scrubber Residue. Elemental constituents typically present in scrub ber residue at concentrations greater than 1 percent (10,000 mg/kg ) are aluminum (SCR on), calcium, iron (SCR on), magnesium, silicon (SCR on) and sulfur. E lemental constituents typically present at concentrations between 0.1 and 1 percent are alumin um (except with SCR on), chloride, fluoride, iron (except with SCR on), potassium, sodium (SCR o n), silicon (except with SCR on), and titanium (SCR on).

Fixated Scrubber Sludge. Elemental constituents typically present in fixat ed scrubber sludge at concentrations greater than 1 percent (10,000 mg/kg ) are aluminum, calcium, iron, potassium, silicon and sulfur. Elemental constituents typicall y present at concentrations between 0.1 and 1 percent are barium, chloride, sodium, phosphorus and s trontium.

Fixated Scrubber Sludge with Lime. Elemental constituents typically present in fixat ed scrubber sludge with lime at concentrations greater than 1 percent (10,000 mg/kg) are aluminum, calcium, iron, magnesium (Mg lime scrubbers), silic on, and sulfur. Elemental constituents typically present at concentrations between 0.1 and 1 percent are chloride, potassium, magnesium (non-Mg lime scrubbers), sodium, and tita nium.

49

### Characterization of Coal Combustion Residues II



### 50 1 10 100 1,000 10,000 100,000 1,000,000AlAsBaBrCaCdCeClCoCrCuFFeGaGeKLaMgMnMoNaNbNiPPbRbScSeSiSrSTiVWYZnZrμg/g

CFA (SNCR Off) AFA (SNCR On) 

### Fac. A. (NO+SNCR+FF)

" Fly Ash

1 10 100 1,000 10,000 100,000 1,000,000AlAsBaBrCaCdCeClCoCrCuFFeGaGeKLaMgMnMoNaNbNiPPbRbScSeSiSrSTiVWYZnZrμg/g

DFA (SCR Off) BFA (SCR On) 

### Fac. B. (NO+SCR+ESP, Mg lime)

" Fly Ash

1 10 100 1,000 10,000 100,000 1,000,000AlAsBaBrCaCdCeClCoCrCuFFeGaGeKLaMgMnMoNaNbNiPPbRbScSeSiSrSTiVWYZnZrμg/g

KFA (SCR On) 

### Fac. K. (NO+SCR+ESP, Mg lime)

" Fly Ash 

### a)

b)

c)

Figure 25. Fly Ash - Total content by XRF.

### Characterization of Coal Cumbustion Residues II



### 51 1 10 100 1,000 10,000 100,000 1,000,000AlAsBaBrCaCdCeClCoCrCuFFeGaGeKLaMgMnMoNaNbNiPPbRbScSeSiSrSTiVWYZnZrμg/g

NAU (Unwashed) NAW (Washed) 

### Fac. N. (FO+SCR+ESP)

" Gypsum

1 10 100 1,000 10,000 100,000 1,000,000AlAsBaBrCaCdCeClCoCrCuFFeGaGeKLaMgMnMoNaNbNiPPbRbScSeSiSrSTiVWYZnZrμg/g

OAU (Unwashed) OAW (Washed) 

### Fac. O. (FO+SCR+ESP)

" Gypsum

1 10 100 1,000 10,000 100,000 1,000,000AlAsBaBrCaCdCeClCoCrCuFFeGaGeKLaMgMnMoNaNbNiPPbRbScSeSiSrSTiVWYZnZrμg/g

PAD (U) (Unwashed) QAU (Unwashed) 

### Fac. P. (FO+SCR & SNCR +ESP)

" Gypsum

Fac. Q. (FO+SCR+ESP)
!" Gypsum 

### a)

b)

c)

Figure 26. Gypsum – Total content by XRF.

### Characterization of Coal Combustion Residues II



### 52 1 10 100 1,000 10,000 100,000 1,000,000AlAsBaBrCaCdCeClCoCrCuFFeGaGeKLaMgMnMoNaNbNiPPbRbScSeSiSrSTiVWYZnZrμg/g

CGD (SNCR Off) AGD (SNCR On) 

### Fac. A. (NO+SNCR+FF)

" Scrubber Sludge

1 10 100 1,000 10,000 100,000 1,000,000AlAsBaBrCaCdCeClCoCrCuFFeGaGeKLaMgMnMoNaNbNiPPbRbScSeSiSrSTiVWYZnZrμg/g

DGD (SCR Off) BGD (SCR On) 

### Fac. B. (NO+SCR+ESP, Mg lime)

" Scrubber Sludge

1 10 100 1,000 10,000 100,000 1,000,000AlAsBaBrCaCdCeClCoCrCuFFeGaGeKLaMgMnMoNaNbNiPPbRbScSeSiSrSTiVWYZnZrμg/g

KGD (SCR On) 

### Fac. K. (NO+SCR+ESP, Mg lime)

" Scrubber Sludge 

### a)

b)

c)

Figure 27. Scrubber Sludge – Total content by XRF.

### Characterization of Coal Cumbustion Residues II



### 53 1 10 100 1,000 10,000 100,000 1,000,000AlAsBaBrCaCdCeClCoCrCuFFeGaGeKLaMgMnMoNaNbNiPPbRbScSeSiSrSTiVWYZnZrμg/g

CCC (SNCR Off) ACC (SNCR On) 

### Fac. A. (NO+SNCR+FF)

" Fixated Scrubber Sludge



### Figure 28. Fixated Scrubber Sludge – Total content by XRF.

### Characterization of Coal Combustion Residues II



### 54 1 10 100 1,000 10,000 100,000 1,000,000AlAsBaBrCaCdCeClCoCrCuFFeGaGeKLaMgMnMoNaNbNiPPbRbScSeSiSrSTiVWYZnZrμg/g

DCC (SCR Off) BCC (SCR On) 

### Fac. B. (NO+SCR+ESP, Mg lime)

" FSSL

1 10 100 1,000 10,000 100,000 1,000,000AlAsBaBrCaCdCeClCoCrCuFFeGaGeKLaMgMnMoNaNbNiPPbRbScSeSiSrSTiVWYZnZrμg/g

KCC (SCR On) 

### Fac. K. (NO+SCR+ESP, Mg lime)

" FSSL

1 10 100 1,000 10,000 100,000 1,000,000AlAsBaBrCaCdCeClCoCrCuFFeGaGeKLaMgMnMoNaNbNiPPbRbScSeSiSrSTiVWYZnZrμg/g

MAD (SCR Off) MAS (SCR On) 

### Fac. M. (IO+SCR+ESP)

" FSSL 

### a)

b)

c)

Figure 29. Fixated Scrubber Sludge with Lime – Total content by XRF.

### Characterization of Coal Cumbustion Residues II



## 3.3. LABORATORY LEACHING TEST RESULTS

Appendix D and Appendix E provide graphical present ation of the results of Solubility and Release as a Function of pH (SR002.1) and Solubilit y and Release as a Function of LS (SR003.1), respectively, for the 13 constituents of interest in this report. Within each appendix, results are grouped by CCR type (fly ash, gypsum, s crubber sludge, FSS, FSSL) and with each CCR type grouping, comparisons are made by constitu ent of interest. First discussed below are typical characteristic results for pH and each of t he 13 constituents of interest (Section 3.3.1) followed by a discussion (Section 3.3.2) comparing the ranges of observed constituent concentrations (from both test methods) with measurements reported elsewhere on field leachate and pore water samples for CCR disposal sites and the database used in the EPA Risk Report (EPA, 2007). Complete data also have been developed for other constituents to facilitate evaluation of geochemical speciation of constituent s of concern and provide more thorough evaluation of leaching under alternative management scena rios in the future if warranted.

For each CCR evaluated, results of the leaching tests provid e the following information:

! 

### Leachate concentrations for the constituents of int erest as a function of pH over the range of reported field management conditions (from test method SR002.1);

! 

### pH titration curves (from test method SR002.1). Thi s information is useful in characterizing the CCR and assessing how it will respond to enviro nmental stresses and material aging (e.g., carbon dioxide uptake, acid precipitation, co-disposal, m ixing with other materials); and,

! 

### Leachate concentrations for the constituents of int erest, pH and electrical conductivity as a function of LS ratio when contacted with distilled water (from test meth od SR003.1). This information provides insight into the initial leach ate concentrations expected during land disposal and effects of pH and ionic strength at lo w LS ratio. Often these concentrations can be either greater than or less than concentrations observed at higher LS ratio (i.e., LS=10 mL/g as used in SR002.1) because of ionic strength and co-constituent concentration effects.

The MCL is used as a reference threshold for the co nstituent of interest. However, releases identified here are estimates of concentrations pot entially leaching from landfills. Any assessment of the environmental impact of these rel eases needs to consider the dilution and attenuation of these constituents in ground water, and the plausibility of drinking water well contamination resulting from the release. Dilution and attenuation factors for metals (DAFs) have been estimated to be potentially as low as 2 t o 10 on a national basis or as high as 8,000 at a particular site with hydrogeology that indicated lo w transport potential 23 

### . Therefore, comparison with thresholds greater than the MCL and developed for speci fic scenarios may be appropriate.

23 

### See 60 FR 66372, Dec. 21, 1995, for a discussion o f model parameters leading to low DAFs, particularly the assumption of a continuous source landfill. Implied DAFs for the metals of interest here

can be found at 60 FR 66432-66438 in Table C-2. Si te specific high-end DAFs are discussed in 65 FR 55703, September 14, 2000.



### 55

### Characterization of Coal Combustion Residues II



### 3.3.1. Typical Characteristic Leaching Behavior as a Function of pH and LS
Figure 30 through Figure 45 provide comparisons of typical leaching behavior as a function of pH for each constituent, as examples reproduced fro m Appendix D. These comparisons illustrate on an empirical basis some of the differences in le aching behavior for different CCRs that result from the combination of the coal rank combusted, co mbustion conditions and specific combustion facility design and operation. Also note d but not shown is the observed behavior for

each constituent as a function of LS at the materia l’s natural pH (see Appendix E). Elements with predominantly oxyanionic species (e.g., boron, molybdenum, selenium, etc.) typically exhibited non-linearly increasing extract concentra tions as LS was decreased from 10 mL/g to 0.5 mL/g, in many cases increasing by a factor of 5 or 1 0 or greater.

These figures illustrate that for a particular const ituent, the chemistry controlling release or aqueous-solid equilibrium may be similar within a m aterial type (i.e., mercury behavior for fly ash or scrubber sludge) or across material types (i .e., the same behavior for aluminum in fly ash and fixated scrubber sludge) but that there are not necessarily generalized behaviors present for each constituent across all samples within a materi al type or between material types. The most robust groupings of leaching behavior will result f rom the development of geochemical speciation models of the materials that account for the underlying solid phase speciation (e.g., solid phases, adsorption behavior) and modifying so lution characteristics (e.g., dissolved organic matter, pH, ionic strength, co-dissolved constituen ts). Development of the needed geochemical speciation models, and associated leaching behavior groupings as a function of coal rank, combustion facility design, and CCR type, will be the basis of a subsequent report. The resul ting models and groupings, in turn, are expected to allo w for more detailed constituent release predictions based on limited testing for a broader set of facilities.

Mercury. Figure 30 (a, b) compares the impact of SNCR usag e (Facility A) on the release behavior of mercury from fly ash. The increased mer cury release, reaching a maximum at pH~8, when SNCR is in use, is likely a consequence of add itional ammonium present and consequent formation of an ammonium mercury complex in solutio n (Wang, 2007). For all fly ash samples except AFA (Facility A, SNCR[+]), the mercury relea se indicated apparently random scatter with solution concentrations ranging from 0.01 to 0 .1 μg/L. This behavior is similar to that reported earlier in this study (Sanchez et al., 200 6) and is indicative of adsorption of elemental mercury as the primary release mechanism. For gypsu m samples, mercury release was either (i) similar to that observed for fly ash (Figure 30d, F acility P), (ii) at very low concentration near or below the MDL (Facility O, unwashed and washed; Facility N washed ) potentially indicative of adsorption onto carbon char, or (iii) had increased release at pH<6 potentially indicative of adsorbed ionic mercury being displaced by hydrogen ions at acidic pH (Facility A, unwashed; Facility Q). For scrubber sludge, mercury release w as either (i) similar to that observed for fly ash, (ii) had increasing release concurrent with de creasing pH at pH<8 (Facility B, Figure 30c), or (iii) had increased release at pH~8 (local peak, indicative of ammonium complexation) and then increasing release with decreasing pH at pH<6 (Facility K). For FSS, behavior was either (i) analogous to that observed for fly ash (Facility A) , or (ii) analogous to that observed for scrubber sludge illustrated in Figure 30c (Facilities B, K, M). Mercury extract concentrations were not significantly affected by LS.

Aluminum. Figure 31 (a, b) compares the impact of SNCR usag e (Facility A) on the release behavior of aluminum from fly ash and illustrates o ne of the three types of aluminum behavior observed across the CCR types. One type of observed aluminum behavior was amphoteric

56

### Characterization of Coal Cumbustion Residues II



### behavior (minimum release at pH~6-8, with increasin g release as pH decreases and increases outside of this range) with a local maximum of appr oximately 10,000 μg/L at pH~12 and a maximum of ca. 100,000 to 1,000,000 μg/L at pH~3. T he concentration of the minimum at 6<pH<8 is typically influenced by the amount of DOC complexing aluminum in solution (increased complexation increases dissolved aluminu m). This behavior was present for fly ash from Facilities A and K. Other samples exhibited in creasing aluminum release with decreasing pH at pH<8 but without substantially increased rele ase at pH>8 (fly ash from facility B; scrubber sludge from facilities B, K). Several samples exhib ited increasing release with decreasing pH for pH<6 and a local maximum at pH~10 (Figure 31c, scru bber sludge from Facility A; FSS from Facility B). In addition, several samples exhibited relatively constant release (ca. 100 μg/L) at pH>8 with increasing release with decreasing pH at pH<8 (Figure 31d, scrubber sludge for facility B with SCR[-]; FSS from facilities A, B, K ). Aluminum extract concentrations typically were either relatively constant or decreasing (salt ing out) with decreasing LS. The notable exception was the scrubber sludge from facility B with SCR off (DGD) and FSS from facility M with SCR on (MAS), where aluminum concentration increased with decreasing LS.

Antimony. Figure 32a illustrates antimony behavior with loc al maxima at pH~8 and pH<3, which was observed for fly ash from facilities A an d B, and FSS from facility A. Figure 32b illustrates behavior that was observed for gypsum f rom Facility Q and scrubber sludge from Facility A. For gypsum samples other than from Faci lity Q, antimony release appeared random at concentrations of <MDL to 3 μg/L at pH>4 with a gen eral slight increase in concentration at pH<4. Figure 32c and d illustrates behavior that wa s observed for the remaining CCR samples. For some samples, antimony concentrations in extrac ts increased by up to a factor of 5 with decreasing LS, while it remained constant or decrease d for other samples.

Arsenic. Figure 33 illustrates the four typical release behaviors observed for arse nic release as a function of pH. Each of these four behaviors was ob served for a least one of the samples from each material type (fly ash, gypsum, scrubber sludg e, FSS). Leaching from gypsum generally was less than 10 μg/L for pH>6 and reached a maximu m of approximately 30-100 μg/L at pH<5.

Arsenic concentrations in extracts were either cons tant or increased by up to a factor of 2 with decreasing LS.

Barium. Figure 34 illustrates the four typical release beh aviors observed for barium. For fly ash, barium was either relatively constant at approximat ely 100 μg/L as a function of pH or exhibited increases at pH< 4 (Figure 34a) and pH>9 to approxi mately 1000 μg/L (i.e., facility K). For gypsum, Figure 35d illustrates the typical behavior . Behaviors illustrated by Figure 34b and c are typical of that observed for scrubber sludge and FS S, with both behaviors observed for both material types. Barium extract concentrations remai ned constant with decreasing LS, with the exception of fly ash from facility A, where barium concentrations increased by up to a factor of 5 with decreasing LS.

Boron. Figure 35 (a, b, c) illustrates the three typical release behaviors for boron: (i) decreasing concentration with increasing pH for pH>8 (Figure 35a, fly ash from facilities A, B; scrubber sludge from facility K; FSS from facilities A, M), (ii) relatively constant concentration with a slight decrease at 8<pH<10 (Figure 35b, scrubber sl udge from facility B, FSS from facility K), (iii) relatively constant or with a slight increase at pH>10 (Figure 35d). Comparison of Figure

35c and d illustrates the reduction in leachable bo ron achieved through the washing step (facility N, unwashed and washed). Boron concentrations in extracts were either constant or increased b y up to a factor of 10 with decreasing LS.

57

### Characterization of Coal Combustion Residues II



### Cadmium. Figure 36 illustrates typical release behavior fo r cadmium, which is similar for all cases. The maximum concentration at pH<4 reflects t he total content in the sample, and the slope and pH shift in the increasing cadmium concentratio n with decreasing pH typically reflects the presence or absence of complexants in solution (e.g., c hloride or DOC). Cadmium concentrations in extracts were either constant or increasing with dec reasing LS.

Chromium. Figure 37 and Figure 38 illustrate typical releas e behavior for chromium. Comparison of the pairs Figure 37a and b, Figure 37 c and d, and Figure 38a and b illustrate the effect of NOx control on chromium release from fly ash, scrubber sludge, and FSS respectively for Facility B. Use of SCR at this facility appears to result in a larger fraction of the chromium in the residue being oxidized (Cr +6 

### ), forming chromate, which is more soluble at neutr al pH. The SCR catalyst used for Facility B may have contribut ed to increased overall total chromium present in the CCRs from that facility when SCR was in use. Increased leachability of chromium as a consequence of NOx control was also observed f or Facility A (comparing results for SNCR[-] with SNCR[+]), even though total chromium c ontent was similar for cases with and without NOx control. Figure 38c and d illustrates t he typical amphoteric behavior for reduced chromium (Cr

+3 

### ), which was observed for gypsum samples. Chromium concentrations in extracts were either constant (for cases with low leachable chromium), or increasing by up to a factor of 10 (cases with Cr +6 

### as the apparently dominant chromium form) with decreasi ng LS.

Cobalt. Figure 39 illustrates typical release behavior fo r cobalt, which is similar for all CCRs tested. Cobalt release increases with decreasing pH at pH<8, with the maximum concentration reflecting the total leachable content and the slop e and relative pH shift in the slope typically reflecting the presence or absence of complexants i n solution. Cobalt concentrations in extracts (where greater than the MDL) were typically increas ing by up to a factor of 5 with decreasing

LS.

Lead. Figure 40 illustrates typical release behavior for lead, which generally is expected to be amphoteric (Figure 40a, c). However, many samples d id not have sufficient lead content or complexants present in solution to produce amphoter ic behavior at pH<12 (Figure 40b, d). Lead concentrations in extracts were not significantly changed at decreasing LS.

Molybdenum. Figure 41 and Figure 42 illustrate typical releas e behaviors for molybdenum. Figure 41a illustrates increased concentration peak ing at pH~8 most likely from complexation with ammonium present from use of SNCR (Facility A) . Note the similar release behavior observed for fly ash, FSS and gypsum illustrated by Figure 41b and Figure 42b, c, albeit at different orders of magnitude in concentration. Fig ure 41c, d and Figure 42b, d illustrate three additional observed behaviors, present across multi ple CCR types. Molybdenum concentrations typically increased with decreasing LS, in some cas es by a factor much greater than 10 (e.g., FSS from Facility A).

Selenium. Figure 43 and Figure 44 illustrate typical seleni um release behaviors observed for fly ash, scrubber sludge and FSS. For gypsum, selenium release was either constant as a function of pH (facilities O, P) or amphoteric (facilities N, Q). Selenium concentrations in extracts typically increased by up to a factor of 6 with decreasing LS.

Thallium. Figure 45 illustrates typical release behavior for thallium. Most cases w ere either analogous to Figure 45a or Figure 45c (increasing c oncentration with decreasing pH at pH<9) or Figure 45d (relatively constant as a function of pH ). For gypsum, washing resulted in at least an

58

### Characterization of Coal Cumbustion Residues II



### 59 order of magnitude reduction in the observed leachi ng concentrations (facilities N, O). Thallium concentrations typically increased by up to a factor of 5 with decreasing LS.

MDL ML 10.3 0.044 MCL

0.001 0.01 0.1 1

2 4 6 8 10 12 14Hg [μg/L]

pH

SR2-CFA - A SR2-CFA - B

SR2-CFA - C

Fly Ash !" Fac. A. (NO+SNCR[

" ]+FF) MDL ML 10.5 0.116 MCL

0.001 0.01 0.1 1

2 4 6 8 10 12 14Hg [μg/L]

pH

SR2-AFA - A SR2-AFA - B

SR2-AFA - C

Fly Ash !" Fac. A. (NO+SNCR[+]+FF )

MDL ML 9.1 0.040 MCL

0.001 0.01 0.1 1 10

2 4 6 8 10 12 14Hg [μg/L]

pH

SR2-DGD - A SR2-DGD - B

SR2-DGD - C

Scrubber Sludge !" Fac. B. (NO+SCR[

" ]+ESP,Mg Lime) MDL ML 6.7 0.029 MCL

0.001 0.01 0.1 1 10

2 4 6 8 10 12 14Hg [μg/L]

pH

SR2-PAD - A SR2-PAD - B

Gypsum

" Fac. P. (FO+SCR[+]&SNCR[+]+ESP) 

### a) b)

c) d)

Figure 30. Mercury - Examples of characteristic le aching behavior as a function of pH (SR002.1 results).

### Characterization of Coal Combustion Residues II



### 60 MDL 1000000

100000

10000 1804]L 1000/g[μ 100Al 10

1

0.1 10.3 2 4 6 8 10 12 14

ML pH

SR2-CFA - A SR2-CFA - B

SR2-CFA - C

Fly Ash !" Fac. A. (NO+SNCR[

" ]+FF ) MDL 1000000

100000

13427 10000]L 1000/g[μ 100Al 10

1

0.1 10.5 2 4 6 8 10 12 14

ML pH

SR2-AFA - A SR2-AFA - B

SR2-AFA - C

Fly Ash !" Fac. A. (NO+SNCR[+]+FF )

MDL 1000000

100000

10000]L 1000/g 496[μ 100Al 10

1

0.1 7.3 2 4 6 8 10 12 14

ML pH

SR2-CGD - A SR2-CGD - B

SR2-CGD - C

Scrubber Sludge !" Fac. A. (NO+SNCR[

" ]+FF) MDL 1000000

100000

10000]L 1000/g[μ 100 37.0Al 10

1

0.1 9.1 2 4 6 8 10 12 14

ML pH

SR2-DGD - A SR2-DGD - B

SR2-DGD - C

Scrubber Sludge !" Fac. B. (NO+SCR[

" ]+ESP) 

### a) b)

c) d)

Figure 31. Aluminum. Examples of characteristic leaching behavior as a functio n of pH.

### Characterization of Coal Cumbustion Residues II



### 61 MDL ML 10.3 6.43 MCL

0.1 1 10 100 1000

2 4 6 8 10 12 14Sb [μg/L]

pH

SR2-DFA - A SR2-DFA - B

SR2-DFA - C

Fly Ash !" Fac. B. (NO+SNCR[

" ]+FF) MDL ML 6.9 2.53 MCL

0.1 1 10 100

2 4 6 8 10 12 14Sb [μg/L]

pH

SR2-QAU - A SR2-QAU - B

Gypsum

" Fac. Q. (FO+SCR[+]+ESP)

MDL ML 9.1 5.44 MCL

0.1 1 10 100 1000

2 4 6 8 10 12 14Sb [μg/L]

pH

SR2-DGD - A SR2-DGD - B

SR2-DGD - C

Scrubber Sludge !" Fac. B. (NO+SCR[

" ]+ESP, Mg Lime) MDL ML 12.2 1.76 MCL

0.1 1 10 100 1000

2 4 6 8 10 12 14Sb [μg/L]

pH

SR2-DCC - A SR2-DCC - B

SR2-DCC - C

FSSL !" Fac. B. (NO+SCR[

" ]+ESP,Mg Lime) 

### a) b)

c) d)

Figure 32. Antimony. Examples of characteristic leaching b ehavior as a function of pH.

### Characterization of Coal Combustion Residues II



### 62 MDL ML 10.3 46.8

MCL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14As [μg/L]

pH

SR2-DFA - A SR2-DFA - B

SR2-DFA - C

Fly Ash !" Fac. B. (NO+SCR[

" ]+ESP,Mg Lime) MDL ML 10.1 29.0

MCL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14As [μg/L]

pH

SR2-BFA - A SR2-BFA - B

SR2-BFA - C

Fly Ash !" Fac. B. (NO+SCR[+]+ESP,Mg Lime)

MDL ML 9.1 0.545 MCL

0.1 1 10 100 1000

2 4 6 8 10 12 14As [μg/L]

pH

SR2-DGD - A SR2-DGD - B

SR2-DGD - C

Scrubber Sludge !" Fac. B. (NO+SCR[

" ]+ESP,Mg Lime) MDL ML 12.2 2.09 MCL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14As [μg/L]

pH

SR2-DCC - A SR2-DCC - B

SR2-DCC - C

FSSL !" Fac. B. (NO+SCR[

" ]+ESP,Mg Lime) 

### d) b) a)

c)

Figure 33. Arsenic. Examples of characteristic leac hing behavior as a function of pH.

### Characterization of Coal Cumbustion Residues II



### 63 MDL ML 10.3 192 MCL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14Ba [μg/L]

pH

SR2-DFA - A SR2-DFA - B

SR2-DFA - C

Fly Ash !" Fac. B. (NO+SCR[

" ]+ESP,Mg Lime) MDL ML 11.0 113 MCL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14Ba [μg/L]

pH

SR2-KGD - A SR2-KGD - B



### Scrubber Sludge !" Fac. K. (NO+SCR[+]+ESP,Mg Lime)

MDL ML 12.2 2286 MCL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14Ba [μg/L]

pH

SR2-DCC - A SR2-DCC - B

SR2-DCC - C

FSSL !" Fac. B. (NO+SCR[

" ]+ESP,Mg Lime) MDL ML 7.3 80.0 MCL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14Ba [μg/L]

pH

SR2-OAW - A SR2-OAW - B

Gypsum (Gyp

" W)

" Fac. O. (FO+SCR[+]+ESP) 

### d) b) a)

c)

Figure 34. Barium. Examples of characteristic leach ing behavior as a function of pH.

### Characterization of Coal Combustion Residues II



### 64 MDL ML 10.3 3551 DWEL

0.1 1 10 100 1000 10000 100000

2 4 6 8 10 12 14B [μg/L]

pH

SR2-DFA - A SR2-DFA - B

SR2-DFA - C

Fly Ash !" Fac. B. (NO+SCR[

" ]+ESP,Mg Lime) MDL ML 9.1 3331 DWEL

0.1 1 10 100 1000 10000 100000

2 4 6 8 10 12 14B [μg/L]

pH

SR2-DGD - A SR2-DGD - B

SR2-DGD - C

Scrubber Sludge !" Fac. B. (NO+SCR[

" ]+ESP,Mg Lime)

MDL ML 7.2 2214 DWEL

0.1 1 10 100 1000 10000 100000

2 4 6 8 10 12 14B [μg/L]

pH

SR2-NAU - A SR2-NAU - B

Gypsum (Gyp

" U)

" Fac. N. (FO+SCR[+]+ESP) MDL ML 7.1 48.6 DWEL

0.1 1 10 100 1000 10000 100000

2 4 6 8 10 12 14B [μg/L]

pH

SR2-NAW - A SR2-NAW - B

Gypsum (Gyp

" W)

" Fac. N. (FO+SCR[+]+ESP) 

### d) c) b) a)

Figure 35. Boron. Examples of characteristic leach ing behavior as a function of pH.

### Characterization of Coal Cumbustion Residues II



### 65 MDL ML 10.3 0.795 MCL

0.1 1 10 100

2 4 6 8 10 12 14Cd [μg/L]

pH

SR2-DFA - A SR2-DFA - B

SR2-DFA - C

Fly Ash !" Fac. B. (NO+SCR[

" ]+ESP,Mg Lime) MDL ML 11.0 0.200 MCL

0.1 1 10 100

2 4 6 8 10 12 14Cd [μg/L]

pH

SR2-KGD - A SR2-KGD - B

Scrubber Sludge !" Fac. K. (NO+SCR[+]+ESP,Mg Lime)

MDL ML 6.9 6.03 MCL

0.1 1 10 100

2 4 6 8 10 12 14Cd [μg/L]

pH

SR2-QAU - A SR2-QAU - B

Gypsum (Gyp

" U)

" Fac. Q. (FO+SCR[+]+ESP) MDL ML 8.4 0.634 MCL

0.1 1 10 100

2 4 6 8 10 12 14Cd [μg/L]

pH

SR2-ACC - A SR2-ACC - B

SR2-ACC - C

FSSL

" Fac. B. (NO+SCR[+]+ESP,Mg Lime) 

### d) c) b) a)

Figure 36. Cadmium. Examples of characteristic leaching behavior as a function of pH.

### Characterization of Coal Combustion Residues II



### 66 MDL ML 10.3 132
MCL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14Cr [μg/L]

pH

SR2-DFA - A SR2-DFA - B

SR2-DFA - C

Fly Ash !" Fac. B. (NO+SCR[

" ]+ESP,Mg Lime) MDL ML 10.1 851

MCL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14Cr [μg/L]

pH

SR2-BFA - A SR2-BFA - B

SR2-BFA - C

Fly Ash !" Fac. B. (NO+SCR[+]+ESP,Mg Lime)

MDL ML 9.1 2.98 MCL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14Cr [μg/L]

pH

SR2-DGD - A SR2-DGD - B

SR2-DGD - C

Scrubber Sludge !" Fac. B. (NO+SCR[

" ]+ESP,Mg Lime) MDL ML 10.1 228 MCL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14Cr [μg/L]

pH

SR2-BGD - A SR2-BGD - B

SR2-BGD - C

Scrubber Sludge !" Fac. B. (NO+SCR[+]+ESP,Mg Lime) 

### d) c) b) a)

Figure 37. Chromium. Examples of characteristic leaching behavior as a functio n of pH.

### Characterization of Coal Cumbustion Residues II



### 67 MDL ML 12.2 11.2 MCL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14Cr [μg/L]

pH

SR2-DCC - A SR2-DCC - B

SR2-DCC - C

FSSL !" Fac. B. (NO+SCR[

" ]+ESP,Mg Lime) MDL ML 8.0 715

MCL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14Cr [μg/L]

pH

SR2-BCC - A SR2-BCC - B

SR2-BCC - C

FSSL !" Fac. B. (NO+SCR[+]+ESP,Mg Lime)

MDL ML 7.2 2.87 MCL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14Cr [μg/L]

pH

SR2-NAU - A SR2-NAU - B

Gypsum (Gyp

" U)

" Fac. N. (FO+SCR[+]+ESP) MDL ML 7.1 0.235 MCL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14Cr [μg/L]

pH

SR2-NAW - A SR2-NAW - B

Gypsum (Gyp

" W)

" Fac. N. (FO+SCR[+]+ESP) 

### d) c) b) a)

Figure 38. Chromium. Examples of characteristic leaching behavior as a functio n of pH.

### Characterization of Coal Combustion Residues II



### 68 MDL ML 10.3 0.255

0.1 1 10 100 1000

2 4 6 8 10 12 14Co [μg/L]

pH

SR2-CFA - A SR2-CFA - B

SR2-CFA - C

Fly Ash !" Fac. A. (NO+SNCR[

" ]+FF) MDL ML 10.5 7.72

0.1 1 10 100 1000

2 4 6 8 10 12 14Co [μg/L]

pH

SR2-AFA - A SR2-AFA - B

SR2-AFA - C

Fly Ash !" Fac. A. (NO+SNCR[+]+FF)

MDL ML 9.1 0.255

0.1 1 10 100 1000

2 4 6 8 10 12 14Co [μg/L]

pH

SR2-DGD - A SR2-DGD - B

SR2-DGD - C

Scrubber Sludge !" Fac. B. (NO+SCR[

" ]+ESP,Mg Lime) MDL ML 7.5 1.65

0.1 1 10 100 1000

2 4 6 8 10 12 14Co [μg/L]

pH

SR2-OAU - A SR2-OAU - B

Gypsum (Gyp

" U)

" Fac. O. (FO+SCR[+]+ESP) 

### d) c) b) a)

Figure 39. Cobalt. Examples of characteristic leaching behavior as a function of pH.

### Characterization of Coal Cumbustion Residues II



### 69 MDL ML 10.5 0.339 MCL

0.1 1 10 100 1000

2 4 6 8 10 12 14Pb [μg/L]

pH

SR2-AFA - A SR2-AFA - B

SR2-AFA - C

Fly Ash !" Fac. A. (NO+SNCR[+]+FF) MDL ML 6.8 0.354 MCL

0.1 1 10 100 1000

2 4 6 8 10 12 14Pb [μg/L]

pH

SR2-AGD - A SR2-AGD - B

SR2-AGD - C

Scrubber Sludge !" Fac. A. (NO+SNCR[+]+FF)

MDL ML 8.4 0.569 MCL

0.1 1 10 100 1000

2 4 6 8 10 12 14Pb [μg/L]

pH

SR2-ACC - A SR2-ACC - B

SR2-ACC - C

FSSL

" Fac. A. (NO+SCR[+]+ESP,Mg Lime) MDL ML 7.5 0.140 MCL

0.1 1 10 100 1000

2 4 6 8 10 12 14Pb [μg/L]

pH

SR2-OAU - A SR2-OAU - B

Gypsum (Gyp

" U)

" Fac. O. (FO+SCR[+]+ESP) 

### d) c) b) a)

Figure 40. Lead. Examples of characteristic leaching behavior as a function of pH.

### Characterization of Coal Combustion Residues II



### 70 MDL ML 10.5 587 DWEL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14Mo [μg/L]

pH

SR2-AFA - A SR2-AFA - B

SR2-AFA - C

Fly Ash !" Fac. A. (NO+SNCR[+]+FF) MDL ML 10.3 1956

DWEL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14Mo [μg/L]

pH

SR2-DFA - A SR2-DFA - B

SR2-DFA - C

Fly Ash !" Fac. B. (NO+SCR[

" ]+FF)

MDL ML 7.3 10.2 DWEL

0.1 1 10 100 1000

2 4 6 8 10 12 14Mo [μg/L]

pH

SR2-CGD - A SR2-CGD - B

SR2-CGD - C

Scrubber Sludge !" Fac. A. (NO+SNCR[

" ]+FF) MDL ML 9.1 135 DWEL

0.1 1 10 100 1000

2 4 6 8 10 12 14Mo [μg/L]

pH

SR2-DGD - A SR2-DGD - B

SR2-DGD - C

Scrubber Sludge !" Fac. B. (NO+SCR[

" ]+ESP, Mg Lime) 

### d) c) b) a)

Figure 41. Molybdenum. Examples of characteristic leaching behavior as a function of pH.

### Characterization of Coal Cumbustion Residues II



### 71 MDL ML 8.4 241 DWEL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14Mo [μg/L]

pH

SR2-ACC - A SR2-ACC - B

SR2-ACC - C

FSSL

" Fac. A. (NO+SCR[+]+ESP,Mg Lime) MDL ML 12.2 138 DWEL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14Mo [μg/L]

pH

SR2-DCC - A SR2-DCC - B

SR2-DCC - C

FSSL !" Fac. B. (NO+SCR[

" ]+ESP,Mg Lime)

MDL ML 7.5 18.8 DWEL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14Mo [μg/L]

pH

SR2-OAU - A SR2-OAU - B

Gypsum (Gyp

" U)

" Fac. O. (FO+SCR[+]+ESP) MDL ML 6.9 14.3 DWEL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14Mo [μg/L]

pH

SR2-QAU - A SR2-QAU - B

Gypsum (Gyp

" U)

" Fac. Q. (FO+SCR[+]+ESP) 

### d) c) b) a)

Figure 42. Molybdenum. Examples of characteristic leaching behavior as a function of pH.

### Characterization of Coal Combustion Residues II



### 72 MDL ML 10.3 9.27 MCL

0.1 1 10 100 1000

2 4 6 8 10 12 14Se [μg/L]

pH

SR2-DFA - A SR2-DFA - B

SR2-DFA - C

Fly Ash !" Fac. B. (NO+SCR[

" ]+ESP,Mg Lime) MDL ML 9.2 123

MCL

0.1 1 10 100 1000

2 4 6 8 10 12 14Se [μg/L]

pH

SR2-KFA - A SR2-KFA - B

Fly Ash !" Fac. K. (NO+SCR[+]+ESP,Mg Lime)

MDL ML 9.1 21.9 MCL

0.1 1 10 100 1000

2 4 6 8 10 12 14Se [μg/L]

pH

SR2-DGD - A SR2-DGD - B

SR2-DGD - C

Scrubber Sludge !" Fac. B. (NO+SCR[

" ]+ESP,Mg Lime) MDL ML 10.1 2.31 MCL

0.1 1 10 100 1000

2 4 6 8 10 12 14Se [μg/L]

pH

SR2-BGD - A SR2-BGD - B

SR2-BGD - C

Scrubber Sludge !" Fac. B. (NO+SCR[+]+ESP,Mg Lime) 

### d) c) b) a)

Figure 43. Selenium. Examples of characteristic leaching behavior as a function of pH.

### Characterization of Coal Cumbustion Residues II



### 73 MDL ML 12.2 16.3 MCL

0.1 1 10 100 1000

2 4 6 8 10 12 14Se [μg/L]

pH

SR2-DCC - A SR2-DCC - B

SR2-DCC - C

FSSL !" Fac. B. (NO+SCR[

" ]+ESP,Mg Lime) MDL ML 8.2 22.6 MCL

0.1 1 10 100 1000

2 4 6 8 10 12 14Se [μg/L]

pH

SR2-KCC - A SR2-KCC - B

FSSL !" Fac. K. (NO+SCR[+]+ESP,Mg Lime)

MDL ML 7.2 18.5 MCL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14Se [μg/L]

pH

SR2-NAU - A SR2-NAU - B

Gypsum (Gyp

" U)

" Fac. N. (FO+SCR[+]+ESP) MDL ML 6.9 325

MCL

0.1 1 10 100 1000 10000

2 4 6 8 10 12 14Se [μg/L]

pH

SR2-QAU - A SR2-QAU - B

Gypsum (Gyp

" U)

" Fac. Q. (FO+SCR[+]+ESP) 

### d) c) b) a)

Figure 44. Selenium. Examples of characteristic leaching behavior as a function of pH.

### Characterization of Coal Combustion Residues II



### 74 MDL ML 10.3 0.773 MCL

0.1 1 10 100 1000

2 4 6 8 10 12 14Tl [μg/L]

pH

SR2-DFA - A SR2-DFA - B

SR2-DFA - C

Fly Ash !" Fac. B. (NO+SCR[

" ]+ESP,Mg Lime) MDL ML 9.2 38.0

MCL

0.1 1 10 100 1000

2 4 6 8 10 12 14Tl [μg/L]

pH

SR2-KFA - A SR2-KFA - B

Fly Ash !" Fac. K. (NO+SCR[+]+ESP,Mg Lime)

MDL ML 12.2 15.6

MCL

0.1 1 10 100 1000

2 4 6 8 10 12 14Tl [μg/L]

pH

SR2-DCC - A SR2-DCC - B

SR2-DCC - C

FSSL !" Fac. B. (NO+SCR[

" ]+ESP,Mg Lime) MDL ML 8.2 2.98 MCL

0.1 1 10 100 1000

2 4 6 8 10 12 14Tl [μg/L]

pH

SR2-KCC - A SR2-KCC - B

FSSL !" Fac. K. (NO+SCR[+]+ESP,Mg Lime) 

### d) c) b) a)

Figure 45. Thallium. Examples of characteristic le aching behavior as a function of pH.

### Characterization of Coal Cumbustion Residues II



### 3.3.2. Comparisons of the Ranges of Constituent Concentra tions from Laboratory Testing with Measurements of Field Samples and the EPA Risk Report Database
Figure 46 through Figure 59 present comparisons of the range of constituent concentrations observed in laboratory extracts from testing as a f unction of pH and LS (SR002.1 and SR003.1) over the pH range from 5.4 to 12.4 and LS ratios fr om 0.5 to 10. This pH range represents the 5 th



### and 95 th 

### percentiles of pH observed in field samples from C CR landfills and surface impoundments, as discussed in Section 2.6. For labo ratory leaching test extracts, the presented data represent the observed minimum, natural pH, an d maximum concentration, considering all results from both test methods. Including results f rom testing as a function of LS allows consideration of potentially higher concentrations observed for initial releases that may occur at low LS ratios in the field. The MCL or DWEL is included in each figure as a dashed horizontal line to provide a reference value. However, the con centration ranges indicated in the figures as results of this study are direct measurements of la boratory extracts and do not consider attenuation that may occur in the field. Ranges of field observations are included for comparison as derived from the EPRI database, considering only observations from disposal sites associated

with facilities that have wet FGD scrubbers. The 5 th 

### , median, and 95 th 

### percentile of field data is presented for surface impoundments [“Surface Imp. ( EPRI)”] and landfills [“Landfill (EPRI)”]. Surface impoundment data are compared with scrubber sludge results because scrubber sludges are most likely to be disposed in this manner (see S ection 1). Landfill data are compared with

FSS and FSSL because these blended materials are th e likely to be disposed in landfills. Also included for comparison is the 5 th 

### , median, and 95 th 

### percentile of the database used to carry out human and ecological health risk evaluations in the EPA Risk Report (EPA, 2007) (“CCW Ash,” “CCW FGD,” and “CCW Ash and Coal Waste” referring t o monofilled fly ash, disposed FGD scrubber sludge, and combined CCR disposal, respectiv ely).

pH. The natural pH of the fly ash samples evaluated i n this report was alkaline 24 

### , scrubber sludge samples were neutral to alkaline, gypsum samples were neutral and FSS samples were mildly alkaline (pH ~8) to very alkaline (pH>11), m ost likely depending on the amount of lime

added.

Mercury. Laboratory extract concentration ranges for two o f the scrubber sludge samples (Facility B) and four of the FSS samples (facilities B, K, M) exceeded the MCL for mercury. The mercury concentration ranges indicate that the greatest leaching concentrations are expect ed from scrubber sludge and blending with fly ash and lime to produce FSS does not substantially decrease, and may increase, mercury leaching. All n atural pH samples were less than the MCL, most by more than an order of magnitude. All fly as h and gypsum data were less than the MCL, regardless of pH. Mercury field data were very sparse.

Aluminum. There was no reference limit available for alumin um. The range of laboratory extract concentrations from scrubber sludge samples agreed well with field observations. The range of field observations for landfills tended to be similar to somewhat lowe r than the values observed for laboratory extracts. However, the rang e used in the EPA Risk Report (EPA, 2007) had an upper bound approximately one order of magni tude greater than the field data and the laboratory extracts.

24 

### Some fly ash samples reported on in Sanchez et al. (2006) were acidic.



### 75

### Characterization of Coal Combustion Residues II



### Antimony. Fly ash and FSS had the highest concentrations of antimony in laboratory extracts. The range of field observations for surface impound ments (EPRI) was much greater than for laboratory extracts of scrubber sludge, but also li kely reflects co-disposal of fly ash with scrubber sludge in surface impoundments. If the fie ld data includes co-disposal data, then the concentration range reported for field observations is entirely consistent with the laboratory testing. The range of field observation for landfil ls (EPRI) was lower than observed in laboratory extracts. This comparison suggests the potential fo r attenuation or immobilization under field conditions, many of which may be reducing in contra st to the oxidizing conditions used in the laboratory testing. For gypsum, all natural pH resu lts were less than the MCL.

Arsenic. Leachable arsenic appears to be distributed between fly ash and scrubber sludge. Results for Facility A (fly ash, scrubber sludge, a nd FSS), Facility B (scrubber sludge and FSS) and Facility M (FSS) suggest that NOx controls incr ease the leachability of arsenic at the material’s natural pH. Results from field observati ons indicate narrower ranges than laboratory testing. Ranges used in the EPA Risk report (EPA, 2 007) appear to be much higher than the laboratory testing results, except for Facility M. All results for gypsum were less than the MCL.

Barium. Laboratory testing results indicate a much broade r range of concentrations than field observations. Two samples of FSS, both with NOx con trols off (Facility B and Facility M), had much greater laboratory extract concentrations than the other samples. All natural pH results were less than the MCL for fly ash, scrubber sludge and gypsum.

Boron. Most notable for boron is a reduction of approxim ately an order of magnitude in leachable boron from gypsum as a consequence of was hing (facilities N, O). There is no clear trend amongst the material types for boron. Laborat ory results are consistent with field observations. All gypsum natural pH results were less th an the DWEL.

Cadmium. Cadmium concentrations in laboratory extracts wer e generally lower for the scrubber sludge than for the other materials. For s crubber sludge, cadmium concentrations observed in laboratory extracts were less than the concentrations reported for field observations for surface impoundments. For all cases, cadmium co ncentrations in laboratory extracts were

consistent with field observations for landfills. I n addition, the measured concentrations in laboratory extracts from this study and reported fo r field results are approximately an order of magnitude less than the upper bound reported for CC W and coal waste in the Risk Report (EPA 2007).

Chromium. The range of field observations appears low in comparison to the labor atory testing results. The increase in chromium leaching, apparen tly as a consequence of NOx controls, is evident for facilities A, B and M. Six cases exceed the MCL by greater than one order of magnitude. Test results for all of the gypsum sampl es are well below the MCL. The field observations for both surface impoundments and land fills are up to two orders of magnitude less than the laboratory testing results.

Cobalt. The use of NOx controls appears to increase cobalt leaching from fly ash bas ed results for facilities A and B. The data range used by the EPA risk report (EPA, 2007) for combined management of ash and coal waste is one to two orde rs of magnitude greater than the observations for laboratory extracts and field observations.

76

### Characterization of Coal Cumbustion Residues II



### 77 Lead. Laboratory test results indicate concentration ra nges generally lower than or consistent with field observations for surface impoundments an d landfills and much lower than the values used in the EPA risk report (EPA, 2007). All fly as h and gypsum samples were less than the

MCL.

Molybdenum. Leachate molybdenum concentrations exceeding the DWEL by up to two orders of magnitude were observed for fly ash and FSS. Lea chate molybdenum concentrations generally less than the DWEL were observed for gypsum.

Selenium. Similar ranges of selenium concentrations are exp ected for all materials.

Thallium. Laboratory test results indicate a concentration range in excess of two orders of magnitude for all materials and the observed concen tration can exceed the MCL for thallium by more than one order of magnitude. Washed gypsum had significantly lower extra ct concentrations of thallium than unwashed gypsum.

4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0Fac. A (CFA) -Fac. A (AFA) +Fac. B (DFA) -Fac. B (BFA) +Fac. K (KFA) +CCW Ash [EPA]Fac. A (CGD) -Fac. A (AGD) +Fac. B (DGD) -Fac. B (BGD) +Fac. K (KGD) +Surface Imp. [EPRI]Fac. N (NAU) +UFac. N (NAW) +WFac. O (OAU) +UFac. O (OAW) +WFac. P (PAD) +UFac. Q (QAU) +UFac. A (CCC) -Fac. A (ACC) +Fac. B (DCC) -Fac. B (BCC) +Fac. K (KCC) +Fac. M (MAD) -Fac. M (MAS) +Landfill [EPRI]CCW FGD [EPA]Ash & Coal Waste [EPA]pH (SI)

Fly!! Ash!!!!!!!!!!!!!!!!! |!!! Scrubber Sludge!!!!!!!!!!! |!!!!!!!!!!!!! Gypsum!!!!!!!!!!!!!!!!! | Fixated Scrubber Sludge

Nat. Ox. Nat. Ox.!!!!!! | I. Ox. Nat. Ox. Forced Ox.



### Figure 46. Natural pH (pH in distilled water at LS=10) observed in SR02 extracts.

### Characterization of Coal Combustion Residues II



### 78 0.001 0.010 0.100 1.000 10.000Fac. A (CFA) -Fac. A (AFA) +Fac. B (DFA) -Fac. B (BFA) +Fac. K (KFA) +CCW Ash [EPA]Fac. A (CGD) -Fac. A (AGD) +Fac. B (DGD) -Fac. B (BGD) +Fac. K (KGD) +Surface Imp. [EPRI]Fac. N (NAU) +UFac. N (NAW) +WFac. O (OAU) +UFac. O (OAW) +WFac. P (PAD) +UFac. Q (QAU) +UFac. A (CCC) -Fac. A (ACC) +Fac. B (DCC) -Fac. B (BCC) +Fac. K (KCC) +Fac. M (MAD) -Fac. M (MAS) +Landfill [EPRI]CCW FGD [EPA]Ash & Coal Waste [EPA]Hg (!g/L)

Max Min own pH MCL = 2

! g/L Nat. Ox. Nat. Ox.!!!!!! | I. Ox. Nat. Ox. Forced Ox.

Fly!! Ash!!!!!!!!!!!!!!!!! |!!! Scrubber Sludge!!!!!!!!!!! |!!!!!!!!!!!!!!!! Gypsum!!!!!!!!!!!!!! | Fixated Scrubber Sludge

0.1 1.0 10.0 100.0 1,000.0 10,000.0 100,000.0 1,000,000.0Fac. A (CFA) -Fac. A (AFA) +Fac. B (DFA) -Fac. B (BFA) +Fac. K (KFA) +CCW Ash [EPA]Fac. A (CGD) -Fac. A (AGD) +Fac. B (DGD) -Fac. B (BGD) +Fac. K (KGD) +Surface Imp. [EPRI]Fac. N (NAU) +UFac. N (NAW) +WFac. O (OAU) +UFac. O (OAW) +WFac. P (PAD) +UFac. Q (QAU) +UFac. A (CCC) -Fac. A (ACC) +Fac. B (DCC) -Fac. B (BCC) +Fac. K (KCC) +Fac. M (MAD) -Fac. M (MAS) +Landfill [EPRI]CCW FGD [EPA]Ash & Coal Waste [EPA]Al (!g/L)

Max Min own pH Fly!! Ash!!!!!!!!!!!!!!! |!!! Scrubber Sludge!!!!!!!!!!! |!!!!!!!!!!!!! Gypsum!!!!!!!!!!!!!!!! | Fixated Scrubber Sludge

Nat. Ox. Nat. Ox.!!!!!! | I. Ox. Nat. Ox. Forced Ox.



### Figure 47 and Figure 48. Mercury and Aluminum. Comparison of maximum, minimum and natural pH concentrations observed in SR02 and SR03 extracts over the pH domain 5.4 ! pH ! 12.4. (key: - = NOx control off; + = NOx control on ; U = unwashed gypsum; W = washed gypsum; Nat. Ox. = natural oxidation; Forced Ox. = forced oxidation; I.Ox. = inhibited oxidation).

### Characterization of Coal Cumbustion Residues II



### 79 0.1 1.0 10.0 100.0 1,000.0Fac. A (CFA) -Fac. A (AFA) +Fac. B (DFA) -Fac. B (BFA) +Fac. K (KFA) +CCW Ash [EPA]Fac. A (CGD) -Fac. A (AGD) +Fac. B (DGD) -Fac. B (BGD) +Fac. K (KGD) +Surface Imp. [EPRI]Fac. N (NAU) +UFac. N (NAW) +WFac. O (OAU) +UFac. O (OAW) +WFac. P (PAD) +UFac. Q (QAU) +UFac. A (CCC) -Fac. A (ACC) +Fac. B (DCC) -Fac. B (BCC) +Fac. K (KCC) +Fac. M (MAD) -Fac. M (MAS) +Landfill [EPRI]CCW FGD [EPA]Ash & Coal Waste [EPA]Sb (!g/L)

Max Min own pH MCL = 6

! g/L

Fly!! Ash!!!!!!!!!!!!!!!!! |!!! Scrubber Sludge!!!!!!!!!!! |!!!!!!!!!!!!!!!! Gypsum!!!!!!!!!!!!!! | Fixated Scrubber Sludge

Nat. Ox. Nat. Ox.!!!!!! | I. Ox. Nat. Ox. Forced Ox.

0.1 1.0 10.0 100.0 1,000.0 10,000.0 100,000.0Fac. A (CFA) -Fac. A (AFA) +Fac. B (DFA) -Fac. B (BFA) +Fac. K (KFA) +CCW Ash [EPA]Fac. A (CGD) -Fac. A (AGD) +Fac. B (DGD) -Fac. B (BGD) +Fac. K (KGD) +Surface Imp. [EPRI]Fac. N (NAU) +UFac. N (NAW) +WFac. O (OAU) +UFac. O (OAW) +WFac. P (PAD) +UFac. Q (QAU) +UFac. A (CCC) -Fac. A (ACC) +Fac. B (DCC) -Fac. B (BCC) +Fac. K (KCC) +Fac. M (MAD) -Fac. M (MAS) +Landfill [EPRI]CCW FGD [EPA]Ash & Coal Waste [EPA]As (!g/L)

Max Min own pH MCL = 10

! g/L

Fly!! Ash!!!!!!!!!!!!!!!!! |!!! Scrubber Sludge!!!!!!!!!!! |!!!!!!!!!!!!!!!! Gypsum!!!!!!!!!!!!!! | Fixated Scrubber Sludge Nat. Ox. Nat. Ox.!!!!!! | I. Ox. Nat. Ox. Forced Ox.



### Figure 49 and Figure 50. Antimony and Arsenic. Co mparison of maximum, minimum and natural pH concentrations observed in SR02 and SR03 extracts over the pH domain 5.4 ! pH ! 12.4. (key: - = NOx control off; + = NOx control o n; U = unwashed gypsum; W = washed gypsum; Nat. Ox. = natural oxidation; Forced Ox. = forced oxidation; I.Ox. = inhibited oxidation).

### Characterization of Coal Combustion Residues II



### 80 1 10 100 1,000 10,000 100,000Fac. A (CFA) -Fac. A (AFA) +Fac. B (DFA) -Fac. B (BFA) +Fac. K (KFA) +CCW Ash [EPA]Fac. A (CGD) -Fac. A (AGD) +Fac. B (DGD) -Fac. B (BGD) +Fac. K (KGD) +Surface Imp. [EPRI]Fac. N (NAU) +UFac. N (NAW) +WFac. O (OAU) +UFac. O (OAW) +WFac. P (PAD) +UFac. Q (QAU) +UFac. A (CCC) -Fac. A (ACC) +Fac. B (DCC) -Fac. B (BCC) +Fac. K (KCC) +Fac. M (MAD) -Fac. M (MAS) +Landfill [EPRI]CCW FGD [EPA]Ash & Coal Waste [EPA]Ba (!g/L)

Max Min own pH MCL = 2000

! g/L Nat. Ox. Nat. Ox.!!!!!! | I. Ox. Nat. Ox. Forced Ox.

Fly!! Ash!!!!!!!!!!!!!!!!! |!!! Scrubber Sludge!!!!!!!!!!! |!!!!!!!!!!!!!!!! Gypsum!!!!!!!!!!!!!! | Fixated Scrubber Sludge

1 10 100 1,000 10,000 100,000 1,000,000Fac. A (CFA) -Fac. A (AFA) +Fac. B (DFA) -Fac. B (BFA) +Fac. K (KFA) +CCW Ash [EPA]Fac. A (CGD) -Fac. A (AGD) +Fac. B (DGD) -Fac. B (BGD) +Fac. K (KGD) +Surface Imp. [EPRI]Fac. N (NAU) +UFac. N (NAW) +WFac. O (OAU) +UFac. O (OAW) +WFac. P (PAD) +UFac. Q (QAU) +UFac. A (CCC) -Fac. A (ACC) +Fac. B (DCC) -Fac. B (BCC) +Fac. K (KCC) +Fac. M (MAD) -Fac. M (MAS) +Landfill [EPRI]CCW FGD [EPA]Ash & Coal Waste [EPA]B (!g/L)

Max Min own pH DWEL= 7000

Fly!! Ash!!!!!!!!!!!!!!!!! |!!! Scrubber Sludge!!!!!!!!!!! |!!!!!!!!!!!!!!!! Gypsum!!!!!!!!!!!!!! | Fixated Scrubber Sludge

Nat. Ox. Nat. Ox.!!!!!! | I. Ox. Nat. Ox. Forced Ox.



### Figure 51 and Figure 52. Barium and Boron. Comparison of maxi mum, minimum and natural pH concentrations observed in SR02 and SR03 extract s over the pH domain 5.4 ! pH ! 12.4. (key: - = NOx control off; + = NOx control on; U = unwashed gypsum; W = washed gypsum; Nat. Ox. = natural oxidation; Forced Ox. = forced ox idation; I.Ox. = inhibited oxidation).

### Characterization of Coal Cumbustion Residues II



### 81 0.01 0.1 1 10 100Fac. A (CFA) -Fac. A (AFA) +Fac. B (DFA) -Fac. B (BFA) +Fac. K (KFA) +CCW Ash [EPA]Fac. A (CGD) -Fac. A (AGD) +Fac. B (DGD) -Fac. B (BGD) +Fac. K (KGD) +Surface Imp. [EPRI]Fac. N (NAU) +UFac. N (NAW) +WFac. O (OAU) +UFac. O (OAW) +WFac. P (PAD) +UFac. Q (QAU) +UFac. A (CCC) -Fac. A (ACC) +Fac. B (DCC) -Fac. B (BCC) +Fac. K (KCC) +Fac. M (MAD) -Fac. M (MAS) +Landfill [EPRI]CCW FGD [EPA]Ash & Coal Waste [EPA]Cd (!g/L)

Max Min own pH MCL = 5

! g/L Nat. Ox. Nat. Ox.!!!!!! | I. Ox. Nat. Ox. Forced Ox.

Fly!! Ash!!!!!!!!!!!!!!!!! |!!! Scrubber Sludge!!!!!!!!!!! |!!!!!!!!!!!!!!!! Gypsum!!!!!!!!!!!!!! | Fixated Scrubber Sludge

0.1 1.0 10.0 100.0 1,000.0 10,000.0Fac. A (CFA) -Fac. A (AFA) +Fac. B (DFA) -Fac. B (BFA) +Fac. K (KFA) +CCW Ash [EPA]Fac. A (CGD) -Fac. A (AGD) +Fac. B (DGD) -Fac. B (BGD) +Fac. K (KGD) +Surface Imp. [EPRI]Fac. N (NAU) +UFac. N (NAW) +WFac. O (OAU) +UFac. O (OAW) +WFac. P (PAD) +UFac. Q (QAU) +UFac. A (CCC) -Fac. A (ACC) +Fac. B (DCC) -Fac. B (BCC) +Fac. K (KCC) +Fac. M (MAD) -Fac. M (MAS) +Landfill [EPRI]CCW FGD [EPA]Ash & Coal Waste [EPA]Cr (!g/L)

Max Min own pH MCL = 100

! g/L

Fly!! Ash!!!!!!!!!!!!!!!!! |!!! Scrubber Sludge!!!!!!!!!!! |!!!!!!!!!!!!!!!! Gypsum!!!!!!!!!!!!!! | Fixated Scrubber Sludge Nat. Ox. Nat. Ox.!!!!!! | I. Ox. Nat. Ox. Forced Ox.



### Figure 53 and Figure 54. Cadmium and Chromium. Co mparison of maximum, minimum and natural pH concentrations observed in SR02 and SR03 extracts over the pH domain 5.4 ! pH ! 12.4. (key: - = NOx control off; + = NOx control o n; U = unwashed gypsum; W = washed gypsum; Nat. Ox. = natural oxidation; Forced Ox. = forced oxidation; I.Ox. = inhibited oxidation).

### Characterization of Coal Combustion Residues II



### 82 0.1 1.0 10.0 100.0 1,000.0 10,000.0Fac. A (CFA) -Fac. A (AFA) +Fac. B (DFA) -Fac. B (BFA) +Fac. K (KFA) +CCW Ash [EPA]Fac. A (CGD) -Fac. A (AGD) +Fac. B (DGD) -Fac. B (BGD) +Fac. K (KGD) +Surface Imp. [EPRI]Fac. N (NAU) +UFac. N (NAW) +WFac. O (OAU) +UFac. O (OAW) +WFac. P (PAD) +UFac. Q (QAU) +UFac. A (CCC) -Fac. A (ACC) +Fac. B (DCC) -Fac. B (BCC) +Fac. K (KCC) +Fac. M (MAD) -Fac. M (MAS) +Landfill [EPRI]CCW FGD [EPA]Ash & Coal Waste [EPA]Co (!g/L)

Max Min own pH Nat. Ox. Nat. Ox.!!!!!! | I. Ox. Nat. Ox. Forced Ox.

Fly!! Ash!!!!!!!!!!!!!!!!! |!!! Scrubber Sludge!!!!!!!!!!! |!!!!!!!!!!!!!!!! Gypsum!!!!!!!!!!!!!! | Fixated Scrubber Sludge

0.01 0.10 1.00 10.00 100.00Fac. A (CFA) -Fac. A (AFA) +Fac. B (DFA) -Fac. B (BFA) +Fac. K (KFA) +CCW Ash [EPA]Fac. A (CGD) -Fac. A (AGD) +Fac. B (DGD) -Fac. B (BGD) +Fac. K (KGD) +Surface Imp. [EPRI]Fac. N (NAU) +UFac. N (NAW) +WFac. O (OAU) +UFac. O (OAW) +WFac. P (PAD) +UFac. Q (QAU) +UFac. A (CCC) -Fac. A (ACC) +Fac. B (DCC) -Fac. B (BCC) +Fac. K (KCC) +Fac. M (MAD) -Fac. M (MAS) +Landfill [EPRI]CCW FGD [EPA]Ash & Coal Waste [EPA]Pb (!g/L)

Max Min own pH MCL = 15

! g/L

Fly!! Ash!!!!!!!!!!!!!!!!! |!!! Scrubber Sludge!!!!!!!!!!! |!!!!!!!!!!!!!!!! Gypsum!!!!!!!!!!!!!! | Fixated Scrubber Sludge

Nat. Ox. Nat. Ox.!!!!!! | I. Ox. Nat. Ox. Forced Ox.



### Figure 55 and Figure 56. Cobalt and Lead. Compari son of maximum, minimum and natural pH

concentrations observed in SR02 and SR03 extracts o ver the pH domain 5.4 ! pH ! 12.4. (key: - = NOx control off; + = NOx control on; U = unwashed gypsum; W = washed gypsum; Nat. Ox. = natural oxidation; Forced Ox. = forced oxidation; I.Ox. = inhibited oxidation).

### Characterization of Coal Cumbustion Residues II



### 83 0.1 1.0 10.0 100.0 1,000.0 10,000.0 100,000.0Fac. A (CFA) -Fac. A (AFA) +Fac. B (DFA) -Fac. B (BFA) +Fac. K (KFA) +CCW Ash [EPA]Fac. A (CGD) -Fac. A (AGD) +Fac. B (DGD) -Fac. B (BGD) +Fac. K (KGD) +Surface Imp. [EPRI]Fac. N (NAU) +UFac. N (NAW) +WFac. O (OAU) +UFac. O (OAW) +WFac. P (PAD) +UFac. Q (QAU) +UFac. A (CCC) -Fac. A (ACC) +Fac. B (DCC) -Fac. B (BCC) +Fac. K (KCC) +Fac. M (MAD) -Fac. M (MAS) +Landfill [EPRI]CCW FGD [EPA]Ash & Coal Waste [EPA]Mo (!g/L)

Max Min own pH DWEL= 200

! g/L Nat. Ox. Nat. Ox.!!!!!! | I. Ox. Nat. Ox. Forced Ox.

Fly!! Ash!!!!!!!!!!!!!!!!! |!!! Scrubber Sludge!!!!!!!!!!! |!!!!!!!!!!!!!!!! Gypsum!!!!!!!!!!!!!! | Fixated Scrubber Sludge

1.0 10.0 100.0 1,000.0 10,000.0Fac. A (CFA) -Fac. A (AFA) +Fac. B (DFA) -Fac. B (BFA) +Fac. K (KFA) +CCW Ash [EPA]Fac. A (CGD) -Fac. A (AGD) +Fac. B (DGD) -Fac. B (BGD) +Fac. K (KGD) +Surface Imp. [EPRI]Fac. N (NAU) +UFac. N (NAW) +WFac. O (OAU) +UFac. O (OAW) +WFac. P (PAD) +UFac. Q (QAU) +UFac. A (CCC) -Fac. A (ACC) +Fac. B (DCC) -Fac. B (BCC) +Fac. K (KCC) +Fac. M (MAD) -Fac. M (MAS) +Landfill [EPRI]CCW FGD [EPA]Ash & Coal Waste [EPA]Se (!g/L)

Max Min own pH MCL = 50

! g/L

Fly!! Ash!!!!!!!!!!!!!!!!! |!!! Scrubber Sludge!!!!!!!!!!! |!!!!!!!!!!!!!!!! Gypsum!!!!!!!!!!!!!! | Fixated Scrubber Sludge

Nat. Ox. Nat. Ox.!!!!!! | I. Ox. Nat. Ox. Forced Ox.



### Figure 57 and Figure 58. Molybdenum and Selenium. Comparison of maximum, minimum and natural pH concentrations observed in SR02 and SR03 extracts over the pH domain 5.4 ! pH ! 12.4. (key: - = NOx control off; + = NOx control o n; U = unwashed gypsum; W = washed gypsum; Nat. Ox. = natural oxidation; Forced Ox. = forced oxidation; I.Ox. = inhibited oxidation).

### Characterization of Coal Combustion Residues II



### 84 0.1 1.0 10.0 100.0 1,000.0Fac. A (CFA) -Fac. A (AFA) +Fac. B (DFA) -Fac. B (BFA) +Fac. K (KFA) +CCW Ash [EPA]Fac. A (CGD) -Fac. A (AGD) +Fac. B (DGD) -Fac. B (BGD) +Fac. K (KGD) +Surface Imp. [EPRI]Fac. N (NAU) +UFac. N (NAW) +WFac. O (OAU) +UFac. O (OAW) +WFac. P (PAD) +UFac. Q (QAU) +UFac. A (CCC) -Fac. A (ACC) +Fac. B (DCC) -Fac. B (BCC) +Fac. K (KCC) +Fac. M (MAD) -Fac. M (MAS) +Landfill [EPRI]CCW FGD [EPA]Ash & Coal Waste [EPA]Tl (!g/L)

Max Min own pH MCL = 2

! g/L

Fly!! Ash!!!!!!!!!!!!!!!!! |!!! Scrubber Sludge!!!!!!!!!!! |!!!!!!!!!!!!!!!! Gypsum!!!!!!!!!!!!!! | Fixated Scrubber Sludge

Nat. Ox. Nat. Ox.!!!!!! | I. Ox. Nat. Ox. Forced Ox.



### Figure 59. Thallium. Comparison of maximum, minimum a nd natural pH concentrations observed in SR02 and SR03 extracts over the pH domain 5.4 ! pH ! 12.4. (key: - = NOx control off; + = NOx control on; U = unwashed gypsum; W = washed gypsum; Nat. Ox. = natural oxidation; Forced Ox. = forced ox idation; I.Ox. = inhibited oxidation).

### Characterization of Coal Cumbustion Residues II



## 4. SUMMARY OF RESULTS, CONCLUSIONS AND RECOMMENDATIO NS

The following sections present conclusions from the results presented in this report.

Tables 8 through 11 summarize the results obtained from this study for fly ash, FGD gypsum, scrubber sludge, and FSS, respectively. The set of 23 CCRs evaluated in this report reflects 84 and 74 percent, respectively, of the current and fu ture facility configuration types with acid gas scrubbers based on generating capacity, but only a limited number of facilities within each configuration type. Each table provides the following att ributes, and associated ranges, related to each material type and constituent examined:

1. Total content (mg/kg, dw) from acid digestion.

2. The minimum and maximum elemental concentrations m easured in laboratory leaching

test extracts over the domain of 5.4 ! pH ! 12.4 from leaching evaluation as a function of pH at LS=10 mL/g (SR002.1) and as a function of 0.5 ! LS ! 10 mL/g dw (SR003.1). This range is intended to represent the potential range of leachate concentrations expected to be observed in the field from management of each of the material types in monofilled management conditions. Concentration ranges for ind ividual samples of each material type are compared in Section 3.3.2.

3. The minimum and maximum elemental concentrations m easured in laboratory leaching

test extracts when extracted with deionized water o nly (“natural pH”) and 0.5 ! LS ! 10 mL/g dw (SR003.1). The resulting pH range is also indicated

. 4. The MCL or DWEL and TC (as available) for each con stituent to provide reference

concentrations for evaluation of the concentration results summarized as described above. However, the expected leachate concentration ranges derived directly from laboratory testing and probabilistic assessments do not includ e any dilution and attenuation that may occur prior to impacting water resources. Previous studies have indicated dilution and

attenuation factors of as low as 2 to 10 on a natio nal basis or as high as 8,000 at a particular site 25 

### . Thus, comparisons with the MCL, DWEL or TC for an y constituent

must be done with caution.

5. Variability in extract concentration as a function of pH based on results from laboratory leaching testing (SR002.1). Classification of varia bility is as follows: (a) Low = concentration range ! 1 order of magnitude, (b) Med. = concentration ran ge of 1 to 2 orders of magnitude, (c) High = concentration range of >2 orders of magnitude.

In addition, results are emphasized through coding as follows:

1. Expected concentration values that exceed either t he MCL or DWEL for the given

constituent are in red bold typeface

. 2. Constituents are underlined in the column heading (e.g., Cd in Table 9) when one of the expected concentration ranges exceeds either the MCL or DWEL.

25 

### See Section 3.3.



### 85

### Characterization of Coal Combustion Residues II



### Based on the results of testing and evaluations in this study, the following conc lusions are drawn:

1. For each CCR type the following constituents excee ded either the maximum contaminant level (MCL) or drinking water equivalent level (DWE L) in at least one laboratory leaching test condition over the range of pH and LS ratios considered, and therefore potentially may present unacceptable environmental risks under some management

scenarios. These cases warrant more detailed evalua tion, including consideration of sitespecific conditions.

a. Fly ash – antimony, arsenic, boron, cadmium, chr omium, molybdenum, selenium

and thallium.

b. FGD gypsum – boron, cadmium, molybdenum, selenium and thallium.

c. Scrubber sludge – mercury, antimony, arsenic, bo ron, chromium, lead, molybdenum, selenium and thallium.

d. Fixated scrubber sludge – mercury, antimony, arsen ic barium, boron, cadmium, chromium, lead, molybdenum, selenium and thallium.

However, (i) typically, evaluation results from onl y a subset of samples of a given material type exceeded the indicated criteria, (ii) never did the full range reported exceed the indicated threshold, and (iii) this analysis does not account for additional dilution and attenuation processes that may occur under field management scenarios. These results suggest that (i) consideration of dilution and attenuation factors for specific management scenarios may indicate that rel ease concentrations may be higher than exposure concentrations, and that relea se concentrations above the MCL or DWEL may not result in exposure concentrations a bove those levels; (ii) linear partition coefficients (Kds) are not appropriate fo r representing source term release from CCRs for a range of constituents and materials ; and, (iii) evaluation of individual CCR sources may indicate that the enviro nmental compatibility of specific types of CCRs with general management scenarios wil l depend on the source (reflected through leaching characteristics) of the ma terial.

2. Leaching of individual constituents may vary over several orders of magnitude, depending on the conditions of the management scenario. Thus, these re sults can be used to suggest design conditions that would reduce or m inimize constituent release (e.g., pH, and other conditions).

3. Leaching concentrations do not correlate with tota l content except for specific

constituents in selected materials where the consti tuent (a) is weakly retained, and (b) leaching concentrations have a low variability rela tive to pH. Thus, total content is not a good indicator of leaching.

4. Results of this study suggest that it appears that Cr leachability is associated with the use of post-combustion NOx controls. This is based on a limited set of paired samples from the same facility operating with and with SCR or SN CR in use. This finding will be

further evaluated as additional data are collected.

5. The systematic leaching behavior of COPCs observed in the range of samples evaluated suggests that the geochemical mechanisms controllin g leaching can be discerned and

86

### Characterization of Coal Cumbustion Residues II



### quantified using geochemical speciation modeling, w hich in turn, can serve as the basis for evaluating and improving design of CCR manageme nt scenarios. Development of generalized geochemical speciation models for the m aterials evaluated in this study is

recommended.

6. Ranges of concentrations of some constituents in l aboratory leaching test extracts and field data included in this study suggest applicabl e concentration ranges for risk

evaluation are different from the concentration ran ges used in a recent report by USEPA (EPA, 2007). The new information reported here will help provide a more up-to-date and comprehensive dataset for future risk assessments.

87Characterization of Coal Combustion Residues IITable 8. Fly Ash. Summary of results.Hg Sb As Ba B Cd Cr Co Pb Mo Se TlTotal in Material(mg/kg)0.04 -0.63 - 15 70 - 90600 -1,500NA0.71.5- 100 -20020 - 50 40 - 90 10 - 20 2 - 30 3 - 13Leaching test and assessment resultsConc. Rangefor5.4!pH!12.4<0.01- 0.5<0.3 -2007 -30090 -4,000200 -300,000<0.230- 1 -4,000<0.3 -200<0.2 -2100 -40,0007 -400<0.3 -300(μg/L)Conc. range atnatural pH(7.7!pH!11.1)<0.01– 0.4<0.3 -507 -7590 –4,000300 –300,000<0.230- 20 –4,000<0.3 -20<0.2 –0.7400 –40,0007 -400<0.3 -300MCL (or DWEL)(μg/L)2 6 10 2,0007,000DWEL5 100 - 15200DWEL50 2TC (μg/L) 200 - 5,000 100,000 6,500 1,000 5,000 5,000 5,000 -1,000 -Variabilityrelative to pHLowtoHighMed.ToHighLow toMed.LowMed. toHighHighLow toMed.High Med.Low toMed.Low toMed.Med.NA – not analyzed (total content for boron estimated based on leaching test results); ND – not determined.88Characterization of Coal Cumbustion Residues IITable 9. FGD Gypsum. Summary of results.Hg Sb As Ba B Cd Cr Co Pb Mo Se TlTotal inMaterial(mg/kg)0.01 -0.52 - 6 2 - 4 3 - 60 NA0.30.5-6 -20 1 - 4 1 -12 2 - 12 2 - 30 0.6 - 2Leaching test and assessment resultsConc. Rangefor5.4!pH!12.4(μg/L)<0.01- 0.1<0.3 -9<0.5 -1040 -40040 -70,000<0.250- <0.3 -50<0.6 -50<0.2 -101 -4004 -3,000<0.3 -20Conc. rangeat natural pH(3.8!pH!8.1)<0.01– 0.1<0.3 -15<0.5 -940 -15040 –70,000<0.215- <0.3 -201 - 50<0.2 -123 -4004 –3,000<0.3 -20MCL (orDWEL whereindicated)(μg/L)2 6 10 2,0007,000DWEL5 100 - 15200DWEL50 2TC (μg/L) 200 - 5,000 100,000 6,500 1,000 5,000 5,000 5,000- 1,000 -Variabilityrelative to pHLow -Med.LowLow -Med.LowLow -Med.HighMed. -HighLow Low LowLow -Med.LowNA – not analyzed (total content for boron estimated based on leaching test results); ND – not determined.89Characterization of Coal Combustion Residues IITable 10. Scrubber Sludge. Summary of results.Hg Sb As Ba B Cd Cr Co Pb Mo Se TlTotal in Material(mg/kg)0.04 –0.64 - 15 4 - 4080 –2,500NA0.3 –1.59 - 350 1 - 40 2 - 30 9 - 30 2 - 4 2- 12Leaching test and assessment resultsConc. Rangefor5.4!pH!12.4(μg/L)<0.01-9<0.3 -200.6 -10020 –2,00020 –200,000<0.2 -4<0.8 -800<0.3 -250<0.2 -250.4 –1,5002 -300<0.3 -100Conc. range atnatural pH(6.5!pH!11.0)<0.01– 0.07<0.3 -100.6 -2030 -95020 –200,000<0.2 -42 -800<0.3 -60<0.2 -2510 –1,5002 -2002 -90MCL (or DWELwhere indicated)(μg/L)2 6 10 2,0007,000DWEL5 100 - 15200DWEL50 2TC (μg/L) 200 - 5,000 100,000 6,500 1,000 5,000 5,000 5,000 -1,000 -Variabilityrelative to pHLow -HighLow -Med.Med. -HighLow -Med.Low -HighHigh Low High LowLow -HighMed. HighNA – not analyzed (total content for boron estimated based on leaching test results); ND – not determined.90Characterization of Coal Cumbustion Residues IITable 11. Fixated Scrubber Sludge. Summary of results.Hg Sb As BaBCd Cr Co Pb Mo Se TlTotal in Material(mg/kg)0.02 -1.05 - 20 3 - 7080 -1,000NA 0.7 - 240 -1502 - 50 4 - 100 9 - 30 2 - 30 0.8 - 8Leaching test and assessment resultsConc. Rangefor5.4!pH!12.4(μg/L)<0.01-30<0.3 -2000.5 -4,0009 -10,0006 -200,000<0.2 -20<0.3 -2,000<0.3150- <0.2 -5010 -40,0009 -1,0002 -100Conc. range atnatural pH(5.8!pH!12.3)<0.01– 0.7<0.3 -600.5 –4,00015 –10,000100 –200,000<0.2 -20<0.3 –2,000<0.350- <0.2 -5010 –40,0009 -5003 - 50MCL (or DWELwhere indicated)(μg/L)2 6 10 2,0007,000DWEL5 100 - 15200DWEL50 2TC (μg/L) 200 - 5,000 100,000 6,500 1,000 5,000 5,000 5,000 -1,000 -Variabilityrelative to pHLow -HighLow -HighMed -HighLow -Med.HighLow -HighLow High Low LowLow -Med.Low -Med.NA – not analyzed (total content for boron estimated based on leaching test results); ND – not determined.91

### Characterization of Coal Combustion Residues II



## 5. REFERENCES

ACAA (American Coal Ash Association), 2007. 2006 Coal Combustion Product (CCP) Production and Use Survey. http://www.acaa-usa.org/CCPSurveyShort.htm (accessed May 2008).

ASTM, 2002. Method D 6784-02, “Standard Test Methodfor Elemental, Oxidized, ParticleBound, and Total Mercury in Flue Gas Generated fromCoal-Fired Stationary Sources (OntarioHydro Method).” American Society for Testing and Materials, 2002.

Clean Air Mercury Rule. Code of Federal Regulations, 70 FR 28606; May 18, 2005.

Clean Air Interstate Rule. Code of Federal Regulations, 70 FR 25162; May 12, 2005.

DOE-EIA (Official Energy Statistics from the U.S. G overnment - Energy Information Administration), 2007. Annual Energy Outlook 2007 with Projections to 2030

. http://www.eia.doe.gov/oiaf/aeo/index.html (accessed November 2007).

Duong, D. Do., 1998. Adsorption Analysis: Equilibria and Kinetics, London: Imperial College Press, 1998, 892 p.

EPA, 1988. Report to Congress – Wastes from the Combustion of Coal by Electric Utility Power

Plants , EPA/530-SW-88-002. Washington, DC: U.S. Environme ntal Protection Agency, Office of Solid Waste and Emergency Response, 1988.

EPA, 1996. Method 3052, “Microwave Assisted Acid Digestion of Siliceous and Organically Based Matrices.” Test Methods for Evaluating Solid Waste, Physical/Chemical Methods (SW846). U.S. Environmental Protection Agency, 1996.

EPA, 1998a. Method 7470A, “Mercury in Liquid Waste (Manual Cold-Vapor Technique).” Test Methods for Evaluating Solid Waste, Physical/Chemic al Methods (SW-846). U.S. Environmental Protection Agency, 1998.

EPA, 1998b. Method 7473, “Mercury in Solids and Sol utions by Thermal Decomposition, Amalgamation, and Atomic Absorption Spectrophotomet ry.” Test Methods for Evaluating Solid Waste, Physical/Chemical Methods (SW-846). U.S. Environ mental Protection Agency, 1998.

EPA, 1999. Report to Congress-Wastes from the Combustion of Fo ssil Fuels: Volume 2- Methods, Findings and Recommendations, EPA 530-R-99-010. Washington, DC: U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, 1999.

EPA, 2000. Characterization and evaluation of landfill leachat e , Draft Report. 68-W6-0068. U.S. Environmental Protection Agency, September 2000.

Kilgroe, J., C. Sedman, R. Srivastava, J. Ryan, C.W . Lee, S. Thorneloe, 2001. Control of Mercury Emissions from Coal-Fired Electric Utility Boilers: Interim Report, EPA-600/R-01- 109, Dec. 2001.

EPA, 2002. Characterization and Management of Residues from Co al-Fired Power Plants, Interim Report, EPA-600/R-02-083. U.S. Environmental Protection Ag ency, December 2002.

EPA, 2003. Technical Support Document for the Assessment of De tection and Quantitation Approaches. U.S. Environmental Protection Agency, 2003. Availa ble at http://epa.gov/waterscience/methods/det/index.html . (accessed June 2008).

92

### Characterization of Coal Cumbustion Residues II



### EPA, 2005. Control of Mercury Emissions from Coal Fired Electr ic Utility Boilers: An Update

. Air Pollution Prevention and Control Division, Nati onal Risk Management Research Laboratory, Office of Research and Development, U.S. Environmen tal Protection Agency, Research Triangle Park, NC, Feb 18, 2005. http://www.epa.gov/ttn/atw/utility/ ord_whtpaper_hgcontroltech_oar-2002-0056-6141.pdf (accessed May 5, 2005).

EPA, 2006. 2006 Edition of the Drinking Water Stand ards and Health Advisories. EPA 822-R06-013 (updated August, 2006). Office of Water, U.S. Environmental Protection Agency. Washington, DC.

EPA, 2007. Human and Ecological Risk Assessment of Coal Combustion Wastes. Docket # EPA-HQ-RCRA-2006-0796; Docket Item# EPA-HQ-RCRA-2006-0796-0009. Released as part of notice of data availability on August 29, 2007; http://www.epa.gov/epaoswer/other/fossil/noda07.htm

. EPRI, 2005. Personal communication of Electric Powe r Research Institute (EPRI) leaching database (as of June 2005); summary information fro m K. Ladwig to D. Kosson.

EPRI, 2006, Characterization of Field Leachates at Coal Combustion Product Management Sites: Arsenic, Selenium, Chromium, and Mercury Spe ciation, EPRI Report Number 1012578. Electric Power Research Institute (EPRI), Palo Alto , CA and U.S. Department of Energy, Pittsburgh, PA, 2006.

Hensel, B., 2006. Sampling and Analysis Plan for Plant 14090, EPRI SAP1674. Electric Power Research Institute (EPRI), 2006.

Hutson, N.D., 2008. Mercury Capture on Fly Ash and Sorbents: The Effects of Coal Properties and Combustion Conditions, Water Air Soil Pollut: Focus (2008) 8:323-331.

Kilgroe, J., C. Sedman, R. Srivastava, J. Ryan, C.W . Lee, S. Thorneloe. Control of Mercury Emissions from Coal-Fired Electric Utility Boilers: Interim Report, EPA-600/R-01-109, Dec.

2001.

Kosson, D. S., H. A. van der Sloot, F. Sanchez, and A. C. Garrabrants, 2002. An Integrated Framework for Evaluating Leaching in Waste manageme nt and Utilization of Secondary

materials. Environmental Engineering Science 19(3):159-204 (2002).

Laudal, D.L., J.S. Thompson, C.A. Wocken (2004) Selective Catalytic Reduction Mercury Field Sampling Project

, EPA-600/R-04-147, November 2004.

Ladwig, K. Personal communication , Nov. 15, 2007.

MTI (McDermott Technology, Inc.), 2001. Mercury Emissions Predictions

. http:// www.mtiresearch.com/aecdp/mercury.html#Coal%20Analy ses%20and%20Mercury%20Emissio

ns%20Predictions (accessed November 2002).

Munro, L. J., K. J. Johnson, and K. D. Jordan, 2001 . An interatomic potential for mercury

dimmer. Journal of Chemical Physics 114(13): 5545-5551 (2001).

Rudzinski, W., W. A. Steele, and G. Zgrablich, 1997

. Equilibria and dynamics of gas adsorption on heterogeneous solid surfaces , Amsterdam: Elsevier, 1997.

Ruthven, D. M., 1984. Principles of Adsorption and Adsorption Processes, New York: Wiley, 1984, 433 p.

93

### Characterization of Coal Combustion Residues II



### Pavlish, J. H., E. A. Sondreal, M. D. Mann, E. S. O lson, K. C. Galbreath, D. L. Laudal, and S. A Benson, 2003. Status Review of Mercury Control Options for Coal-Fired Power Plants. Fuel Processing Technology 82: 89-165 (2003).

SAB (EPA Science Advisory Board, Environmental Engi neering Committee), 2003. “TCLP Consultation Summary.” Presented at the Science Advisory Board (SAB) Environmental Engineering Committee consultation with U. S. Envir onmental Protection Agency , Washington, D.C., June 17-18, 2003.

Sanchez, F., and D. S. Kosson, 2005. Probabilistic approach for estimating the release of contaminants under field management scenarios. Waste Management 25(5), 643-472 (2005).

Sanchez, F., R. Keeney, D. S. Kosson, and R. Delapp , 2006. Characterization of MercuryEnriched Coal Combustion Residues from Electric Uti lities Using Enhanced Sorbents for Mercury Control, EPA-600/R-06/008. Prepared for the U.S. Environmenta l Protection Agency – Air Pollution Prevention and Control Division, Contract No. EP-C-04-023, Work Assignment 1- 31, February 2006. www.epa.gov/nrmrl/pubs/600r06008/600r06008.pdf

Srivastava, R.K., W. Jozewicz, 2001. Flue Gas Desu lfurization: The State of the Art. Journal of Air and Waste Management 51, 1676-1688.

Srivastava, R.K., N. Hutson, B. Martin, F. Princiotta, J. Staudt, 2006. Control of Merc ury Emissions from Coal-Fired Electric Utility Boilers, Environmental Science & Technology, 41

, 1385.

Thorneloe, S., 2003. “Application of Leaching Proto col to Mercury-Enriched Coal Combustion Residues”, Presentation to the U. S. Environmental Protection Agency (EPA) Science Advisory Board (SAB), Environmental Engineering Committee, Washin gton, D.C., June 17, 2003.

Thorneloe, S., 2006. Evaluating Life-Cycle Environmental Tradeoffs from the Management of Coal Combustion Residues Containing Mercury and Oth er Metals, Thesis for Masters of Environmental Management, Nicholas School of the En vironment and Earth Sciences, Duke University, May 2006.

Thorneloe, S., D. Kosson, F. Sanchez, B. Khan, P. Kariher, 2008. Improved Leach Testin g for Evaluating the Fate of Mercury and Other Metals fro m Management of Coal Combustion Residues, Proceedings for the Global Waste Manageme nt Symposium, Copper Mountain Conference Center, Colorado, USA, Sept 7-10, 2008.

Vidic, R.D., 2002. Combined Theoretical and Experimental Investigation of Mechanisms and Kinetics of Vapor-Phase Mercury uptake by Carbonace ous Surfaces, Final Report. Grant No. DE-FG26-98FT40119 to U. S. Department of Energy (DOE), National Energy Technology Laboratory, 2002.

Wang, J., Wang, T., Mallhi, H., Liu, Y., Ban, H. an d Ladwig, K., 2007. The role of ammonia on mercury leaching from coal fly ash. Chemosphere 69:1586-1592.

94