CONTAMINANTS AND REMEDIAL OPTIONS
AT SOLVENT-CONTAMINATED SITES
Roy F. Weston, Inc.
Edison, NJ 08837
Contract No. 68-03-3482
Work Assignment 3-713
Foster Wheeler Enviresponse, Inc.
Edison, NJ 08837
Contract No. 68-C9-0033
Work Assignment 2-R030
Kenneth Wilkowski
Technical Support Branch
Superfund Technology Demonstration Division
Edison, New Jersey 08837
RISK REDUCTION ENGINEERING LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45219
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NOTICE
The information in this document has been funded wholly or in part by the United States Environmental
Protection Agency (U.S. EPA) under contract It has been subjected to the Agency's peer and administrative
review, and it has been approved for publication as a U.S. EPA document Mention of trade names or
commercial productions does not constitute endorsement or recommendation for use.
ii
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FOREWORD
Today's rapidly developing and changing technologies and industrial products and practices frequently carry
with them the increased generation of materials that, if improperly dealt with, can threaten both public health
and the environment. The U.S. Environmental Protection Agency (U.S. EPA) is charged by Congress with
protecting the nation's land, ah-, and water resources. Under a mandate of national environmental laws, the
Agency strives to formulate and implement actions leading to a compatible balance between human activities
and the ability of natural resources to support and nurture life. These laws direct the U.S. EPA to perform
research which defines environmental problems, measures their impacts, and searches for solutions.
The Risk Reduction Engineering Laboratory (RREL) is responsible for planning, implementing, and managing
research, development, and demonstration programs. Further, the RREL provides an authoritative, defensible
engineering basis in support of U.S. EPA policies, programs, and regulations with respect to drinking water,
wastewater, pesticides, toxic substances, solid and hazardous wastes, and Superfund-related activities. This
publication is one of the products of that research, and it provides a vital communication link between the
researcher and the user community.
This guidance document was prepared to assist federal and state remedial project managers, local agencies,
private cleanup companies, and support contractors that may plan and implement remedial actions at National
Priorities List (NPL) and other solvent-contaminated sites. The primary purpose of this document is, to
provide guidance on carrying out concurrent remedial action planning and accelerating project
implementation for the cleanup of solvent-contaminated sites. It is also designed for use in conjunction with
the U.S. EPA's guidance document on conducting remedial investigations and feasibility studies (Guidance
for Conducting Remedial Investigations and Feasibility Studies under CERCLA). This guidance document
will provide the user with a systematic approach to remedial actions for solvent-contaminated sites. However,
mamy unique and potentially hazardous conditions at NPL sites require very specialized considerations.
E. Timothy Oppelt, Director
Risk Reduction Engineering Laboratory
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ABSTRACT
This document provides information which facilitates the selection of treatment technologies and services to
meet established cleanup levels at solvent-contaminated sites. It does not provide risk-assessment information
or policy guidance related to the determination of cleanup levels. It will assist federal, state, or private site
removal! and remedial managers operating within the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA), Resource Conservation and Recovery Act (RCRA), or state rules.
This document is designed for use with other remedial guidance documents issued for RCRA, CERCLA,
and/or other state mandated cleanup activities to accelerate the remediation of solvent-contaminated sites.
Solvents are organic compounds; they are common contaminants found at Superfund sites. They are used
in a variety of industrial and commercial processes, including chemical and product manufacturing, and as
cleaning agents. The improper use, storage, and handling of solvents have resulted in soil, sediment, and
sludge contamination, secondary contamination of underlying soils, and potential groundwater pollution. Most
solvents are amenable to many remediation methods, but the same characteristics which assist remediation
also allow solvent transport through the environment which in turn potentially exposes humans to toxic
compounds.
The remedial manager faces the challenge of selecting remedial options which will achieve established cleanup
levels. Often, more than one technology is implemented in the remediation strategy of a solvent site in order
to meet its cleanup goals. Three general options exist: immobilization, destruction, and
separation/concentration. Separation/concentration technologies prepare pesticides for further remediation
by destruction or immobilization technologies. The remedial manager also adds pre- and post-treatment
components with the principal technology(ies) into treatment trains. In the Remedial Options section of tMs
document, treatment trains are outlined, and examples are given to emphasize their importance to a remedial
strategy.
Section 2, Contamination at Solvent Sites, discusses solvent uses, then* characteristics, and then* behavior in
the environment Section 3, Remedial Options, details innovative and emerging technologies and proven
treatments. It includes a discussion about the implementation and selection of the cleanup technology, names
criteria for the selection of a remediation strategy, and introduces the concept of high-energy destruction
techniques to reach more stringent contaminant residual levels. The technology performance data provided
can assist the remedial manager to narrow the options to those most likely to succeed in achieving site-specific
cleanup goals in the most cost effective and permanent way possible.
Additionally, this remedial aid document provides an extensive bibliography, organized by relevance to each
section, which complements the information offered in these pages.
This report was submitted hi fulfillment of contract number 68-03-3482 by Roy F. Weston, Inc. and contract
number 68-C9-0033 by Foster Wheeler Enviresponse, Inc. under the sponsorship of the U.S. Environmental
Protection Agency. This report covers a period from September 1991 to October 1993, and work was
completed as of September 1994.
EV
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CONTENTS
Page
Notice ii
Foreword iii
Abstract iv
Figures vii
Tables viii
Abbreviations and Symbols x
Acknowledgments -dti
Section 1 Introduction 1
Purpose 1
Organization 3
Treatment Trains 4
Cleanup levels 4
Stages of Technology Development 5
Complementary Bibliography 5
Important references 5
References 8
Section 2 Contaminants at Solvent Sites 10
Historical Uses of Solvents 10
Halogenated Solvents 14
Nonhalogenated Solvents 14
Solvent Uses and Their Residues 14
Paint and Allied Products 20
Surface Cleaning 20
Dry Cleaning 20
Production of Pesticides, Pharmaceuticals, and Other Organic Chemicals . 21
Solvent Production and Uses 21
Liquid Halogenated Solvents 21
Gaseous Halogenated Solvents 21
Liquid Nonhalogenated Solvents 25
Nonchlorinated Phenols 27
Behavior, Fate, and Transport 28
Predicting Contaminant Behavior 28
Transport 33
Locating Free Liquids 36
Transformations 38
References 48
Section 3 Remedial Options 54
Cleanup Goals and Selection of Options 54
Typical Treatment Combinations 55
Treatment Costs 56
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CONTENTS (Continued)
Page
Immobilization Technologies 57
Containment Technology !.!.!!!! 57
Stabilization/Solidification Technologies 61
Destruction Technologies !.'!!!"" 67
Thermal Destruction Technologies 69
Chemical Destruction Technologies 7g
Bioremediation Technologies '.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'. 80
Separation/Concentration Technologies 96
Description of In Situ Technologies 99
Separation/Concentration Technologies for Treatment
of Excavated Soil U2
Water-Treatment Technologies 123
Destruction Technologies for Water Treatment 126
Separation/Concentration Technologies for Water
Treatment
References
Section 4 Bibliography ] " '.'.'.'.'.'.'.'.'.'.'.'.'.'. '
Appendices
A. Treatment Comparisons at Selected Solvent Sites 153
VI
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FIGURES
Number Page
3-1 Schematic for Ex-Situ Solidification/Stabilization of Contaminated Soils 61
3-2 Schematic for Rotary Kiln Incineration of Contaminated Soils, Sediments and
Sludges (Ex-Situ) 70
3-3 Effect Of Site Size on Incinerator Cost 73
3-4 Schematic for Pyrolysis (Ex-Situ) for Contaminated Soils, Sediments, and Sludges .... 76
3-5 Schematic for Dehalogenation (Ex-Situ) of Contaminated Soils, Sediments and Sludges 79
3-6 Schematic for Solid-Phase Bioremediation 83
3-7 Schematic for Slurry-Phase Bioremediation (Ex-Situ) for Contaminated Soils,
Sediments, and Sludges ... 84
3-8 Schematic for In-Situ Bioremediation for Contaminated Soil 86
3-9 Schematic for Bioventing (In-Situ) of Contaminated Soil 88
3-10 Schematic for Vapor Extraction (In-Situ) of Contaminated Soils . 99
3-11 Schematic for Steam Extraction (In-Situ) of Contaminated Soils 105
3-12 Schematic for Radio Frequency Heating of Contaminated Soils 108
3-13 Schematic for Soil Flushing (Iri-Situ) of Contaminated Soils 110
3-14 Schematic for Thermal Desporption (Ex-Situ) for Contaminated Soils, Sediments,
and Sludges 113
3-15 Schematic for Soil Washing of Contaminated Soils, Sediments, and Sludges 117
3-16 Schematic for Solvent Extraction (Ex-Situ) of Contaminated Soils, Sediments,
and Sludges . 120
3-17 Schematic for Chemical Oxidation of Contaminated Groundwater 127
3-18 Schematic for Bioremediation (In-Situ) of Contaminated Groundwater 128
3-19 Schematic for Carbon Adsorption of Contaminated Groundwater 129
3-20 Schematic for Filtration of Contaminated Groundwater 130
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TABLES
Number Page
1-1 Solvents Commonly Found at Solvent-Contaminated Sites 2
2-1 Contaminants Commonly Found at Superfund Sites (Ground-water) 11
2-2 22 Most Frequently Occurring Organic Contaminants in Groundwater 12
2-3 20 Most Frequently Occurring Substances Reported at Final JNPL Sites 1-3
2-4 Consumption of Major Solvents 15
2-5 Priority Solvent Industrial End Uses 17
2-6 End Uses of Selected Chlorinated Solvents in 1987, by Percentage 18
2-7 Production of Solvent Chemicals 19
2-8a Selected Properties of Contaminants Commonly Found at Superfund Sites 29
2-8b Selected Properties of Contaminants Commonly Found at Superfund Sites ......... 30
2-9 Compounds Formed from Transformation of Cj and C2 Halogenated
Hydrocarbons 40
2-10 Laboratory Measurements of Hydrolysis or Dehalogenation Half-lives
of Halogenated Aliphatic Hydrocarbons 43
2-11 In Situ or Estimated Half-lives of Halogenated Aliphatic
Hydrocarbons in Groundwater 44
3-1 Capping Costs , 59
3-2 Vertical Barrier Costs 60
3-3 S/S Metal Treatability Test Results 65
3-4 Factors Affecting S/S Treatment 67
3-5 Typical Treatment Combinations for Destruction Technologies 68
3-6 Applicability of Destruction Technologies to Contaminant Classifications .......... 68
3-7 Incinerator Selections at Solvent Sites 71
3-8 Summary of Performance Data for Incineration 74
3-9 Factors Affecting Incineration Performance 74
3-10 Factors Affecting Pyrolysis Performance . 77
3-11 Factors Affecting Dehalogenation Performance 80
3-12 Summary of Performance Data for Bioremediation 88
3-13 In Situ Bioremediation of Contamination from Solvent Chemicals 89
3-14 Factors Affecting Bioremediation Performance 90
3-15 Factors Affecting Bioremediation Performance 95
3-16 Typical Treatment Combinations for Separation/Concentration Technologies 96
3-17 Applicability of Separation/Concentration Technologies . 98
3-18 SVE Selections at Solvent Sites 100
3-19 Summary of Performance Data for In Situ Soil Vapor Extraction 102
3-20 Factors Affecting SVE Performance 104
3-21 Summary of Performance Data for Steam Extraction 107
3-22 Factors Affecting Steam Extraction Performance 107
3-23 Summary of Performance Data for RF Heating 109
3-24 Factors Affecting RF Heating Performance 109
viii
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TABLES (Continued)
Number Page
3-25 Factors Affecting In Situ Soil Flushing Performance HI
3-26 Full-Scale Performance Results for LT3 System 114
3-27 Summary of Performance Data for Thermal Desorption 114
3-28 Factors Affecting Thermal Desorption Performance 116
3-29 Summary of Performance Data for Soil Washing at Superfund Sites 118
3-30 Factors Affecting Soil-Washing Performance 119
3-31 Summary of Performance Data for Solvent Extraction 122
3-32 Factors Affecting Solvent-Extraction Performance 122
3-33 Effectiveness of Groundwater-Treatment Technologies on Solvent-
Contaminant Groups 125
3-34 Summary of Performance Data for In Situ Air Sparging 133
3-35 Factors Affecting In Situ Air Sparging Performance 133
3-36 Typical Groundwater Treatment Combinations 134
3-37 Water-Treatment Costs 137
3-38 Data Requirements for Water-Treatment Technologies 138
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ABBREVIATIONS AND SYMBOLS
ACL Alternate Concentration Limit
AEB Air Force Base
Ag Silver
APC air pollution control
APEG alkali polyethylene glycol
ARARs Applicable or Relevant and Appropriate Requirements
As arsenic
ATTIC Alternative Treatment Technology Information Center
Ba barium
BCDP base-catalyzed decomposition process
BDAT best demonstrated available technology
BTEX benzene, toluene, ethylbenzene, xylene
BTU British thermal unit
CARD CLP analytical results database
Cd cadmium
CEC cation exchange capacity
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act
CFB circulating fluidized bed
CLP Contract Laboratory Program
CN cyanide
CO2 carbon dioxide
C-N-P carbon-nitrogen-phosphorous
COE , U.S. Army Corps of Engineers
Cr chromium
CT carbon tetrachloride
DCA dichloroethane
DCE dichloroethylene
DNAPL dense nonaqueous-phase liquid
DOE Department of Energy
DOI Department of the Interior
EDB ethylene dibromide
EPA United States Environmental Protection Agency
EPRI Electric Power Research Institute
Fe iron
FWEI Foster Wheeler Enviresponse, Inc.
g gram
GAC granular-activated carbon
GC/MS gas chromatography/mass spectrometry
H2O water
HC1 hydrogen chloride
HOPE high-density polyethylene
HELP hydrologic evaluation of landfill performance
Hg mercury
K potassium
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ABBREVIATIONS AND SYMBOLS (Continued)
Kh
KPEG
L
LEEP
LLNL
LNAPL
LTTA
LT3
MC
MDL
MEK
mg
MIBK
MPEG
MSWRMB
NaPEG
NAPL
NPL
NWWA
OERR
ORD
PAH
Pb
PCB
PCE
PCP
ppb
ppm
PVC
RCRA
RF
RH
RI/FS
RO
RREL
ROD
SCAR
Se
SITE
S/S
SVE
TCA
TCE
TCLP
TPH
USEPA
Henry's law constant
adsorption coefficient
octanol/water partition coefficient
potassium polyethylene glycolate
liter
low energy extraction process
Lawrence Livermore National Laboratory
light nonaqueous-phase liquid
low temperature thermal aeration
low temperature thermal treatment
methylene chloride
method detection limit
methyl ethyl ketone
milligram
methyl isobutyl ketone
methoxypolyethylene glycolate
Municipal Solid Waste & Residuals Management Branch
sodium polyethylene glycolate
nonaqueous-phase liquid
National Priority List
National Water Well Association
Office of Emergency and Remedial Response
Office of Research and Development
polycyclic aromatic hydrocarbons
lead
polychlorinated biphenyls
tetrachloroethylene
pentachlorophenol
parts per billion
parts per million
poly vinyl chloride
Resource Conservation and Recovery Act
radio frequency
RCRA Facility Investigation
remedial investigation/feasibility studies
reverse osmosis
Risk Reduction Engineering Laboratory
Record of Decision
Superfund chemical analysis results
selenium
Superfund Innovative Technology Evaluation
solidification/stabilization
soil-vapor extraction
trichloroethane
trichloroethylene
Toxicity Characteristic Leaching Procedure
total petroleum hydrocarbons
United States Environmental Protection Agency
XI
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ABBREVIATIONS AND SYMBOLS (Continued)
USITC United States Internal Trade Commission
UST underground storage tank
UV ultraviolet
VC vinyl chloride
VOCs volatile organic compounds
xil
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ACKNOWLEDGMENTS
This document is the product of a cooperative effort between the U.S. EPA's Office of Emergency and Remedial
Response (OERR) and the Office of Research and Development (ORD). The text was prepared by Roy F. Weston,
Inc. under U.S. EPA Contract No. 68-03-3482 and Foster Wheeler Enviresponse, Inc. (FWEI) under U.S. EPA
Contract 68-C9-0033 and The EPA Work Assignment Manager was Kenneth WilkowsM of the RREL, Technical
Assistance Section. Gerard Sudell was the FWEI Project Leader and primary author; George Wolf and Ari
Selvakumar served as co-authors.
The authors express their appreciation to the following persons who contributed portions of major sections: John
Matthews of the Robert S. Kerr Environmental Research Laboratory, Ada, Oklahoma (Contaminants at Solvent Sitss);
Robert Landreth, Patricia Erickson, and Carlton Wiles of RREL (Remedial Options).
Special recognition is paid to Frank Freestone of RREL for his ongoing support, suggestions, and technical insight.
The following U.S. EPA reviewers contributed to the depth of this report through comments based on their
considerable expertise:
Michelle Simon of RREL, Mark Meckes of RREL, Paul de Percin of RREL, Robert Landreth of RREL, John
Matthews of RREL, Mary Stinson of RREL, Richard Koustas of RREL, Michael Royer of RREL, Andrew Zownir
of the Environmental Response Team, Gregory Sayles of RREL, Abraham Chen of Battelle, James Yezzi of RREL
Patricia Erickson of RREL, and Chi-Yuan Fan of RREL
The authors express their appreciation to Walter Vassar, editor, Michelle DeFort, word processor, and Pacita Tibay
graphics illustrator.
Additionally, thanks are extended to all those who contributed information and their time toward the completion of
the Appendix section of this document.
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SECTION 1
, INTRODUCTION
PURPOSE
Tihis document provides federal, state, and local Remedial Project Managers (RPMs), On-Scene Coordinators
(OSCs), private cleanup companies, and support contractors with data concerning solvent contaminants. Sources and
types of solvent contaminants, their characteristics, and their behavior in the environment will be named, and
remedial options, i.e., principal proven and innovative technologies selected for solvent sites will be described. It
is designed for use with other remedial guidance documents issued for Resource Conservation and Recovery Act
(RCRA), Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), and/or state
cleanups to accelerate solvent site cleanup. The authors assume the reader is familiar with the appropriate policy
issues (RCRA, CERCLA, state), risk assessment, and the determination of cleanup guidelines.
A1992 review of the record of decision (ROD) summary database revealed over 400 sites where solvents were
identified as a site contaminant. Remedial managers typically can expect sites to contain mixtures of solvents, other
organics, and metals. Within this document, solvents are divided into halogenated and nonhalogenated species.
Table 1-1 lists solvents commonly found at solvent-contaminated sites.
This text emphasizes source identifications: primary, such as a surface spills, and secondary, such as a
subsurface migration from the primary source. "Source" in this use can mean the following:
• Process or equipment generating the contamination
Contaminated soil, sludge, or sediment migrating from contamination
• Migrated surface/subsurface water contamination
This approach allows the remedial manager to target remediation in terms of contaminated zones. For
example, the remedial manager may consider the relative practicality of remediating a highly contaminated surface
zone versus a deeper, less contaminated zone. The manager may achieve significant contaminant and exposure
reductions at a lower cost by remediating a more accessible zone before a less accessible one.
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TABLE 1-1. SOLVENTS COMMONLY FOUND AT
SOLVENT-CONTAMINATED SITES
BOAT
Class
W01m
W04
W07
W09
Class
Description
Halogenated non-polar aromatics
Halogenated aliphatics
Heterocyclics & simple nonhalogenated
aromatics
Other polar organic compounds
Specific Contaminants
Found at Solvent-
Contaminated Sites
1,2-Dichlorobenzene
Chlorobenzene
1,1,2,2-Tetrachloroethane
1,1,1-Trichloroethane (TCA)
1,1,2-Trichloroethane
1,1-Dichloroethane (DCA)
1,2-Dichloroethane
1,2-Dichloropropane
Dichlorodifluoromethane
Carbon tetrachloride
Chloroethane
Chloroform
Chloromethane
Ethylene dibromide
Methylene chloride (MC)
Tetrachloroethylene (PCE)
Trichloroethylene O~CE)
Trichlorofluoromethane
Vinyl chloride (VC)
1,1 -Dichloroethene
1,2-Dichloroethene (trans-1,2-
dichloroethene)
Benzene
Ethylbenzene
o-Xylene
p-xylene
Styrene
Toluene
m-Xylene
1,4-Dioxane
Acetone
Cresols
Phenol
Cyclohexanone
Ethyl acetate
Isobutanol
Methanol
Methyl ethyl ketone (MEK)
Methyl isobutyl ketone (MIBK)
Tetrahydrofuran
(1> "W" codes obtained from Summary of Treatment Technology Effectiveness for Contaminated Soil, EPA/540/2-
89/053 <».
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First, this strategy should mitigate the most toxic/mobile materials, and later, the less toxic/mobile ones. The
remedial manager also should consider the risk to human health when determining the remediation strategy and how
to control contaminant migration.
The remedial manager can anticipate the presence of sediment and sludge. Natural water bodies such as ponds
and streams can become contaminated directly as holding ponds/lagoons, or secondarily by the migrating of solvent
compounds. Usually, pretreatment dewatering allows sediment to be processed as a soil. Sludge from lagoon
bottoms and processing equipment also requires treatment; however, the options for treating sludge are more
limited.
ORG4JSIZATION
Specifically, this document is concerned with the treatment of soils contaminated with solvents; the
technology descriptions address soil remediation. It identifies the most important uses of solvents, presents factors
to predict their behavior in the environment, and identifies treatment options to remediate solvent-contaminated sites.
The Remedial Options section describes the four principal treatment groups for the solvent media/
contaminant matrix.
* Immobilization technologies minimize migration, either through construction of physical barriers,
through chemical reaction, or by a combination of physical and chemical means.
« Destruction technologies use thermal, chemical, or biological mechanisms to alter toxicity.
« Separation/concentration technologies use physical or chemical processes to separate contaminants
from the associated media without altering the contaminant's toxicity or mobility.
» Water-treatment technologies treat surface water, groundwater, and the process residuals from the applied
technology groups.
The presentation of the technologies in this document is not an indication of the relative importance or success
of the technology. The Remedial Options section stresses the use of treatment trains to achieve cleanup levels.
It also introduces the concept of high-energy destruction techniques to reach stringent contaminant residual levels
versus lower energy techniques for less rigorous cleanup requirements. The remedial manager can use the
technology performance data to narrow the options to those most likely to succeed in achieving site-specific cleanup
goals.
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Descriptions of remedial options include innovative and emerging technologies as well as proven treatments.
The Water-Treatment section options provide only a brief overview of remedial techniques because they have
already been discussed in other U.S. EPA publications referenced in Section 3 - Remedial Options - Water
Treatment.
Treatment Trains
Generally, no single technology can remediate an entire solvent site; remediation often requires a combination
of control and treatment options to achieve toxicity reduction and/or contaminant immobilization. This treatment
train concept combines incremental or sequential control and treatment technologies to achieve site-specific
objectives and acceptable residual contaminant levels. The technical data and technology-specific considerations
addressed in the Remedial Options section aids in the selection of alternatives that will maximize the benefits of
the treatment train approach at a particular site.
Cleanup Levels
Cleanup levels are usually determined by risk assessment and compliance with applicable or relevant and
appropriate requirements (ARARs). Although this document does not discuss the process for establishing cleanup
levels, the remedial manager faces the challenge of selecting remedial options that meet these established cleanup
levels. Two available options are destruction or immobilization. Separation/concentration technologies prepare
solvent waste matrices for either destruction or immobilization.
Cleanup goals are more stringent for remediation technologies selection when they are based on carcinogenic
compounds and/or residential exposures because of the increased health risks and potential for contact with the
contaminants. For stringent cleanup levels, the selected remedial option will probably require high-energy input,
such as incineration or pyrolysis. When less stringent cleanup levels are acceptable, a low-energy technology such
as soil vapor extraction may be more appropriate.
The Remedial Options section of this document focuses on technologies that can meet a required cleanup
levels. Many factors can influence a cleanup level, including the toxicity of contaminants, location and future use
of the site, and hydrogeology. Several criteria also influence the remedy choice, including feasibility, ease of
implementation, and cost.
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Stages of Technology Development
The technologies discussed in this document are in different developmental stages: proven, innovative, and
emerging. Some, such as incineration and capping, have been proven at commercial scale. Others, such as
microbial degradation and soil flushing, are less proven, or innovative, and will require site-specific treatability tests
to ensure they can meet the established cleanup levels. Emerging technologies, such as horizontal barriers, have
yet to be shown effective in site remediation. The descriptions provided in the Remedial Options section will
familiarize the manager with the newer technologies. This section also offers performance data and treatability
study results (where available) for contaminants found at solvent sites or for analogous compounds.
COMPLEMENTARY BIBLIOGRAPHY :
For the remedial manager who wishes to delve into specific topics, a comprehensive bibliography, organized
to correspond with each section, is provided in Section 4 of this document.
IMPORTANT REFERENCES
The authors assume the remedial manager is already familiar with appropriate policy issues (RCRA,
CERCLA, state), risk assessment, the determination of cleanup levels, and (as appropriate) with the references listed
below.
Policy
Corrective Action for Solid Waste
Management Units at Hazardous Waste
Management Facilities; Proposed Rule.
55 FR 145, July 27, 1990®.
Proposed Subpart S rule which defines
requirements for conducting remedial
investigations and selecting and implementing
remedies at RCRA facilities.
Technical
Guidance for Conducting Remedial
Investigations and Feasibility Studies
Under CERCLA ® EPA/540/G-89/004.
Provides the user with an overall understanding
of the remedial investigation/feasibility study
(RI/FS) process.
Guide for Conducting Treatability
Studies Under CERCLA (currently under
revision) (4) EPA/540/2-91/13a.
Describes the necessary steps in conducting
treatability studies to determine the effective-
ness of a technology in remediating a CERCLA site.
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U.S. EPA Guide for Conducting Treatability
Studies Under CERCLA: Aerobic
Biodegradation Remedy Screening Guide ffl>
EPA/540/2-91 /13a.
Describes the necessary steps in conducting
treatability studies specifically for aerobic
biodegradation remedy screening.
U.S. EPA Guide for Conducting Treatability
Studies Under CERCLA: Soil-Vapor
Extraction (6> EPA/540/2-911019a.
Describes the necessary steps in conducting
treatability studies for assessing the applicability
of soil vapor extraction.
U.S. EPA Guide for Conducting Treatability
Studies Under CERCLA: Soil Washing m
EPA/540/2-91/002a.
Describes the necessary steps in conducting
treatability studies for assessing the applicability
of soil washing.
U.S. EPA Guide for Conducting Treatability
Studies Under CERCLA: Chemical
Dehalogenation <*> EPA/540/R-92/013a.
Describes the necessary steps in conducting
treatability studies for assessing the applicability
of chemical dehalogenation.
Handbook on In Situ Treatment of ,
Hazardous Waste Contaminated Soils
EPA/540/2-90/002.
Provides state-of-the-art information on in situ
technologies for use on contaminated soils.
Summary of Treatment Technology
Effectiveness for Contaminated Soila)
EPA/540/2-89/053.
Presents information on a number of treatment
options that apply to excavated soils, and
explains the BOAT contaminant classifications.
Technology Screening Guide for
Treatment of CERCLA Soils and Sludges™
EPA/540/2-88/004.
Contains information on technologies which may
be suitable for the management of soil and sludge
containing CERCLA waste.
RCRA Facility Investigation (RFI)
Guidance (Volumes 1 through 4) (11),
EPA 530/SW-89-031.
Recommends procedures for conducting an
investigation, and for gathering and interpreting
the data.
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la addition, U.S. EPA has also published engineering bulletins on topics that discuss single technologies,
including the following: \
Chemical Dehalogenation Treatment: APEG Treatment
Chemical Oxidation Treatment
Air Stripping of Aqueous Solutions
Granular Activated Carbon Treatment
In Situ Soil-Vapor Extraction Treatment
In Situ Steam Extraction Treatment
In Situ Soil Flushing
Mobile/Transportable Incineration Treatment
Soil Washing Treatment
Solvent Extraction Treatment
Slurry Biodegradation
Thermal Desorption Treatment
U.S. EPA documents may be obtained from the National Technical Information System (NTIS). The U.S.
EPA Publications Bibliography cross references U.S. EPA publication numbers and titles with NTIS order numbers,
as well as price codes.
Much information is being collected in data bases for quick retrieval. Many of these can be found in the
following documents:
The Federal Database Finder 'J2;.
A comprehensive listing of federal databases and data
files.
Technical Support Services for
Superfund Site Remediation a3).
Identifies technical support services available
to field staff.
Bibliography of Federal Reports
and Publications Describing Alternative
and Treatment Technologies for
Corrective Action and Site Remediation °4).
Contains references for documents and reports
from U.S. EPA, COE, U.S. Navy, U.S. Air Force,
DOE, and DOI.
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Bibliography of Articles from
On-Line Databases Describing
Alternative and Innovative
Technologies for Corrective Action
and Site Remediation I1B>
Provides information for U.S. EPA remedial
managers and contractors who are evaluating
cleanup remedies.
Alternative Treatment Technology
Information Center (ATTIC) °6).
A compendium of information from many
available databases. Data relevant to the use of
treatment technologies in Superfund actions are
collected and stored in ATTIC.
REFERENCES
1. U.S. EPA (U.S. Environmental Protection Agency). 1989. Summary of Treatment Technology Effectiveness
for Contaminated Soil. Office of Emergency and Remedial Response, Washington, D. C. EPA/540/2-89/053.
2. "Corrective Action for Solid Waste Management Units at Hazardous Waste Management Facilities: Proposed
Rule," 55 Federal Register 30798. (27 July 1990) n. page.
3. U.S. EPA. 1988. Guidance for Conducting Remedial Investigations and Feasibility Studies Under CERCLA.
Office of Emergency and Remedial Response, Washington, D.C. EPA/540/G-89/004.
U.S. EPA. 1989. Guide for Conducting Treatability Studies Under CERCLA - Interim Final. Office of Solid
Waste and Emergency Response, Washington, D.C. EPA/540/2-89/058.
U.S. EPA. 1991. Guide for Conducting Treatability Studies Under CERCLA: Aerobic Biodegradation Remedy
Screening Guide. Office of Solid Waste and Emergency Response, Washington, D.C. EPA/540/2-9l/13a.
U.S. EPA. 1991. Guide for Conducting Treatability Studies Under CERCLA: Soil Vapor Extraction. Office
of Emergency and Remedial Response, Washington, D.C. EPA/540/2-9l/019a.
4.
5.
6.
7.
8.
9.
U.S. EPA. 1991. Guide for Conducting Treatability Studies Under CERCLA: Soil Washing. Office of
Emergency and Remedial Response, Washington, D.C. EPA/540/2-9l/020a.
U.S. EPA. 1991. Guide for Conducting Treatability Studies Under CERCLA: Chemical Dehalogenation.
Office of Emergency and Remedial Response, Washington, D.C. EPA/540/R-92/013a.
U.S. EPA. 1990. Handbook on In Situ Treatment of Hazardous Waste Contaminated Soil. Risk Reduction
Engineering Laboratory, Cincinnati, OH. EPA/540/2-90/002.
10. U.S. EPA. 1988. Technology Screening Guide for Treatment of CERCLA Soils and Sludges. Office of Solid
Waste and Emergency Response, Washington, D.C. EPA/540/2-88/004.
11. U.S. EPA. 1989. RCRA Facility Investigation (RFI) Guidance (Volumes 1 through 4). n.p. EPA 530/SW-89-
031.
-------
12. Information USA. 1990. The Federal Database Finder - A Directory of Free and Fee-Based Databases and
Files Available from the Federal Government. 3rd Ed. Kensington, MD.
13. U.S. EPA. 1990. Technical Support Services for Super/and Site Remediation. 2nd Ed. Office of Solid Waste
and Emergency Response, Washington, D.C. EPA/540/8-90/011.
14. U.S. EPA. 1991. Bibliography of Federal Reports and Publications Describing Alternative and Innovative
Treatment Technologies for Corrective Action and Site Remediation. Center for Environmental Research
Information, Cincinnati, OH.EPA/540/8-91/007.
15. U.S. EPA. 1991. Bibliography of Articles from Commercial On-Line Databases Describing Alternative and
Innovative Technologies for Corrective Action and Site Remediation. Information Management Services
Division, Washington, D.C.
16. ATTIC (Alternative Treatment Technology Information Center) On-Line System, Computerized Database and
Electronic Bulletin Board on Treatment of Contaminated Materials. U.S. EPA. Washington, D.C.
-------
SECTION 2
CONTAMINANTS AT SOLVENT SITES
HISTORICAL USES OF SOLVENTS
Solvents are usually organic substances (liquids) capable of dissolving or dispersing one or more other
substances. They can be halogenated or nonhalogenated and are widely used in many industrial and commercial
applications. Solvents are commonly and most importantly used in chemical feedstocks; as intermediates and carriers
in chemical manufacturing; in surface cleaning and preparation; in paints, varnishes, and strippers; as extractant
processes in chemical and food processing; in textile processing and dry cleaning; and in industrial manufacturing
processes. They also are used as aerosol propellants, foam blowing agents, refrigeration brines, and flame
retardants(I). The major solvent-using industries, which account for approximately 80 percent of their total use, are
paint, allied product and industrial operations (especially surface cleaning), dry cleaning operations, and pesticide,
pharmaceutical, and other organic chemical manufacturers (1).
The most common contaminants found in groundwater at Superfund sites are listed in Table 2-1 (2>.
Halogenated and nonhalogenated solvents are two of the most common classes of these contaminants. The
compounds presented are quite varied and include halogenated volatile organics (liquid solvents and gases),
nonhalogenated volatile organics (ketones/furans and aromatics), halogenated semivolatile organics [polychlorinaited
biphenyls (PCBs), pesticides, chlorinated benzenes, and chlorinated phenols], nonhalogenated semivolatile organics
[polycyclic aromatic hydrocarbons (PAHs) and nonchlorinated phenols], and inorganics (metals). A ranked list of
the top 22 organic groundwater contaminants identified at Superfund sites is presented in Table 2-2; the 20 most
frequently identified contaminants are shown in Table 2-3. Note that the tables contain many halogenated amd
nonhalogenated solvents — thus indicating their wide use.
10
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11
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TABLE 2-2. 22 MOST FREQUENTLY OCCURRING ORGANIC
CONTAMINANTS IN GROUNDWATER
Rank
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18 ;
19
20
21
22
Groundwater Contaminant
Acetone
Bis(2-ethylhexyl)phthalate
Toluene
TCE
Chloroform
MC
1 ,2-DCE
1,1,1-TCA
Benzene
Tetrachloroethylene (PCE)
Xylenes
1,1 -DCA
Ethylbenzene
Di-n-butylphthalate
Naphthalene
MEK
Chlorobenzene
1,1 -DCE
Phenol
Carbon disulfide
VC
1 ,2-DCA
Source: Superfund Chemical Analysis Results (SCAR), Downloaded from the CLP
Analytical Results Database (CARD) Published in 1988.
12
-------
TABLE 2-3. 20 MOST FREQUENTLY OCCURRING SUBSTANCES
REPORTED AT FINAL NPL SITES
Rank
1
2
3
4
5 :
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Substance
1,1,2-TCE
Lead
Chromium and
compounds
Toluene
Benzene :
PCE
1,1,1-TCA
Chloroform
Arsenic
PCBs
Cadmium
Zinc and compounds
Copper and compounds
Xylenes :
1,2-Trans-DCE :
Ethylbenzene
Phenol
1,1-DCA
MC ;
1,1-DCE
Source: Final National Priorities List (NPL) Sites as of March 1991. This list contains substances
documented during HRS Score Preparation.
13
-------
Halogenated Solvents
The largest use of halogenated solvents occurs in degreasing/cleaning metal surfaces; the second involves the
use of itetrachloroethylene (PCE) for dry cleaning (I). Other important applications involve their use in extraction
processes, adhesives, aerosol products, paint and coating solvents, and industrial solvent blends. The four most
widely used chlorinated solvents are 1,1,1-trichloroethane (TCA), methylene chloride (MC), trichloroethylene
(TCE), and PCE. Table 2-4 shows consumption of these four chemicals.
Nonhallogenated Solvents
Nonhalogenated solvents account for 64 percent of total solvent consumption. They are used most often as
ingredients and wash solvents in the paint and allied products. Nonhalogenated solvents are used as process
solvents, in the manufacture of adhesives, and in cold-cleaning operations. Xylene, toluene, methyl ethyl ketone
(MEK), methanol, acetone, ethyl acetate, and methyl isobutyl ketone (MIBK) are the most frequently used
nonhalogenated solvents (4).
SOLVENT USES AND THEIR RESIDUES
Major uses for the most common halogenated and nonhalogenated solvent chemicals are summarized in Table
2-4. Priority solvent industrial end uses are presented by category in Tables 2-5 and 2-6. Yearly production of
solvent chemicals is presented in Table 2-7.
14
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-------
TABLE 2-5. PRIORITY SOLVENT INDUSTRIAL END USES
Use Category
Adhesives
Dry Cleaning
Industrial Paint Stripper
Inks
Paint/Coatings
Process Solvent
Vapor Degreasing/Cold Clean-
ing
Miscellaneous
Total Industrial Uses
Percent of Use Category by
Solvent Type
Halo-
genated
23.0
100.0
100.0
0.0
1.3
37.5
84.3
100.0
36.3
Nonhalo-
genated
77.0
0.0
0.0
100.0
98.7
62.5
15.7
0.0
63.7
Percent of Solvent
Type by Use Category
Halo-
genated
3.8
19.9
6.5
0.0
1.3
18.8
49.7
0.0
100
Nonhalo-
genated
7.3
O.O
0.0
3.0
56.8
18.0
5.3
9.6
100
Percentage
of Total
RCRA
Industrial
Solvent Usage
6.0
9.5
2.4
2.0
36.7
18.4
18.9
6.1
100
Source: (4)
17
-------
TABLE 2-6. END USES OF SELECTED CHLORINATED
SOLVENTS IN 1987, BY PERCENTAGE
Adhesives
Aerosols
Chemical inter-
mediate
Cleaning/
degreasing
Coatings/inks
Dry cleaning
Electronics
Paint stripping
Pharmaceuticals
Plastics
Textile process-
ing
Urethane foam
Methylene
Chloride
~
18
~
10
—
—
8
33 i
4
16
:
5 i
Tetra-
chloroethylene
—
—
33
11
—
50
—
—
—
—
—
~
Tri-
chloroethylene
1
~
5
87
—
—
—
1
—
—
—
-
1,1,1-
Trichloroethane
10
13
6
54
8
2
4
—
..
—
—
—
— Use is small, but has not been quantified.
Source: ®
18
-------
TABLE 2-7. PRODUCTION OF SOLVENT CHEMICALS
Chemical
Carbon tetrachloride
Chloroform
Chloromethane
1,1-Dichloroethane
1 ,2-DichIoroethane
1 ,2-Dichloropropane
Ethylene dibromide
Methylene chloride
Tetrachloroethylene
1 , 1 ,2,2-Tetrachloroethane
1,1,1 -Trichloroethane
1 , 1 ,2-Trichloroethane
Trichloroethylene
Chloroethane
Vinyl chloride
Dioxane
Tetrahydrofuran
Acetone
Methyl ethyl ketone
Methyl isobutyl ketone
Toluene
Ethylbenzene
Styrene
Xylenes
Chlorobenzene
1 ,2-Dichlorobenzene
Production
(millions of pounds)
645.608
587.606
! 460,558.000
502.000
13,382.874
76.953
155.000
' 481.639
: 482.238
201 .000
783.334
720.000
180.000
670.204
10,134.86
9.217
172.567
2,524.338
450.089
170.845
5,249.313
9,235.984
8,336.905
988,417.508
298.848
52.236
Year
85
89
89
77
89
80
83
89
89
77
89
77
85
76
89
81
89
89
89
89
84
89
89
89
89
84
Source
6
7
8
6
8
6
6
8
8
6
8
6
6
7
8
6
8
8
8
8
6
8
8
8
; s
6
19
-------
Paint and Allied Products
The largest solvent end use occurs within the paint and allied products industry; this accounts for
approximately 50 percent of industrial solvent use. More than 98 percent of solvent consumption involves
nonhalogenated solvents; xylene, toluene, MEK, and acetone.
Waste solvent streams from the paint and allied products industry contain solvent concentrations varying from
trace levels to over 90 percent (4). Solvent-bearing coatings and ink wastes from tank and equipment cleaning
operations consist of a blend of solvents with solids concentrations up to 10 percent. Approximately one-third of
equipment cleaning solvents are reclaimed, resulting in annual solvent disposal of 7 million gallons(1).
Similar to the paint industry, the manufacturing of inks, adhesives, dyes, and various types of coatings and printing
applications involves nonhalogenated solvents in component formulations and equipment cleaning.
Surface Cleaning
The primary uses of solvents for surface cleaning are in the metal working and service-related industries.
Degreasing operations involve removal of oils, greases, waxes, lubricants, tars, water, and oil from surfaces. In
1980, the total number of solvent degreasing units in use was estimated to be 1.1 million in 336,000 plants. Surface
cleaning and degreasing operations are concentrated in California, Illinois, Massachusetts, Michigan, New Jersey,
New York, Ohio, Pennsylvania, and Texas (1).
Halogenated solvents are the primary cleaning agents used in vapor degreasers. The most widely used
degreasing solvent is TCA; fluorocarbons, TCE, MC, and PCE are also common.
Chlorinated solvent use in surface cleaning is declining. Significant remedial trends include the substitution
of petroleum-based solvents or alkaline reagents in cold cleaning; improvement in equipment design and operating
procedures to reduce solvent emissions; and use of heat-pump technology for energy conservation in vapor
degreasers.
Spent solvent composition depends on the degreasing application and may contain up to 90 percent of the
original solvent. Sludges from recovery processes generally contain from 10 to 50 percent of the original solvent;
heavy metal fines and other organics also are present(1> 2).
Dry Cleaning
Estimates of the number of dry cleaning establishments which use solvents range from 21,000 to 40,000.
Approximately 70 percent use tetrachloroethylene with annual consumption of 349 million pounds. About 30
20
-------
percent use petroleum solvents such as Stoddard's™ solvent, a petroleum distillate (1).
Solvents used in dry cleaning are filtered to remove suspended materials and color bodies to allow their reuse.
Filter cartridges, which are drained, reclaimed, or disposed, are used in approximately 75 percent of dry cleaning
facilities. Dry cleaning wastes contain about 50 to 60 percent solvents contaminated with soil, lint, dirt, and
detergent (4) originating from distillation residues or spent filter cartridges.
Production of Pesticides, Pharmaceuticals, and Other Organic Chemicals
Solvents are used in the production of pesticides, Pharmaceuticals, and other organic chemicals as a reaction
medium and in equipment cleaning. Nonhalogenated solvents are the most commonly used.
Methylene chloride and TCA are chlorinated solvents used in pesticide formulation. Their use has decreased
significantly during the past decade mainly due to costs. Where practicable, chlorinated solvents have been replaced
by aqueous emulsions, deodorized kerosene, other organic solvents, and dry flowable formulations. Use of TCE
and PCE has been curtailed due to concerns about their toxicity; carbon tetrachloride-based fumigants are no longer
manufactured.
These industrial production processes generate solvent wastes from equipment cleaning, solvent recovery still
bottoms, and off-specification materials. Much of this material is reclaimed, either on or off site, or incinerated
SOLVENT PRODUCTION AND USES
Liquid Halogenated Solvents
Carbon Tetrachloride
Carbon tetrachloride is used as a chemical intermediate in chlorofluorocarbon production and as a reaction
medium in the polymer technology (6). Ninety-one percent of carbon tetrachloride is used to produce
trichloromonofluoromethane (Fluorocarbon 11, or F-ll) and dichlorodifluoromethane(Fluorocarbon 12, or F-12).
The remaining carbon tetrachloride produced is exported or used as a nonsolvent chemical intermediate <4).
Carbon tetrachloride was used formerly in metal degreasing, dry cleaning, agricultural grain fumigation, and
the manufacturing of fluorocarbons for aerosols, refrigerants, and fire extinguishers (6> 7). Because of its toxicity,
this solvent was replaced by less toxic chlorinated hydrocarbons in metal and fabric cleaning applications (8> 9).
Fluorocarbons 11 and 12 were widely used as aerosols in personal-care items until they were banned for use as
spray-can propellants.
21
-------
Chloroform
Approximately 93 percent of chloroform demand is as a chemical intermediate in the production of
monocHorodifluoromethane (Fluorocarbon 22, or F-22) for use as a refrigerant(4). Additionally, it is used in the
preparation of dyes and pesticides and as an extractant in the production of penicillin, vitamins, and flavors; a
general solvent for adhesives, resins, Pharmaceuticals, and pesticides; a solvent for removing fat from waste
products; and a dry cleaning spot remover w> 6-7-10).
1,1-DkWoroethane (1,1-DCA)
1,1-dichloroethane is used as an intermediate in the production of TCA. It is used also as a solvent, a high-
coupbng agent in antiknock gasoline, and a paint, varnish, and finish remover (8> 10).
1,2-Dichloroethane (1,2-DCA)
Approximately 83 percent of the 1,2-DCA produced is used for production of VC to make polyvinyl chloride
(PVC) ®. A second important use is as a starting material for production of PCE, TCE, 1,1-dichloroethylene,
(1,1-DCE) and TCA. 1,2-dichloroethane also is used as a solvent, an additive in antiknock gasoline, a lead
scavenger, and a fumigant a-10).
1,1-DichIoroethyIene (1,1-DCE)
1,1-dichloroethylene is used as an intermediate in production of "vinylidene polymer plastics" such as Saran
and Velon (used in screens, upholstery, fabrics, carpets, etc.). It is copolymerized with VC or acrylonitrile to form
various kinds of Saran. It also is used in the manufacture of 1,1,1-TCA, as a component of synthetic fibers, and
in adhesives °'10).
1,2-Dichloroethylene (1,2-DCE)
1,2-dichloroethylene is used as a low-temperature extraction solvent for organic materials such as dyes,
perfumes, lacquers, thermoplastics, and heat-sensitive solutions such as caffeine. Additionally, it is used as a
chemical intermediate in organic synthesis of chlorinated solvents and compounds (6> 7> 10).
1,2-Dichloropropane I
1,2-Dichloropropane is used in solvent mixtures for cellulose esters and ethers, and as an intermediate for
PCE arid carbon tetrachloride, a lead scayenger for antiknock fuels, a solvent for fats, oils, waxes, gums, and
resins, a soil fumigant for nematodes, a scouring compound, a metal degreasing agent, and an insecticidal fumigant
(«, 7, 10)
Ethylene Dibromide (EDB) (1,2-Dibromoethane)
Ethylene dibromide is used in fumigation operations for preplanting and on grains, fruits, and vegetables; as
a scavenger for lead in antiknock fluids and fuels; as a general solvent; in the production of water-proofing agents,
22
-------
fire extinguishing agents, and gauge fluids during the manufacture of measuring instruments; in organic synthesis
during the production of dye, Pharmaceuticals, and ethylene oxide production; and as a specialty solvent for resins,
gums, and waxes (6> r>.
Methylene Chloride (MC) (Dichloromethane)
The most common industrial method of producing dichloromethane uses a vapor-phase process. The oldest
method to produce it was to react natural gas with chlorine; chloromethane, chloroform, and carbon tetrachloride
are formed as coproducts (8). ~
Methylene chloride is used as a solvent in approximately 60 percent of its applications. It is used most widely
as a solvent for paint removal. Other significant applications include its use hi chemical processing, as an extractant
in food processing and for oil dewaxing, as a metal degreaser, and in electronics. It is important as an extractant
in naturally-occurring, heat-sensitive substances, and for cellulose acetate. As a nonsolvent, MC is used primarily
in the production of aerosols, urethane foam blowing agents, polycarbonate insecticides and herbicides, and as a
vapor-pressure depressant in consumer products. The urethane foam industry uses MC to clean foam heads and
lines between production runs (4> 7> 10).
1,1,2,2-TetrachIoroethane (1,1,2,2-TCA)
Primary solvent uses of 1,1,2,2-TCA include its use as a dry-cleaning agent and in metals cleansing and
degreasing. Additionally, it is used in the manufacture of PCE, 1,1-DCE, artificial silk, leather, pearls, paint,
varnish, and rust removers. Other applications include employment as a soil fumigant; as a herbicide; as a solvent
for chromium chloride impregnated in furs; in the estimation of water content in tobacco and many drugs; and in
the production of photographic films, resins, lacquers, and waxes (7> 10).
TetracMoroethylene (PCE) (Perchloroethylene)
The dry-cleaning and textile-processing industries are the primary users of PCE. Textile processing involves
PCE use in fabric scouring and as a carrier solvent for fabric finishes, water repellents, sizing, and desizing
operations. A significant portion of solvent demand involves metal degreasing. TetracMoroethylene is used when
high melting waxes and greases are removed, higher cleaning efficiency is required, or when water is present on
part surfaces. The solvent also is used in coatings and adhesives applications (4> 7-10).
As a nonsolvent, PCE is used as a chemical intermediate in the production of fluorocarbon F-l 13 (42 percent)
and for export. !
1,1,1-TetrachIoroethane (1,1,1-TCA)
Currently, 1,1,1-TCA is the most widely used degreasing solvent in the United States. As a solvent, it is used
mainly for cold cleaning, vapor degreasing, adhesive formulations, electronics equipment cleaning, process solvent,
23
-------
and coatings. As a nonsolvent, 1,1,1-TCA is utilized for adhesive applications. 1,1,1-tetrachloroethane is used
during liquid Drano™ production, for photographic film processing, as a propellant, and during printed circuit board
production. 1,1,1-tetrachloroethane is available in uninhibited and inhibited grades, and it uses such stabilizers as
nitromethane, methylpyrole, 1,4-dioxane, butylene oxide, 1,3-dioxane, and secbutyl alcohol t4'6-7).
1,1,2-TetrachIoroethane (1,1,2-TCA)
1,1,2-tetrachloroethane is used as a chemical intermediate in the manufacture of 1,1-DCE, and as a solvent
for chlorinated rubber, fats, oils, waxes, and resins (7).
Trichlaroethylene (TCE)
Trichloroethylene is used as a degreasing solvent for approximately 80 percent of its total demand (S>.
Additional solvent uses involve paints, coatings, fats, waxes, resins, oils, rubbers, extraction of caffeine from
coffee, and general solvent applications. It also is used to flush liquid oxygen in aerospace operations and as a
chemical intermediate in pesticides and herbicides (4> 6> 7).
Because TCE has a lower boiling point than PCE, it is preferred for use in vapor degreasing operations.
Stabilized grades of TCE for use in vapor degreasing and other cleaning operations have been developed to remain
effective through repeated distillations and in degreasing aluminum.
Chlorobenzene
Major solvent applications of chlorobenzene are pesticide formulation and toluene diisocyanate processing.
Also, it is used as a degreasing and dye assist agent, and synthetic rubber solvent for dipping applications. Total
solvent use for these applications represents 42 percent of its current demand. Nonsolvent uses involve the
production of nitrochlorobenzenes, diphenyl oxide, and phenylphenols(4'6> 10).
Dichlorobenzene
Both 1,2-dichlorobenzene and 1,4-dichlorobenzene are produced almost entirely as by-products of
monochlorobenzene production <7). Dichlorobenzenes are produced by benzene chlorination. The most common
products of this method are monochlorobenzene, 1,2-dichlorobenzene, 1,4-dichlorobenzene, and 1,2,4-
trichlorobenzene (6).
1,2-Dichlorobenzene is used as a process solvent for manufacturing toluene diisocyanates; in the production
of 3,4-dichloroaniline; as an intermediate! for dyes and some agricultural chemicals; in degreasing operations; in
limited application as a heat transfer fluid; and as an ingredient in fumigants, herbicides, and metal polishes(4> e> 10).
As a nonsolvent, it is used in pesticides manufacturing.
1,3-Dichlorobenzene usually occurs as a contaminant of 1,2-dichlorobenzene and 1,4-dichlorobenzene
24
-------
production, and is used as a fumigant and insecticide (7).
Historically, 90 percent of the total production of 1,4-dichlorobenzene has been used for making insecticides
or air deodorants. Additinally, 1,4-dichlorobenzene is used in the manufacture of dyes and intermediates,
Pharmaceuticals, moth repellents, and as a soil fumigantCT.
Gaseous Halogenated Solvents
Chloroethane
Chloroethane is employed as an ethylating agent in the manufacture of tetraethyl lead, dyes, drugs, perfumes,
and ethyl cellulose. Other uses involve application as a refrigerant; as an anesthetic; as a solvent for fats, oils,
waxes, phosphorus, sulfur, acetylene, and many resins; in organic synthesis of perchloroethane, esters, and Grignard
reagents; as a propellant in aerosols; and as an insecticide and alkylating agent(6> 7'lo).
Vinyl Chloride (VC)
Primarily, VC is used in the production of polyvinyl chloride (PVC). It also is utilized in copolymers,
adhesives for plastics, organic syntheses, ,and as a refrigerant(6> 7).
Liquid Nonhalogenated Solvents
Acetome
Acetone is utilized as a solvent for fats, oils, waxes, resins, nitrocellulose, cellulose, acetylene, paint, varnish,
lacquer, and many other substances. Other applications involve use in organic chemical manufacturing, dyestuffs,
sealants and adhesives, acetylene gas storing, precision equipment drying and cleaning, paraffin purifying, tissue
hardening and dehydrating, specification testing of vulcanized rubber products, smokeless-powder manufacturing,
and nail-polish remover (4> 6).
Benzeme
Because of its toxicity, benzene is used currently as a solvent only when less hazardous compounds, such as
toluene or xylene, cannot be substituted. Benzene was used previously as a solvent in cold cleaning, fabric
scouring, and in the paint and coatings industry (4> 6' 10). Major nonsolvent uses involve production of
ethylbenzene/styrene, cumene/phenol, cyclphexane, nitrobenzene/aniline, detergent alkylate, chlorobenzenes, maleic
anhydride, and miscellaneous chemicals.
1,4-Dioxane
1,4-Dioxane is used as a solvent for cellulose acetate, ethyl cellulose, benzyl cellulose, resins, oils, waxes,
25
-------
oil- and spirit-soluble dyes, and many other organic and some inorganic compounds. Other solvent uses involve
lacquers, paints, varnishes, cements, cosmetics, deodorants, fumigan|s, emulsions, and paint and varnish removers.
It also is utilized as a wetting and dispersing agent in textile processing, dye baths, stain and printing compositions,
cleaning and detergent preparations, polishing compositions, scintillation counters, and as a stabilizer for
chlorinated solvents (6> 7> I0).
Effliylbenzene
Ethylbenzene is employed in the conversion to the styrene monomer, the spray application of vinyl resin
surface coatings, the manufacture of paints, varnishes, and other surface coatings, during the oven baking and drying
of surface coatings, and as an intermediate in dye manufacture. Other applications include the production of
acetophene, cellulose acetate, styrene, and synthetic rubber. Ethylbenzene is present in mixed xylenes and. is a
constituent of naphtha. It is used as an antiknock agent, especially in airplane fuels, and comprises 4.6 percent by
weight in high octane gasoline ^10).
Methyl Ethly Ketone (MEK) (2-Butanone)
2-butanone is used primarily as a solvent in vinyl nitrocellulose, acrylic and other coatings, and as a solvent
in adhesives, magnetic tapes, printing inks, and lube oil dewaxing. Its most common nonsolvent use is as a
chemical intermediate (4 percent). Other applications involve vegetable-oil extraction, azeotropic distillation in
refineries, and cold cleaning <«•* * "». Because of its rapid drying capability and strong solvency for lacquer binders
(nitrocellulose, acrylics, vinyls, etc.), MEK is the preferred solvent for thinning epoxy and PVC coatings and,
occasionally, as a stripper (4>7).
Methyl fcobutyl Ketone (MIBK) (4-MethyI-2-Pentanone)
The primary use of MIBK is in solvent applications, especially in the coatings industry as a solvent in
nitrocellulose lacquers. Additionally, 4-methyl-2-penatone is used for various coatings, adhesives, and inks. It is
a good solvent for high solids coatings, such as acrylics, polyesters, alkyds, and acrylic/urethanes, because of its
strong solvency, low density, and high electrical resistivity. 4-methyl-2-penatone is employed also as a solvent in
pesticides or Pharmaceuticals (tetracyclene antibiotics purification), as a rare-metal extractant, and as a denaturant.
It may be blended with MEK for use in high-solids lacquers and vinyl-resin solutions <"• «• 10>.
Styrene
Major uses of styrene include the formation of polystyrene, resins, protective coatings (styrene-butadiene latex
and alkyds), styrenated polyesters, rubber-modified polystyrene, and copolymer resins.
Tetrahydrofuran
Tetrahydrofuran is used primarily as a solvent for natural and synthetic resins, especially PVC and vinylidene
chloride copolymers. It is used to cast PVC films, coat substrates with vinyl and vinylidene chloride, and solubilize
26
-------
adhesives based on or containing PVC resins. A second major use is as an electrolytic solvent in the Grignard
reaction-based production of tetraethyl and tetramethyl lead. Tetranydrofuran also is used as an intermediate in
production of polytetramethylene glycol(6> 7> 10).
Toluene
The majority of toluene solvent uses involve the paints and coatings industry. It is used also in formulating
adhesives, inks, Pharmaceuticals, chemical processing, and cold cleaning. Toluene is used with other aromatics
as a wash solvent and for thinning resins that are difficult to solubilize by aliphatics. Major nonsolvent uses are
the production of benzene, toluene diisocyanate, benzoic acid, benzyl chloride, and other chemicals. Toluene also
is used in aviation gasoline and high-octane blending stock, explosives (TNT), toluene sulfonates (detergents), and
as a scintillation cocktail(4> 6> 7> I0). >
o-, m-, and p-Xylenes
Xylenes used during solvent applications are mixed xylenes which have been depleted in o-xylene and p-
xylene. Xylene is used extensively in the paint and coatings industry as a wash solvent and a stripping and general
solvent because of its ability to solubilize resins and lacquers, its lower cost compared to other solvents, and its
rapid evaporation. This use accounts for about 58 percent of mixed xylene demand. Additional solvent applications
involve adhesives, process solvent use, agricultural sprays, cold cleaning and fabric scouring, and miscellaneous
uses(4). ;
7n-Xylene is used often as a solvent and as an intermediate for dyes and organic synthesis, especially
isophthalic acid. Other applications include insecticides and aviation gasoline <7> 10). o-Xylene is used in the
manufacture of phthalic anhydride, in vitamin and pharmaceutical synthesis, and in dyes, insecticides, and motor
fuels (6)7). p-Xylene finds uses in the synthesis of terephthalic acid for polyester resins and fibers (Dacron, Mylar,
Terylene), vitamin and pharmaceutical syntheses, and insecticides (7'10).
Norachlorinated Phenols
0-5 m-, and p-Cresols
Major solvent uses of cresols include utilization as an enamel solvent in producing magnetic wire, and as a
cleaning compound and an intermediate in the production of phosphate esters, resins, antioxidants, perfumes,
herbicides, and disinfectants. Additionally, cresols are used as ore flotation and textile scouring agents (4> 7-10).
Phenol
Phenol is used as a selective solvent for refining lubricating oils and as an ingredient in the production of
phenolic resins, epoxy resins (biphenyl-A), nylon-6 (caprolactam), 2,4-dichlorophenoxy acetic acid, adipic acid,
27
-------
salicylic acid, phenolphthalein, PCP, acetophenetidin, picric acid, germicidal paints, phannaceuticals, dyes, and
indicators. Phenol also is employed as a laboratory reagent, slimidide, biocide, and general disinfectant(6j 7> 10).
BEHAVIOR, FATE, AND TRANSPORT
Predicting Contaminant Behavior
Physical and chemical properties of contaminants determine their fate in subsurface systems. This section
deals with the properties that describe the physical state of solvents frequently found at Superfund sites as well as
properties pertinent to their environmental fate and transport in the subsurface. Values of contaminant properties
are found in Tables 2-8a and 2-8b.
» Boiling point is the temperature at which the vapor pressure of a liquid equals the atmospheric pressure.
The boiling point of a substance at 1 atmosphere (760 mm Hg) is the normal boiling point of that
substance.
» The melting point is the temperature at which a solid undergoes a phase change to a liquid. Solvents with
melting points less than 30° C could be present as mobile nonaqueous phase liquids (NAPL). Those with
melting points above 30° C are solids in the pure form or dissolved in water or an organic solvent.
» Henry's Law Constant (H) is the ratio of a compound's partial pressure in air to its concentration in water
at a given temperature under equilibrium conditions. The larger the Henry's Law Constant, the more likely
the contaminant will volatilize from an aqueous solution and be amenable to vacuum extraction treatment.
Henry's Law Constants in the range of IGr3 to 10'5 atm-rnVmol indicate volatilization as an important
transfer mechanism, with rapid volatilization at values greater than IQr3 atm-m3/mol.
» Octanol/water partition coefficient (K^,) is the ratio of a contaminant's concentration in the octanol phase
to its concentration in the aqueous phase in a two-phase octanol/water system. The coefficient is a measure
of the tendency of a contaminant to partition into an organic phase or an aqueous phase. Contaminants
with K,^, values less than 10 are relatively hydrophilic, with high solubility in water, low soil sorption
coefficients, and small bioconcentration factors. Hydrophobic compounds have K^, values greater than 10,
and tend to accumulate in organic; substances rather than water. Knowledge of the K^ value of a particular
contaminant can help predict its tendency to sorb to subsurface solids or move with infiltrating water to
reach groundwater.
28
-------
TABLE 2-83. SELECTED PROPERTIES OF CONTAMINANTS
COMMONLY FOUND AT SUPlfiFUND SITES
Chemical
Holoaennted Volatile Organic*
Liquid Solvents
Carbon Tetrachloride
Chloroform
cis-1 ,2-Dichloroethylene
1,1-Dichioroethane
1 ,2-Dichloroethane
1 , 1 -Dichloroethylene
1 ,2-Dichloropropane
Ethylene Dibromide
Methylene Chloride
1 ,1 ,2,2-Tetrachloroethane
Tetrachloroethylene
trans-1 ,2-Dichloroethylene
1 ,1 ,1-Trichloroethane
1 ,1 ,2-Trichloroathane
Trichloroethylene
Gases
Chloroethane
Vinyl Chloride
Nonhaloaenated Volatile Oraanlcs
Cyclic
1 ,4-Dioxane
Tetrahydrofuran
Ketoms/furans
Acetone
Methyl ethyl ketone
Methyl isobutyl ketone
AmmaMcs
Benzene
Ethyl benzene
Styreno
Toluen*
m-Xylene
o-Xylene
p-Xylsna
Melting
Point
<°C)
-23 '"'
-64 <">
. 81 ""'
- 97.4 '">
- 3B.4 ""
-122.6""
- 90 '"'
9.7 1"'
-97 ""
-43 ""
-22.7""
-60 ""'
-32 ""
-36 '">
-87 '"'
-136.4 ""
-163.8""
11.8""
-1O8.5 "ol
- 94.4 ""
- 86.4 ""
-83 ""
6.5 '">
- 94.97 ""
-30.6 ""
-96.1 ""
- 50 «"'
- 2.5 ""
13 ("1
Boiling
Point
<°C)
- 22.6 ""
-63.5 ""
60 <"»
67.3 ""
83t.6 ""
31.9 ""
96.8 ""
' 131.36 '">
40.5 ""
146.6 ""
120.97 ""
48 "0)
74.08 '"'
-36.5 ""
86.8 '"'
: 12.5 ""
-13.9 ""
101.1 '">
66.0 '"
56.5 ""
79.6 "«
119.0 «"
80.1 ""
136.19 ""
145.2 <">
110.8 »"
138.5 ""
144.4 ""
138,i ""
Dynamic
Viscosity
(cp)
0.966(11)
0.563 ""
0.467 ""
0.377 ""
0.84 '"•
0.33 ""
0.84 ""
1.676""
0.43 ""
1.77 '"'
0.89 <"'
0.404 ""
0.858 ""
0.119 ""
0.670 ""
O.278 ""
0.262-">c""
1.43915C(1"
O.66 '">
0.331 '")
0.40 ""
0.5848 ""
0.6468 '">
0.678 ""
0.761 "1
0.68 '"'
0.608 ""
0.802 ""
O.S3S «
2.49 '"'
2.1 7 '""
2.42 Bl
1.43"a
0.60 "21
-0.27 ""
0.46 Bl
-0.24 ""
0.29 "2I
1.26 <">
2.1 3 "2>
3.1 5 "1
3.1 6 "2|
2.73 "21
3.20 "21
3.1 2 l'21
3.1i l'»
Log
K_
2.64 "2I
1.64"21
1.5 "2>
1.48"2'
T.1B'"
1.81 l">
1.71 "2I
1.45 »2'
0.94 "a
2.34 I'2'
2.82 l121
1.77 "2I
2.1 8 '«
1.75 I'2'
2.10 '"I
1.17'12>
0.91 "*>
log 17
log 1.77
-0.43 "2I
0.65 "a
1.38"2'
1.81 "2I
2.83 "2'
2.87 "2'
2.41 "21
2.84 "2I
2.84 "2I
2.84 "»
29
-------
TABLE 2-8a. (Continued)
Chemical
Chlorinated Benzenes
Chlorobenzene
1 ,2-Dichlorobenzene
1 ,4-Dichlorobenzene
Nomhlortnated Phenols
/n-Cresol
o-Cresol
p-Creaal
Phenol
Melting
Point
<°C)
. 46 "°>
-17"°'
63 "°>
12 «1
31.0"°'
34.8 '"»
41 "01
Boiling
Point
(°C)
.
131.7 ""
180.5 ""
174.66 1"'
201 I'2"
191.0 ""
201 «*
181.7 '"1
Dynamic
Viscosity
(cp)
0.756 ""
1.302""
1.268""
nd
4.49*°clnl
nd
3.02 '»'
Kinematic
Viscosity
(0)
0.683 ""
0.997 ""
1.0081"'
nd
4.37 *)cl"1
nd
3.87 ""
Log
Ko,
2.84 "2>
3.38 "2I
3.39 <">
1.86 'M'
1.96'"'
1.94"°'
1.46 "*
Log
K.
2.2 I'2'
3.06 l">
3.07 "21
1 .43 <">
1.23"5'
1 .28 <">
1.16"21
(c) calculated
O value at 25°C
TABLE 2-8b. SELECTED PROPERTIES OF CONTAMINANTS
COMMONLY FOUND AT SUPERFUND SITES
Chemical
Haloganated Volatile Oraanics
Liquid Solvents
Carbon Tetrachloride
Chloroform
Cis-1 ,2-dichloroethylene
1,1-Dichloroethane
1,2-Dichloroethane
1 , 1 -Dichloroethylene
1 ,2-Dichloropropane
Ethylene Dibromide
Methylene Chloride
1 , 1 ,2,2-Tetrachloroethane
Tetrachloroethylene
Trans-1 ,2-dichloroethylene
1,1,1-Trichloroethane
1,1,2-Trichloroethane
Trichloroethylene
Gases
Chloroethane
Vinyl Chloride
.Water
Solubility
: (mgfll
800 "2I
8,000 "21
3,500 ""
5,500 ""
8,690 "a
400 "2I
2,700 "2l
3,400 ""
20,000 <">
2,900 "2I
150 m
150. l12'
4,400 M
4,600 <">
1,100 "2I
57,000 "«
1,1000™
Vapor
Pressure
(mm Hg)
91.3 ""
160 ""
200 "°l
182 *""
83.35 ""
500 ""
39.5 ""
11 ""
350 ""
6 ""
14 ""
265 <"'
100 ""
19 ""
67.8 ""
1,000 ""
2,300 1'"
Henry's Law
Constant
(atm-m'/moll
0.0302 "a
0.0029 *1121
O.0076 *""
0.0043 •'"'
0.00091 *"21
0.021 *"2'
0.0023 »1121
0.000318 ™
0.0020 *<">
0.00038 *"21
O.0163 "21
0.384 *"21
0.018 *"21
0.00074 ""
O.OO91 »"a
0.01 1 1 "2I
0.696 ™
Liquid
Density
(g/cc)
1.5947 ""
1.485 ""
1.284 ""
1.175 <">
1.263 ""
1.214 ""
1.168 ""
2.172 ""
1.326 ""
1.600 ""
1.625 ""
1.257 ""
1.325 ""
1.4436""
1.4649""
O.8978 ""
0.9121 <">
Vapor
Specific Gravity
6.5 ""
4.12 ""
3.34 ""
3.44 ""
3.4 ""
3.25 ""
3.9 ""
6.48 ""
2.93 ""
5.79 '"'
6.83 ""
3.34 ""
5.45 *«"
6.45 *""
4.53 <"'
2.22 ""
2.16 ""
30
-------
TABLE 2-8b. (Continued)
Chemical
NonhaToaenated Volatile Organic*
Cyclic
1 ,4-Dioxane
Tetrahydrofuran
Kelcnts/furana
Acetone
Methyl Ethyl Ketone
Methyl Isobutyl Ketone
AromaSos
Benzene
Ethylbunzene
Styreno
Toluene
m-Xylene
o-Xylene
p-Xylene
Chlorinated Benzenes
Chlorobenzene
1 ,2-Dichlorobenzene
1 ,4-Dichlorobenzene
Nonchlvrinatad Phenols
/n-Cresol
o-Cresol
p-Cresol
Phenol
Water Vapor
Solubility Pressure
(ma/1) (mm Hg)
i
miscible**"" 38.09*""
miscible "" 46.6 *"«
miscible "a 181.72 ""
28,600 "2> 71.2 ""
17,000 "2I 16 '"'
1,780 m 76 ""
162 "a 7.1 ""
300 "2I 5 110)
616 "a 22 ""
173»C"> g mi
152 "" 7 ""
198 ."21 9 <"i
600 l121 8.8 ""
100 "a 0.0019 "2I
59 I12> 0.0031 m
23,50O '"» 0.163 "•"
31,000 40°C"01 0.246 "4i
24,000 400C "ol 0.108 '"'
84,000 <"> 0.529 "«
Henry's Law
Constant
(otm-rrv'/rnolj
4.80 E-6*1"1
0.00011 Bl
0.0000397*"21
0.0000274 Bl
O.000166 l131
0.00548 "='
0.0066 m
0.00261 "2I
0.0067 «»
0.0070 "»
0.00627 "2I
0.0071 lla
0.00303 |12)
0.0019 "2I
0.0031 "2l
0.000038 M
0.000047 I1;"
0.00035 I1"
7.80 E-07C
Liquid
Density
(0/cc) !
'
1.035 ""
0.8892 '"»
0.791 ""
0.805 ""
0.8017""
0.8766 ""
0.8670 ""
0.9060 «*
0.8669 ""
0.8642 ""
O.880 ""
0.8610 ""
1.106 ""
1.306 I'"
1.288 ""
1.038 "« :
1.0273 "1
1.0347 '"»
1.0676 ""
Vapor
Specific Gravity
2.22 ""
nd
2.0 ""
2.6 ""
3.46 ""
2.77 '"1
3.66 ""
4.26 "2'
3.14 ""
3.66 »«
3.7 ""
3.66 '"'
3.9 »"
5.1 '""
6.07 '">
nd
3.72""
nd
3.02 ""
(c) calcuktcd
(*) value at 2S°C
(**) miscible in all proportions
31
-------
• Adsorption coefficient (K^ is the ratio of the mass of contaminant adsorbed per unit weight of organic
carbon in soil to the concentration of the contaminant in solution at equilibrium. The adsorption coefficient
describes the tendency of a contaminant to partition between solid and solution phases of a water-saturated
or unsaturated soil. Sorption affects mobility, volatilization,,hydrolysis, and biodegradation potential of
a contaminant.
• Aqueous solubility is the maximum amount of the compound that will dissolve in pure water at a specific
temperature. It is expressed in units of mg/L, g/L, parts per million (ppm), or weight percent (WT %).
Highly soluble contaminants are easily distributed in water and tend not to sorb to subsurface solids. These
chemicals are amenable to removal by pump-and-treat methods and are usually biodegradable.
• Specific gravity is the ratio of the density of a substance to the density of a reference substance at a specific
condition. The reference for the specific gravity of liquids is usually water at a temperature of 4°C.
Contaminants with specific gravity greater than 1 potentially will migrate under the influence of gravity
through saturated and unsaturated subsurface materials. These contaminants are called dense nonaqueous-
phase liquids (DNAPLs); examples include TCE and PCE. Compounds with specific gravity less than 1
tend to float on the water table. These contaminants are called light nonaqueous-phase liquids (LNAPLs);
examples include gasoline and fuel oils. Highly soluble compounds with specific gravity less than 1 may
dissolve completely in groundwater; examples include acetone and MEK.
• Vapor specific gravity is the ratio of the vapor density of a pure compound to that of air at the same
temperature and pressure. The vapor specific gravity of air is 1. The vapor specific gravity can be
determined using the ideal gas law and is equal to the ratio of the molecular weight of the compound to
the molecular weight of air.
• Vapor pressure of pure compounds is the pressure exerted by the vapor of a substance under equilibrium
conditions. It provides an indication of the extent to which the contaminant will volatilize. The higher the
vapor pressure, the greater the tendency for volatilization. Contaminants with high vapor pressures are
more amenable to vacuum extraction treatment technologies.
• Dynamic viscosity is the ratio between applied shear stress and shear rate. The mobility of a contaminant
in pure form is inversely proportional to its dynamic viscosity.
• Kinematic viscosity is the ratio of a contaminant's dynamic viscosity to its density. The lower the
kinematic viscosity, the greater the tendency to migrate downward. In the case of groundwater
contamination by DNAPLs, the lower the kinematic viscosity of the DNAPL, the more likely it will
penetrate finer-grained layers in the subsurface.
32
-------
Transport
i. -7
Subsurface contamination by halogenated or petroleum solvents exists initially as a separate phase within the
soil pores. Over time, the solvents dissolve into the aqueous phase, adsorb to the subsurface solids, and volatilize
to the atmosphere. However, significant NAPLs can remain on the soil and aquifer solids as either residual
saturation or continuous-phase liquid. A review by Mercer and Cohen<17) on properties, models, characterization,
and remediation of immiscible fluids in the subsurface is a recommended reference.
Contaminant flow may occur through a number of mechanisms. Volatilization from residual saturation or
bulk liquid into the unsaturated pore spaces produces a vapor plume. Migration of this vapor plume is independent
of groiimdwater movement(18> I9) and may occur due to both advection and diffusion(20). Advection is the process
by which the vapor plume contaminants are transported by the movement of air and may result from gas pressure
or gas density gradients m. Diffusion is the movement of contaminants from areas of high vapor concentrations
to areas of lower vapor concentrations. The vapor plume is enriched with compounds of high vapor pressure and
lower aqueous solubility.
For compounds with vapor densities greater than air, density-driven flow of the vapor plume may occur due
to gas density gradients m. Toluene, ethylbenzene, xylenes, chlorobenzene, naphthalene, and phenols are less dense
than water and unlikely to move by density-driven flow. However, they may be capable of diffusive transport,
causing vapor plumes to move away from residual saturation in the unsaturated zone(21). Residual saturation is the
portion of the liquid contaminant that remains in the pore spaces due to capillary attraction after the DNAPL moves
through the soil(22>. Volatilization from contaminated groundwater also may produce a vapor plume of compounds
with high vapor pressures and high aqueous solubilities. Dissolution of contaminants from residual saturation or
bulk liquid into water may occur in either the unsaturated or saturated portions of the subsurface with the
contamination then moving with the water. Contaminant dissolution from nonaqueous phase liquid under laminar
flow conditions typical of aquifers is mass transfer limited, requiring decades for dissolution and producing a dilute
waste stream of massive volume (23>24).
Transport of DNAFLs in the Unsaturated Zone
Halogenated aliphatic hydrocarbons introduced into the unsaturated portion of the subsurface potentially exist
in four phases ^r
• Air phase: contaminants present as vapors
• Solid phase: contaminants adsorbed or partitioned onto the soil or aquifer material
• Water phase: contaminants dissolved into the water according to their solubility
• Immiscible phase: contaminants present as DNAPLs
33
-------
Because the vapor-specific gravity of DNAPL,
i,,,,
*" " *' **
of
Iimitelioil ^
' -
and PCE *» water
-. P.nneab.e
, , „„ flow
low
pemeability zones «».
flowllori2ollMv
flow
well, although M. mxb slow<,r
wffl
Tramport of DNAPL, in fte Sat|lrated
The saturated zone contain^ DNAp,.
34
-------
One or more of the three fluid phases (gaseous, aqueous, immiscible) may occupy the pore spaces in the
unsaturated zone. Sorbed DNAPLs are considered immobile, but slow desorption of TCE from the organic matter
i
in the unsaturated zone has been reported (26>.
Residual saturation is the portion of the bulk liquid retained by capillary attraction in the porous media (25).
The DNAPL is no longer a continuous phase, but is present as isolated residual globules. Dense nonaqueous-phase
liquid held in residual saturation is immobile under normal subsurface pressures; further migration will occur only
by dissolution into water or by vapor movement(18). The residual-phase saturation acts as a source of contamination
to infiltrating water in the unsaturated zone. Dissolution of the DNAPL bulk liquid or vapor readily occurs as water
percolates through the unsaturated soil material, producing saturated solutions even with low flow rates(18). Particle
grain size and degree of saturation are soil physical properties important for controlling residual saturation(2e> 27).
Vapor movement of NAPLs is independent of groundwater movement (18'19). Vapor transport of contaminants
may be due to both advection and diffusion. Gas-phase advection may result from gas pressure or gas density
gradients (20). For example, upward diffusion of dichloromethane in a dry, uniform sand has been shown to take
three times longer than the time required for downward diffusion
-------
reduced or an impermeable depression is reached that immobilizes the DNAPL. Any DNAPL present as residual
saturation is mobile only by dissolution of the contaminant into the water. Although DNAPL sorbed onto aquifer
solids is usually considered immobile, slow release of TCE from long-contaminated soils has been observed in
column studies <29>.
Transport of LNAPLs
Similar to denser-than-water solvents, contamination of petroleum-derived solvents in the unsaturated zone
exists in four phases: vapor in the pore spaces; sorbed to subsurface solids; dissolved in water; or as NAPL.
The nature and extent of transport is determined by the interactions between contaminant transport properties
(density, vapor pressure, viscosity, and hydrophobicity) and the subsurface environment (geology, aquifer
mineralogy, and groundwater hydrology). Vapor-phase transport usually results in a relative enrichment of the more
volatile compounds. This evidence of contamination migrating in a hydraulically upgradient direction by vapor-
phase transport has been observed at a subsurface fuel spill <19). The observers found that the enrichment of
groundwater [by aliphatic hydrocarbons of high-vapor pressures and low solubilities relative to the more soluble
volatile aromatics compounds such as benzene, toluene, ethylbenzene, and xylenes (BTEX compounds)] increased
with distance from the source. This enrichment is characteristic of vapor-phase transport. At another site, high
concentrations of aliphatic hydrocarbons (compared to BTEX compounds) were observed in wells surrounding a
gasoline spill C9). Vapor-phase transport of the aliphatic hydrocarbons — with subsequent dissolution in the
groundwater — may explain why the aliphatic rather than the aromatic components of the gasoline were found in
groundwater distant from the spill location.
After a spill occurs, the NAPL migrates vertically in the subsurface until residual saturation depletes the liquid
or the capillary fringe above the water table is reached. Some spreading of the bulk liquid occurs until pressure
from the infiltrating liquid develops sufficiently to penetrate to the water table. The pressure of the infiltrating liquid
pushes the spill below the surface of the water table. Bulk liquids less dense than water spread laterally and float
on the surface of the water table, forming a mound that becomes compressed into a spreading lens. The
concentration of constituents dissolving from the contaminant liquid into the water under the floating product remains
relatively uniform regardless of the distance from the spill<19). However, as the plume of dissolved constituents
moves away from the floating bulk liquid, interactions with the aquifer solids affect dissolved concentrations.
Compounds more attracted to the aquifer material move at a slower rate than the groundwater and are found closer
to the source; compounds less attracted to the aquifer material move most rapidly and are found in the leading edge
of a contaminant plume.
Solubility and Sorption
Most solvent sites are contaminated by a mixture of several chemicals. The presence of other contaminants
can affect the partitioning behavior, and therefore, the fate and transport of individual contaminants by altering their
35
-------
aqueous solubilities. The effect of organic cosolvents on the sorption and aqueous solubility of hydrophobic organic
chemicals by soils was studied by Rao et al. <30) and Final et al. (31). The hydrophobic chemicals studied were
diuron, anthracene, naphthalene, biphenyl, fluoranthene, and pyrene. Nonpolar, partially miscible organic solvents
such as toluene, p-xylene, and TCE did not influence sorption by soils significantly when present as a
cosolvent/cosolute in the aqueous phase, or as a separate liquid phase. However, polar, partially miscible organic
solvents with high aqueous solubilities, such as nitrobenzene and o-cresol, were found to decrease sorption and
enhance solubility of the hydrophobic chemicals significantly. The presence of a completely miscible organic
solvent, such as methanol or dimethyl sulfoxide, increases the solubility of the partially miscible organic solvents,
resulting in increased solubility and decreased sorption of the hydrophobic organic chemicals.
Recent work by Ball and Roberts 02) tested long-term sorption of PCE and tetrachlorobenzene on aquifer
material containing low organic carbon. The long-term sorption of PCE and tetrachlorobenzene exceeded, the
predictions of hydrophobic partitioning into soil organic matter by more than an order of magnitude.
Locating Free Liquids
Soil-Gas Monitoring
Soil-gas monitoring is a valuable tool for determining contaminant vapors in the subsurface and detecting
groundwater plumes(33> 34). Halogenated and petroleum-derived hydrocarbon solvents commonly found at Superfund
sites are amenable to soil-gas analysis because of their volatility. The more soluble solvents such as acetone,
tetrahydrofuran, 1,4-dioxane, MEK, MIBK, phenol, and cresols are potentially amenable to soilrgas analysis if they
result from a leak or spill in relatively dry soil. Chlorobenzenes and dichloropropane are detectable by soil-gas
techniques only where probes can sample near contaminated soil or groundwater.
Compounds with high Henry's Law Constants may be present in the unsaturated zone as a result of
volatilization 0S). Identification of other gases, e.g., carbon dioxide, methane, oxygen, and nitrogen, in both the
unsaturated and saturated zones is useful in determining subsurface microbial activity and redox conditions.
LNAEL •
Subsurface contamination by residual-phase NAPLs serves as a continuous contaminant source to infiltrating
waters and fluctuating water tables. Most petroleum-derived solvents are less dense than water and exist as floating
pools on the water table when hi contact with groundwater. Detection of floating pools in monitoring wells is an
indication of LNAPL contamination<36>.
LNAPL Sites: Soil-gas monitoring is important in identifying LNAPL sites. Reliance on visual identification
in core samples is not advised due to the heterogeneous distribution or potentially low residual contamination.
Chemical analysis can measure the total contaminant concentration on the subsurface solids, but cannot determine
36
-------
NAPL directly <36>. :
More volatile LNAPL compounds readily partition into the air phase. A soil gas sample collected from an
area contaminated by vapor-phase transport typically contains relatively greater concentrations of the more volatile
compounds than one contaminated by groundwater transport<19). Vapor-phase transport occurs with subsequent
dissolution in groundwater. Aqueous-phase contaminants with high Henry's Law Constants can be expected to
volatilize into the pore spaces.
DNAEL
Hazardous waste sites that contain residual or continuous-phase chemicals with densities greater than that of
water and which are found below the water table are termed DNAPL sites. Identification of DNAPL sites is
important to site characterization because these sites can have complex contamination distributions that are difficult
to locate and remediate.
DNAPL Sites: The most common DNAPLs are chlorinated solvents, such as PCE, TCE, and 1,1,1-TCA,
used in degreasing and cleaning operations. At some sites, chemicals other than DNAPLs may have been used,
resulting in a waste mixture. For example, petroleum-derived solvents plus chlorinated solvents and other
contaminants are common mixtures. DNAPL sites may also contain creosote, pesticides, or PCBs.
Direct evidence of DNAPL contamination is free-product detection in a monitoring or pump-and-treat well.
Normally, this direct evidence is quite difficult to obtain. Absence of free product is not evidence that DNAPL does
not exist at the site. DNAPL accumulates at the bottom of the well in a thin layer. Recovering the DNAPL
requires bottom-of-the-well sampling devices. If the sand pack or filter pack extends below the bottom of the well
screen, the DNAPL may be found at the bottom of the sand pack and cannot be recovered.
The extent of residual saturation or continuous-phase DNAPL may be small compared to the spacing of
monitoring wells; direct interception by monitoring wells may be insufficient. Direct evidence of DNAPL is
difficult to obtain even when intercepted by monitoring wells. At most sites, indirect evidence of DNAPL
contamination is more economical and efficient. Both direct and indirect evidence are used to determine if a site
contains DNAPL (37).
The possible presence of DNAPL compounds can usually be determined from a detailed history of site
activities and land use. Types of activities associated with DNAPL sites are solvent manufacturing, recycling, and
packing; any activity involving metal working or engine maintenance; dry cleaning; electronics manufacturing;
industrial waste storage or disposal; and many others. The DNAPL below the water table frequently results from
small routine solvent leaks, spills, releases, or disposals. Although the quantity lost routinely seems small compared
to inventory, the impact to groundwater may be significant.
37
-------
Other indirect evidence is concentrations of DNAPLs in monitoring wells as low as 1 percent of the solubility
of the DNAPL chemical. Values near the solubility limit of a chemical would be unusual due to dilution of DNAPL
dissolving from residual saturation into less contaminated groundwater. Saturated concentrations of DNAPL cannot
be observed unless monitoring wells are installed within or close to residual saturation or continuous-phase product.
The direction of DNAPL migration below the water table is controlled by gravity, geological structure, and
permeability, not by the direction of groundwater flow. The DNAPL identified in monitoring wells upgradient or
across gradient may be used as indirect evidence of DNAPL location. Uncontrolled disposals in locations not
identified previously as disposal areas may also account for DNAPL in upgradient monitoring wells. Migration of
DNAPL vapors also can cause upgradient groundwater contamination also, but normally this contamination is
shallow.
Identification of DNAPL dissolved in groundwater at depths well below the water table is additional indirect
evidence of DNAPL contamination. It is necessary at DNAPL sites to determine maximum depth of contamination,
especially in fractured rock materials that allow DNAPL to migrate to great depths. However, determination of
maximum depth of DNAPL contamination is difficult in fractured rock aquifers.
Soil gas monitoring identifies residual saturation in the vadose zone due to the high vapor concentrations close
to the DNAPL. Location of residual saturation may identify entry location of DNAPL below the water table.
These locations are identified frequently by locally erratic or isolated high concentrations. The DNAPL located only
below the water table will not produce high concentrations of vapor in the vadose zone. High concentrations of
DNAPL at the water table only, but not at depth, is an indication of soil vapor contamination.
Feenstra et al. 06) describes a method for NAPL determination using the results of chemical and physical
analyses of the soil, and fundamental principles of chemical partitioning in unsaturated or saturated soil. The
method allows determination of residual NAPL in subsurface environments. Additional information concerning
DNAPL sites may be found in Mercer (17), Feenstra et al. , Villaume (38), and Mackay et al. <*».
Transformations
Biological and Chemical Reactions of Solvent Chemicals
Solvent chemicals are subject to biological and chemical reactions when introduced into the subsurface.
Halogenated aliphatic compounds may undergo abiotic (hydrolysis and chemical dehalogenation) and/or biological
reactions in subsurface environments. Although petroleum-derived solvents are quite degradable biologically, they
are relatively resistant to chemical transformations. Abiotic transformations are nonbiological reactions, and they
are usually elimination or hydrolysis reactions. Alkaline hydrolysis reactions are abiotic transformations that occur
38
-------
at pH values greater than 7.
Microbial transformations are broadly classified into aerobic and anaerobic processes. Aerobic conditions
occur in the presence of oxygen, in which bacteria use oxygen as a terminal electron acceptor during respiration.
Complete aerobic biodegradation converts organics to carbon dioxide, water, and other organic products (depending
upon the constituent of the starting material). Transformation products of biological and chemical reactions of
halogenated solvents are shown in Table 2-9.
Anaerobic conditions occur in the absence of molecular oxygen and include two major classes of reactions.
Anaerobic fermentation reactions transform organics into intermediate organic products. In anaerobic respiration,
microorganisms may use other alternative electron acceptors to oxidize organics in the absence of molecular oxygen.
The most common alternate electron acceptors include nitrate (with the microbial process termed dentrification),
sulfate (sulfate reduction), and carbon dioxide (termed methanogenesis due to the production of methane).
Methanogenic refers to strictly anaerobic conditions in which bacteria produce methane, typically from carbon
dioxide.
In addition to these fundamental microbial processes, a variety of other microbial transformations may take
place. Of particular interest for transformation of certain solvents is reductive dehalogenation (reductive
dechlorination for chlorinated solvents), in which halogen atoms are selectively removed from organic molecules
leaving lower halogenated or nonhalogenated organic products. Reductive dehalogenation also results ki the
cometabolic transformation of chlorinated solvents where they are transformed by microorganisms while oxidizing
other substrates.
The occurrence of these biological processes depends upon the specific organic substrates, the types of
microbial populations present, and the environmental conditions. These factors should be understood in evaluating
the fate of solvents in the environment.
39
-------
TABLE 2-9. COMPOUNDS FORMED FROM TRANSFORMATION
OF C, AND C2 HALOGENATED HYDROCARBONS
Compound
1 , 1 -Dichloroethylene
1 ,2-t)ichloroethylene
cis-
trans-
Trichloroethylene
Tetrachloroethylene
1,1-Dichloroethane
1 ,2-Dichloroethane
1 , 1 ,2,2-Tetrachloroeth-
ane
1,1,1 -Trichloroethane
Products
Vinyl chloride
Carbon dioxide
Chloroacetylene
Vinyl chloride
Carbon dioxide
Chloroethane (92%)
Vinyl chloride (8%)
Vinyl chloride
1 ,2-Dichloroethylene
25 times more cis-
than trans-1,2-Dichloroethylene
50% to all cis- above
trans-1 ,2-Dichloroethylene
One measure of more trans- than
cis-1 ,2-dichloroethylene
1 , 1 -Dichloroethylene
Vinyl chloride
Carbon dioxide
Carbon dioxide
Carbon dioxide
Trichloroethylene
25 times more cis-
than trans-1, 2-Dichloroethylene
70% to all cis- above
trans-1 ,2-Dichloroethylene
1 , 1 -Dichloroethylene
Vinyl chloride
Trichloroethylene
Dichloroethylene
Vinyl chloride
Carbon dioxide (24%)
Ethylene
Vinyl chloride
Chloroethane
Carbon dioxide
Vinyl chloride •
Carbon dioxide
Carbon dioxide
Chloroethanol
Vinyl chloride
Ethylene glycol
1 ,1 ,2-Trichloroethane
Trichloroethylene
1,1-Dichloroethane
Chloroethane
Carbon dioxide
Methylene chloride
1,1 -DCE (26% product)
Acetic acid
Vinyl chloride
1 , 1 -Dichloroethylene
Condition
Anaerobic
Anaerobic
Alkaline hydrolysis
Anaerobic
Anaerobic
Anaerobic
Anaerobic
Anaerobic
Anaerobic
Anaerobic
Anaerobic
Anaerobic
Anaerobic
Anaerobic
Anaerobic soil column
Aerobic, methane
cometabolism
Aerobic column.
methane cometabolism
Anaerobic
Anaerobic
Anaerobic
Anaerobic
Anaerobic
Methanogenic column
Methanogenic column
Methanogenic column
Methanogenic column
Anaerobic
Anaerobic
Anaerobic
Anaerobic
Alkaline hydrolysis
Anaerobic
Aerobic
Aerobic
Alkaline hydrolysis
Neutral hydrolysis
Anaerobic
Aerobic
Anaerobic
Anaerobic,
Anaerobic
Anaerobic
Abiotic
Abiotic
Abiotic
Abiotic
References;
48,49,50,51
49
43
51
52,53
48
48
48,50
50
51
53
54
51
50,51,54
40
55
56
51,53,54
51
53,54
51
51
40
40
40
40
57
11
51
42
43
52
58
43
43
43
43
49,51,53,54
50
49
51
49,59
49
49
60
40
-------
TABLE 2-9. (Continued)
Compound
1,1 ,2-TrichIoroethane
Chloroform
Carbon tetrachloride
Ethylene dibromide
Methylene chloride
.Vinyl chloride
Vinyl chloride
Products
Chloroacetic acid
i Glyoxylic acid
Vinyl chloride
1 ,2-Dichloroethylene
Methylene chloride
Carbon dioxide
Methane (9%)
Carbon dioxide (98%)
Methane 1-2%)
Chloroform
Methylene chloride
Carbon dioxide
Carbon dioxide (99%)
Methane (0-2%)
Chloroform
Carbon dioxide
Bromomethane
Ethylene glycol
Ethylene (2 mo.)
Bromide ion (2 mo.)
Carbon dioxide
Carbon dioxide
Carbon dioxide
Ethylene
Methane
Chloromethane
Carbon dioxide
Carbon dioxide
Condition
Aerobic
Aerobic
Aerboic
Alkaline hydrolysis
Anaerobic
Anaerobic
Anaerobic
Methanogenic
Methanogenic
Anaerobic
Anaerobic
Anaerobic
Methanogenic
Methanogenic
Denitrifying
Denitrifying
Abiotic
Abiotic
Abiotic
Aerobic
Aerobic
Aerobic
Anaerobic
Anaerobic
Anaerobic
Anaerobic
Anaerobic
Aerobic
References
61
61
61
43
51
52
52
52
52
51,53,54
51
52
52
52
62
62
45,63
63
64
64
65
66
66
52
52
52
52
67
Source: Adapted from Mallon, 1989 <29)
Chemical Transformations
Transformation reactions can be classified as oxidation and reduction substitution (hydrolysis), or
dehydrodehalogenation (chemical dehalogenation) (40). Oxidation and reduction reactions require external electron
transfer, while substitution and dehydrodehalogenation reactions do not. Although biological transformations are
usually dominant, both abiotic and slow biological transformation reactions can be important due to the long
residence times of contaminants in aquifers with slow-moving groundwater.
Hydrolysis results from the introduction of a hydroxyl group (-OH) from water or hydroxide to a carbon atom
and displaces an atom such as chlorine (41). In this reaction, the halogen is removed from one carbon atom with
removal of a hydrogen atom from an adjacent carbon.
41
-------
Initial hydrolysis of halogenated aliphatic hydrocarbons produces alcohols, which, if halogenated, are further
hydrolyzed to carboxylic acids or aldehydes. Chloroform is resistant to hydrolysis (42). While only neutral
hydrolysis occurs for carbon tetrachloride and TCA, chlorinated ethenes react with hydroxide under extreme
conditions and exhibit no neutral hydrolysis(43). Calculated rate constants for hydrolysis of halogenated ethenes are
so small at environmental temperatures and pH conditions that their hydrolysis can be regarded as negligible(43).
The rate and pattern of hydrolysis of alkyl halides are sensitive to pH, temperature, and ionic strength of the water
(44). Hydrolysis is more likely than chemical dehalogenation for halogenated alkanes. Slower substitution reactions
and longer half-lives occur with increased halogenation (40> M'45). Alkanes, benzenes, halogenated aromatics,
alcohols, phenols, and ketones are compounds that are chemically resistant to hydrolysis(41). Lists of half-lives for
some halogenated compounds are shown in Tables 2-10 and 2-11.
Dehydrodehalogenation is an elimination reaction in which alkenes are produced from alkanes, such as the
formation of TCE from 1,1,2,2-tetrachloroethane (46-47). In this reaction, a halogen is removed from one carbon
and a hydrogen is removed from an adjacent carbon.
Elimination reactions generally are favored by higher temperatures and strong basic conditions which are not
found in groundwater. An elimination reaction may compete with hydrolysis for organic compounds that contain
good donor groups such as a halide (4I), resulting in both reactions occurring in groundwater. The formation of
acetic acid from hydrolysis of TCA plus formation of 1,1-dichloroethylene from its dehydrodehalogenation from
TCA is one example of this<42>49). These elimination and substitution reactions occur in a ratio of 1:3, independent
of temperature and pH (69).
42
-------
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-------
TABLE 2-11. IN SITU OR ESTIMATED HALF-LIVES OF HALOGENATED
ALIPHATIC HYDROCARBONS IN GROUNDWATER
Compound
Trichloroethyl-
ene
Tetra-chloroeth-
ylene
1,1,1-Trichloro-
ethane
Chloroform
Ethylene dibrom-
ide
Half-Life
(year)
0.6
Fast
2
0.6
0.1 to 1
Faster
0.6
1
0.6
0.1 to 1
23 to 57
Conditions, Sediment Type, Etc.
Observed disappearance, Palo Alto
Baylands Aquifer, injected groundwa-
ter recharge experiment
Waterloo, Ontario landfill
Estimated from well sample data,
Noordwijk Dump, The Netherlands
Observed disappearance, Palo Alto
Baylands
Estimated from contamination data for
groundwater in The Netherlands
Faster than Waterloo, Ontario landfill
transport
Observed disappearance, Palo Alto
Baylands Aquifer, injected groundwa-
ter recharge experiment
Estimated from well sample data,
Noordwijk Dump, The Netherlands
Observed disappearance, Palo Alto
Baylands Aquifer, injected groundwa-
ter recharge experiment
Estimated from well sample data,
Noordwijk Dump, The Netherlands
Estimated time from diffusion equa-
tions to reach 50% equilibrium of
residual ethylene dibromide in Con-
necticut soils
Reference
Roberts, 1985
Reinhard et al.,
1984
Zoeteman et al.,
1984
Roberts, 1985
Zoeteman et al.,
1980
Reinhard et al.,
1984
Roberts, 1985
Zoeteman et al.,
1980
Roberts, 1985
Zoeteman et al.,
1980
Steinberg et al.,
1987
Source: Mallon, 1989 m
44
-------
Mkrobial Transformations
Microbial transformations include both aerobic and anaerobic processes by which microorganisms obtain
energy for growth, and a variety of other transformation processes (i.e., reductive dechlorination or cometabolic
transformations).
Microorganisms obtain energy from a variety of electron donors and acceptors under different redox.
conditions; the order of preference for electron acceptors is O2 (aerobic metabolism), NO^ (denitrification), SO^
(sulfate reduction), and CO2/carbonate (methanogenesis) (70). The redox state of aquifer and soil solids is an
important factor controlling microbial transformations and the geochemistry of many inorganic and organic
compounds ^ 72). Redox conditions determine the dominant electron acceptor of a subsurface system. Most pristine
groundwaters are oxygenated(70), but introduction of organic contaminants depletes available oxygen. Microorgan-
isms then use alternate electron acceptors (NO^, SO,,., and HCO3.) commonly found in shallow groundwatejr m.
Many subsurface materials contain manganese oxides and iron oxyhydroxides, which also may act as electron
acceptors in microbial processes <72). Microbial reduction of these solid-phase minerals may account for oxidation
of organic matter and mobilization of Fe2+ and MN2" in groundwater (72>73).
Transformations of Halogenated Solvents
In oxygenated subsurface materials, chlorinated solvents, such as TCE, TCA, PCE, and others, are not
ordinarily biodegradable and tend to persist in those environments <28> 70). In anaerobic environments, PCE, TCE,
and TCA undergo reductive dehalogenation <53> 59> 74). Transformation products of TCE are dichloroethylenes and
VC; those of TCA are 1,1-dichloroethane and chloroethane(48> 7S> 59). [TCA also can be nonbiologically transformed
to 1,1-dichloroethylene (1,1-DCE) by an elimination reaction, and to acetic acid by hydrolysis (69).] In addition,
TCA also has a nonbiological fate, whereby 1,1-dichloroethylene is formed from the abiotic dehydrochlorination
of TCA. Acetic acid is a second transformation product formed by abiotic processes with potential of further
biodegradation of 1,1-DCE to VC (49> 59> 74). These reactions can occur in conditions of dilute aqueous solutions at
neutral pH and 20° C common to groundwater. Transformation products of TCE and TCA are more mobile in
groundwater than the parent compounds, and in the case of VC, more carcinogenic. With an estimated half-life
between 0.9 to 2.5 years (40), TCE is resistant to hydrolysis.
Although aerobic biodegradation of TCE and related compounds does not occur under ordinary aerobic
conditions ^ recent work has shown bacteria that oxidize certain other organics including gaseous hydrocarbons
(methane, ethane, propane, or butane) are also able cometabolically to oxidize TCE and other low molecular weight
halogenated compounds (56> 76> "•78> 79). Cometabolism is the biodegradation of an organic substance by a microbe
that cannot use the compound for growth and, hence, must rely on other compounds for carbon and energy.
45
-------
Use of alkalies such as methane, propane, or butane as primary substrates for co-oxidation of chlorinated
compounds has advantages. First, the alkane serves as the primary source of carbon and energy needed to sustain
a stable microbial community when the target pollutant is present in trace amounts as in the case of TCE in
groundwater. These alkanes are commonly used, inexpensive industrial chemicals that are nontoxic to humans and
easily biodegraded.
Transformations of Petroleum-Derived Solvents
Volatile aromatics such as benzene, toluene, ethylbenzene, and BTEX compounds are more soluble in water
than the aliphatic and higher-molecular-weight aromatic constituents of petroleum products m. The presence of
these compounds in groundwater is therefore indicative of subsurface petroleum contaminants<81). Once released
to the subsurface, petroleum compounds are subject to aerobic and anaerobic processes. Low-molecular weight
alkanes and aromatics are readily biodegraded in oxygenated groundwater, and deplete the groundwater of
available oxygen ^ B). Reoxygenation of groundwater may occur through re-aeration from soil gases, groundwater
recharge, and mixing with surrounding oxygenated groundwater(84> 8S>. Mixing processes in aquifers are not efficient.
Although groundwater near the perimeter of the contaminant plume may be re-oxygenated, the interior of the plume
will remain anoxic for a distance downgradient.
Anaerobic biological processes can account for most of the BTEX removal from the plume (86). However,
biogeochemical mechanisms that contribute to anaerobic processes in the subsurface are not well understood.
The impact of anaerobic microbial processes on the fate of monoaromatics, substituted aromatics, and
chlorinated hydrocarbons in anoxic subsurface environments has been studied in laboratory and field
situations ^ Wi 89). Field evidence of biotransformation of xylenes was observed in methanogenic landfill leachate
with their preferential removals compared to other alkylbenzenes present(90).
Although aromatic hydrocarbons were thought to be recalcitrant to biological action without molecular
oxygen(M) or oxygen-containing substituent groups (92), recent field and laboratory data indicate biotransformation
of benzene and alkylbenzenes does occur under anoxic conditions (93> 94>. The products of biotransformatious of
benzene and alkylbenzenes identified under anaerobic conditions included phenol o-, m-, and p-cresols, and various
benzoic acids (94> 95). In other studies, at least 50 percent of toluene and benzene were metabolized anaerobically
to carbon dioxide and methane by a mixed microbial population(96). Intermediates consistent with ring hydroxylation
of benzene and toluene, and methyl oxidation of toluene (such as phenol, cresols, and aromatic acids) were
identified.
Analyses of water downgradient from a crude oil spill at Bemidji, Minnesota, showed phenol plus aromatic,
alicyclic, and straight- and branched-chain aliphatic organic acids that were not original constituents of the oil and
were not found outside the contaminant plume(94). The source of the phenol and aromatic organic acids was thought
; 46
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to be the result of anaerobic biodegradation of benzene and alkylbenzenes. Oxidized products of anaerobic
transformations of benzene, toluene, xylenes, plus six additional substituted benzenes, were identified by gas
chromatograph/mass spectrometer (GC/MS).
Styrene has been biotransformed to styrene oxide by aerobic microorganisms and fungi isolated from soil and
water samples (97).
A variety of environmental factors also may affect transformation of solvents. Such factors may include
nutrient levels, the presence of other chemicals, and certain hydrologic properties of the aquifer itself. Microbial
degradation of m-cresol, toluene, and chlorobenzene were found to vary with transmissivity (a measure of the rate
of groundwater flow through an aquifer) of subsurface layers ™. m-Cresol is an analog of naturally occurring
organic matter that is degraded easily in all layers. Toluene and chlorobenzene degraded most rapidly in moderately
transmissive uniform fine sand. Degradation of compounds that are components of naturally occurring organic
matter, such as phenol, is rapid. Degradation rates of compounds that are not major components of naturally
occurring organic matter, such as toluene, are more variable.
47
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53. Parsons, F. and G.B. Lage. 1985. "Chlorinated Organics in Simulated Groundwater Evironments." Journal
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54. Parsons, R., P.R. Wood, and J. DeMarco. 1984. "Transformations of Tetrachloroethene and Trichloroeth-
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55. Little, C.C., A.V. Palumbo, S.E. Herbes, M.E. Lidstrom, R.L. Tyndall, and P.L. Gilmer. 1988.
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56. Wilson, J.T. and B.H. Wilson. 1985. "Biotransformation of Trichloroethylene in Soil." Applied and
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Compounds by Xanthobacter Autotrophicus GJ10." Applied and Environmental Microbiology, 49:673-677.
59. Vogel, T.M. and P.L. McCarty. 1987. "Abiotic and Biotic Transformations of 1,1,1-Trichloroethane under
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60. Pearson, C.R. and G. McConnell. 1975. "Chlorinated Cl and C2 Hydrocarbons in the Marine
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61. Castro, C.E. and N.O. Belser. 1990. "Biodehalogenation: Oxidative and Reductive Metabolism of 1,1,2-
Trichloroethane by Pseudomonas putida—Biagenetation of Vinyl Chloride." Environmental Toxicology and
Chemistry, 9:707-714.
62. Bouwer, E.J. and P.L. McCarty. 1983. "Transformations of Halogenated Organic Compounds under
Denitrification Conditions." Applied and Environmental Microbiology, 45:1295-1299.
63. Weintraub, R.A., G.W. Jex, and H.A. Moye. 1986. Evaluation of Pesticides in Groundwater. W.Y.
Garner, R.C. Honeycutt, and H.N.Nigg, Editors. American Cancer Society, Washington, D.C.
64. Castro, C.E. and N.O. Belser. 1968. "Biodehalogenation, Reductive Dehalogenation of the Biocides
Ethylene Dibromide, l,2-Dibromo-3-Chloropropane,and 1,2-DibromobutaneinSoil." Environmental Science
and Technology, 2:779-783.
65. Steinberg, S.M., JJ. Pignatello, and B.L. Sawhney. 1987. "Persistence of 1,2-Dibromoethane in Soils:
Entrapment in Intraparticle Micropores." Environmental Science and Technology, 21:1201-1208.
66. Davis, J.W. and S.S. Madsen. 1991. "The Biodegradation of Methylene Chloride in Soils." Environmental
Toxicology and Chemistry, 10:463-474.
67. Davis, J.W. and C.L. Carpenter. 1990. "Aerobic Biodegradation of Vinyl Chloride in Groundwater
Samples." Applied and Environmental Microbiology, 56(12):3878-3880.
68. Mallon, B.J. 1989. Transport and Environmental Chemistry of Selected C, and C2 Chlorinated Compounds
and Petroleum Hydrocarbons in Soils and Groundwater. Lawrence Livermore National Laboratory. n.p.
69. Haag, W.R. and T. Mill. 1988. "Effect of Subsurface Sediment on Hydrolysis of Haloalkanes and
Epoxides." Environmental Science and Technology, 22(6):658-663.
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70. Ghiorse, W.C. and J.T. Wilson. 1988. "Microbial Ecology of the Terrestrial Subsurface." Advances in
Applied Microbiology, 33:107-172.
71. Freeze, R.A. and J.A. Cherry. 1979. Groundwater. Prentice-Hall, Englewood Cliffs, NJ.
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72. Matthess, G. 1982. The Properties of Groundwater. John Wiley, New York, NY.
73. Lovely, D.R., M.J. Baedecker, D.J. Lonergran, I.M. Cozzarelli, EJ.P. Phillips, and D.I. Siegel. 1989.
"Oxidation of Aromatic Contaminants Coupled to Microbial Iron Reduction." Nature, 339:297-300.
74. Klecka, G.M., S.J. Gonsior, and D.A. Markham. 1990. "Biological Transformations of 1,1,1-
Trichloroethane in Subsurface Soils and Groundwater." Environmental Toxicology and Chemistry, 9:1437-
1.451.
75. Barrio-Lage, G.A., F.Z. Parsons, R.M. Narbaitz, and P.A. Lorenzo. 1990. "Enhanced Anaerobic
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76. Wilson, B.H. and M.V. White. 1986. "A Fixed-Film Bioreactor to Treat Trichloroethylene-Laden Waters
from Interdiction Wells." In: Proceedings, Sixth National Symposium and Exposition on Aquifer Restoration
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78. Wilson, B.H., D.W. Pogue, and L.W. Canter. 1988. "BiologicalTreatment of Trichloroethylene and 1,1,1-
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Phase after Mixing." Archives of Environmental Contamination and Toxicology, 13:171-178.
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86. Cozzarelli, I.M., R.P. Eganhouse, and MJ. Baedecker. 1988. "The Fate and Effects of Crude Oil in a
Shallow Aquifer. II. Evidence of Anaerobic Degradation of Monoaromatic Hydrocarbons." In: U.S.
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91/027.
88. Lovely, D.R., and D.J. Lonergan. 1990. "Anaerobic Oxidation of Toluene, Phenol, and p-cresol by the
Dissimilatory Iron-Reducing Organism." Applied and Environmental Microbiology, 56(6): 1858-1864.
89. Kuhn, E.P., P.J. Colberg, J.L. Schnoor, O. Wanner, AJ.B. Zehnder, and R.P. Schwarzenbach. 1985.
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Laboratory Column Studies." Environmental Science and Technology, 19(10):961-968.
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in Two Landfill Leachate Plumes." Environmental Science and Technology, 18:953-961.
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95. Wilson, B.H., J.T. Wilson, D.H. Kampbell, B.E. Bledsoe, and J.M. Armstrong. 1990. "Biotransformation
of Monoaromatic and Chlorinated Hydrocarbons at an Aviation Gasoline Spill Site." Geomicrobiology
Journal, 8:225-240.
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Cultures." Applied and Environmental Microbiology, 53(2):254-260.
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SECTION 3
REMEDIAL OPTIONS
CLEANUP GOALS AND .REMEDIAL OPTIONS
The remedial manager must select treatment options to meet cleanup action levels; the two available
options are immobilization or destruction. Separation/concentration technologies prepare solvent-contaminated
matrices for either destruction or immobilization. The order in which the treatment technologies are presented in
this document is not indicative of the importance of success of the technology.
To achieve stringent remediation objectives, a more energy-dependent remediation technology, such as
incineration or pyrolysis, may be necessary. If less stringent cleanup levels are acceptable, a low-energy
technology, such as soil vapor extraction, may be more appropriate. If only volatiles are present, separation or
concentration technologies may apply. If dioxins are present, only thermal or dechlorination techniques may
apply due to the more restrictive cleanup levels required. Sites with higher concentrations of volatile
components will stress separation/concentration techniques. Sites with higher concentrations of semivolatile co-
contaminants will rely most likely on destruction options to achieve desired cleanup levels. However, with
further development, innovative technologies such as thermal desorption and soil washing may be considered in
the future. The matrix, i.e., soil, sediment, or sludge, also affects the type of technology needed to treat the
contaminants. Sludge and sediment can increase treatment and material handling costs.
Sites contaminated with pure solvent are not likely to be found. Thus, combinations of different
technologies and pre- and post-treatment handling components, either used in series or simultaneously, may be
required to meet cleanup levels. The selection of technology(ies) and treatment train components will be highly
dependent on the concentrations and types of co-contaminants. The presence of metal co-contaminants, for
instance., can make remediation more complex by requiring additional treatment. Metals require immobilization
or solidification/stabilization (S/S) considerations of residuals from other treatments. Thus, depending on which
classes of co-contaminants are present at the site, a treatment train may be required.
The appendix tables compare CERCLA solvent sites with the treatment combinations selected. A
technology chosen as the principal component of a treatment train in one case — for example, incineration
followed by S/S — might act as a secondary component (post-treatment) in a different treatment train — such as
solvent extraction followed by incineration. The remedial manager must consider each element of the process,
from excavation, materials handling, and primary treatment, to treatment of residual streams. One concern at
54
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solvent sites is air emissions from organic volatilization. They may occur as a result of physical operations such
as drilling, excavation, stockpiling, and handling; as a byproduct of chemical reactions during treatment, such as
S/S; and from biological digestion processes.
Some technology descriptions that follow include a schematic diagram for an overall treatment process,
from excavation to post-treatment.
TYPICAL TREATMENT COMBINATIONS
The treatment combinations described below deal primarily with solvent-contaminated soil. The
remedial manager may find sediment and sludge on site. Ponds and streams can become contaminated directly
as holding ponds/lagoons or by migration of solvent compounds. Sludge from lagoon bottoms and processing
equipment will require treatment Sediment, which may also require treatment, contains a smaller particle size
distribution and higher moisture content than soil. After pretreatment dewatering, sediment can be processed as
a wet soil. In comparison to sediment, sludge contains highly concentrated contaminants in a noncohesive and
unsupportive matrix. Sludge treatment options are more limited because dewatering the matrix is difficult.
On-site remedial techniques for optimal recovery of pure compounds or mixture of compounds should
precede implementation of the selected destruction technology. A physical separation option, such as soil-vapor
extraction to lower the level of VOCs in the soil, should be considered for pretreatment at a solvent site to help
prevent fugitive emissions during excavation. Soil-vapor extraction may offset excavation costs when emission
controls are implemented.
Solvent-contaminated sites may contain highly mobile organic compounds. The most common solvent-
contaminated sites contain BTEX and chlorinated solvents. Other hydrocarbon solvents and BTEX are low-
solubility floating compounds, while chlorinated organics are low-solubility sinking compounds. Thus,
groundwater contamination almost always constitutes an immediate concern. Remedial options for these sites
always must include groundwater treatment.
Pretreatment by recovering solvent contamination (Tight nonaqueous-phase liquid - LNAPL) floating on
top of an aquifer may reduce the contaminant load in many sites. The groundwater level is lowered by pumping
a well placed in the middle of a spill area, thereby concentrating the relatively nonsoluble contaminant at the
lowest point as it flows with the groundwater in the well. Then, LNAPL is collected.
There are many options for a remediation strategy. The subsections on destruction and separa-
tion/concentration technologies include tables which describe technologies and pre- and post- treatment handling
techniques commonly used with them.
55
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Frequently used materials handling procedures at hazardous waste sites include:
• Excavation and removal „
<,• ^
• Dredging
• Size and volume reduction
• Dewatering
• Conveying systems
A wide range of equipment is available for conducting materials handling procedures. Due to the volatility
of solvents, it may be necessary to enclose equipment under negative pressure with air pollution control. Further
information about materials handling can be found in Survey of Materials Handling Technologies at Hazardous
Waste Sites m.
Treatment Costs
When evaluating total treatment costs, the remedial manager must compare all elements of each train,
including the principal components and costs of material handling through the final disposal of residuals. The
treatment costs for well developed and field-tested technologies (such as incineration and bioremediation) can be
quite reliable, but estimates for innovative and emerging technologies become increasingly less reliable. The
following are some of the capital and operation and maintenance (O&M) costs typically considered when estimating
how much a remediation will cost.
Direct costs include the following:
• Remedial action construction costs
• Component equipment costs
* Land- and site-development costs
• Building and services costs
• Relocation of affected population costs
« Disposal of waste material costs
Indirect capital costs include the following:
• Engineering expenses
* Contingency costs
• Project management costs
56
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Operation and maintenance costs are those that must be incurred after construction but during the remediation phase
to ensure continued efficiency of the treatment process. The major components of O&M costs include:
» Operating labor
» Maintenance materials and labor
* Auxiliary materials and energy
» Residuals disposal costs
* Purchased services
» Administrative costs
» Insurance, taxes, and licenses
» Maintenance reserve and contingency costs
IMMOBILIZATION TECHNOLOGIES
Containment Technology
Containment is a common component in the overall remediation of a solvent site. Initial on-site actions to
establish containment provisions will accomplish the following:
* Minimize migration of contaminated groundwater from the site
« Prevent the increase of groundwater contamination due to water percolation and precipitation
• Control population exposure to contaminants
* Contain contaminants while remediation proceeds
o Reduce air emissions
Thus, containment control ranges from a surface cap that limits infiltration of uncontaminated surface water
to subsurface vertical or horizontal barriers that limit migration of contaminated groundwater.
Capping Systems
Capping systems reduce surface-water infiltration, control population exposure, prevent erosion, control gas
and odor emissions, improve aesthetics, and provide a stable surface over the waste. Caps can range from a simple
native soil cover or plastic to a full RCRA Subtitle C composite cover. If a cap is temporary, knowledge of final
remedial options may help in determining the type of cap to be used so as not to increase remedial costs later in
the project. The following RREL computer models will assist the remedial manager in cap design.
57
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* Hydrologic Evaluation of Landfill Performance (HELP) evaluates the rate of infiltration of surface water
through capping material.
• F-COVER evaluates potential design problems in the individual capping elements.
* VegCov provides guidance on the selection of a vegetative cover.
RREL programs are available from the U.S. EPA Municipal Solid Waste & Residuals Management Branch
(MSWRMB) at (513) 569-7871.
Vertical Barriers
Vertical barriers minimize the movement of contaminated groundwater off site or limit the flow of
uncontaminated groundwater on to the site. Common vertical barriers include slurry walls in excavated trenches,
grout curtains formed by injecting grout into soil borings, cement-bentonite filled borings or holes formed by
withdrawing beams driven into the ground, and sheet-pile walls formed of driven steel.
Solvent compounds can affect caps and vertical barriers. The permeability of bentonite may increase
significantly when it is exposed to high concentrations of water-soluble salts, electrolytes (sodium, calcium, heavy
metals), strong organic/inorganic acids, and solvents having a very low dielectric constant. Specific gravity of salt
solutions greater than 1.2 affects bentonite. In general, bentonite permeability does not change significantly if the
leachate is at least 50 percent water and no separate-phase organic chemicals are present. High concentrations of
solvents floating atop the groundwater can lead to degradation of the bentonite. In general, soil/bentonite blends
resist chemical attack best if they contain only 1 percent bentonite and 30 to 40 percent!natural soil fines.
Treatability tests should be performed to evaluate the chemical stability of the barrier if these conditions are
suspected.
Concrete and cement mortars can be vulnerable to attack from organic solvents and liquids. The presence of
free-phase solvents in the groundwater can influence the integrity of a grout curtain. Therefore, chemical
compatibility of the grout with the solvent should be evaluated prior to construction.
Carbon steel used in pile walls quickly corrodes in dilute acids, slowly corrodes in brines or salt water, and
remains mostly unaffected in organic chemicals or water. The water-soluble salts reduce the service life of a steel
sheet pile; corrosion-resistant coatings extend their anticipated life. Major steel suppliers will provide site-specific
recommendations for cathodic protection of piling.
Geomembranes can be used to form vertical barriers in applications where chemical degradation of
conventional grouts is anticipated. Geomembranes are used as liners in lagoons and landfills and significant
58
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chemical resistance data about them is available. The geomembrane curtain can be placed as an outer protective
component of a conventional slurry wall, or as the primary vertical curtain without the slurry wall component.
Geomembrane curtains are commercially available in the form of interlocking high-density polyethylene (HDPE)
panels. A hydrophilic polymer that swells in the presence of water is used to seal them. The impact of potential
contaminants on the integrity of the HDPE and the seal must be determined using the EPA 9090 test prior to field
use. In general, solvents will not degrade the physical properties of HDPE.
Horizontal Barriers
Horizontal barriers underlie a sector of contaminated materials without removing the hazardous waste or soil.
Grouting techniques reduce the permeability of underlying soil layers. Studies performed by the U.S. Army Corps
of Engineers (COE) ® indicate that conventional grout technology does not produce an impermeable horizontal
barrier because it does not ensure uniform lateral placement of the grout. These same studies found greater success
with jet-grouting techniques in soils that contain sufficient fines to prevent collapse of the wash hole and no large
stones or boulders to deflect the cutting jet.
Implementation Costs
Accurate costs have not been established for horizontal barriers since few have been constructed. Typical
equipment costs range from $1,200 to $3,000 per day. Borehole spacing is a function of grout penetration; it is
site specific. Typical borehole spacing ranges from 6- to 10-feet centers. Horizontal barrier costs for boring and
injection may exceed $80 per square foot. The cost of the grout is a relatively minor expense.
Construction costs for capping systems are shown in Table 3-1. Costs for vertical barriers are shown in Table
3-2.
TABLE 3-1. CAPPING COSTS
Component
Installation
Total Cost
Bedding layer
On-site excavation, hauling, spreading, com-
paction
1.00 to 2.50/yd3
Gas collecting layer
Off-site excavation, hauling, spreading, and
collector pipes
Geonet alternative
12.00 to 18.00/yd2
0.40/ft2
Composite barrier: clay
On-site excavation, hauling, spreading, com-
paction
Geosynthetic clay liner
Add for off-site clay «20 mile haul)
2.40 to 6.00/yd3
,0.85/ft2
8.00 to 14.00/yd3
59
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TABLE 3-1 (Continued)
Component
Composite barrier: geomembrane
Drainage layer
Protective layer
Vegetative layer
Asphalt hardened cap option
(4-6 in)
Concrete hardened cap option
(4-6 in)
Installation
Installed
HOPE - 60 mil
PVC - 40 mil
Off-site excavation, hauling, spreading, and
collector pipes
Geonet alternative
On-site excavation, hauling, spreading, com-
paction
Topsoil hauling, spreading, and grading
Delete protective and vegetative layers, haul-
ing, spreading, rolling
Delete protective and vegetative layers, on-
site mixing, hauling, spreading, finishing
Total Cost
<$)
0.50/ft2
0.35/ft2
12.00 to 18.0O/yd2
0.40/ft2
1 .00 to 2.50/yd3
10.00 to 16.00/yd3
4.00 to 6.00/yd2
6.00 to 1 1 .00/yd2
TABLE 3-2. VERTICAL BARRIER COSTS
Component
Soil/bentonite slurry wall
Cement/bentonite slurry wall
Vibrating beam
Injection grout
Steel sheet-pile wall
Depth
30ft
30 to 50 ft
50 to 1 25 ft
30ft
30 to 50 ft
50 to 1 25 ft
30ft
30 to 50 ft
50 to 1 25 ft
Cost
($/ft2)
3 to 7
6 to 11
9 to 15
3 to 7
6 to 11
9 to 15
9 to 35
1 8 to 55
27 to 75
1 6 to 28
60
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S/S TECHNOLOGIES
S/S processes reduce the mobility of a contaminant, either by physically restricting its contact with a mobile
phase (solidification) or by chemically altering/binding the contaminant to reduce its mobility (stabilization). Figure
3-1 depicts a schematic diagram of an S/S process. Stabilization can be achieved without solidification, while
solidification usually includes stabilization. Solidification also refers to the use of binders for waste bulking to
facilitate the handling of liquid wastes.
Binding agents fall into several classes. The most common are cementitious and pozzolanic materials,
including Portland™ cement, fly ash/lime, and fly ash/kiln dust. Binding agents form a solid, resistant,
aluminosilicate matrix that can occlude waste particles, bind various contaminants, and reduce permeability of the
waste/binder mass. Proprietary agents added to the binder may improve specific properties of S/S-treated waste,
such as strength, curing rate, contaminant binding, pore size, or waste dispersion.
*r-Qperata
I Slu^aSsdrrer*
Transfer Purp
•I
Sirfee/Sedmert
Etewateiing Uit
Filtrate to
• AcfcWonsI
Dewafering
Ogriiamirated 'jj Bjpass
[fewaered
u&Maiz iiao/sa
Figure 1
Figure 3-1 Schematic for Ex Situ SolidificationJSfciiilizatiMi of Cojrtam hafed Soils
61
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Treatment Combinations
Immobilization treatment usually does not apply to sites contaminated with organics only. However, when
the contaminants are inorganics or volatile organics, S/S technology can be combined with other remediation
processes in successfiil treatment trains such as soil vapor extraction (SVE) or biotreatment followed by S/S for in
situ treatment, and solvent extraction, thermal desorption, or biotreatment followed by S/S for ex situ treatment.
Data suggest that silicates used with lime, cement, or other setting agents can stabilize sludges and soils
contaminated with solvents 0).
Technology Applicability
Organic Compounds: Two considerations for organic compounds in S/S treatment are the immobilization
of the organic contaminant and the potential effects of organic compounds on the solidification matrix or on
immobilization of other contaminants.
Organic compounds at varying contaminant levels can retard or prevent setting of typical S/S matrices.
Connor(4) found that many types of organics have adverse effects on set/cure times, cement hydration, and product
properties. For example, unconfined compressive strength decreases with increasing organic content. To date,
concentration levels for organics not treatable with conventional binder systems have not been established.
Owing to the relatively high vapor pressure of many solvents, S/S is not a preferred remediation method
because of its inability to reduce the contaminant's mobility and because of the volatilization which occurs during
curing. However, in three specific cases, S/S technology may be useful: (1) when used to control residual
contamination (such as metals) following primary treatment for solvent removal or destruction, (2) when used to
control low levels of semivolatile organics, and (3) when used to improve materials-handling properties of a liquid
or sludge prior to remedial treatment.
Organic compounds, although present below cleanup action levels, may interact with a binder or inorganic
contaminants. They can exert a negative influence on S/S treatment by forming complexes which hinder reactions
that immobilize metals. Organic compounds that form anions at the particular pH level of the waste, such as
alcohols and carboxylic acids, are most likely to bind with cationic metals. In addition, the organic compounds may
be hydirophobic; thus, they can hinder the intimate waste-binder contact necessary for metals immobilization.
Organics may volatilize during mixing and the period between mixing and curing of waste in the S/S material
handling process. Even organics with low vapor pressures can be dispersed into the air. Organic volatilization is
enhanced when treatment produces heat, as with some cementitious binders. Volatilization must be addressed at
sites containing benzene and low molecular weight solvents since they exert appreciable vapor pressures at 20° C.
62
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Solidification, or waste bulking, sometimes facilitates the handling of organic-dominated
wastes/sediments/sludges in preparation for off-site disposal/treatment or for interim management prior to oil-site
remediation. Two entries in the Alternative Treatment Technology Information Center (ATTIC) database describe
this apjproach: solidification followed by RCRA capping. This process usually produces containment of NAPLs.
The treatment agent is often a lime-containing waste, such as baghouse dust from limestone calcination or cement
production (sometimes called kiln dust or fly ash) and fly ash from coal-fired power plants. As with S/S treatment,
the possibility of organic volatilization must be considered in waste-bulking processes. There is no clear evidence
that organics will volatilize in the bulking process, but prudence suggests testing for volatilization until sufficient
scientific data can prove the practice safe.
Metals: Often, S/S has been applied to wastes and soils containing metals. Solvents and other contaminants
such as metals commonly are found at the same site. Unlike organic compounds that can be destroyed, metals can
only be changed in oxidation state, chemical species, and physical form. Thus, the goal of S/S is to convert the
metal to a less mobile form and physically restrict its contact with water and air. Cementitious materials are the
most common binders. In addition to solidification, calcium hydroxide in these binders can cause precipitation of
many metals as sparingly-soluble oxyhydroxides. Additionally, metals can adsorb to the aluminosilicate matrix or
replace cations normally present in the crystalline structures of cement.
The high alkalinity that favors precipitation of many metals can hinder immobilization if the metals form
soluble anionic hydroxides at a high pH. Cadmium, for example, can precipitate at a moderately alkaline pH as
cadmium hydroxide, but becomes increasingly soluble at a higher pH, owing to the formation of an anionic cadmium
hydroxide. Because the pH for minimum ;solubility differs for each metal, one set of conditions may not cover all
metal-insoluble hydroxides.
Sulfide agents can produce highly insoluble metal compounds with cationic metal species, such as copper.
However, the stability of these compounds depends on the permanent exclusion of oxygen and other oxidizers from
contact with the metal sulfide(5). For some metals, the oxidation state also affects toxicity, for example, trivalent
versus Ihexavalent chromium.
Another complication in S/S treatment is the speciation of metals in the raw waste. Chromium, arsenic,
selenium, and some other metals form both soluble cationic species and soluble oxide anions, for example, chroinate
and arsenite. The latter form will not precipitate as hydroxides; their sorption differs from that of cationic species
in a cement matrix. Although rarely performed, analyses of raw wastes and their leachates for metal oxidation state
and chemical species are important in designing the most effective immobilization treatment.
Technology Status/Performance
Treatability test data compiled from numerous sources indicate that the metals found as co-contaminants
63
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at solvent sites are amenable to S/S. The particular S/S system that will perform well on a given contaminated
material must be determined by site-specific screening and treatability tests. Some results are shown in Table 3-3.
The chromium-containing wastes illustrate the importance of the contaminant oxidation state in stabilization. Ideally,
the waste is tested for contaminant speciation so that prior experience with the same chemical form of the
contaminant can assist decision makers in the selection of binders for treatability testing. Reduction of hexavalent
chromium followed by precipitation as chromium hydroxide is a common water-treatment method that applies to
S/S technology since the hydroxide is compatible with cement matrices and any solubilized metal exists hi the less
toxic form.
Multiple metals may not need to be remediated at all sites since sometimes there is need for only one or two
metals. However, a process can be developed to meet cleanup criteria for multiple metals. The appearance of
increased leachable metals in residuals following treatability tests is not unusual. It can result from contaminant
destabilization (soluble complex formation with treatment agents), sample heterogeneity, or analytical error.
Representative sampling, sample homogenization, multiple treatment, and analytical replication may be necessary
to ensure useful results.
The performance of S/S technology is assessed by physical tests (compressive strength, permeability,
resistance to physical weathering, etc.) by chemical tests that measure the leachability of contaminants after
treatment and by total waste analysis. The Toxicity Characteristic Leaching Procedure (TCLP) is a laboratory
method specified for characteristically toxic wastes regulated under RCRA. A detailed description of how to
evaluate S/S technology as a remedial method for a particular waste is given in Solidification/Stabilization of
CERCLA and RCRA Wastes: Physical Tests, Chemical Testing Procedures, Technology Screening and Field
Activities ®.
No existing theoretical or empirical method can predict the degree of immobilization attained by applying S/S
technology to a particular waste. Site-specific screening and treatability tests determine whether S/S is a suitable
and cost-effective remediation method; they can also optimize the ingredient. In addition to ensuring compliance
with contaminant- or site-specific leachability limits, these tests can identify the S/S mix that balances cost and
volume increases hi achieving immobilization. The volume increase upon S/S treatment can cause a significant
impact upon disposal space, transportation, and landfill costs.
64
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TABLE 3-3. S/S METAL TREATABILITY TEST RESULTS
Contaminant
Arsenic
Chromium (III)
Chromium (VI)
Copper
Initial
Concentration
420 mg/L
33 to 3,960 mg/L
ND
ND
Reduction
(%)
22 to 91
ND
34 to 99
76 to 88
ND
97 to 99
51 to 99
Binders
Cement kiln dust;
slag/lime/fly ash/ silica;
silicate
Cement kiln dust;
slag/lime/fly ash/silica;
sulfide silicate
Sulfide silicate
Cement; cement/ addi-
tives; cement/ sulfide;
lime/fly ash
ND = No data available
Source: U.S. EPA, KREL, Cincinnati, Ohio
Implementation Costs
The cost of treatability screening (initial S/S applicability) for a specific site can range from $10,000 to
$20,000. Treatability costs for remedy selection are higher and more variable depending on the ratio and matrix
of binder types and water contents to be investigated. Associated analytical costs increase dramatically as the
number of organic compounds analyzed increases. Costs of $50,000 or more are not unusual.
Connor(4) estimated the cost of treatment, transportation, and landfill disposal for some common S/S systems:
prices ranged from $74 to $397 per ton for landfilling on site, and from $119 to $517 per ton for landfilling 200
miles from the contaminated site. The cost was quite dependent on binder cost and on the solids content of the
waste, since much more binder is required to solidify low-solids wastes. Locally available waste products — fly
ash and kiln dust — can be inexpensive S/S agents, while manufactured treatment agents — organic polymers —
can be quite expensive.
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Data Requirements
Some of the factors affecting S/S are shown in Table 3-4. Collecting and evaluating physical and chemical
data about these factors can help determine the applicability of S/S to the contaminant and matrix.
From a remediation viewpoint, the most important consideration in binder selection is the chemical
composition of the material to be treated. Numerous samples from various locations on site should be analyzed for
the active solvent ingredients and other characteristically hazardous compounds. Test samples should include full
extracts or digestates of the raw waste, TCLP, and any other regulation-mandated test to facilitate an estimate of
the leachability of each constituent. Areas determined by site characterization data to be sources of migrating
contaminants should be the targets of a more extensive sampling program.
la addition to chemically characterizing the waste, the data will locate typical and worst-case samples for
treatability tests. In multi-contaminant wastes, several worst-case samples include high metals/moderate orgaoics,
moderate metals/high organics, and metals and organics in hydrophobic carrier solvents.
The remedial manager should study the chemical characterization of the waste and research the available
literature and vendor treatability data to determine whether the waste is comparable to another material that has been
successfully treated. With organic contaminants, only treatability data- that clearly indicate no volatilization or
volatile recovery during treatment are relevant.
66
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TABLE 3-4. FACTORS AFFECTING S/S TREATMENT
Factor
Cyanides content
Halide content
Inorganic salts content (soluble salts of man-
ganese, tin, zinc, copper, and lead)
Oil and grease content ,
Organic content
Particle size
Phenol concentrations
Semivolatile organics
Sodium arsenate, borate, phosphate, iodate,
sulfide, carbohydrate concentrations
Sulfate
Solids content
Volatile organic concentrations
Potential Effect
Increases setting time by interfering with
bonding of waste materials (>3,000 ppm).
Retards setting; leaches easily.
Adversely affects product strength and curing
rates. Reduces dimensional stability (swelling,
cracking) of the cured matrix, thereby increas-
ing teachability potential.
Weakens bonds between waste particles and
cement by coating the particles (>10%).
Adversely affects setting and curing of binder.
Typical maximum (20 to 45 wt% total organic
content). Decreases durability.
Can delay setting and curing (insoluble materi-
al passing through a No. 200 sieve). Small
particles coat larger particles, weakening
bonds between particles and cement or other
reagents. Particle > 1 inch in diameter not
suitable.
Lowers product strength (>5%).
Interferes with bonding {> 10,000 ppm) of
waste materials.
Retards setting and curing of cement. Reduc-
es the ultimate strength of the product.
Retards the setting of concrete. Causes swel-
ling due to the formation of calcium sulfoalu-
minate hydrate.
Wastes with <15% solids requires large
volumes of reagents, greatly increasing the
volume and weight of the end product.
Volatiles not effectively immobilized. Driven
off by heat of reaction.
Source: U.S. EPA, 1988 (6>
DESTRUCTION TECHNOLOGIES
Destruction technologies for remediation of contaminated soil, sludge, and sediment at solvent sites can be
divided into three categories: thermal, chemical, and biological. Destruction technologies either destroy or detoxify
hazardous wastes by altering the chemical structure of the constituents or breaking down the chemical structure into
its basic components.
67
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Table 3-5 lists the typical treatment combinations for destruction options. Waste preparation includes
excavation and/or dredging, conveying the soil, dewatering sediment/sludge, screening to remove debris, and
reducing particle size. Table 3-6 shows the applicability of destruction technologies to typical contaminant groups
found at solvent sites.
TABLE 3-5. TYPICAL TREATMENT COMBINATIONS FOR
DESTRUCTION TECHNOLOGIES
Pretreatment/Materials
Handling
Free-product pumping
Soil-vapor extraction
Excavation/conveying
Dewatering
Screening/size reduction
In situ steam stripping
Free-product pumping
Soil-vapor extraction
Excavation/conveying
Screening/size reduction
In situ steam stripping
Free-product pumping
Soil vapor extraction
Plowing
Free-product pumping
Soil-vapor extraction
Excavation/conveying
Screening/size reduction
In situ steam stripping
Destruction
Technology
Incineration or
Pyrolysis
Biodegradation (excavated soil)
. Biodegradation (in situ)
Chemical dehalogenation
Post-Treatment/Residuals
Management
Air pollution control
Scrubber effluent treatment/disposal
Ash treatment/disposal
Solids dewatering
Solids treatment/disposal
Water treatment/disposal, recycle
VOC emission control
G rou nd wate r treatme nt/re-i njecti on
Air pollution control
Solids treatment/disposal
Washwater treatment/disposal
TABLE 3-6. APPLICABILITY OF DESTRUCTION TECHNOLOGIES
TO CONTAMINANT CLASSIFICATIONS
Group
No.
W01
W04
W07
W09
Contaminant
Group
Halogenated nonpolar
aromatics
Halogenated aliphatics
Heterocyclics and simple
nonhalogenated aromatics
Other polar organic com-
pounds
Destruction Options
Thermal
Destruction
•
•
•
: •
Chemical
Dehalogenation
e
e
o
o
Bioremediation
«
e
e
•
In Situ
Bioremediation
e
! e
•
•
w - Demonstrated effectiveness
Q - Potential effectiveness
O - No expected effectiveness
Source: U.S. EPA Engineering Bulletins
68
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Thermal Destruction Technologies
Incineration and pyrolysis are two thermal technologies that destroy contaminants in soil, sludge, and sediment
but leave noncombustible inorganics.
Incineration
Incineration treats organic contaminants in solids, liquids, and gases by subjecting them to temperatures
greater than 1,000° F in the presence of oxygen. This causes the volatilization and combustion of the organic
contaminants and converts them to carbon dioxide, water, hydrogen chloride, nitrogen oxides, and sulfur oxides.
Three common types of incineration systems can treat contaminated solids: the rotary kiln, the infrared incinerator,
and the circulating fluidized bed units. The rotary kiln and the infrared units contain a primary chamber that usually
operates in the temperature range of 1,000° F to 1,800° F. The rotary kiln is a refractory-lined, slightly-inclined,
rotating cylinder that serves as a combustion chamber. Figure 3-2 is a schematic diagram of a rotary kiln
incineration process. The infrared unit uses electrical resistance heating elements or indirect-fired radiant U-tubes
to heat material passing through the chamber on a conveyor belt.
As material passes through the primary chamber, the unit evaporates moisture, volatilizes, and partially
combusts the organic contaminants. Since conversion of the organic contaminants is inadequate in the primary
chamber, the system sends the partially combusted gases to a secondary combustion chamber that usually operates
between 1,600° F to 2,200° F. The gases are held at temperature for a residence time of 2 seconds to ensure
adequate destruction of contaminants. These units are most commonly used for solids and sludges. The operating
conditions (temperature, residence time, etc.) vary depending on contaminants and regulations as specified in 40
CFR Part 264 Subpart O and Part 265 Subpart O for RCRA-regulated units, and 40 CFR Part 270 for TSCA-
regulated units.
The circulating fluidized bed (CFB) unit uses high-velocity air to circulate and suspend the waste particles
in a combustion loop. The CFB is excellent for treating sludges. Operation of the CFB is sensitive to particle size
and cannot tolerate feeds that slag at low temperatures. The CFB operates in the temperature range of 1,500-1,800"
F and does not need a secondary combustion chamber to achieve adequate destruction of organic contaminants. It
can handle liquids and gaseous waste better than other incinerators, operates at a lower temperature, and produces
less emissions.
Incinerator off-gas requires treatment by an air pollution-control (APC) system to remove particulates and
neutralize and remove acid gases (HC1, NOX, and SOJ. Baghouses, venturi scrubbers, and wet electrostatic
precipitators remove particulates; packed-bed scrubbers and spray driers remove acid gases. Limestone added to
the combustor loop removes acid gases in,the CFB.
69
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AF-Cpeatd
•Hue(geiBe
-------
controlled by equipment design (enclosed feed, ash, and dust-control systems) and operating procedures.
Technology Applicability: Incineration has effectively treated soil, sludge, sediment, and liquids containing
many of the organic contaminants found at solvent sites including halogenated and nonhalogenated volatiles and
semivolatiles, and other organics such as dioxins/furans, PCP, and PAHs. Incineration has treated solvent wastes
at the most stringent cleanup levels. A substantial body of trial burn results and other quality-assured data verify
that incineration can remove and destroy organic contaminants from a variety of waste matrices to the ppb or even
the parts-per-trillion (ppt) level (7>8). However, incineration does not destroy metals. They will be present in
different residuals (bottom ash, cyclone ash, and liquid) depending on the volatility of their compounds and the
incinerator operating conditions (9).
The moisture content and heating value of the contaminated wastes are important parameters that affect the
economics of the incineration process. High moisture content and low heating value increase fuel requirements.
High moisture content and very high heating values reduce the incinerator's capacity. Several feasibility studies
have screened out incineration due to the high moisture content of the wastes. The studies are questionable,
however, since engineering solutions can improve the economics. When a waste has both high heating value and
moisture content, the moisture content cools the products of combustion efficiently and permits higher throughputs
(7). In addition, mechanical or thermal dewatering techniques can reduce high moisture content, and blending high
heating value wastes with wastes of low heating value can reduce incineration costs.
Technology Status/Performance: Thermal destruction has been proven in commercial use. Newer techniques
being, studied lower temperatures in primary incineration chambers and add agents — lime, iron oxide, fly ash,
proprietary inorganics — to bind and treat volatile metals in the incinerated material.
Incineration is the most regulated remediation technology and the process most frequently chosen for the
destruction of organic contaminants. Of the approximately 400 RODs written for solvent-contaminated sites, 32
specified incineration as the remedial technology. These sites are listed in Table 3-7.
TABLE 3-7. INCINERATOR SELECTIONS AT SOLVENT SITES*
Region
1
1
1
1
1
1
Site Name
Baird & McGuire
Davis Liquid Waste
Cannon Engineering Corp.
Charles George Reclamation Trust
Pinette's Salvage Yard
Wells G&H
Location
Hoibrook, MA
Smithfield, Rl
Bridgewater, MA
Tyngborough, MA
Saco, ME
Woburn, MA
71
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TABLE 3-7. (Continued)
Region
1
2
2
2
2
2
2
2
2
3
3
3
3
4
5
5
5
5
6
6
6
6
6
7
8
8
10
Site Name
W.R. Grace and Co., Inc.
Hooker-Hyde Park
Bridgeport Rental & Oil Services
Ewan Property
Reich Farms
Bog Creek Farm
Claremont Polychemical
SMS Instruments, Inc.
FAA Technical Center
Wildcat Landfill
Drake Chemical
Greenwood Chemical Co.
MW Manufacturing
Celanese Corp.
Acme Solvents
Big D Campground
Cliff/Dow Dump
Pristine, Inc.
Brio Refinery Co.
Sikes Disposal Pit
Triangle Chemical
North Cavalcade Street
Motco, Inc.
Vogel Paint and Wax Co.
Woodbury Chemical Co.
Sand Creek Industrial
Western Processing
Location
Acton, MA
Niagara Falls, NY
Logan Township, NJ
Shamong Township, NJ
Dover Township, NJ
Howell Township, NJ
Old Bethpage, NY
Deer Park, NY
Pomona, NJ
Dover, DE
Lock Haven, PA
Newton, VA
Valley Township, PA
Shelby, NC
Winnebago, IL
Kingsville Township, OH
Marquette, Ml
Reading, OH
Friendswood, TX
Crosby, TX
Bridge City, TX
Houston, TX
La Marque, TX
Maurice, IA
Commerce City, CO
Commerce City, CO
Kent Valley, WA
72
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Implementation Costs: The cost of incineration includes fixed and operational costs. Fixed costs are one-
time expenses including site preparation, permitting, mobilization/demobilization, trial burn, and equipment costs.
Operational costs are ongoing expenses including labor, utilities, fuel, and maintenance. Fixed costs are relatively
independent of site size. Operational costs vary significantly depending on the type of waste treated. Total costs
vary significantly depending on the site size. Figure 3-3 shows the effect of site size on incinerator costs(10). On
the average, total costs for incineration range from $200 to $1,500 per ton. These figures include excavation,
materials handling, and disposal.
Vfery Small Smal Medium Large
<5,000 5,000-15,000 15,000^30,000 >3Q,000
Site SEE (Tons Tisrfed)
F1GURE3-3 Effect of Site Size en kicherator Cost [1O]
73
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Data Requirements: A summary of performance data for incineration is presented in Table 3-8. A summary
of factors affecting incineration performance is given in Table 3-9. These factors determine the data requirements
for incineration, i.e., the type of information (site/waste characterization, treatability study, etc.) needed to
implement this technology at a solvent site.
TABLE 3-8. SUMMARY OF PERFORMANCE DATA FOR INCINERATION
Site Name
Lenz Oil, Lemont, IL (11)
Sydney Mines, Brandon,
FL ""
Stockton, CA (11)
Brio Site, Friendswood,
TX '"'
McColl Superfund Site, Fulle-
rton, CA "31
System
ENSCO rotary kiln
ENSCO rotary kiln
Ogden CFB
Shirco Infrared System
Ogden circulating fluidized bed
(full scale)
Initial
Hydrocarbons
Hydrocarbons
Total hydrocarbons
Carbon tetrachloride
Carbon tetrachloride
Performance
Reduced concentrations to
<5.0 mg/kg
Treated to <5.0 mg/kg
Treated to < 1 .0 mg/kg
99.99% removal
99.99% removal
TABLE 3-9. FACTORS AFFECTING INCINERATION PERFORMANCE
Factor
Ash fusion temperature
Halogenated organic compound concen-
tration
Heating value
Metals content
Nonvolatile heavy metals (Cr, Ag, Ba)
Volatile heavy metals (Hg, Pb, Cd,
As)
Alkali metals (Na, K)
Moisture content
Organic phosphorous content
Particle size
PCBs, dioxins
Potential Effect
Operation of the kiln at or near the ash fusion temperature can cause
melting and agglomeration of inorganic salts (slagging).
Forms acid gases, which may attack refractory material and/or impact air
emissions.
Auxiliary fuel is required to incinerate waste with a heating value < 8,000
Btu.
Ash may fail TCLP. Trivalent Cr can be oxidized to more toxic hexavalent
Cr.
Vaporize; become difficult to remove using conventional APC equipment.
Ash may fail TCLP.
Salts have low melting points; may cause slagging.
Higher moisture content increases feed handling and energy requirements.
Forms acid gas (high concentrations), which contributes to refractory
attack and slagging problems.
Oversized material requires size reduction. May hinder processing. Fines
affect particulate carryover
Requires higher temperatures and long residence times for destruction.
May require special permits. '.
74
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Pyrolysis
Pyrolysis (high-temperature thermal desorption/distillation) is an innovative treatment technology that differs
from incineration because it uses heat in the absence of oxygen to volatilize and decompose organic materials.
Figure 3-4 depicts a schematic diagram of a pyrolysis process. It transforms hazardous organic contaminated
materials into less hazardous gaseous components, liquid fractions containing concentrated contaminants, and a solid
residue (coke) containing fixed carbon and ash. The soil remains in its original state. The gas product contains
lower molecular weight hydrocarbons, CO, H2, and methane. Pyrolysis is an energy intensive process that can treat
the same kind of contaminants as incineration.
Pyrolysis operates at temperatures between 1,000 and 2,200° F. Contaminated materials are heated indirectly
in stages at temperatures which exceed the boiling points of the targeted constituents to volatilize light organics and
water, hydrocarbons, and heavier organics such as PAHs, PCB, and dioxin. Clean solids are discharged and the
gases are condensed or incinerated. Cracking organic contaminants produces coke by-products and gas, while
desorption mechanisms concentrate the contaminants. The coke and gas can be burned to reduce external fuel
requirements. Pyrolysis allows more control, permits higher throughput than incineration, and has the potential to
produce fewer air pollutants and operate at lower temperatures. Chlorinated compounds can be dechlorinated using
catalysts or other additives.
75
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Corrtereate
Light Oigan'c
Liquid Phase «>
Rinher Treatment
W Ftecoveiy
-+\
Aqueous Phase to
1 Fur" ~ -
*—+
HsavyOigar* Liquid
Phase (ifaiy)to
" FurtharTisatitEi*
Recoveiy
Su-eWtfcr Bedamofon
Figure 3-4 Schematic for Pyrolysis
-------
may not be appropriate for solvent-only contaminated sites.
Technology Status/Performance: Pyrolysis is an emerging technology; performance data are limited. Tests
have been performed on PCBs at the Wide Beach Superfund site in Bryant, New York, and the Waukegan Harbor
Superfund site outside Chicago, and on PAHs at the Pensacola Superfund site, in Pesacola, Florida. Current uses
of pyrolysis technology are in the oil industry where tank bottoms, oily soil, and separator sludge are being
recycled.
Implementation Costs: Pyrolysis costs are comparable to those of incineration and are a function of site size.
Capital equipment, mobilization and demobilization, and energy costs are high. There are also added costs for waste
stream treatment.
Data Requirements: Table 3-10 is a summary of the primary factors affecting pyrolytic performance. These
factors determine the data requirements for pyrolysis — the type of information (site/waste characterization,
treatability study, etc.) needed to implement this technology at a solvent site.
TABLE 3-10. FACTORS AFFECTING PYROLYSIS PERFORMANCE
Factor
Temperature
Residence time
Moisture content
pH «5AND >11)
PCBs, PCP, dioxins
Particle size
Halogenated organic compound concentration
Ash fusion temperature
Metals content
Nonvolatile heavy metals (Cr, Ag, Ba)
Volatile metals (Hg, Pb, As, Cd)
Alkali metals (Na, K)
Potential Effect
Stages affect contaminant segregation and concentrations
in condensate.
Short residence time causes inadequate destruction efficien-
cy-
High moisture content increases energy requirements and
reduces feed rate. Low moisture content affects reactions
involving halogenated organics.
Increases component corrosion.
Require higher temperatures and dechlorination catalysts.
Oversized debris requires size reduction; May hinder pro-
cessing; Fines increase paniculate carryover.
Forms acid gases, which may attack refractory material
and/or impact air emissions.
Operation of the equipment at or near the ash fusion tem-
perature can cause melting and agglomeration of inorganic
salts (slagging).
Ash may fail TCLP.
Vaporize, become difficult to remove using conventional
APC equipment. Ash may fail TCLP.
Salts have low melting points. May cause slagging.
77
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Chemical Destruction Technologies
Delhalogenation
Dehalogenation is an innovative chemical destruction technology applicable to contaminated soil, sludge, and
sediment at solvent sites. A schematic diagram of a dehalogenation process is depicted in Figure 3-5.
The dehalogenation process is effective potentially in detoxifying chlorinated organic contaminants such as
dioxins, PCBs, chlorobenzenes, and PCPs. This converts the more toxic compounds into less toxic, sometimes
more water-soluble products and leaves compounds that are more readily separated from the soil and treated (15).
In dehalogenation of halogenated aromatic compounds, a nucleophilic substitution reaction replaces a chlorine atom
with an ether or hydroxyl group. Dehalogenation or dechlorination of chlorinated aliphatic compounds occurs
through an elimination reaction and the formation of a double or triple carbon-carbon bond<16).
Field and laboratory tests have identified several types of solutions that can dechlorinate PCBs, dioxins, and
furans. These solutions include potassium polyethylene glycolate (KPEG), sodium polyethylene glycolate (NaPEG),
and methoxypolyethylene glycolate (MPEG). These are generally classified as alkali polyethylene glycolate (APEG)
solutions. Base-catalyzed decomposition (BCD) process is another technology for removing chlorine molecules from
contaminants such as PCBs, dioxins, and PCP. It requires the soil to be sized and screened. For the reaction to
be effective, contaminated soils are combined with sodium bicarbonate and a catalyst or sodium hydroxide and
sucrose and are heated at 340°C .
78
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fi&ftUgSS&f
<& CcnomircrBd *
If audgBorStdma*/
/sZK-xxw-a&aiy
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Equ'fmaTt
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#-:4-?Zr-*r:-r7Zf*".f%Zr~i#:-e^
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WtehWaero ftecycfeM FunherTreatne*
Figure3-S Schematic for Dehalogensrtfco(Bc-Siki) of
Contaminated Soils,SedkneniG,«id Sludges.
Typical Treatment Combinations: Dehalogenation generates three residuals: treated soil, washwater, and
air emissions. This treatment is effective for dioxin/furan, PCB, PCP, chlorobenzenes, and halogenated
phenol/creosol groups. The presence of other contaminants may demand post-treatment, such as bioremediation
or incineration. The washwater may require treatment prior to discharge. Volatile air emissions can be controlled
by condensation and/or activated carbon adsorption.
Technology Applicability: Chemical dehalogenation is primarily for treating and destroying halogenated
aromatic contaminants in a waste matrix consisting of soil, sludge, or sediment. However, this technology has
achieved removal efficiencies up to 98 percent in bench-scale studies for chlorobenzene (17). Dehalogenation has
been shown at laboratory-scale to be effective on halogenated aliphatic compounds such as ethylene, dibromide,
carbon tetrachloride, chloroform, and methylene chloride. The presence of other contaminants may require a
treatment combination that will add bioremediation, incineration, or another option.
Technology Status/Performance: Chemical dehalogenation is an innovative alternative to
conventional technologies such as incineration. Bench and pilot-scale testing has been successful for treating
dioxins, PCB, chlorinated pesticides, and PCP.
79
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Implementation Costs: Chemical dehalogenation costs are estimated to range from $200 to $500 per ton
(18)
Data Requirements: Table 3-11 is'a summary of the factors affecting dehalogenation efficiency and, thus,
illustrates the important data requirements for chemical dehalogenation.
TABLE 3-11. FACTORS AFFECTING DEHALOGENATION PERFORMANCE
Factor
Aliphatic organics, inorganics,
metals
Aluminum and other alkaline !
reactive metals
Chlorinated organics (>5%)
Clay and silty soils
Humic content
Moisture content (>20%)
Low pH «2)
Particle size
Potential Effect
Achieves best results with aromatic halides— PCB, dioxins,
chlorophenols, chlorobenzenes
Requires increased use of reagent under highly alkaline
conditions.
Requires excessive volumes of reagent.
Increases reaction time due to binding of contaminants.
Increases reaction time due to binding of contaminants.
Requires excessive volumes of reagent because water
reacts with and dilutes the reagent. Higher moisture con-
tent increases feed handling and energy requirements.
Increases costs due to increased reagent requirements.
Oversized material requires size reduction. May hinder
processing.
Source: <19>
Bioremiediation Technologies
Bioremediation uses microorganisms to biochemically degrade or transform organic contaminants. It attempts
to foster and optimize the natural bioremediation and biotransformation processes which occur in soils. All of the
aerobic and anaerobic processes discussed in the Section 2 may be used in bioremediation processes.
Complete degradation of organic contaminants to carbon dioxide, water, and inorganic products may be
achievable in some cases. In other situations, transformation of the original contaminants to other organic products
occurs. The fate and effects of these products should be considered in developing bioremediation alternatives.
While transformation products are often less toxic than the original contaminant, this is not always the case. In
addition, the mobility of the transformation product may differ from that of the original contaminant.
Both bacteria and fungi are involved in bioremediation processes. Most research has centered on bacteria,
but some investigators have found that fungi can play an important role, especially with halogenated compounds(20).
80
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Bioremediation relies on the combined activity of a variety of microorganisms, rather than one or a few, to degrade
organic contaminants. Transformation of contaminants is optimized by choosing and maintaining appropriate
conditions for activity of the microorganisms. If biodegradable contamination in the soil has endured for more than
a few months and the microorganisms have grown and reproduced in the contaminated soil, native microorganisms
generally can transform the wastes. Management techniques can optimize the biological transformation. Little or
no evidence is available to indicate that augmentation with cultured microorganisms enhances the natural
bioremediation process.
Incomplete bioremediation may also result in secondary products which are more mobile due to increased
solubility resulting from the introduction of oxygen into the molecular structure during the initial microbial attack
of the contaminant(s), for example, reductive dechlorinationof PCE, TCE, and the dichloroethylenes (DCE) results
in production of VC, which is more toxic and more mobile than its parent compounds.
In terms of degree of contaminant removal and final residual levels, the extent of treatment achievable in
bioremediation depends upon various factors including the types of contaminants present, and bioremediation process
used, and site-specific environmental conditions. In general, bioremediation does not achieve contaminant
destruction efficiencies comparable to incineration. Performance comparisons with other contaminant removal or
destruction processes should be made on a case-by-case basis. Even when lower contaminant removal or destruction
is achieved, as long as remedial action goals are met, bioremediation may be a favored alternative based upon
factors such as cost, implementability, and public acceptability. Three principal bioremediation processes generally
apply to soils at solvent sites: solid-phase, slurry-phase, and in situ bioremediation.
Solid-Phase Bioremediation
Solid-phase bioremediation places contaminated soil in a thin layer, (typically, 12- to 18-inches deep) in a
lined treatment bed. A schematic diagram of a solid-phase bioremediation process is illustrated in Figure 3-6.
Generally nutrients such as nitrogen and phosphorous are added. The bed is usually lined with clay or plastic liners,
furnished with irrigation, drainage, and soil-water monitoring systems, and surrounded by a berm. Aeration,
temperature control, and a leachate collection system may increase efficiency. This process is one of the older and
more widely used technologies for hazardous waste treatment. It has been particularly successful in the IMted
States, especially at petroleum refinery sites treated under RCRA. Solid-phase treatment is relatively simple and
inexpensive to implement and may prove effective for a wide range of contaminants. Where greater process control
is required to achieve particular performance or operating criteria, other bioremediation approaches may be
necessary. Solid-phase treatment is also relatively land intensive due to the thin layer of soil required for aerobic
treatment.
81
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Several variations of conventional solid-phase treatment may also be considered. Soil heap bioremediation is
conducted by piling the soil to be treated in deeper piles (typically several feet thick) shaped into rows. Containment
requirements are similar to those used for solid-phase treatment. Perforated piping entails blowing air through the
piping system with a mechanical blower. Nutrients and other supplements may also be added through the piping
system as liquids. As compared to conventional solid-phase treatment, soil heap treatment may provide a higher
level of process control and requires less space due to the deeper soil layer. Cost may be somewhat higher due to
the mechanical components required, and mixing to improve treatment efficiency is not possible.
Composting is a variation of solid-phase bioremediation. The composting process can treat highly
contaminated soil by adding a bulking agent (straw, bark, manure, wood chips) and organic amendments to the soil.
The soil/amendment mixture is formed into piles and aerated (natural convection or forced air) in a contained system
or by mechanically turning the pile. Bulking agents are added to the compost to improve texture, workability, and
aeration; carbon additives provide a source of metabolic heat. Waste decomposition occurs at higher temperatures
resulting from the increased biological activity within the bed. One potential disadvantage of composting is the
increased volume of treated material due to the addition of bulking agents. Irrigation techniques can optimize
moisture, pH, and nutrient control, and an enclosed system can achieve volatile emissions control.
As conventionally applied, all of these processes are aerobic bioremediation processes. However, anaerobic
treatment may be possible by modifying operating conditions. Deleting aeration systems and covering the soil piles
will foster oxygen depletion by the microorganisms and result in development of effective anoxic (low oxygen) or
anaerobic conditions.
82
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Figure 3-6 Schematic lor Solid-Phase Bioranediatkn
Slurry-phase Bioremediation
During slurry-phase bioremediation, excavated soil or sludge is mixed with water in a tank or lagoon to create
a slurry, which is then mechanically agitated CI). A schematic of a slurry-phase bioremediation process is depicted
in Figure 3-7. The procedure adds appropriate nutrients and controls the levels of oxygen, pH, and temperature.
Potential advantages of slurry-phase treatment as compared to solid-phase bioremediation include the possibility for
more effective treatment due to the high degree of mixing, and the effective contact between contaminated soils and
nutrients. These possible advantages should be weighed against the higher capital and operating costs for a slurry
reactor system. The majority of slurry phase treatment to date has focused upon aerobic biodegradation and has
been conducted at bench or pilot scale.
83
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This process is suitable for high concentrations of organic contaminants in soil and sludge. Following
treatment in the reactor, the soil is separated from the slurry by gravity settling and/or mechanical dewatering for
redisposal. The water from the slurry may be recycled and/or treated and disposed. However, the presence of
heavy metals can inhibit microbial metabolism.
VfcSSSflfiWS'
* Ocnemiraed ;*
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f'-t ••»<»-» :m _. ••>•<•*
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Figure 3-7 Schematic tot Skiir^r-Phase Bioreniediatwi (Bi-SHu) for
Ccniaminated Soife, Sediiictite, aid Skidges.
84
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In Situ Bioremediation
Jh situ bioremediation promotes and accelerates natural processes in undisturbed soil. Figure 3-8 presents
a schematic diagram of in situ bioremediation for soil. It can involve recirculation of extracted groundwateir that
is supplemented above ground with nutrients and oxygen. Vacuum or injection methods can supply oxygen to the
subsurface soil. Under appropriate conditions, this technology can destroy organic contaminants in place without
the high costs of excavation and materials handling. Also, it can minimize the release of volatile contaminants into
the air. In situ bioremediation requires that nutrients and (for aerobic bioremediation) oxygen be transported
through the contaminated zone. Adequate oxygen transfer is often the most difficult to achieve, due in part to the
relatively low solubility of gaseous oxygen in water. In some cases and for certain types of wastes, chemical
oxygen sources such as hydrogen peroxide, or alternative electron acceptors such as nitrate ^ *' (see Section 2)
can be used.
Currently, significant attention is focused on developing in situ bioremediation for chlorinated organics. This
attention derives from the wide use of chlorinated solvents, with TCE being one of the most commonly observed
contaminants at CERCLA sites. Recent research has evaluated both anaerobic in situ treatment and methanotrophic
in situ treatment for chlorinated organics
-------
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-------
continuation of normal site operations. Although the system is cost efficient to install and maintain, treatment of
the extracted vapors can increase total costs greatly. During bioventing, SVE operating conditions are modified to
enhance biodegradation. Specifically, operating flow rates and flow configuration are changed and moisture, and/or
nutrient plus moisture are added <2S).
Bioventing overcomes limitations due to oxygen concentration that affect biodegradation in groundwater. At
normal groundwater temperatures, oxygen concentrations range from 5 to 8 ppm in the water. Although hydrogen
peroxide and pure oxygen added to water can greatly increase oxygen concentrations, they do not approach the
oxygen concentrations present in the atmosphere. Bioventing can be a valuable remediation tool for vadose-zone
contaminants that are readily degraded aerobically. A list of factors affecting bioventing performance is contained
in Table 3-12.
A successful field demonstration of bioventing has been demonstrated by Du Pont et al. (25). The site was the scene
of a January 1985 JP-4 jet-fuel spill at Hill Air Force Base in Utah which resulted from the release of approximately
27,000 gallons of fuel from an underground storage tank. Unrecovered fuel migrated away from the tank area and
contaminated an area of approximately 1 acre and to a depth of 50 feet. Initial remediation involved the recovery
of 2,000 gallons of free product and installation of a venting system that came on-line in December 1988.
Measurement of total petroleum hydrocarbon (TPH) in soil before and after the bioventing treatment demonstrated
maximum removals from 970 mg/kg to 5.6 mg/kg at the 15-feet depth interval. This field effort demonstrated
enhanced biodegradation of JP-4-contaminated soils compared to removals seen with traditional soil-vacuum
extraction. It is estimated that 44 percent of the contaminants were biodegraded and 56 percent were volatilized.
Another bioventing project involving JP-4 jet fuel was performed at Tyndall AFB in Florida.
87
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TABLE 3-12. FACTORS AFFECTING BOIVENTING PERFORMANCE4
Factor
Moisture Content
Nutrients (C-N-P)
SVIE Flow Rate
Potential Effect
Moisture depleted by SVE «40%)
may inhibit aerobic degradation.
C:N:P of 120:10:1 is necessary for
optimum degradation.
High flow rates increase volatilization,
thus decreasing the amount to be
degraded.
* Other factors are noted in the SVE and bioremediation sections.
ecsseis ftioa
<%85ii2*0i%%:0:^^
Figure 3-9 Schematic for Btovmthg ( h-Sttu) o» Ccnfam haled Soil
88
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Typical Treatment Combinations
Performance is highly dependent on contaminant types and concentrations as well as site conditions. In case
of high molecular weight contaminants, the treated and dewatered solids may contain residual organic contaminants,
and these media may require further treatment. When the solids are contaminated with heavy metals, stabilization
to immobilize the metals following bioremediation may be necessary. High concentrations of toxic metals may
inhibit the bioremediation process. The process water also may require on-site treatment prior to discharge.
Depending on the waste characteristics, air pollution-control measures, such as adsorption by activated carbon, may
be necessary. Surface treatment of recovered groundwater may accompany the in situ bioremediation process.
Technology Applicability
Bioremediation can treat soil, sludge, and sediment contaminated with organic contaminants such as
nonhalogenated aromatics, other polar organic compounds (including many solvents), and PAHs. The type of
bioremediation process (aerobic or anaerobic) and its implementation (solid, slurry, or in situ) will depend upon the
type of contaminant and site-specific factors. Bioremediation of nonhalogenated aromatics, heterocyclics, and other
polar compounds have exhibited an average removal efficiency of 99 percent based on pilot and full-scale tests (17).
Halogenated aliphatic compounds were also successfully treated; however, the average of 99 percent removal from
the available data may be a result of volatilization in addition to bioremediation(17). Bioremediation has been less
successful with halogenated compounds. However, research and technology developed for chlorinated organics is
ongoing, and recent advances have been made.
Technology Status/Performance
Solid-phase treatment is one of the oldest and most widely used technologies for hazardous waste treatment.
Slurry-phase treatment currently exists at the pilot stage, with full scale equipment available for near-term
implementation. In situ bioremediation holds promise for cost-effective treatment of contaminated soil and
groundwater. Table 3-13 presents a summary of CERCLA, RCRA, and state solvent-contaminated sites considering
bioremediation. Results of additional in situ bioremediation efforts are presented in Table 3-14.
TABLE 3-13. SUMMARY OF PERFORMANCE DATA FOR BIOREMEDIATION
Site Name
BRIO/DOP Site, Friendswo-
od, TX 127]
Whitehouse Waste Oil Pits
Site, Jacksonville, FL [28]
System
ECOVA Corporation's solid-phase biore-
mediation pilot scale
ReTec soil washing followed by biorem-
ediation
Initial
Methylene chloride: 16 to 17,000 ppb
1 ,2,-Dichloroethane: 25 to 195,000 ppb
1,1,1-Trichloroethane: 25 to 195,000 ppb
Phenanthrene: 1,392 to 16,083 ppb
Anthracene: 440 ppb
Fluorene: 563 ppb
Total petroleum hydrocarbons, PAHs
Performance
More than 99% removal of
VOCs within 21 days due to
air stripping. Biodegradation
of SVOCs was much slower.
Treated below detection limit
89
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w'itharawai and treatment by an activated-sludge process and recharge of aerated nutrient-
laden water: 90% reduction of contaminated plume after 3 years operation; biodegradation
based on monitoring well data, some coring data, and increased C02 in contaminated
compared to uncontaminated areas.
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Implementation Costs * ' .
£ •;•
One vendor estimates the cost of a full-scale, slurry-phase biodegradation operation ranges from $80 to $150
per cubic yard of soil or sludge, depending on the initial concentration and the treatment volume. The cost to use
slurry-phase bioremediation varies depending upon the need for additional pretreatment, post-treatment, and air
emission-control equipment<21).
Costs for solid-phase land treatment range between $50 and $80 per cubic yard, according to the need for a
liner and the extent of excavation required. Composting costs approximately $100 per cubic yard. Costs of in situ
treatment range from $8 to $15 per pound of contaminant(29).
92
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In Situ Biotransformation of Chlorinated Aliphatic Hydrocarbons
Although chlorinated solvent compounds are among the most widespread contaminants found in groundwater
and soils at Superfund sites, few reports of in situ bioremediation for these chemicals have been published.
Chlorinated solvents such as TCE or PCE are persistent in oxygenated environments. Reductive dechlorination of
these compounds occurs in anaerobic systems.
Complete dechlorination of TCE and/or PCE to ethylene has been observed at field scale (40> 41). Final
dechlorination from VC to ethylene is the limiting step in completion of dechlorination. If further dechlorination
of VC is not achieved, the transport and effects of this contaminant must be considered and may prevent the use
of bioremediation. Knowledge of reductive dechlorination is not yet adequate to predict whether dechlorinatiori will
go to completion at a particular site.
Recent studies have attempted to enhance bioremediation of the chlorinated solvents. Various chlorinated
compounds can be oxidized aerobically by cometabolism using low-molecular weight alkanes, such as methane,
propane, or butane, as primary substrates for carbon and energy. Solvents such as PCE and carbon tetrachloride
(CT) are not amenable to co-oxidation, but TCE, the DCEs, and VC are cometabolized to oxygenated secondary
products. A second cometabolism involves microbial growth on aromatics such as toluene or phenol (42). The
potential of using methane-oxidizing microorganisms has been evaluated at pilot scale, and initial results are
promising for remediation of TCE, DCE, and VC . Pilot-scale evaluation of microorganisms that oxidize
aromatic compounds is comparable to the methane oxidizing process. Use of methane to remediate volatile
chlorinated compounds in the vadose zone may be quite feasible due to the ease of moving methane and air in the
unsaturated subsurface. These innovative systems are in the initial stages of evaluation. Though they are
promising, more engineering development is needed to provide a practical alternative to current pump-and-treat
technology, and much research remains to be accomplished before widespread implementation at field scale.
Chlorinated solvents transformation also has been observed in denitrifying environments (bacteria that use
nitrate as the terminal electron acceptor during respiration). Because denitrifying conditions are less reducing than
methanogenic or sulfate-reducing environments, using denitrification in remediation activities is advantageous. For
example, reductive dechlorination of carbon tetrachloride (CT) has been observed under denitrifying conditions.
In batch-fed mixed denitrifying cultures, CT was observed to degrade with the production of cell mass and carbon
dioxide(43). The production of cellular mass during the degradation suggests that microorganisms are growing and
reproducing on the waste rather than simply transforming the wastes. Chloroform was identified as a transformation
intermediate, demonstrating that reductive dechlorination occurred to some degree. In other studies, biotransforma-
tion of CT was observed in both methanogenic and denitrifying conditions in anoxic biofilms(44). Under denitrifying
conditions, 41 percent of CT was mineralized to carbon dioxide, 14 percent was converted to chloroform, and 45
percent was transformed to an unknown nonvolatile product.
93
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Denitrifying conditions are less reducing than methanogenic or sulfate-reducing environments. Subsequently,
production of dissolved iron or manganese, sulfides, or other odor-causing compounds (found in more reducing
environments) may be avoided in aquifers. Denitrifying bacteria also grow more rapidly and probably are
distributed more widely in subsurface environments than sulfate-reducing or methanogenic bacteria.
Under both field and laboratory conditions, indigenous denitrifying bacteria were tested for their ability to
biotransform CT when given an appropriate environment for growth pl). Assessment of biotransformation was made
by controlled addition, frequent sampling, quantitative analysis, and mass-balance comparisons. In addition, fate
of background contaminants (TCA, freon-11, and freon-113) under denitrifying conditions were observed. This
study demonstrated in situ biotransformation of CT and TCA by indigenous microorganisms.1 Rapid rates were
observed with half-lives on the order of hours to days in the absence of oxygen, with the addition of acetate in the
presence of nitrate and sulfate. Chloroform was formed as an intermediate in the transformation of CT and may
pose ari impediment to implementing this process. Nitrate was removed readily by denitrifying organisms in the
subsurface upon addition of acetate as a growth substrate. Over 90 percent biotransformation of CT was measured
at the field site with 30 to 60 percent transformed to chloroform. Transformation of CT was more rapid following
nitrate depletion with a lower fraction transformed to chloroform. Rates of biotransformation of the background
contamination were slower than that of CT, with extent of transformation for CT at 95 to 97 percent, and TCA at
11 to 19 percent.
Data Requirements
The factors that may restrict bioremediation and its various effects are summarized in Table 3-15. A remedial
manager can derive data requirements for biological destruction from this list. The data requirements include site
factors and waste characteristics.
94
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TABLE 3-15. FACTORS AFFECTING BIG-REMEDIATION PERFORMANCE
Factor
Contaminant solubility
Presence of elevated levels of
heavy metals, highly chlorinated
organics, some pesticides, inor-
ganic salts
Moisture content
Nutrients (C-N-P)
Oil and grease concentrations
Oxygen
pH
Soil permeability
Suspended solids concentration
Temperature
Variable waste composition
Redox potential
Potential Effect
Contaminants with Idw solubility are harder to biodegrade
because the waste must be solubilized to enable organisms
to use the waste as a food source.
Can be highly toxic to microorganisms. Low concentra-
tions of some metals are needed for biological activity (Fe,
Mn, Mg, Ca).
May inhibit solid-phase aerobic remediation (land farming)
of soils if >80% residual saturation. Soil remediation
inhibited if <40% residual saturation. Soil-slurry reactors;
may have 80-90% moisture content. Liquid-phase reac-
tors may have >99% moisture content.
Microbial growth limited if lacking nutrients (suggested
C:IM:P ratio of 120:10:1). Nutrients can be added if neces-
sary.
Inhibit soil remediation at concentrations > 5% by weight.
Sustains aerobic activity (>0.2 mg/l dissolved), inhibits
anaerobic activity (> 1 %).
Optimal in a range of 6-8, may work in a range of 4.5 to
8.5.
Affects movement of water and nutrients for in situ treat-
ment.
Should be < 1 % (can vary greatly in different types of
bioremediation).
Inhibits microbial activity. (Optimal in the range 15-35°C.)
However, in some cases, can be conducted at tempera-
tures to freezing and over 1 00° F.
Large variations affect biological activity, especially where
continuous flow liquid bioreactors are used. Inconsistent
biodegradation.
Inhibits microbes. Optimal >50 millivolts aerobes, <50
millivolts anaerobes.
95
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SEPM^ATION/CONCEISfTRATION TECHNOLOGIES
Separation/concentration technologies remove contaminants from soils by thermal, physical, or chemical
means to form a concentration which can be treated more easily by other means. These technologies can be used
either for excavated or in situ soil. ' Several such technologies include:
In Situ Soil Technologies
SVE
Steam extraction
Radio frequency (RF) heating
Soil flushing
Excavated Soil
Thermal desorption
Soil washing
Solvent extraction
Typical remedial combinations for separation/concentration technologies are listed in Table 3-16. Table 3-17
is a summary of the applicability of these technologies on contaminant groups and media. For these ratings,
"demonstrated effectiveness" means that at some scale (e.g., bench-scale for innovative technologies), treatability
tests showed that the technology was effective. "Potential effectiveness" means that the technology requires further
development, and "no expected effectiveness" means this technology does not work.
TABLE 3-16. TYPICAL TREATMENT COMBINATIONS FOR
SEPARATION/CONCENTRATION TECHNOLOGIES
Pretreatment/Materials
Handling
Separation/Concentration
Technology
Post-Treatment
Residuals Management
Free-product pumping
SVE
Groundwater air stripping
Condensate air stripping
Carbon regeneration
Solvent disposal
Catalytic oxidation
Free-product pumping
SVE
Steam extraction
Groundwater air stripping
Carbon regeneration
Solvent disposal
Catalytic oxidation
Free-product pumping
RF heating
Groundwater air stripping
Carbon regeneration
Solvent disposal '
Free-product pumping
Soil flushing
Groundwater air stripping
Carbon regeneration
Solvent disposal
96
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TABLE 3-16. (Continued)
Free-product pumping
SVE
Excavation
Screening/size reduction
Soil Washing
Solids disposal
Water treatment
VOC emission control
Free-product pumping
SVE
Excavation
Dewatering
Screening/size reduction
Solvent extraction
Solids dewatering
Solids disposal
Solvent disposal
Water treatment
VOC emission control
Free-product pumping
SVE
Excavation
Screening/size reduction
Dewatering
Thermal desorption
Solids disposal
GAC regeneration
Water treatment
Solvent disposal
Catalytic oxidation
97
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Description of Li Situ Technologies
SVE | *• '*
Soil vapor extraction physically separates and concentrates volatile organic compounds (VOCs) dispersed in
contaminated soil. A schematic diagram of a vapor extraction process, an in situ technology that applies a vacuum
to withdraw vapors from soil, is depicted in Figure 3-10. Another mode of operation injects air into the soil. An
enhancement to the technology injects hot air as it applies a vacuum to remove contaminated vapors. Following
removal of contaminants from the soil, equipment either condenses the vapors, collects them on activated carbon,
or destroys them by catalytic oxidation. Condensed vapors are disposed of off site or destroyed by a suitable
technology.
Vent
Air
Blower
Ambient
• Air
Bypass
Air Tight
Containment
Contaminated
Soil
Vapor
Phase
Carton
Adsorber
Gondensae
Treated
Waster to
Discharge
Liquid
Phase
Carton
Adsorber
15690SH 7KXHO
Figure 3-10 Schem atfc for Vapor Edracfion (IrvSitu) of Ccntau kiafed Soils
99
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Typical Treatment Combinations: SVE generates the following waste streams: vapor and liquid residuals,
contaminated groundwater, and soil tailings from well drilling. The usual vapor treatments are carbon adsorption
and thermal destruction. Other (less common) treatments include condensation, biological degradation, and
ultraviolet oxidation. Contaminated groundwater can be treated and discharged. Highly contaminated soil tailings
must be collected for treatment by another technology, such as incineration.
Technology Applicability: SVE effectively processes VOCs at sites where the soils are well drained, contain
low levels of organic carbon, and present a relatively high pneumatic permeability. Site heterogeneities may impede
implementation of SVE. The design and proper location of SVE wells, however, can sometimes overcome the
problem of site heterogeneities. Soil vapor extraction is feasible when a compound has vapor pressure of at least
0.5 TOIT at ambient temperatures. The limit for site pneumatic permeability is 1 X lO"10 cm2. Any site with values
below this level should not be considered for SVE application. Unless site soils are arid, SVE is less effective for
! ;
removing solvents that are highly soluble in water.
Technology Status/Performance: SVE is an accepted technology that has operated commercially for several
years. It is a frequently selected remedial alternative for VOC-contaminated sites; more than 30 RODs have
specified SVE as a remedial action. The technology has remediated many underground storage tank (UST) and
RCRA sites as well. Growing experience in technology performance indicates that a properly designed system based
on results from pilot-scale operations may produce a system capable of meeting performance goals and site-cleanup
objectives. Table 3-18 shows sites where SVE has been selected as a remedial option. Table 3-19 presents a
summary of typical SVE performance data.
TABLE 3-18. SVE SELECTIONS AT SOLVENT SITES
Region
1
1
1
1
1
2
2
3
3
3
4
Site Name
Groveland Wells
Wells G&H
Kellogg-Deering Well Field
South Municipal Water Supply Well
Tinkham's Garage
FAA Technical Center
Upjohn Facility
Bendix Flight Systems Division
Henderson Road
Tysons Dump
Martin Marietta Sodyeco Div.
Location
Groveland, MA
Woburn, MA
Norwalk, CT
Peterborough, NH
Londonderry, NH
Pomona, NJ
Barceloneta, PR
Bridge water Twp., PA
Upper Merion Twp., PA
Upper Merion Twp., PA
Mt. Holly, NC
100
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TABLE 3-18. (Continued)
Region
4
4
5
55
E>
5
5
5
5
5
6
6
7
&
9
9
9
9
9
9
9
9
Site Name
Stauffer Chemical Co. Gold Creek Plant
Stauffer Chemical Co. Axis Plant
Kysor Industrial Corporation
Long Prairie
MIDCO 1
Seymour Recycling
Miami County Incinerator
Pristine, Inc.
Verona Well Field
Wausau Groundwater Contamination
South Valley
Hardage/Criner
Hastings Groundwater Contamination
Sand Creek Industrial
Motorola, Inc. (52nd St. Plant)
Litchfield Airport Area
Fairchild Semiconductor Corp.
Fairchild Semiconductor Corp.
Intel Corp. (Santa Clara III)
Intersil, Inc. /Siemens Components
Raytheon Corp.
Spectra-Physics, Inc.
Location
Cold Creek, AL
Lemoyne, AL
Cadillac, Ml
Long Prairie, MN
Gary, IN
Seymour, IN
Troy, OH
Reading, OH
Battle Creek, Ml
Wausau, Wl
Albuquerque, NM
Criner, OK
Hastings, NE
Commerce City, CO
Phoenix, AZ
Goodyear, AZ
San Jose, CA
Mountain View, CA
Santa Clara, CA
Cupertino, CA
Mountain View, CA
Mountain View, CA
101
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TABLE 3-19. SUMMARY OF PERFORMANCE DATA FOR IN SITU SVE
Site
Industrial, CA
Custom Products, Stevensville,
Ml
Prison Construction Site, Ml
Sherwin-Williams Site, OH
Upjohn Site, Barceloneta, PR
UST Bellview Site, FL
Verona Wellfield Site, Battle
Creek, Ml
Valley Manufactured Products
Co., Groveland, MA
San Fernando Valley Superfund
Site, Area, 1 , Burbank, CA
Ponders Corner, Lalcewood,
WA
Twin Cities Army Ammunitions
Plant, Ml
Hinson Chemical, SC
Equipment
IMA
NA
NA
Midwest Water Resources
- Vaportech (full scale)
Terra Vac Corp. (full
scale) ,
Terra Vac Corp. (pilot
scale)
Terra Vac Corp. (pilot
scale)
Terra Vac Corp. SITE
Program
AWD Technologies SITE
Program
ECOVA
NA
OHM Remediation Servic-
es Corp.
Initial
TCE 0.53 mg/kg
PCE 5,600 mg/kg
TCA 3.7 mg/kg
Paint solvents 38 mg/kg
CCI4 2,200 mg/kg
BTEX 97 mg/kg
TCE, PCE, TCA 1 ,380
mg/kg
TCE 96.1 mg/kg
PCE, DCE
VOCs: TCE, PCE
PCE 3.88 mg/kg
TCE 3.6 mg/kg
TCE 2060 mg/kg
B2, TCE, PCE, DCA,
MEK
Performance
0.06 mg/kg TCE after
treatment <461
0.70 mg/kg PCE after
treatment (46)
0.01 mg/kg TCA after
treatment (48)
0.04 mg/kg (46)
<0.005 mg/kg (45-46)
<0.006 mg/kg (46-48)
Ongoing (46-46)
4.19 mg/kg (45-48'
98 to 99% removal (46)
97.97% removal
99.76% removal
0.0085 mg/kg
< 1 0 ppm total VOCs I47)
NA = Not available
Implementation Costs: Typical costs for SVE treatment range from $10 to $150 per ton (45). Capital costs cover
well construction, vacuum blowers, vapor and liquid treatment systems, pipes, fittings, and instrumentafdon.
Operations and maintenance costs include labor, power, maintenance, and monitoring activities. Costs also vary
according to site, soil, and contaminant characteristics.
Data Requirements: The factors affecting SVE performance are listed in Table 3-20. From these factors,
which are noted in the following, the remedial manager can begin to develop the data necessary to evaluate the
technology.
» Vapor pressure is a measure of a substance's tendency to evaporate or give off vapor. A vapor
pressure greater than 0.5 Torr indicates potential for removal by SVE.
102
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<» Henry's constant is a constant of proportionality that relates the partial pressure of a compound to its
concentration in a dilute aqueous solution. A Henry's constant greater than 0.01 indicates potential for
removal by SVE.
« The saturation zone is that region of the soil where the pores are filled with water. Soil vapor
extraction cannot be applied effectively below the water table. However, SVE can sometimes be used
in combination with air sparging to handle contamination below the water table. Addtionally, it can be
applied if a site can be dewatered economically.
» Soil permeability is a measure of a soil's ability to permit fluid flow. Soil vapor extraction is most
applicable to soils of moderate to high permeability.
» Soil water content is expressed as percent residual saturation. A completely saturated soil has 100
percent residual saturation. The presence of water decreases the soil's ability to permit air flow
(decreases air permeability). A soil with greater than 50 percent residual saturation has very low air
permeability.
s
» The soil gas relative humidity is the moisture concentration in the soil/vapor phase divided by the
moisture concentration of saturated vapor multiplied by 100 percent. High soil humidity reduces
the tendency of contaminants to adsorb on the soil particles.
» Soil organic carbon consists of humus, peat, and other naturally occurring materials which adsorb and
hold organic compounds. Thus, high levels of organic carbon adversely affect the applicability of SVE.
103
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TABLE 3-20. FACTORS AFFECTING SVE PERFORMANCE
Factor \
Vapor pressure
Henry's constant
Saturation zone/high water table
Soil permeability
Soil water content
Soil relative humidity
Subsurface temperature
Water Solubility >•
Soil organic carbon
Potential Effect
Affects removal (>0.5 torr indicates good removal) if less,
consider steam strip or thermal desorption.
Affects removal (>0.01 at ambient temperature suggests
good removal). Relates partial pressure to water solubility.
SVE not cost-effective below water table or when water
table is <5 ft. De watering or air sparging is necessary.
Permits solvent removal if permeable (gravel,, sand); effi-
ciency decreases for low permeability soils < 10"*cm/s
(silt, clay).
Impedes air permeability; severely when residual saturation
>50%. Diminishes air carrying capacity.
Affects absorption; best results at 94 to 98.5%.
Low temperatures decrease vapor pressures, thus decreas-
ing volatilization.
High water solubility decreases effectiveness of treatment.
VOCs are adsorbed/absorbed by organic carbon. Removal
becomes difficult.
Source: U.S. EPA, 1991 (49>.
Ex Situ Uses: Although SVE is basically an in situ technology, it has been applied to excavated materials. Systems
have been installed in stockpiled soils, and stockpiles have been constructed around SVE systems. Successful
applications of ex situ SVE include remediation of excavated soil from underground storage tanks (USTs) and
remediation of soil tailings from well drilling activities <50). Ex situ systems may be more effective than in situ
systems because of the greater permeability and homogeneity of the soils.
At the Basket Creek site in Douglasville, Georgia, an ex situ SVE system was utilized to remove toluene, MEK,
and MIBK from excavated soils. To complete the treament train, the extracted vapors from the pile were thermally
destroyed. Ex situ SVE was performed also at the Hill AFB in Utah. Levels of JP-4 jet fuel in the soil were
reduced from 410 to 3.8 mg/kg.
Steam Extraction: Steam extraction (steam injection) physically separates volatile and semivolatile organics from
soil, sediment, and sludge. Figure 3-11 is a schematic diagram of a steam extraction process. The process uses
a combination of thermal and mechanical energies generated by steam, hot air, infrared elements, and electrical
systems to volatilize and transport the contaminants in the vapor phase.
Steam extraction is an emerging technology that appears promising, particularly if used in conjunction with
SVE. Due to the heating of the soil, steam extraction can remove more of the less volatile compounds than SVE.
104
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Compounds boiling at or below 350° F (51) (e.g., aniline, chlorobenzene, 1,3-dichlorobenzene, chlorophenol) can
be removed by steam extraction.
Steam extraction systems may be mobile or stationary. A mobile system injects steam through rotating cutter
blades that disperse it through the contaminated medium. This system is potentially applicable in low permeability
soils because the steam has good access to the contaminants. In a stationary system, steam flows through individual
valves from the manifold to the injection wells. Recovery wells are used to remove gases and liquids from the soil.
The system then recovers the contaminants as condensed organics or activated carbon.
Steam
Vent
Water
Supply"
Vapor
Phase
Carbon
Adsorber
LjghtOrganio
Liquid Ptese to
Further Treatment*
Recovery
Aqueous Phase O
*• Further Twumentf
Discharge
HeavyOrganb Liquid
Phase (if snyje
Recovery
Figure 3-11 Schematic for Steam Eriracticn (h-Siti) of Content hated Soils.
Typical Treatment Combinations: Steam extraction generates vapor and liquid residuals and contaminated
water. Stationary systems also generate soil tailings for drilling wells. The vapor treatment usually consists of
contaminant condensation followed by removal of trace contaminants with carbon adsorption. The condensed
contaminants are sent off site for further treatment or disposal.
The contaminated water is treated to remove residual contaminants before disposal or reuse; the activated
carbon can be regenerated or disposed. Contaminated soil tailings are sent off site for treatment or disposal.
105
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Technology Applicability: Steam extraction has been shown effective in removing VOCs, halogenated
solvents, and petroleum wastes. It should be effective in removing low-boiling-point semivolatile compounds such
as aniline and dichlorobenzene. It may be effective for halogenated nonpolar aromatics and other polar organic
compounds.
During a Superfund Innovative Technology Evaluation (SITE) program demonstration at the GATX Annex
Terminal site in San Pedro, California, a mobile steam extraction system by Novaterra, Inc. reduced average volatile
concentrations from 466 mg/kg to 71 mg/kg, achieving an 85 percent average removal efficiency for volatile
contaminants (52> S3\ The primary VOCs were trichloroethene, tetrachloroethene, ethylene, and chlorobenzene.
A mobile unit using cutter blades in concert with steam and hot-air injection is applicable to shallow (<30
ft) unconsolidated soils. The surface must be relatively flat (< 1 percent slope), and the soil must be capable of
supporting the weight of the rig. There must be ample vertical clearance (>35 ft) to overhead obstacles and
unimpeded site access must be available. Underground utilities and solid obstacles (rocks larger than approximately
6 in) limit application of this process. Since the cutter blades reduce the low permeability materials to sizes of
three-eights of an inch, silts and clays can be effectively treated, but an increase in treatment time and cost should
be expected. Past field experience in treating medium- to high-permeability soils have demonstrated 50 percent
removal of semivolatile compounds (53). Results of bench-scale tests prior to the field demonstration showed 45 to
85 percent removal of semivolatile compounds *53).
Stationary steam extraction techniques require the installation of steam injection and fluid extraction wells in
a pattern that most effectively recovers the contaminants without dispersing them further. Soils of medium to high
permeability can be treated with this technique, and application below and/or above the water table is possible. Low
permeability soils are difficult to treat because steam flows through zones of higher permeability, and heat must be
transferred across a longer path to reach contaminants in the stagnant areas. The mobilized wastes are pumped, out
of the fluid extraction wells to recover the contaminated aqueous- and separate-phase liquid contaminant. This
technique is particularly applicable to deep contamination since deeper injection allows greater well spacing, and
it lowers costs. Limited field experience has demonstrated 90 percent removal of volatile and semivolatile
compounds, with better recovery in higher permeability zones and lower recoveries of high aqueous-phase solubility
compounds in lower permeability regions.
Technology Status/Performance: In situ steam extraction is an emerging technology for remediation of low
vapor-pressure VOCs and semivolatiles. Novaterra, Inc. mobile technology has been demonstrated under the SITE
Program at the GATX Annex Terminal site in the Port of Los Angeles, California. It is being considered as a
component of the selected remedy for the San Fernando Valley site in Burbank, CA. A full-scale stationary system
is planned by Solvent Service, Inc. for soil contaminated by various solvents. Table 3-21 is a summary of typical
performance data for steam extraction.
106
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TABLE 3-21. SUMMARY OF PERFORMANCE DATA FOR STEAM EXTRACTION
Site
GATX Annex Terminal,
San F'edro, CA
GATX Annex Terminal,
San F'edro, CA
Lockheed
Burbank, CA
Solvent Services, Inc.,
San Jose, CA
Equipment
Novaterra, Inc. (formerly
Toxic Treatments USA)
mobile detoxifier SITE
Program (full scale)
Novaterra, Inc. (formerly
Toxic Treatments USA)
mobile detoxifier (bench
scale)
AQUADETOX moderate
vacuum steam stripper
Solvent services steam
injection/vapor extraction
stationary unit (pilot scale)
Initial
VOCs: trichloroethene,
tetrachloroethene, chlor-
obenzene
VOCs: trichloroethene,
tetrachloroethene, chlor-
obenzene
Soil gas 6000 ppm VOCs
VOCs 1 ,200 mg/kg
Performance
Average removal rate of
85% VOCs, 50%
SVOCs1531
Average removal of 97%
VOCs, 86% SVOCs (53)
(Vendor's claim)
<100 ppm VOCs (ongo-
ing)
Reduced contaminant
concentration to <22
mg/kg in high permeabili-
ty zones (54)
Implementation Costs: According to site-to-site characteristics, estimates place costs for a stationary steam
extraction system at about $50 to $300 per cubic yard (52). For a mobile technology, a SITE demonstration reported
costs of $111 to $317 per cubic yard for 10-cubic-yard-per-hour and 3-cubic-yard-per-hour treatment rates,
respectively (70 percent on-line operating factor). Cost estimates for this technology strongly depend on the
treatment rate (a function of the soil type) the contaminant, and the on-line operating factor (53).
Data Requirements: Table 3-22 illustrates important performance factors for steam extraction. Data for these
factors should be collected.
TABLE 3-22. FACTORS AFFECTING STEAM EXTRACTION PERFORMANCE
Factor
Constituent vapor pressure
Variable soil composition/ consistency
Infiltration rate
Soil moisture content
Soil Temperature
Potential Effect :
Low vapor pressure decreases removal efficiencies; vapor pressure curve
required for each pollutant.
Inconsistent removal rates. Silt and clay may become unstable and
treatment time.
increase
Excessive rate hinders removal of organics.
High moisture increases energy requirements.
Low temperatures inhibit volatilization; increase treatment time.
107
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Radio Frequency (RF) Heating
RF an innovative treatment technology for rapid and uniform in situ heating of large volumes of soil. Figure
3-12 is a schematic of a radio frequency heating process. The process uses electromagnetic wave energy to heat the
soil evenly to the point where volatile and semivolatile contaminants are vaporized in the soil matrix. Vented
electrodes recover the gases formed in the soil matrix. The concentrated extracted gas and particulate streams can
be incinerated or subjected to other treatment methods such as carbon absorption (55). Full implementation of an
RF heating system at a contaminated hazardous site requires four major systems:
» RF energy deposition array
«> RF power generating, transmitting, monitoring, and controlling
« Vapor barrier and containment
» Gas and liquid condensate handling and treatment
15700x0 AH too
Figure 3-12 Schematic far Radio Frequency Heathg of Ccntam hatd Safe.
Technology Applicability: Heating by RF is applicable to materials that typically volatilize in the temperature
range of 80° to 300°C such as aliphatic and aromatic fractions of jet fuels and gasoline, chlorobenzene, TCE, DCA,
and PCE. This technology is applicable to predominantly sandy soils.
108
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Technology Status/Performance: RF heating is a new technology for the cleanup of hazardous waste sites.
It had previously been used in the petroleum industry for oil recovery. It is currently in the pilot- and field-scale
demonstration stage and has been tested at the Volk Field ANGB, Wisconsin. On the average, 94.3 percent of the
semivolatile aliphatics and 99.1 percent of the semivolatile aromatics were removed from the treated soil. Table
3-23 shows the summary of performance data for RF heating.
TABLE 3-23. SUMMARY OF PERFORMANCE DATA FOR RF HEATING
Site
An Abandoned Fire Training
Area at Volk Air National Guard
Base, Camp Douglas, Wiscon-
sin
Sandy soil
Equipment
ITT Research Institute
field demonstration
Pilot scale
Initial
Volatile aromatics and
aliphatics; semivolatile
aromatics and aliphatics
Chlorobenzene
1 0 to 1 ,000 ppm
Tetrachloroethylene
1 0 to 1 000 ppm
Performance
99.1 % removal of vola-
tile aromatics, aliphatics,
and semivolatile aromat-
ics; 94.3% of semivola-
tile aliphatics
94 to 98% removal was
achieved.
Source: (55>.
Implementation Costs: The estimated treatment cost varies between $50 to $90 per ton of treated soil, depending
on the amount of native moisture present in the soil and the exact temperature of treatment, j
Data Requirements: Table 3-24 shows the factors that affect RF heating. :
TABLE 3-24. FACTORS AFFECTING RF HEATING PERFORMANCE
Factor
Type of soil
Presence of metal drums; metallic debris
Type of contaminants
Moisture content
Potential Effect
Low permeable soils increase costs and decrease contaminant recovery.
Disrupts current flow. May increase treatment costs.
Must be supplemented with other treatment methods if nonvolatile
taminants (boiling point greater than 300° C) are present.
con-
: High moisture increases energy requirements.
109
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Soil Flushing
Soil flushing technology extracts contaminants from soil with water or other suitable aqueous solutions. Figure
3-13 is a schematic diagram of a soil flushing process. Soil flushing introduces extraction fluids into soil using an
in situ injection or infiltration process. This method may apply to all types of soil contaminants. Soil flushing
accomplishes permanent removal of contaminants from the soil; it proves most effective in permeable soils. The
process must have an effective collection system to prevent contaminants and potentially toxic extraction fluids from
migrating into uncontaminated areas of the aquifer. Soil flushing introduces potential toxins (flushing solution) into
the soil system; the physical/chemical properties of the system may be altered because of the introduction of the
flushing solution.
Figure 3-13 Schematic foe Soil Fhiehiq (ki-SHu) erf Conbm hated Soils.
Typical Treatment Combinations: Typically, soil flushing is used in series with other treatments that destroy
contaminants or remove them from the extraction fluid and groundwater. Soil flushing in conjunction with
bioremediation may be a cost-effective means of soil remediation at sites contaminated with organic constituents such
as solvents, creosote, etc. For soils contaminated with both inorganic and organic constituents, a combination of
pretreatment that reduces or eliminates the metal constituents in the elutriate by precipitation followed by activated
110
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carbon or air stripping may be a feasible cost-effective method of treatment. Wherever possible, treated water
should recycle to the front end of the soil-flushing process. The wastewater sludge and solids (such as spent carbon)
require appropriate treatment before disposals
Technology Applicability: Depending on the type of flushing additive [acidic solutions for metals and organic
constituents (including amines, ethers, and anilines), basic solutions for metals (zinc, lead, and tin), and surfactants
for hydrophobic organics], in situ soil flushing can treat contaminants such as halogenated aliphatics, simple
nonhalogenated aromatics, other polar organic compounds, and nonvolatile and volatile metals (5Q.
Technology Status/Performance: Soil flushing is an innovative technology. Its performance depends upon
the contact between the flushing solution and the contaminants. The U.S. EPA has selected it as one of the source
control remedies for 10 Superfund sites. In situ soil flushing has been demonstrated on a limited basis at a few sites
contaminated by petroleum hydrocarbons and TCE. In Germany, soil flushing was used to cleanup a TCE spill,
and a 50 percent decrease in TCE over an 18-month period was achieved (57). At the Lipari Landfill in Gloucester,
New Jersey, a successful treatability test for in situ soil flushing was conducted, and an operational full-scale unit
is being used for VOC removal.
Implementation Costs: Soil flushing costs lie in the range of $50 to $120 per cubic yard (58).
Data Requirements: Table 3-25 illustrates some important parameters affecting in situ soil flushing
performance. These factors can provide a basis for determining data needs.
TABLE 3-25. FACTORS AFFECTING IN SITU SOIL FLUSHING PERFORMANCE
Factor
pH buffering capacity
Heavy metals
Total organic carbon content
Solubility data
Cation exchange capacity (CEC)
Hydraulic conductivity (permeability)
Site hydrogeology
Complex mixtures of waste types (e.g.,
metals with organics)
Variable soil conditions
Soil pH
Moisture content
Potential Effect
High buffering capacity increases reagent requirements, especially acids.
May require pH adjustment (leaching) for removal.
Inhibits desorption of contaminants. '
Determines formula of suitable washing fluid. :
High CEC (>100 meq) interferes with metals removal.
Low permeability (k < 1 0"5 cm/s) reduces percolation and decreases
effectiveness.
Affects flow patterns that permit flushed contaminants recapture.
Formulation of suitable flushing fluids difficult.
Inconsistent flushing.
Affects the speciation of metal compounds.
High moisture decreases flushing fluid transfer.
Ill
-------
Separation/Concentration Technologies for Treatment of Excavated Soil
Thermal Desorption
l^hermal desorption technology physically separates volatile and some semivolatile contaminants with low
boiling points from excavated soil, sediment, and sludge. A schematic diagram of a thermal desorption process is
shown in Figure 3-14. Thermal desorption uses indirect or direct heat exchange to volatilize contaminants and water
from soil into a carrier gas stream for further treatment. The carrier gas stream may be either air or an inert gas.
Depending on the process selected, this technology heats contaminated media to temperatures between 200° and
1,000° F. Off-gases may be burned in an afterburner, catalytically oxidized, condensed for disposal, or captured
by carbon adsorption beds (59).
Typical Treatment Combinations: Thermal desorption systems create up to seven residual streams: treated
media, oversized contaminated rejects, condensed contaminants, water, particulates, clean off-gas, and/or spent
carbon. Debris and oversized rejects may be suitable for on-site disposal. Solidification may be necessary,
depending on the residual content of nonvolatile heavy metals in the treated medium. Condensed contaminants
require further treatment.
Technology Applicability: Thermal desorption can successfully treat most of the contaminants found at
solvent sites. It cannot separate metals (arsenic, cadmium, lead, zinc, chromium) or PAHs with boiling points
above 1,000° F effectively. Mercury, a volatile metal, can be treated with some thermal desorption units. Bench-,
pilot-, and full-scale studies have demonstrated that thermal desorption achieves treatment efficiencies of 99 percent
or greater for VOCs and semivolatile organic compounds (SVOCs). Some higher temperature units can treat PCBs,
pesticides, and dioxins/furans (60> 61).
112
-------
Vent
Fil»rote-b
(Wd!fen«l
TKMrant
(Air,
Non-
Coretensablesl
C^ndereate
JT
X
Caibon
Aioi'jer
L^MOiganb
Liquid Fteseto
Further T
Recoveiy
Aqueous phase C
FwtherTiealmem'
Dbohaige
Heavy Orgs nle Liqiicl
Phase (if anji)to
srTieaOTemf
Raxveiy
Figure 3-14 SdiematicfccTliennalDeEOfpticn (Ex-Siki>fcr Content hafed Soils, Sedhients, aid Sludges.
113
-------
Technology status/performance: Commercial-scale, thermal-desorption units are already in operation.
Thermal desorption has been selected in one or more operable units at 14 Superfund sites. It is one of the
technologies of choice for the cleanup of VOCs, semivolatiles, PAHs, and PCBs. The following companies have
units: Roy F. Weston, Inc., Chemical Waste Management, Canonie Environmental, TDI Services, and Remediation
Technologies, Inc. Table 3-26 contains the results of a full-scale performance test for the Roy F. Weston, Inc. LT3
System. Table 3-27 is a summary of typical performance data for thermal desorption.
TABLE 3-26. FULL-SCALE PERFORMANCE RESULTS FOR LT3 SYSTEM159'
Contaminant
Benzene
Toluene
Xylene
Ethyl benzene
Naphthalene
Carcinogenic
Priority PNAs
Noncarcinogenic
Priority PNAs
Soil Range
(ppb)
1,000
24,000
110,000
20,000
4,900
< 6,000
890 to 6,000
Treated Range
(ppb)
5.20
5.20
<1.00
4.80
<330
<330 to 590
<330 to 450
Removal Efficiency
(%)
99.5
99.9
>99.9
99.9
>99.3
<90.2 to 94.5
< 62.9 to 94.5
TABLE 3-27. SUMMARY OF PERFORMANCE DATA FOR THERMAL DESORPTION
Site
USATHAMA Letterken-
ney Army Depot, Cham-
bersburg, PA
Cannon Bridgewater
Superfund Site, Bridge-
water, MA
Cannon Bridgewater
Site, Bridgewater, MA
Ottati & Goss Superfu-
nd, Kingston, NH
USATHAMA Tinker Air
Force Base, Oklahoma
City, OK
TP Industrial, Inc.,
South Kearney, NJ
Equipment
Weston Low Tempera-
ture Thermal Treatment
System (LT3) (pilot
scale)
Weston Low Tempera-
ture Thermal Treatment
System (LT3) (full scale)
Canonie Low Tempera-
ture Direct Desorber
Thermal desorption,
Canonie Engineering
Weston Low Tempera-
ture Thermal Treatment
System (LT3) (full scale)
Canonie Environmental
Services (full scale)
Initial
Benzene, trichloroethylene, tetra-
chloroethylene, xylene
Total VOCs: 32,000 ppm
TCE, DCE, PCE toluene, xylene,
vinyl chloride 500 to 3,000 ppm
total VOCs
Total VOCs
TCE, PCE, DCA, benzene up to
2,000 ppm total VOCs
Up to 6,100 ppm TCE
Up to 10,000 ppm VOCs
Performance
>99% removal
4,480 ppb
<0.25 ppm total VOCs
(48, 65}
Reduced to <0.1 mg/kg
< 1 ppm total VOCs (4S- "•
65)
Met required cleanup
levels l661
Average reduction in
concentration to 0.3 pprn
VOCs I66>
114
-------
TABLE 3-27. (Continued)
Site
Confidential Site in
Illinois
Privately-funded site.
South Kearney, NJ
McKin, Maine
Coal and Tar Contami-
nated Soils
Gas Station, Cocoa, FL
Equipment
Weston Low Tempera-
ture Thermal Treatment
System (LT3) (full scale)
Canonie Environmental
Low Temperature Ther-
mal Aeration LTT A™
(full scale) :
Canonie Environmental
Low Temperature Ther-
mal Aeration LTTA*"
(full scale)
Remediation Technolo-
gies, Inc. (ReTEC) (pilot
scale)
OHM Low Temperature
Direct Desorber
Initial
Benzene 1 ,000 ppb
Toluene 24,000 ppb
Xylene 110,000 ppb
Ethyl benzene 20,000 ppb
VOCs 177.0 ppm (avg.)
PAHs 35.31 ppm (avg.)
VOCs ND-3,310ppm
Up to 1 ,000 ppm TCE
Benzene 1 .7 ppm
Toluene 2.3 ppm
Xylene 6.3 ppm
Ethyl benzene 1 .6 ppm
Benzene, toluene, xylene
Performance
Benzene 5.2 ppb
Toluene 5.2 ppb
Xylene < 1 .0 ppb
Ethyl benzene 4.8 ppb
VOCs 0.87 ppm (avg.)
PAHs 10.1 ppm (avg.)
VOCs ND to 0.04 ppm
0.1 ppm TCE (48-85)
Benzene <0.1 ppm
Toluene <0.1 ppm
Xylene <0.3 ppm
Ethyl benzene <0.1 ppm
Treated to <0.1 mg/kg
Implementation costs: Several vendors have documented processing costs that range from $80 to $350 per
ton of feed processed <62> 0> M). Cost must be considered in context, because the base year of the estimates varies.
Costs also differ due to the quantity of waste to be processed, the term of the remediation contract, the moisture
content, the organic constituency of the contaminated medium, and the cleanup standards to be achieved.
Data Requirements: Table 3-28 describes the factors affecting thermal desorption performance. Data
requirements can be derived from these factors.
115
-------
TABLE 3-28. FACTORS AFFECTING THERMAL DESORPTION PERFORMANCE
Factor
Clay or tightly aggregated particles
Mercury (Hg) content
Metals, inorganics, nonvolatile organics
Metals (As, Cd, Pb, Cr)
Moisture content
pH
Particle size
Constituent vapor pressure
Volatile organic concentrations
Potential Effect
Incomplete volatilization of contaminants due to
caking.
Increased temperatures to treat and air pollution
control costs.
Not likely to be effectively treated.
Residue may fail TCLP.
High moisture content (> 20%) increases energy
requirements. Dewatering or pretreatment may be
required.
Causes corrosion of system components (outside 5 to
1 1 range).
Oversized ( > 1 in) debris material requires size reduc-
tions; fines generate fugitive dusts and a greater dust
loading will be placed on the downstream air pollu-
tion-control equipment.
Low vapor pressure decreases removal efficiencies;
Requires vapor pressure curve for each pollutant.
Equipment limits: Rotary Dryer up to 1 0%; Thermal
Screw 50 to 60% (68).
Source:
Soil Washing
Soil washing technology is a water-based process for mechanically scrubbing excavated soil to remove
contaminants. Figure 3-15 depicts a schematic diagram of a soil washing process, which removes contaminants in
two ways: by dissolving or suspending them in the wash solution, or by concentrating thein into a smaller volume
of soil through particle size separation techniques. Soil washing systems that incorporate tfoti
greatest success for soils contaminated with heavy-metal and organic contaminants. Contaminants tend to bind
chemically and physically to clay and silt particles. The silt and clay, in turn, tend to attaci physically to sand and
gravel. The particle size separation aspect of soil washing first scours and separates the
clean sand and gravel particles. The process then scrubs the soluble contaminants from tjie particle surfaces and
dissolves them in the liquid phase.
The soil-washing process uses various additives (surfactants, acids, chelating agents) to increase separation
efficiencies. After successful testing, the washed soil can be returned to the site or reclaimed. The aqueous phase
silts and clays from the
and the clay/silt/sludge fraction contain high concentrations of contaminants. These two si
for other on- or off-site treatment
teams
become waste feed
116
-------
technologies. The washwater may also be recycled back to the process.
To Puttier :
TrsstmaTt
arrfoi Disposal
Blowdown
Wa-er
To Further
f TteatttEntandbr
Fteooveiy
tsedojrii neo/aa
Figure 3-16 Schematic for Sail Wash ing of Cental! hated Soils, Sediments, aid Sludges.
Typical Treatment Combinations: Soil washing generates four main waste streams: contaminated solids,
washwater, washwater treatment sludge, and air emissions. Contaminated clay fines and sludge may require further
treatment with technologies such as incineration, thermal desorption, solidification/ stabilization, or bioremediaftion.
Discharge standards may mandate washwater treatment prior to discharge. Permits may be required for
collection/treatment of air emissions from the preparation area or the washing unit.
Technology Applicability: Soil washing effectively treats waste-containing halogenated phenols and creosols,
nonhalogenated aromatics, and nonvolatile and volatile metals. The parocess is best suited for sandy and sandy loam
soils that are low in soil organic matter and clay content. Removal efficiencies for soil washing depend on the type
of contaminant and washing fluid. Soil washing can be used as a relatively cost effective way to reduce the volume
of material needed to be disposed of or treated by a more energy intensive process. Water alone,may easily remove
volatile organics. Semivolatile organics, pesticides, and hydrophobic contaminants may require the addition of a
surfactant; metals may require pH adjustment with acids or bases or the addition of chelating agents. Complex
contaminant matrix systems, which contain a mixture of metals, nonvolatile organics, and semivolatile organics,
may require sequential washing steps with variations in the wash formulation and operating parameters. Site-
117
-------
specific, bench, or pilot-scale treatability tests determines the best operating conditions and wash fluid compositions.
Soil washing has attained a removal efficiency greater than 99 percent for nonhalogenated aromatics. Bench-scale
studies for nonvolatile and volatile metals achieved 99 percent. However, only 72 percent removal was achieved
for halogenated phenols and creosols (S6).
Technology Status/Performance: Soil washing is widely accepted in Europe but has had limited use in. the
United States; now it is becoming popular. A number of vendors provide soil washing processes. Information from
treatability studies at solvent sites indicates possible applications (Table 3-29). However, sufficient data are not
available at this time.
TABLE 3-29. SUMMARY OF PERFORMANCE DATA FOR SOIL WASHING AT
SUPERFUND SITES
Equipment
MTARRI (bench
scale)
Heijrnan
Initial
1 , 1 -Dichloroethane
Chloroform
1 ,2-Dichlorbethane
1,1,1 -Trichloroethane
1 ,1 ,2-Trichloroethane
Benzene
Toluene
Chlorobenzene
Ethylbenzene
Styrene
Acetone '
Chlorobenzene
Extractable organic halo-
gens
Mineral oil
43 ppm
99 ppm
4,500 ppm
5 ppm
3,700 ppm
8 ppm
30 ppm
79 ppm
453 ppm
280 ppm
61 ppm
Performance
99.9%+ removal
99.9%+ removal
99.8%+ removal
99.9%+ removal
99.7%+ removal
99.9%+ removal
99.9%+ removal
98.9%+ removal
98.7%+ removal
97.5%+ removal
75.4%+ removal*
99.97%
95%
90-99%
*Possible laboratory contamination(69).
Implementation costs: Vendor-supplied treatment costs for soil washing processes range from $50 to $205
per ton of feed soil. Treatment of the residuals may be significant for this process depending on the type and
concentration of the contaminants.
118
-------
Data requirements: Data requirements for soil washing can be derived from the performance factors in Table
3-30.
TABLE 3-30. FACTORS AFFECTING SOIL-WASHING PERFORMANCE
Factor
Silt and clay content
Complex waste mixtures
Humic content
Metals concentration
Particle size distribution
Partition coefficient
Cation exchange capacity
Wash solution
Potential Effect
Increases difficulty to remove contaminants because
of strong adsorption to particles.
May require multiple process steps and wash fluid
formulations.
Inhibits contaminant removal if high.
Resist solubilization (insoluble metals). However,
some metals can be solubilized and removed.
Affect removal from wash fluid (particles < 0.063
mm); oversize debris > 0.25 IN requires removal).
High coefficient requires excessive volumes of leach-
ing liquid (highly-bound contaminant).
High CEC may affect treatment of metallic com-
pounds.
Large volumes become expensive to treat.
Source: (67)
Solvent Extraction :
Solvent extraction is a physical separation process that removes contaminants from soil, sludge, or sediment;
it uses organic solvents to isolate contaminants, unlike soil washing, which uses water or water-based solutions.
Figure 3-16 is a schematic diagram of a solvent extraction process. Solvent extraction is more appropriate for
organic contaminants than inorganics and metals; it reduces contaminant volume by concentrating them in the extract
phase. The three broad categories of the solvent extraction process are conventional solvent extraction, critical
solution temperature fluid, and supercritical fluid extraction (KI).
119
-------
^r-Cpera-Bd
TFartrferPvyp
.t
^udgatSedment
[fewateorg IHt
Qpuua
towH
Filtatsto
*• Adftfloal
Tieawern
/
* Ccntamirated
?™
Bqu'pment
^ -Soil (SiifcttetM
Raclarrat'or}
To Further
TrealnnEntandbi
Recovery
Figure 3-16 Schematic for Solvent Extraction (Ex-SHj) of Ccnlam hated Sails, Sediments, and Sludges.
Conventional solvent extraction uses organic solvents to selectively extract the contaminants of
concern. The process may require several passes to reduce contamination to the desired level. The
extracted solvent can be stripped of the contaminants, condensed, recycled, and reused, therefore
reducing contaminant volume and providing optimum extraction efficiency.
Critical solution temperature fluid extraction uses solvents (aliphatic amines) that are miscible with
water at one temperature and insoluble with water at another temperature; triethylamine is an example.
These solvents can be recycled from the recovered liquid phases by steam stripping because of their
high vapor pressure and low boiling point azeotrope formation.
Supercritical fluid extraction uses highly compressed gases, e.g., carbon dioxide, butane or propane,
raised above their critical temperatures to extract contaminants that generally resist extraction by
conventional solvents. The highly compressed gaseous fluid provides the additional diffusive/solvating
power that is required to extract contaminants from spaces and particle surfaces of an environmental
medium because of irregularities in soil. Supercritical fluid extraction uses higher pressure and
120
-------
temperature than conventional solvent extraction. The process also can recycle and reuse the fluid.
Typical Treatment Combinations: Solvent extraction generates three streams: concentrated contaminants,
treated soil or sludge, and separated solvent. Concentrated contaminants may receive further treatment or disposal;
the treated soil or sludge may require further drying. Depending on the metal content or other inorganic
contaminants remaining, treatment of the cleaned solids by some other technique such as S/S or soil washing may
be necessary. Analysis of the liquid component determines whether further treatment is necessary before disposal.
Technology Applicability: Solvent extraction is effective in treating excavated sediment, sludge, and soil
containing contaminants similar to those at solvent .sites. This technology generally is not used for extracting
inorganics (i.e., heavy metals). Sometimes inorganics that pass through the process experience a beneficial effect
by changing the chemical compound to a less toxic or leachable form.
Technology Status/Performance: Resources Conservation Company (B.E.S.T. Process) and CF Systems
have tested solvent-extraction systems at two Superfund sites under the SITE Program. Solvent extraction would
be specified for a solvent-contaminated site if there were other, more difficult to remediate compounds (such as
PCBs) which could not be handled by SVE or in situ bioremediation. Solvent-extraction technology was used as
the remedial action for the Pinette Salvage Superfund site in Washburn, Maine, which is contaminated with PCBs
and organics (chlorobenzenes, dichlorobenzene, and trichlorobenzene). Other solvent-extraction systems under
consideration at hazardous waste sites include the Extraksol Process by Sanivan International, Inc.; the Low Energy
Extraction Process (LEEP), a joint venture by Harmon Environmental Services and Acurex Corporation; and the
Carver-Greenfield process by DeHydro Tech. Information from treatability studies at solvent sites indicate possible
application (Table 3-31).
121
-------
TABLE 3-31. SUMMARY OF PERFORMANCE DATA FOR SOLVENT EXTRACTION
Site
Star Enterprise Refinery
Port Arthur, TX [71]
Two Petroleum Refiner-
ies [72]
Bayou Bonfouca Superfu-
nd, Stidell, LA [73]
Jannison-Wright Corpo-
ration, Granite City, IL
[73]
Equipment
CF Systems full-scale 50
tpd commercial unit
LEEP (bench scale)
B.E.S.T. Process (pilot
scale)
B.E.S.T. Process (pilot
scale)
Initial
Benzene 30.2 mg/kg
Toluene 1 6.6 mg/kg
Ethylbenzene 30.4 mg/kg
Xylenes 1 3.2 mg/kg
Anthracene 28.3 mg/kg
Naphthalene 42.2 mg/kg
Phenanthrene 28.6 mg/kg
Volatiles and semivolatiles
Semivolatiles
Semivolatiles
Performance
Meets or exceeds BOAT
standards
Benzene 0.18 mg/kg
Toluene 0.18 mg/kg
Ethylbenzene 0.23
mg/k
g
Xylenes 0.98 mg/kg
Anthracene 0.1 2 mg/kg
Naphthalene 0.66 mg/kg
Phenanthrene 1 .01 mg/kg
Reduced to levels below
detection limits
Greater than 99% was
achieved. Total semivola-
tiles concentration was
reduced from 6,688 mg/kg
to 34 mg/kg
Greater than 98% was
achieved for total semivola-
tiles
Implementation costs: Cost estimates for solvent extraction range from $100 to $500 per ton(71). The most
significant factors influencing costs are the waste volume, the number of extraction stages, and the operating
parameters such as labor, maintenance, setup, decontamination, demobilization, and time lost during equipment
operating delays. The cost of solvent-extraction treatment is currently higher than that for thermal desorptiom.
Data requirements: The data needed to evaluate system performance is presented in Table 3-32.
122
-------
TABLE 3-32. FACTORS AFFECTING SOLVENT-EXTRACTION PERFORMANCE
Factor
Complex waste mixtures
Metals (e.g., aluminum)
Particle size
pH
Partition coefficient
Volatiles
Moisture content (>30%)
Heavy metals
Potential Effect
May be combination of solvents needed.
Strong reactions may occur during B.E.S.T. treatment
process because of caustic addition.
Particle size requirements vary with system from
>1/8" to 2" diameter.
Must be in range compatible with extracting solvent
(pH >10 for B.E.S.T. process).
High coefficient requires additional extraction steps
(highly bound) contaminants.
Volatiles may combine with process solvent, requiring
additional extraction steps (high concentrations) or
fractional distillation to separate solvents from the
contaminant for reuse - increases cost if cannot
recycle solvent.
Water may impede some extraction processes. It
may require use of a hydrophilic solvent to remove
water so that contact between hydrophobic solvent
and contaminant will improve.
Not suitable for solvent extraction.
Source: (67)
WATER-TREATMENT TECHNOLOGIES
Water treatment must address three media types at solvent sites: process wastewater, surface water, and
groundwater.
Based on the site-specific contaminants and the selected remedies, the wastewater can require a range of
treatment. Treatment of process wastewater is part of the treatment train. The treatment of any surface water and
remediation of groundwater may occur at the beginning, throughout, or after the other remedial actions. Site-
specific data affects the selection of treatment options.
Also, the future use of the site dictates the remedial methods to be selected for water treatment. Two
treatment categories are destruction technologies and separation/concentration technologies. Destruction technologies
apply only to organic contaminants, whereas separation/concentration technologies treat both organic and inorganic
contaminants.
123
-------
The technologies that treat wastewater, surface water, and groundwater at solvent sites are also appropriate
to other types of sites; a brief overview follows. Groundwater treatment can be performed by both in situ and ex
situ technologies. The effectiveness of ex situ technology is dependent upon removing contaminants along with the
groundwater. This process usually is referred to as pump and treat. If it proves too difficult, other technologies
such as steam extraction or surfactant flushing can be used to improve contaminant removal with the groundwater.
Groundwater technologies are discussed in more detail in other EPA documents (see Bibliography).
Destruction Technologies Separation/Concentration Technologies
Chemical oxidation Adsorption Membrane separation
Biological treatment Filtration Precipitation
Ion exchange Oil/water separation
Air stripping Air sparging
Reverse osmosis
Table 3-33 summarizes the water treatment technologies applicable to various contaminant groups found at
solvenlt sites.
124
-------
TABLE 3-33. EFFECTIVENESS OF GROUNDWATER-TREATMENT TECHNOLOGIES ON SOLVENT
CONTAMINANT GROUPS
i
Fixed-Film
Biological
Treatment
- i
o
5
n
•H C
If
l|
$§
o £
Membrane
Rltration
llll
sf
i
CD
CD
O
•
O
•
•
CD
Halogenated nonpolar aramatics
•
•
•
O
•
O
CD
*
•
i
i
•
•
o
•
o
•
•
•
i
*o>
Ii
1 !
^
•
•
O
•
O
•
•
•
O
1
i I !?
iCDQ
-------
Destruction Technologies for Water Treatment
Chemical Oxidation
Chemical oxidation primarily treats halogenated and nonhalogenated solvents (VOCs and SVOCs), phenolics,
pesticides, PCBs, and nonvolatile and volatile metals. Figure 3-17 is a schematic diagram of a chemical oxidation
process. This process oxidizes ions or compounds to render them nonhazardous or to make them more amenable
to substjquent removal or destruction processes. Chemical oxidants are relatively nonselective; they may oxidize
other compounds as they destroy accompanying contaminants of concern. Due to the cost of chemicals, this process
has limited application to waters with large amounts of oxidizable components or heavily contaminated water.
Chemical oxidation is most useful as a polishing step for dilute, relatively clean, aqueous wastes.
Ultraviolet (UV) radiation/oxidation uses UV radiation, ozone and hydrogen peroxide to destroy organic
compounds in water. Other oxidants are chlorine dioxide, hypochlorites, and chlorine (74>. The process is a well-
established disinfection technology for drinking water and wastewater. UV radiation/oxidation has been
demonstrated as part of the SITE Program (74> 75).
Biological Treatment
Biological treatment of water, like soil biotreatment, detoxifies wastestream organic matter through microbial
degradation. The most prevalent type is aerobic. A schematic diagram of the aerobic bioremediation of
groundwater is shown in Figure 3-18. A number of biological treatment processes can treat water from solvent
sites. These include conventional activated sludge techniques; various modifications of activated sludge techniques,
i.e., those using pure-oxygen activated sludge, extended aeration, and contact stabilization; fixed-film systems
(rotating biological discs); and hi situ biological treatment.
* The activated sludge process introduces aqueous waste into a reactor containing a suspension of
aerobic bacterial cells. The bacteria transform organics into cell constituents, other organics,
carbon dioxide and water. It also produces new bacterial cells.
<> In the pure-oxygen activated sludge process, oxygen or oxygen-enriched air replaces ambient air
and increases the transfer of oxygen.
« Extended aeration uses longer residence times and a higher population of microorganisms.
« Contact stabilization requires a short contact of the aqueous wastes and suspended microbial solids,
subsequent settling, and further treatment to remove sorbed organics.
126
-------
• Fixed-film systems use contact of the aqueous waste stream with microorganisms attached to some
inert medium, such as rock or specially designed plastic material(76).
• Rotating biological contractors cqnsist of a series of rotating discs connected by a shaft set in a
basin or trough. The contaminated water passes through the basin where the microorganisms,
which are attached to the discs, metabolize the organics in the water.
• lii situ bioremediation of groundwater is becoming a frequently selected treatment for low to
intermediate concentrations of organic contaminants. The addition of nutrients into an impacted
aquifer enhances the natural degradation of chemical compounds by indigenous microorganisms.
Treated Water
to Disohaige
or Recharge
4tfft«-Mc 5H-H93
Figure 3-17 Schemafic for Chemical Oxidation at Ccnbm hated Ocundwater
127
-------
Nutrient
Adjustment
,
Adjustment
JU-JU
Atr
Bbwar
To Recharge
Infcctfon
Wei
To Further
(Traatnnet*
>r Disc targe
Groundualer
&w>otbn
Ufefc
Saturated
2one
W///////////////////////^^^^^
Schematic for Bfcramedbtiai
-------
Contaminated
Ground water
Ground water
Extra: ton
Wtelb
Vadose
Zone
Carbon
Adsorbers
Submersibfe
Pump
SaturatEd
Zone
TreaJed Water
->• to Discharge
or Recharge
%%?%2?%^^
Figure 3-19 Schematic for Cart»n Adsctpiion of Ccntamhafed Groundwafer.
Filtration
Filtration isolates solid particles by running a fluid stream through a porous medium. Figure 3-20 is a
schematic diagram of a filtration process. The driving force is either gravity or a pressure differential across the
filtration medium. Filtration techniques include separation by centrifugal force, vacuum, or high pressure.
Therefore, filtration can separate various contaminant particulates from an aqueous stream.
129
-------
Makeup
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Ion Exchange
Ion exchange removes ions from the aqueous phase by the exchange of electrical charges between the
contaminants and the exchange medium. Ion exchange materials may consist of resins made from synthetic organic
materials that contain ionic functional groups to which exchangeable ions are attached. They also may be inorganic
and natural polymeric materials. Ion exchange removes nonvolatile and volatile metals. This should be considered
only if metals co-exist with solvents at solvent-contaminated sites. After the toxic materials have been removed,
the resins can be regenerated for re-use.
Membrane Filtration
Membrane filtration technologies, such as reverse osmosis and ultrafiltration, separate chemical constituents
from water. Reverse osmosis (RO) is a pressure-driven, membrane-separation process. The chemicals are not
destroyed; they are merely concentrated, making reclamation possible. A low-energy process, RO requires no phase
change for separation of the dissolved materials, nor latent heat of vaporization, fusion, or sublimation. However,
RO and. ultrafiltration are sensitive to the presence of fines, which can clog the membranes. Membranes are fragile
130
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and often rupture from over pressure. Ultrafiltration and RO can treat groundwater contaminated with heterocyclics
and simple nonhalogenated aromatics, polar organic compounds, some nonvolatile and volatile metals m.
Precipitation
This physical/chemical process transforms dissolved contaminant into an insoluble solid, facilitating the
contaminant's subsequent removal from the liquid phase by sedimentation or filtration. The process usually uses
pH adjustment, addition of a chemical precipitant, and flocculation. Typically, metals precipitate from the solution
as hydroxides, sulfides, or carbonates. The solubilities of the specific metal contaminants and the required cleanup
standards will dictate the process used. Precipitation is used mainly for metals; this should be considered only if
metals co-exist with solvents.
Oil/Water Separation
Oil/water separation removes oil from water by providing surface contact for de-emulsifying oil particles from
the water phase. It is a frequent pretreatment for other processes.
Air Stripping
Air stripping is a common technique for the removal of VOCs from groundwater. Dissolved VOCs in water
contact air, usually in a packed column. Spray towers and other alternative forms of aeration are sometimes used.
These devices bring the contaminated water into countercurrent contact with air supplied by a blower. The columns
or towers may contain a variety of packing materials, such as recently designed plastic products: polypropylene
pall rings or flexi-rings, saddles, and tellerettes (circular plastic coils). The tower is constructed with stainless steel,
lined carbon steels, or fiberglass.
Air Sparging
In situ air sparging is a relatively new technique for the removal of VOCs from aquifers. Although there is
substantially less experience with air sparging than with S VE, its potential advantages over conventional techniques
such as excavation and groundwater pump-and-treat operations include remediation of the overlying vadose zone,
shorter remediation times, reduced environmental impact, destruction or capture of the contaminant, and potentially
reduced costs. The history of in situ air sparging is limited; therefore, cost estimates are uncertain.
Air sparging involves the injection of compressed air into the lower portion of the contaminated aquifer. The
air percolates up through the contaminated region of the zone of saturation, generates local turbulence in. the
groundwater, and strips VOCs from the aqueous phase into the vapor phase. The increased local turbulence can
be expected to increase the rate of the solution of DNAPL residual droplets trapped in the aquifer. After the gas
leaves the saturation zone, it may be recovered by an SVE system in concert with the sparging operation to
remediate the vadose zone and prevent the vapors from escaping into the atmosphere. If the VOCs are readily
biodegradable, the organic vapors may be destroyed biologically as the moist, oxygen-rich soil gas rises through
131
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the vadose zone.
Factors affecting the applicability and performance of in situ air sparging include the following.
• The vapor pressure of the VOC at the ambient temperature must be sufficient to permit its removal at a
reasonable rate. The criterion for SVE, 0.5 Torr, is reasonable for air sparging.
» The dimensionless Henry's Law Constant of the VOC at ambient temperature must permit efficient
stripping; values of KH less than approximately 0.01 are probably too small.
Most common organic solvents are suitable candidates for sparging (hydrocarbons, chlorinated solvents).
Some oxygenated VOCs (i.e., acetone and alcohols) are soluble in water, so they have unacceptably small Herjtry's
Law Constants. Oxygenated VOCs, however, are biodegradable.
For air sparging to be feasible, air must come in contact with all of the contaminated water. If DNAPL
residual, droplets are present, the circulation of groundwater induced by the injected air must be sufficient to dissolve
them in an acceptable period of time. These considerations appropriate the following requirements.
» The natural rate of groundwater flow must be sufficiently slow to permit adequate contact of the
contaminated groundwater in the air-stripping region around the sparging well.
» The aquifer medium must be sufficiently permeable to permit an adequate flow of air and to allow the
injected air to generate the circulation and turbulence in the groundwater necessary to permit mass transport
of the VOC from the DNAPL and/or aqueous phases into the vapor phase.
• Low-permeability structures (such as clay lenses) may interfere with the movement of air and water in the
vicinity of the well, thereby preventing VOC removal from some domains.
• If molecular diffusion of the VOC in the liquid phase is the only mechanism of mass transport over
distances of even a few centimeters (cm), remediation will be extremely slow, which is expected in porous
fractured rock and in aquifers having highly heterogenous permeabilities.
* The greater the depth of the contaminated zone below the water table, the higher the pressure required to
operate the sparging well, which will affect costs.
• Air sparging is possible underneath buildings and other overlying impermeable structures.
132
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» The removal of residual DNAPL, lying on the underlying aquifer, can be substantially slower than the
removal of the dissolved VOC. The removal of pooled DNAPL can be expected to be slow unless the air-
sparging well injects air into the DNAPL pool.
Table 3-34 contains a summary of performance data for in situ air sparging. Factors affecting in situ air sparging
performance are listed in Table 3-35.
TABLE 3-34. SUMMARY OF PERFORMANCE DATA FOR IN SITU AIR SPARGING
Site
Gasoline service station, Rl
Dry cleaning facility
Savannah River
Consiervancy site, Belen, NM
Initial
BTX up to 21 mg/l
VOCs 41 mg/l
PCE, TCE, DCE
PCE 85 to 1 84 ug/l
TCE 500 to 1,810 ug/l
BTX
Performance
< 1 .0 mg/l
0.897 mg/l
3 to 1 24 ug/l
10 to 1,031 ug/l
49 to 60 % reduction
TABLE 3-35. FACTORS AFFECTING IN SITU AIR SPARGING PERFORMANCE
Factor
Groundwater depth
Water solubility
Volatility
Permeability
Potential Effect
Very deep > 1 50 ft - increased costs.
Very shallow <5 ft - difficult vapor recovery.
The more soluble the contaminant, the more
difficult the treatment.
Henry's Law Constant < 1 0B, the more diffi-
cult the treatment.
Hydraulic conductivity < 0.001 cm/s, the
more difficult the treatment.
133
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Typical Treatment Combinations
Typical treatment combinations for the remediation of water contaminated with solvents are presented in Table 3-36.
It includes pretreatment requirements and post-treatment/residuals management.
Depending on the wastestream characteristics and the primary technology selected, the remedial combination may
include pretreatment to remove free oils using an oil/water separator; pH adjustment; addition of a chemical agent
to enhance coagulation, flocculation, sedimentation; and removal of suspended solids by filtration. In biological
treatment, the water may require heating to reach an optimum temperature and the addition of inorganic nutrients.
The main process residual of an adsorption system is the spent sorbent holding the hazardous contaminants, which
requires treatment or regeneration. The primary process residual streams created with air stripping systems are the
off-gas and liquid effluent. The off-gas is released to the atmosphere after treatment; activated carbon is the
treatment most frequently applied to the off-gas stream. Effluent water containing nonvolatile contaminants may
need additional treatment. Other water-treatment technologies, such as filtration, ion exchange, chemical oxidation,
precipitation, etc., produce contaminated sludge, which also requires treatment prior to disposal (Table 3-36).
Depending on the contaminant, the treated water may need polishing by activated carbon, or biological treatment.
Residuals produced from chemical oxidation systems include partially oxidized products which may require
further treatment. Depending on the oxidizing agent used and the chlorine content of the contaminant, oxidation
of organic compounds may result in the formation of hydrogen chloride (HC1) and nitrogen dioxide. Acid-gas
control is required for reactions that produce HC1.
TABLE 3-36. TYPICAL GROUNDWATER TREATMENT COMBINATIONS
Pretreatment/Materials
Handling
Groundwater-Treatment
Technology
Post-Treatment/Residuals
Management
Pumping
Oil/welter separation
pH adjustment
Filtration
Air stripping
Sludge treatment/disposal
Spent carbon disposal/regeneration
Pumping
Oil/water separation
pH adjustment
Filtration
Granular-activated carbon (GAC)
treatment
Spent carbon disposal/regeneration
Polishing treatment
Pumping
Oil/water separation
pH adjustment
Flocculation/sedimentation
Membrane filtration
Sludge treatment/disposal
134
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TABLE 3-36. (Continued)
Pretreatment/Materials
Handling
Groundwater-Treatment
Technology
Post-Treatment/Residuals
Management
Pumping
Oil/water separation
pH adjustment
Flooculation/sedimentation
Filtration
Precipitation
Sludge treatment/disposal
Pumping
Oil/water separation
pH adjustment
Flocculation/sedimentation
Filtration
Chemical/UV oxidation
Sludge treatment/disposal
Oxidized products treatment/disposal
Injection well/extraction
Well installation
Soil flushing
Oil/water separation
Nutrient addition
pH adjustment
In situ bioremediation
Pumping, flow equalization
Oil/water separation
pH adjustment
Flocculation/sedimentation
Fixed-film biological treatment
Sludge treatment/disposal
Polishing wastewater treatment
Pumping
Oil/water separation
pH adjustment
Filtration
Ion exchange
Sludge treatment/disposal
Technology Status/Performance
To date, more than 100 RODs have specified air stripping as a remedy for VOC-contaminated groundwater.
The performance of the technology is a direct result of the design of the system used for air stripping. Air stripping
commonly achieves nearly 100 percent removal efficiency for VOCs. The Rockaway Township air stripper in
Rockaway Twp., New Jersey, achieved 99.99 percent removal of the VOCs in the groundwater using an air-to-water
ratio of 200, and a 3-inch tellerette packing in a 9-feet diameter column. The compound with the lowest Henry's
Law Constant was chloroform. Reported removal efficiencies at the Brewster Well Field site in New York were
98.5, 93.33, and 95.59 percent for PCE, f CE, and 1,2-DCE, respectively. A removal efficiency of 98.41 percent
135
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for MEK was reported at the Hicksville spill site in New York. At Wurthsmith Air Force Base in Oscoda,
Michigan, air stripping removed 99.9 percent of the TCE.
Granular-activated carbon (GAC) treatment is a specific groundwater treatment remedy for hundreds of
Superftind sites. Operating data from many installations indicate that activated carbon will be completely effective
on solvent site constituents. However, activated carbon is not cost effective when handling a groundwater stream
with high VOC concentrations. In such an instance, air stripping is more economical, followed by GAC treatment
to polish the aqueous effluent.
UV radiation/oxidation is a well-established technology for disinfecting drinking water and wastewater.
Chemical oxidation is effective in treating liquids that contain oxidizable contaminants. Performance of full-scale
chemical oxidation systems has been reported by several sources. Chemical oxidation was listed in the RODs for
several sites. Destruction efficiencies of more than 90, 80, and 60 percent were achieved for TCE; 1,1,1-TCE;
and 1,1-DCA, respectively, at Lorentz Barrel and Drum Superfund site in San Jose, California, by Ultrox
International's Ultrox System. Peroxidation Systems' Perox-Pure™ has been used at a number of sites to reduce
contaminants up to 90 percent. The Punis, Inc. enhanced oxidation system was demonstrated on groundwater at
Lawrence Livermore National Laboratory (LLNL) where BTEX levels were reduced from 5 ppm to as little as 5
ppb.
Membrane filtration has been demonstrated at the laboratory and pilot- and full-scale stages.
Li situ biodegradation has been chosen as a groundwater remedy at four Superfund sites. However, the
solvent contamination is incidental to the PAH contaminants at the sites. Several fixed-film, biological treatment
processes have treated wastewater commercially.
Implementation Costs
Table 3-37 is a summary of the estimated treatment costs for water-treatment technologies. The base years
of the estimates vary. Wastestream flow rates, types of contaminant, toxic concentrations, and the desired cleanup
standards make costs variable.
136
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TABLE 3-37. WATER-TREATMENT COSTS
Water Treatment
Granular activated-carbon
Membrane filtration
Ion exchange
Chemical/ultraviolet oxidation
Precipitation
Fixed-film biological treatment
Air stripping
Cost ($)/1000 Gallon Treated
0.10 to 1 .50 at 100 mgd flowrate
1 .20 to 6.30 at 0.1 mgd
1 .38 to 4.56
0.30 to 0.80'
70 to 1 50
0.07 to 0.28b
50 to 90
0.07 to 0.7 when Kh = 0.01 to 1.0
7 when Kh = 0.005
Reference
(78)
(79)
(80)
(80)
(75)
(80)
(81)
1 1987 dollars
111982 dollars
Ki = Henry's Law Constant
Data Requirements
Table 3-38 is a summary of the data requirements and factors affecting the various for water-treatment
technology options. These requirements provide a basic guideline for the types of information required to remediate
solvent sites.
137
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TABLE 3-38. DATA REQUIREMENTS FOR WATER-TREATMENT TECHNOLOGIES
Technology
Data Needs
Potential Effects
GAC
Molecular weight
Polarity
Suspended solids
Oil and Grease
Organic matter
Humic and Fulvic Acids
Biological organisms
Low molecular weight compounds are removed with
less efficiency.
Highly polar compounds not amendable to GAC.
Can foul carbon (high suspended solids _>.50 mg/L).
May cause carbon fouling (>.10 mg/L).
Rapidly exhaust GAC (high levels of organic matter,
e.g. 1,000 mg/L.
Rapid carbon exhaustion.
May cause fouling
Air stripping
Iron, Manganese, or carbonate
pH
Volatile or semivolatile organic
concentration
Volatility
Elevated levels may reduce removal efficiencies due
to scaling and the resultant channeling effects.
5 < pH > 11 may corrode system components and
auxiliary equipment.
Greater than 0.01 % generally cannot be treated by air
stripping.
Henry's Law Constant < 0.003 reduces efficiencies.
Membrane Filtration
Size of particles
'Oil and grease
Contaminants
May interfere with operation size depends on mem-
brane.
May interfere with the system by decreasing flow
rate.
Successful only with contaminant-specific mem-
branes.
Ion exchange
Oil and grease
Suspended solids
Metals and inorganic ions
pH
Oxidants
May clog resin.
May cause resin blinding (preferable limits _< 50 mg-
/L).
Must be present as soluble species.
May affect ion exchange varies with resin.
May damage resins
Chemical oxidation
Oil and grease
Concentration of contaminants
Optimize the system efficiency (low levels).
Proves too expensive for highly concentrated wastes.
Precipitation
pH
Oil and grease
Adjustment must be made for optimum precipitation.
Can interfere with process.
138
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TABLE 3-38. (Continued)
Technology
; Data Needs
Potential Effects
In-situ biological treatment
Moisture content
pH
Water solubility
Oxygen availability
Temperature
Variable waste composition
Heavy metals, highly chlorinated
organics, some pesticides, inorganic
salts
Nutrients (C,N,P)
Biodegrad ability
Permeability
Soil conditions and heterogeneity
Soil pH
Organic content
Moisture content
Site hydrology
Dissolved oxygen
PH
Inhibits bacterial activity (contents outside 40 to
80%).
Loses effectiveness beyond 4.5 to 8.5.
Low solubility compounds are difficult to biodegrade.
Low oxygen inhibits aerobic activity, sustains anaero-
bic activity.
Effectiveness outside temperature range 15 to 70°C
slows down.
Vary biological activity and cause inconsistent biodeg-
radation.
Can be highly toxic to microorganisms.
Low concentrations can limit activity. Addition of
nutrients may enhance activity.
Certain contaminants are not or only partially biode-
gradable (e.e., dioxins).
Allows movement of water and nutrients through
contaminated area.
Vary biological activity and cause inconsistent biodeg-
radation. •
Inhibit biological growth (pH <5.5).
Low concentrations can limit biological growth.
Limit biological growth (content <10%).
Determine flow patterns that permit pumping for
extraction and re-injection.
Low oxygen content inhibits aerobic activity and
sustains anaerobic activity.
Very high or low pH inhibits activity. Optimal range
pH 6 to 8.
139
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i
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142
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Development, Cincinnati, OH. EPA/540/2-91/006.
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of Solid Waste and Emergency Response, Washington, B.C. EPA/540/2-91/001.
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Office of Emergency and Remedial Response, Washington, D.C. EPA/540/2-91/019A
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Development, Washington, D.C. EPA/540/2-91/003.
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Liquids from the Subsurface 2. Code Validation and Application." Water Resources Research, 28(2):451-
465.
52. U.S. EPA. 1991. "Engineering Bulletin: In Situ Steam Extraction Treatment." Office of Emergency and
Remedial Response, Washington, D.C. EPA/540/2-91/005.
53. U.S. EPA. 1990. "Applications Analysis Report: Toxic Treatments In Situ Steam/Hot-Air Stripping
Technology." Prepared by Science Applications International Corporation, San Diego, CA. For U.S. EPA
Bisk Reduction Engineering Laboratory, Cincinnati, OH.
54. Udell, K., and L. Stewart, Jr. 1989. "Field Study of In Situ Steam Injection and Vacuum Extraction for
B.ecovery of Volatile Organic Solvents." University of California. Berkeley-Seehrl Report No. 89-2.
55. Dev. H., G.C. Sresty, J.E. Bridges, and D. Downey. 1988. "Field Test of the Radio Frequency In Situ Soil
Decontamination Process." In: Superfund '88, Proceedings of the 9th National Conference, pp. 498-502.
The Hazardous Materials Control Research Institute, Silver Spring, MD.
56. U.S. EPA. 1990. Summary of Treatment Technology Effectiveness for Contaminated Soil. Office of
Emergency and Remedial Response, Washington, D.C. EPA/540/2-89/053.
i
57. U.S. EPA. 1991. "Engineering Bulletin: In Situ Soil Flushing." Office of Emergency and Remedial
Response. Washington, D.C., and Office of Research and Development, Cincinnati, OH.
58. Environmental Solutions, Inc. n.d. "On-Site Treatment Hydrocarbon-Contaminated Soils." Under Contract
by Western States Petroleum Association.
59. U.S. EPA. 1991. "Engineering Bulletin: Thermal Desorption Treatment." Office of Research and
Development, Cincinnati, OH. EPA/540/2-91/006.
60. U.S. EPA. dePercin, P. 1991. "Thermal Desorption Technologies." Superfund Technology Demonstration
Division. AWMA Conference, Vancouver, BC, 1991. Risk Reduction Engineering Laboratory, Cincinnati,
OH.
61. U.S. EPA. de Percin, P. 1991. "Thermal Desorption Attainable Remediation Levels." Superfund
Technology Demonstration Division. Risk Reduction Engineering Laboratory Symposium, Cincinnati, OH.
62. Ramin, A. 1990. "Thermal Treatment of Refinery Sludges and Contaminated Soils." Presented at American
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143
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63. Nielson, R., and M. Cosmos. 1988. "Low Temperature Thermal Treatment (LT3) of Volatile Organic
Compounds from Soil: A Technology Demonstrated." Presented at the American Institute of Chemical
Engineers Meeting, Denver, CO.
64. Swanstrom, C., and C. Palmer. 1990. "X*TRAX™ Transportable Thermal Separator for Organic
Contaminated Soils." Presented at Second Forum on Innovative Hazardous Waste Treatment Technologies:
Domestic and International, Philadelphia, PA.
65. Low Temperature Thermal Aeration, Soil Remediation Services. 1990. Canonie Environmental Services
Corp., Porter, IN.
66. Weston Services, Inc. 1988. "Project Summary - LT3 Processing of Soils Contaminated with Chlorinated
Solvents and JP-4." n.p.
67. U.S. EPA. 1988. Technology Screening Guide for Treatment ofCERCLA Soils and Sludges. Office of Solid
Waste and Emergency Response, Washington, D.C. EPA/540/2-88/004.
68. U.S. EPA. 1992. "Thermal Desorption Applications for Treating Nonhazardous Petroleum Contaminated
Soil." Draft. Risk Reduction Engineering Laboratory, Edison, NJ.
69. Trost, P.B., and R.S. Rickard. 1987. "On-Site Soil Washing - A Low Cost Alternative." Presented at
AdPA. Los Angeles, CA, 1987.
70. Meckes, etal. 1992. "Solvent Extraction Processes: A Survey of Systems in the SITE Program." Journal
of Air and Waste Management Association. Vol. 42, No. 8.
71. U.S. EPA. 1990. Engineering Bulletin: Solvent Extraction Treatment. Office of Emergency and Remedial
Response, Washington, D.C. Office of Research and Development, Cincinnati, OH. EPA/540/2-90/013.
72. D.W. Hall, J.A. Sandrin, and R.E. McBride. 1989. "An Overview of Solvent Extraction Treatment
Technologies." Presented at the American Institute of Chemical Engineers, Philadelphia, PA.
73. Halloran, A.R.,R. Troast, andD.G. Gilroy. 1991. "Solvent Extraction of a PAH-Contaminated Soil." In:
Proceedings of the 12th National Conference, n.page. Superfund '91. Hazardous Materials Control Research
Institute.
Remedial Options - Water Treatment
74. U.S. EPA. 1991. The Superfund Innovative Technology Evaluation Program: Technology Profiles, Fourth
Edition. Office of Solid Waste and Emergency Response, Washington, D.C. EPA/540/5-91/008.
75. U.S. EPA. Engineering Bulletin: Chemical Oxidation Treatment. 1991. Office of Emergency and Remedial
Response, Washington, D.C. EPA/540/2-91/025.
76. Canter, L.W., and R.C. Knox. 1985. Groundwater Pollution Control. Lewis Publishers, Inc., Chelsea,
MI.
77. National Environmental Technology'Applications Corporation (NETAC). 1990. A Technology Overview of
Existing and Emerging Environmental Solutions for Wood Treating Chemicals. Prepared for Beazer East,
Inc., Pittsburgh, PA.
78. Nyer, Evan K. Groundwater Treatment Technology. 1985. Van NostrandReinholdCo., New York.
144
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79. U.S. EPA. 1991. Engineering Bulletin: Granular Activated Carbon Treatment. Office of Emergency and
Remedial Response, Washington, D.C. EPA/540/2-91/024.
80. U.S. EPA. 1989. Technologies for Upgrading Existing or Designing New Drinking Water Treatment
Facilities. Office of Drinking Water, Cincinnati, OH. EPA/625/4-89/023.
81. U.S. EPA. 1991. Engineering Bulletin: Air Stripping of Aqueous Solutions. Office of Emergency and
Remedial Response, Washington, D.C. EPA/540/2-91/022.
145
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SECTION 4
BIBLIOGRAPHY
SECTION 1 - Introduction
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SECTION 2 - Contaminants at Solvent Sites
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148
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EPA/625/4-91/025.
U.S. EPA. 1989. Seminar Publication: Requirements for Hazardous Waste Landfill Design, Construction, and
Closure. EPA/625/4-89/022.
U.S. EPA. 1987. Geosynthetic Design Guidance for Hazardous Waste Landfill Cells and Surface Impoundments.
EPA/600/S2-87/097.
U.S. EPA. 1991. Technical Guidance Document: Inspection Techniques for the Fabrication of Geomembrane
Field Seams. EPA/530/SW-91/051.
U.S. EPA. 1991. The Superfund Innovative Technology Evaluation Program: Technology Profiles. 4th ed. Office
of Research and Development and Office of Solid Waste and Emergency Response, Washington, DC EPA/540/5-
91/008.
U.S. EPA. 1984. Compatibility of Grouts with Hazardous Waste. EPA/600/2-84/015.
U.S. EPA. 1984. Slurry Trench Construction for Pollution Migration Control. EPA/540/2-84/001.
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PB87-170338.
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Uranium Mill Tailings and Low-Level Radioactive Wastes. NUREG/CR-5432.
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SECTION 3 - Remedial Options - Destruction
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Development, Cincinnati, OH, and Office of Emergency and Remedial Response, Washingtonj DC.
U.S. EPA. 1990. "Engineering Bulletin: In Situ Biodegradation Treatment (Draft)." Office of Emergency and
Remedial Response, Washington, DC, and Office of Research and Development, Cincinnati, OH.
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149
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Balkwill, D.L. and W.C. Ghiorse. 1985. "Characterization of Subsurface Bacteria Associated with Two Shallow
Aquifers in Oklahoma." Applied and Environmental Microbiology, 50:580-588.
Balkwill, D.L., F.R. Leach, J.T. Wilson, J.F. McNabb, and D.C. White. 1988. "Equivalence of Microbial
Biomass Measures Based on Membrane Lipid and Cell Wall Components, Adenosine Triphosphate, and Direct
Counts in Subsurface Aquifer Sediments." Microbial Ecology, 16:73-84.
Barker,, LF., and G.C. Patrick. 1986. "Natural Attenuation of Aromatic Hydrocarbons in a Shallow Sand
Aquifer." In: Proc. NWWA/API Conf. on Petroleum Hydrocarbon and Organic Chemicals in Ground Water-
Prevention, Detection, and Restoration, pp. 160-177.
Cozzarelli, I.M., R.P. Eganhouse, and MJ. Baedecker. 1990. "Transformation of Monoaromatic
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16:135-141.
Dunlap, W.J., and J.F. McNabb. 1973. Subsurface Biological Activity in Relation to Ground Water Pollution.
Robert S. Kerr Environmental Research Laboratory, Ada, OK. EPA/660/2-73/014.
Egli, C., R. Scholtz, A.M. Cook, and T. Leisinger. 1987. "Anaerobic DecUormation of Tetrachloromethane
and 1,2-dichloroethane to Degradable Products by Pure Cultures of Desulfobacterium sp. and Methanobacterium
sp." FEMS Microbiological Letters, 43:257-261.
Egli, C., T. Tsuchan, R. Scholtz, A.M. Cook, and T. Leisinger. 1988. "Transformation of Tetrachloromethane
to DicMoromethane and Carbon Dioxide by Acetobacterium woodi." Applied and Environmental Microbiology
54:2819-2824.
Ghiorse, W.C., and D.L. Balkwill. 1983. "Enumeration and Morphological Characterization of Bacteria
Indigenous to Subsurface Environments." Developments in Industrial Microbiology, 24:213-224.
Gibson, D.T. 1984. Microbial Degradation of Organic Compounds. Marcel Dekker, New York, NY.
Harvey, R.W., R.L. Smith, and L. George. 1984. "Effect of Organic Contaminants upon Microbial Distribution
and Heterotrophic Uptake in a Cape Cod, Massachusetts Aquifer." Applied and Environmental Microbiology
48:1197-1202.
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Groundwater." Developments in Industrial Microbiology, 16:305-312.
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Tetrachloride, Freon-113, Freon-11, and 1,1,1-TCA Under Anoxic Conditions." In: On-Site Reclamation:
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SECTION 3 - Remedial Options - Separation/Concentration
Houthoofd. J.M., J.H. McCready, and M.'H. Roulier. Soil Heating Technologies for In Situ Treatment: A Review.
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1991. Robert S. Kerr Environmental Research Laboratory, Ada, OK.
U.S. EPA. 1990. Basics ofPump-and-Treat Groundwater Remediation Technology. Robert S. Kerr Environmental
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151
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U.S. EPA. 1990. Engineering Bulletin: Soil Washing Treatment. Office of Emergency and Remedial Response,
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Helsel, R., E. Alperin, A. Groen. 1989. IT Corporation. "Engineering-Scale Demonstration of Thermal
Desorption Technology for Manufactured Gas Plant Site Soils for the Hazardous Waste Research and Information
Center, Savoy, Illinois 61874." Report #HWRIC RR-038, November.
U.S. EPA. 1990. Handbook on In Situ Treatment of Hazardous Waste-Contaminated Soils. Risk Reduction
Engineering Laboratory, Cincinnati, OH. EPA/540/2-90/002.
U.S. EPA, 1991. Guide for Conducting Treatability Studies Under CERCLA: Soil Vapor Extraction, Interim
Guidance. Office of Emergency and Remedial Response, Washington, DC. EPA/540/2-91/019A.
Environmental Solutions, Inc. "On-Site Treatment, Hydrocarbon Contaminated Soils." Irvine, CA. Under Contract
by: Western States Petroleum Association.
SECTION 3 - Remedial Options - Water Treatment
Crawford, Michael A. 1990. Separation and Treatment of Organic Contaminants in Liquids: Physical/Chemical
Treatment of Hazardous Wastes. Center for Environmental Research Information, Cincinnati, OH. CERI/90-16.
Nyer, E.K. 1985. Groundwater Treatment Technology. Van Nostrand Reinhold Co., New York, NY.
152
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APENDIX A
Treatment Comparisons at Selected Solvent Sites
Contaminants and Remedial Options at Solvent-Contaminated Sites
October 1993
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REFERENCES
1. ATTIC On-line System-Alternative Treatment Technology Information Center, Computerized Database and Electronic
Bulletin Board on Treatment of Contaminated Materials. Information: J.Perdek, U.S. EPA, (908) 321-4380; Modem
Access: (301) 670-3808. ',
2. CERCLIS On-line System—Comprehensive Environmental Response, Compensation, and Liability Information System,
Computerized Database. Information: M.Cullen, U.S. EPA, (703) 603-8730; Modem Access for U.S. EPA staff only.
3. RODS On-line System— Records of Decision System, Computerized Database and Electronic Bulletin Board. Information:
M.Cullen, U.S. EPA, (703) 603-8730; Modem Access for U.S. EPA staff only.
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