OOOR05101
Technology Overview
Overview of
In Situ Bioremediation of
Chlorinated Ethene DNAPL Source Zones
October 2005
Prepared by
The Interstate Technology & Regulatory Council
Bioremediation of DNAPLs Team
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ABOUT ITRC
Established in 1995, the Interstate Technology & Regulatory Council (ITRC) is a state-led,
national coalition of personnel from the environmental regulatory agencies of more than 40
states and the District of Columbia, three federal agencies, tribes, and public and industry
stakeholders. The organization is devoted to reducing barriers to and speeding interstate
deployment of, better, more cost-effective, innovative environmental techniques. ITRC operates
as a committee of the Environmental Research Institute of the States (ERIS), a Section 501(c)(3)
public charity that supports the Environmental Council of the States (ECOS) through its
educational and research activities aimed at improving the environment in the United States and
providing a forum for state environmental policy makers. More information about ITRC and its
available products and services can be found on the Internet at www.itrcweb.org.
DISCLAIMER
This document is designed to help regulators and others develop a consistent approach to their
evaluation, regulatory approval, and deployment of specific technologies at specific sites.
Although the information in this document is believed to be reliable and accurate, this document
and all material set forth herein are provided without warranties of any kind, either express or
implied, including but not limited to warranties of the accuracy or completeness of information
contained in the document. The technical implications of any information or guidance contained
in this document may vary widely based on the specific facts involved and should not be used as
a substitute for consultation with professional and competent advisors. Although this document
attempts to address what the authors believe to be all relevant points, it is not an exhaustive
treatise on the subject. Interested readers should do their own research, and a list of references
may be provided as a starting point. This document does not necessarily address all applicable
heath and safety risks and precautions with respect to particular materials, conditions, or
procedures in specific applications of any technology. Consequently, ITRC recommends also
consulting applicable standards, laws, regulations, suppliers of materials, and material safety data
sheets for information concerning safety and health risks and precautions and compliance with
then-applicable laws and regulations. The use of this document and the materials set forth herein
is at the user's own risk. ECOS, ERIS, and ITRC shall not be liable for any direct, indirect,
incidental, special, consequential, or punitive damages arising out of the use of any information,
apparatus, method, or process discussed in this document. This document may be revised or
withdrawn at any time without prior notice.
ECOS, ERIS, and ITRC do not endorse the use of, nor do they attempt to determine the merits
of, any specific technology or technology provider through publication of this guidance
document or any other ITRC document. The type of work described in this document should be
performed by trained professionals, and federal, state, and municipal laws should be consulted.
ECOS, ERIS, and ITRC shall not be liable in the event of any conflict between this guidance
document and such laws, regulations, and/or ordinances. Mention of trade names or commercial
products does not constitute endorsement or recommendation of use by ECOS, ERIS, or ITRC.
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* INTERSTATE *
INTERSTATE TECHNOLOGY & REGULATORY COUNCIL
Document
Evaluation Survey
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Thank you.
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7. Did the use of the document provide you with a better understanding of the regulatory
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8. In which part(s) of the approval process did the use of the ITRC document help?
Please circle as many as apply:
Test Plan / Treatability Study / Remedial Investigation and Feasibility Study /
Remedial Action (Work) Plan / Record of Decision / Other
9. Was the guidance from this document incorporated into your site-specific application?
If yes, please explain how:
lO.Did the use of the document save time / money in the review and application of the technology
11 .Will the use of this document result in time and/or monetary savings at subsequent applications?
12.Overall, did you find the guidance document useful?
13.Overall, did you concur with the guidance outlined in the document?
14.Please identify which sections of the document were most useful in your application.
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Please fax completed surveys to ITRC c/o WPI at: (540) 557-6085.
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Overview of In Situ Bioremediation of
Chlorinated Ethene DNAPL Source Zones
October 2005
Prepared by
The Interstate Technology and Regulatory Council
Bioremediation of Dense Nonaqueous Phase Liquids (Bio DNAPL) Team
Copyright 2005 Interstate Technology & Regulatory Council
444 North Capitol Street, NW, Suite 445, Washington, DC 20001
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Permission is granted to refer to or quote from this publication with the customary
acknowledgment of the source. The suggested citation for this document is as follows:
ITRC (Interstate Technology & Regulatory Council). 2005. Overview of In Situ Bioremediation
of Chlorinated Ethene DNAPL Source Zones. BIODNAPL-1. Washington, D.C.:
Interstate Technology & Regulatory Council, Bioremediation of Dense Nonaqueous
Phase Liquids (Bio DNAPL) Team, www.itrcweb.org.
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ACKNOWLEDGEMENTS
The members of the Interstate Technology & Regulatory Council (ITRC) Bioremediation of
Dense Nonaqueous Phase Liquid (Bio DNAPL) Team wish to acknowledge the individuals,
organizations, and agencies that contributed to this Technology Overview of In Situ
Bioremediation of Chlorinated Ethene DNAPL Source Zones.
As part of the broader ITRC effort, the Bio DNAPL Team effort is funded primarily by the U.S.
Department of Energy. Additional funding and support have been provided by the U.S.
Department of Defense (DoD) and the U.S. Environmental Protection Agency (EPA). ITRC
operates as a committee of the Environmental Research Institute of the States, a Section
501(c)(3) public charity that supports the Environmental Council of the States through its
educational and research activities aimed at improving the environment in the United States, and
providing a forum for state environmental policy makers.
The Bio DNAPL Team wishes to recognize the efforts of specific Bio DNAPL Team members,
as well as members of the former ITRC In Situ Bioremediation Team, who provided valuable
written input in the development of this document. The efforts of all those who took valuable
time to review and comment on this document are also greatly appreciated.
The Bio DNAPL Team recognizes the efforts of the following state environmental personnel
who have contributed to the writing of this document:
• Naji Akladiss, P.E., Maine Department of Environmental Protection (Bio DNAPL Team
Leader)
• Bart Paris, New Mexico Environment Department
• Paul Hadley, California Environmental Protection Agency
• Eric Hausamann, P.E., New York State Department of Environmental Conservation
• Dr. G.A. (Jim) Shirazi, P.G., Oklahoma Department of Agriculture, Food, and Forestry
• Larry Syverson, Virginia Department of Environmental Quality
We also wish to thank Carmen Lebron from the U.S. Naval Facilities Engineering Service Center
and Dr. Hans Stroo from both the Strategic Environmental Research and Development Program
(better known as SERDP) and HydroGeoLogic, Inc. for contributing to the writing of this
document.
Additionally, the Team recognizes the efforts of the following representatives from industry and
non-government organizations who also contributed to the writing of this document:
• James Brannon, P.E., C.S.P., Major, U.S. Army (retired), Northern New Mexico Citizen's
Advisory Board
• Dr. Eric Hood, P.E., GeoSyntec Consultants, Inc.
• Dr. David Major, GeoSyntec Consultants, Inc.
• Dr. Frederick Payne, ARCADIS
• Dr. Kent Sorenson, Jr., P.E., Camp Dresser & McKee
• Anna Willett, Regenesis Bioremediation Products
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• Ryan Wymore, P.E., Camp Dresser & McKee
Thanks to Dr. Eric Hood and Dr. David Major from GeoSyntec Consultants, Inc. and to Grant
Carey from Conestega Rovers & Assoc. for contributing document cover and text graphics.
The efforts of all those who took valuable time to review and comment upon this document are
also greatly appreciated, specifically:
• John Doyon, New Jersey Department of Environmental Protection
• Dr. Dibakar (Dib) Goswami, Washington Sate Department of Ecology
• Rob Hoey, P.G., Maine Department of Environmental Protection
• Judie Kean, Florida Department of Environmental Protection
• Dr. Andrew Marinucci, New Jersey Department of Environmental Protection
• Michael Smith, Vermont Department of Environmental Conservation
• Clay Trumpolt, Colorado Department of Public Health and Environment
• Kimberly Wilson, South Carolina Department of Health & Environmental Control
• Charles G. Coyle, U.S. Army Corps of Engineers
• Linda Fiedler, EPA
• Lisa Moretti, EPA
• Susan Mravik, EPA
• Dr. Ian T. Oserby, U.S. Army Corps of Engineers, New England District
• Travis Shaw, U.S. Army Corps of Engineers, Seattle District
• Dr. Jack Adams, Weber State University
• Dr. Robert Borden, North Carolina State University
• Dr. Konstantinos Kostarelos, Polytechnic University
• Dr. H. Eric Nuttall, University of New Mexico
• Grant Carey, Conestega Rovers & Associates
• Dr. David Ellis, Dupont
• Jeffrey Lund, Engineering Consulting Services, LTD
• Edward Seger, Dupont
• Jennifer Smith, Conestoga Rovers & Associates
Special thanks goes to the EnDyna, Inc. team, Dr. Smita Siddhanti (ITRC Program Advisor) and
Dr. Patricia Harrington, for their technical contribution and assistance to the team in developing
this document.
Lastly, without the leadership, drive, and coordination of Naji Akladiss, the Bio DNAPL Team
Leader, the concepts and ideas presented in this document would still be under discussion.
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EXECUTIVE SUMMARY
This document presents a technological overview of in situ bioremediation (ISB) and some of the
issues to consider when selecting and designing an ISB system for remediation of chlorinated
ethene dense nonaqueous phase liquids (DNAPLs) source zones. ISB is the use of
bioaugmentation and biostimulation to create anaerobic conditions in groundwater and promote
contaminant biodegradation for the purposes of minimizing contaminant migration and/or
accelerating contaminant mass removal. Bioaugmentation is the addition of beneficial
microorganisms into groundwater to increase the rate and extent of anaerobic reductive
dechlorination to ethene. Biostimulation is the addition of an organic substrate into groundwater
to stimulate anaerobic reductive dechlorination. ISB remediation may be implemented separately
or in conjunction with other treatments designed to remediate DNAPLs in groundwater. ISB
treatments generally involve modifications to the subsurface environment to accelerate
biodegradation. ISB is still an emerging, innovative technology, but it has demonstrated
promising results in both pilot-scale and full-scale applications.
DNAPLs are liquids denser than water that do not dissolve or mix easily in water (immiscible),
and form a separate phase from water. Although dechlorinating organisms can withstand high
dissolved concentrations of solvents, ISB does not work directly on free-phase DNAPL. Instead,
ISB technology relies on degradation and solubilization processes that occur near the water-
DNAPL interface. These processes result in enhanced removal through the following proven or
proposed mechanisms:
• increasing the concentration gradient by degradation of the dissolved compounds, thereby
increasing the dissolution rate
• effectively increasing the solubility of chlorinated solvents beyond the DNAPL interface by
transforming highly chlorinated species (e.g., perchloroethene and trichloroethene) to
daughter products that have significantly lower sorption coefficients (e.g., dichloroethene and
vinyl chloride)
• possibly increasing the solubility of the DNAPL constituents due to addition of the electron
donor solution directly and/or indirectly through the effects of its fermentation products
The basic requirements for successful ISB implementation for chlorinated ethene DNAPLs
include sufficient electron donor distribution, appropriate geochemical conditions, sufficient
nutrients, and a capable microbial community. Dechlorinating organisms are widespread in the
subsurface, but are often present in low numbers and may, in fact, be absent at some sites.
Bioaugmentation by adding bacterial populations to accelerate or achieve complete
dechlorination has been used in some ISB applications. While some ISB approaches emphasize
slow enhancement of dissolution via biodegradation mechanisms, others try to maximize the
physical dissolution by frequent injections of donor solutions selected for their cosolvent
properties. The most common ISB treatment approach is enhanced reductive dechlorination,
which consists of adding organic substrates (i.e., electron donors) to ensure highly reducing
conditions and to provide the hydrogen needed by dechlorinating organisms.
Based upon existing information, ISB offers both advantages and disadvantages. The major
advantages of ISB are as follows:
in
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• It may be possible to completely destroy the contaminant, leaving only harmless metabolic
byproducts.
• It is almost always faster than baseline pump-and-treat.
• It is usually less expensive than other remediation options.
• It can treat both dissolved and sorbed contaminants.
• It is not limited to a fixed area, typical of chemical flushing or heating technologies, because
it can move with the contaminant plume.
The disadvantages of ISB include the following:
• Complete contaminant destruction is not achieved in some cases, leaving the risk of a
residual toxic intermediate.
• Some contaminants are resistant to biodegradation.
• Some contaminants (or their co-contaminants) are toxic to the microorganisms.
• Biodegradation of organic species, can sometimes cause mobilization of naturally occurring
inorganic species such as manganese or arsenic.
• Alteration of groundwater redox conditions or substrate supply can reduce the downgradient
effectiveness of natural bioattenuation processes.
• Uncontrolled proliferation of the microorganism may clog the subsurface.
• The hydrogeology of the site may not be conducive to enhancing the microbial population.
While there is considerable interest in the potential for longer-term ISB treatment, most
experience with ISB has been over relatively short time periods. This limited experience has two
important implications. First, it is difficult to predict the long-term impacts of treatment,
particularly on plume longevity or life-cycle costs. Second, it is difficult to predict the impacts of
longer ISB treatment durations. Continuing ISB treatment for several years may well produce
greater decreases in mass and flux, even in difficult hydrogeologic environments or with high-
strength sources, while remaining cost-competitive. The assessment contained in this technology
overview document must be viewed as the current consensus regarding a rapidly developing
technology. Our understanding of the potential of ISB technology is likely to change as
practitioners gain further experience.
ISB is not a "one size fits all" technology, but can be a successful approach to reducing
environmental risks and costs of managing DNAPL sites when applied correctly. The ability of
ISB to meet remediation goals at a specific DNAPL site depends on the functional remediation
objectives, the hydrogeologic setting, and the source characteristics. When considering the use of
ISB, it should be recognized that effectiveness is site-specific and largely dependent on the site
geology and the distribution of DNAPL in the subsurface. Also, implementation of ISB requires
sufficient dechlorinating activity by either indigenous or bioaugmented microorganisms and may
require the addition of an electron donor as biostimulation. Finally, adverse impacts of ISB on
secondary water quality objectives must be carefully balanced against the benefits accruing from
the removal of the target contaminants.
Prior to initiation of any remediation system, it is critical that regulators and remedial program
managers clearly define their site remediation objectives. Remediation objectives may include:
IV
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contaminant mass removal, average concentration or flux reduction, plume longevity reduction,
plume size reduction, or reduction in the life-cycle costs for site management. ISB or any other
technology alone is unlikely to meet typical cleanup criteria, such as site-wide maximum
contaminant levels, at a source zone site, and it is unlikely to prevent continued source migration
at sites with substantial quantities of mobile DNAPL. However, ISB can yield significant (e.g.,
>90%) reductions in the downgradient plume concentration and in the total DNAPL mass at
relatively simple sites. ISB can also be used as a secondary treatment with other cleanup
technologies, such as following surfactant or cosolvent flushing to degrade residual
contamination left behind after the initial treatment, or in combination with in situ thermal
treatment.
Total elimination of a long-standing DNAPL source from an aquifer is difficult using any
available source removal technology. Therefore, identifying appropriate performance measures
is an important aspect for determining the progress and success of ISB activities. Two key
measures of ISB system performance are the contaminant molar balance and rate of increase in
the molarities of the contaminants and their metabolic byproducts.
As with any remediation project, addressing stakeholder concerns is critical to a successful
outcome, and stakeholder input should be sought as early as possible during the remediation
planning process. To help make informed decisions, the public should understand both the
advantages and disadvantages of implementing ISB at a particular site, as well as those for
implementing the various alternative treatment options. While deploying ISB for DNAPL
cleanup can be effective and relatively inexpensive, it is possible that the efficacy of ISB for
DNAPL source zones will remain a controversial and unsettled issue for the foreseeable future.
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TABLE OF CONTENTS
ACKNOWLEDGEMENTS i
EXECUTIVE SUMMARY iii
1. INTRODUCTION 1
1.1 An Introduction to ISB 2
1.2 Purpose of this Technology Overview 3
1.3 Document Organization 4
2. OVERVIEW OF CHLORINATED ETHENE DNAPLs AND ISB 4
2.1 Overview of Chlorinated Ethene DNAPLs 4
2.2 Background Biogeochemistry of ISB 13
2.3 Site Issues Affecting Applicability and Feasibility of ISB Application 16
3. TECHNICAL CONSIDERATIONS FOR ISB OF CHLORINATED ETHENE DNAPL
SOURCE ZONES 18
3.1 Identifying DNAPL Source Zones 19
3.2 Functional Site Remediation Objectives for ISB Application 20
3.3 Geochemical and Biological Mechanisms of ISB for Removal of Chlorinated Ethene
DNAPL Sources 21
3.4 Geochemical and Biological Environmental Requirements for ISB Application 23
3.5 Modeling of Bioremediation Removal Mechanisms for Chlorinated Ethene DNAPL
Sources 25
4. THE STATE OF ISB TECHNOLOGY APPLICATIONS 26
4.1 ISB Strategy Overview 27
4.2 ISB as the Primary Mode of Chlorinated Ethene DNAPL Source Treatment 28
4.3 Bioaugmentation 38
4.4 Using ISB in Combination with Other Treatment Technologies 39
4.5 Strengths and Limitations of ISB Application 44
5. DEFINING AND MEASURING SYSTEM PERFORMANCE OF ISB APPLICATIONS
FOR CHLORINATED ETHENE DNAPL SOURCES 45
5.1 Potential for ISB to Achieve Functional Site Remediation Objectives 46
5.2 Defining and Measuring Success of ISB Application for Chlorinated Ethene DNAPL
Source Treatment 49
5.3 Stakeholder Issues 50
6. CONCLUSIONS 51
7. REFERENCES 52
VII
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LIST OF TABLES
Table 2-1. Chemical and physical properties of chlorinated ethenes 5
Table 2-2. Industries associated with the presence of DNAPLs in the subsurface 6
Table 4-1. Effect of site specific characteristics on ISB applications 30
Table 4-2. Strengths and limitations of ISB 44
Table 5-1. The ability of ISB to meet remediation objectives 48
LIST OF FIGURES
Figure 2-1. Idealized schematic of the distribution of DNAPL constituent mass among the
various physical states in a typical plume (redrawn from Suthersan and Payne
2005) 8
Figure 2-2. Miscible organic contaminant mass distribution (redrawn from Suthersan and
Payne 2005) 10
Figure 2-3. SCM of chlorinated solvents in karst regions of Tennessee (from USGS 1997)...12
Figure 2-4. SCM of DNAPL in fractured bedrock system (from Kueper et al. 2003) 12
Figure 2-5. Estimated ORPs of commonly monitored chemical species 14
Figure 2-6. Reductive dechlorination pathway for chlorinated ethenes (Freedtnan and Gossett
1989) 15
Figure 2-7. Half-reaction potentials of environmentally relevant redox reactions 16
Figure 4-1. Examples of carbon loading strategies for enhanced reductive dechlorination of
PCE and TCE (to-scale) 29
Figure 4-2. Schematic for ISB applications for source containment 35
APPENDICES
APPENDIX A. List of Acronyms
APPENDIX B. Glossary of Terms
APPENDIX C. ITRC Contacts, Fact Sheet, and Product List
Vlll
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OVERVIEW OF IN SITU BIOREMEDIATION OF
CHLORINATED ETHENE DNAPL SOURCE ZONES
1. INTRODUCTION
In August 2002, the Interstate Technology and Regulatory Council (ITRC) In Situ
Bioremediation (ISB) Team published a technical and regulatory guidance document entitled A
Systematic Approach to In Situ Bioremediation in Groundwater: Decision Trees on In Situ
Bioremediation for Nitrates, Carbon Tetrachloride, and Perchlorate, ISB-08 (ITRC 2002a),
which provided guidance on the systematic characterization, evaluation, design, and testing of
ISB for any bio-treatable contaminant. In that document, the ISB team applied this systematic
approach only to nitrate, perchlorate, and carbon tetrachloride. At about the same time, the ITRC
Dense Nonaqueous Phase Liquid (DNAPL) Team acknowledged that several emerging in situ
technologies were being deployed to address DNAPL source zones, and it published the
document DNAPL Source Reduction: Facing the Challenge (ITRC 2002b). One of these
emerging treatment technologies was enhanced bioremediation. Enhanced bioremediation is the
introduction of an electron donor and possibly non-indigenous microbes to increase the rate and
extent of biodegradation of DNAPL constituents via the process of reductive dechlorination
(ITRC 2002a). After the development of the two documents described above, interested
members of the ISB Team and the DNAPL Team joined forces in 2004 to form the ITRC
Bioremediation of DNAPLs (Bio DNAPL) Team and to develop a technology overview
document for bioremediation of source zone chlorinated ethene DNAPLs.
The result of the efforts of the Bio DNAPL Team is this technology overview document,
Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones. This
technology overview provides the regulatory community, potentially responsible parties (PRPs),
remedial program managers (RPMs), and other interested stakeholders with a tool to evaluate the
appropriate use of ISB for chlorinated ethene DNAPL contamination. The document is written
for readers who have a technical background but not necessarily extensive remediation
experience. The scope of this document includes the following topics:
• chemical and physical mechanisms of ISB of DNAPLs
• hydrogeologic conditions associated with DNAPL contamination
• technical considerations for ISB of chlorinated ethene DNAPLs
• the current state of ISB technology application
• potential for ISB to achieve site remediation objectives
• means to measure the progress and effectiveness of ISB of DNAPL contamination
This document is a precursor for future work by the ITRC Bio DNAPL Team in addressing ISB
of DNAPL site contamination, and it is the first in a series of technical and regulatory guidance
documents that the team will develop. As of the date of this document (October 2005), the Bio
DNAPL Team is evaluating several case study projects to assess the application of ISB under
various conditions. Site conditions and data from several sites where bioremediation of DNAPL
has been implemented will be critically evaluated, and the performance of ISB in these case
studies will be assessed by experts in the field of bioremediation. The expert evaluators will
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
prepare written reports of their assessment of the case studies and critique the case studies in a
forum sponsored by the Bio DNAPL Team. The ITRC Bio DNAPL Team will publish a
summary of the expert evaluation reports and forum conclusions in a final case study document
that will be available on the ITRC website, on CD, and in hard copy. The work of the Bio
DNAPL Team will culminate in the publication of a technical and regulatory guidance
document, and classroom and internet training will be developed to supplement this document.
The Bio DNAPL Team goal is to provide extensive, useful information to the environmental
community to aid in deciding between bioremediation and other treatment technologies. To this
end, the Team encourages the participation of all interested parties in the development of
technology guidance.
1.1 An Introduction to ISB
ISB is the use of bioaugmentation and biostimulation to create anaerobic conditions in
groundwater and promote contaminant biodegradation for the purposes of minimizing
contaminant migration and/or accelerating contaminant mass removal. Bioaugmentation is the
addition of beneficial microorganisms into groundwater to increase the rate and extent of
anaerobic reductive dechlorination to ethene. Biostimulation is the addition of an organic
substrate into groundwater to stimulate anaerobic reductive dechlorination. Microorganisms,
such as bacteria, are discrete life forms that require a source of nutrients for their metabolism and
a sustaining environment in which to live and reproduce. Under ideal conditions, bacteria can
produce a new generation every 20 to 30 minutes. This exponential population growth potential
gives rise to the possibility of a population explosion if sufficient food and supportive conditions
prevail. Since the growth of these microbial populations can be regulated by controlling their
critical nutrients or environmental conditions, they are subject to human control. These
controlled, rapidly increasing bacterial populations can effectively break down contaminants and
thus offer potential as a remedial technology.
Bioremediation in its widest sense is not new; composting of food waste (a form of
bioremediation) dates back thousands of years. A more modem understanding of bioremediation
began over 100 years ago when the first biological sewage treatment plant opened in Sussex,
UK, in 1891. As it is commonly understood today, however, the word bioremediation is fairly
new, first appearing in peer-reviewed scientific literature in 1987. The first commercial
application of bioremediation occurred in Santa Barbara County, California, in 1969 and
involved the injection of nutrients and bacteria to treat 7,000 barrels of spilled crude oil and
sediment.
The specific metabolic pathways by which microorganisms transform contaminants are complex
and are the subject of much scientific research and field investigation. In general, microbial
metabolism requires a source of carbon, an electron donor, an electron acceptor, appropriate
nutrients, a suitable temperature and pH, and certain other environmental conditions. However,
the metabolic pathways can vary with the microbial type, the contaminant type, and other
environmental conditions; thus site specific application of ISB requires sufficiently detailed
information about the site microbiology, chemistry, and hydrogeology. For chlorinated
hydrocarbons, biodegradation is understood to occur through one or more of three different
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
pathways, which may occur simultaneously in the subsurface: (1) the use of the contaminant as
an electron acceptor, whereby the contaminant is reduced by the microbe but not used as a
carbon source; (2) the use of the contaminant as an electron donor, whereby the contaminant is
oxidized by the microbe, and the microbe obtains energy and organic carbon from the
contaminant; and (3) by the process of co-metabolism, whereby an enzyme or other factor used
by the microbe for some other purpose fortuitously destroys the contaminant while providing no
benefit to the microbe itself.
In addition to these biochemical pathways, application of ISB can be viewed based on the degree
of human involvement. Two general categories are recognized: (1) monitored natural attenuation
(MNA) and (2) accelerated or enhanced bioremediation. MNA includes a variety of physical,
chemical, or biological processes that, under favorable conditions, act without human
intervention to reduce the mass, toxicity, mobility, volume, or concentration of contaminants in
soil or groundwater. At an MNA site, indigenous microbes degrade the contaminants under the
existing geochemical conditions. The site is characterized, modeled, and monitored to make
predictions about the fate of the contaminant and to evaluate whether the final outcome will be
sufficient to meet regulatory and technical requirements.
In enhanced bioremediation, engineering designs are used to increase the desired activities of the
subsurface microorganisms, thus destroying or transforming the contaminants. Engineered
controls can include: the addition of electron donors, electron acceptors, or other nutrients;
modifications of the subsurface environment to favor the desired activities; or the introduction of
microbes possessing the requisite biodegradation activity and proven to be effective under
similar conditions. The selection of an engineering design depends on site-specific conditions
and on the specific metabolic pathways of the microbe mediating the biodegradation process.
Therefore, enhanced bioremediation requires both considerable study of the biogeochemical
aspects of the process as well as characterization of subsurface conditions and sophisticated
modeling and design of the engineered system.
1.2 Purpose of this Technology Overview
While the design of an ISB application may require significant scientific expertise, this should
not prevent the concerned non-specialist from making sound judgments regarding the potential
uses of ISB technology for contaminated sites. The purpose of this technology overview
document is to review the state of ISB application and to help regulators, PRPs, RPMs, and other
interested stakeholders understand the strengths and limitations of ISB for chlorinated ethene
DNAPL source zones. The document is intended to provide the regulator or project manager
with an adequate understanding of ISB to decide whether ISB might effectively meet cleanup
objectives at a particular site and to help in the process of reviewing, planning, evaluating, and
approving ISB methods and systems.
This document is based only on currently available information and provides the current state of
ISB as it relates to the treatment of DNAPL source zones. It is not intended to be a
comprehensive description of all ISB technologies. For more detailed information on ISB of
chlorinated solvents, the reader should refer to the ITRC Technical and Regulatory Guidance
document Technical and Regulatory Requirements for Enhanced In Situ Bioremediation of
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
Chlorinated Solvents in Groundwater (1998), the EPA document Engineered Approaches to In
Situ Bioremediation of Chlorinated Solvents: Fundamentals and Field Applications (USEPA
2000), or the recent Air Force Center for Environmental Excellence (AFCEE)/Environmental
Security Technology Certification Program (ESTCP) document Enhanced Anaerobic
Bioremediation: Principles and Practices (AFCEE 2004).
This technology overview document presumes that the site to be considered for chlorinated
ethene DNAPL source area remediation has been adequately characterized. For further
discussion on site characterization as it relates to ISB, please refer to Section 3.0 and Figure 1-1
of the ITRC 1SB-08 technical and regulatory guidance document DNAPL Source Reduction:
Facing the Challenge (ITRC 2002b).
1.3 Document Organization
This document is organized to help the reader identify key considerations that must be addressed
to determine the applicability of ISB for a particular site. Basic information about chlorinated
ethene DNAPLs and the mechanisms of ISB are discussed in some detail in Section 2. Section 3
discusses technical considerations for ISB application. Section 4 reviews the state of the practice
and presents summaries of actual ISB laboratory and field applications. Section 5 discusses
measures and procedures that can be used to evaluate ISB performance once implemented.
Section 6 offers conclusions about the state of ISB practice. Section 7 contains cited references.
Appendix A lists acronyms and abbreviations used in this document. Appendix B is a glossary of
terms for ISB. Appendix C provides contact information for ITRC Bio DNAPL Team members
and an ITRC fact sheet and product list.
2. OVERVIEW OF CHLORINATED ETHENE DNAPLS AND ISB
This section provides a basic overview for those readers who may not be familiar with the
chemical and geophysical characteristics of chlorinated ethene DNAPLs or the chemical and
biological mechanisms of ISB. The section is divided into three broad topical areas: an overview
of the chemical and physical properties of chlorinated ethene DNAPLs, DNAPL sources, and
site conceptual models (Section 2.1); an overview of the biogeochemical processes underlying
ISB technology applications (Section 2.2); and an examination of several site issues that may
affect the feasibility of ISB applications, including DNAPL architecture, biofouling, and
subsurface mixing (Section 2.3).
2.1 Overview of Chlorinated Ethene DNAPLs
The chemical and physical properties of chlorinated ethene DNAPLs are discussed in this
section, along with sources of these DNAPLs. The DNAPL hydrogeologic environment and
DNAPL site conceptual models are also presented.
2.1.1 Chemical and Physical Properties of Chlorinated Ethene DNAPLs
The chlorinated ethenes include tetrachloroethene (perchloroethene or PCE), trichloroethene
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones
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(TCE), cis-l,2-dichloroethene (cis-DCE), trans-1,2-dichloroethene (trans-DCE), 1,1-
dichloroethene (DCE), and vinyl chloride (VC). All of these compounds, with the exception of
VC, have a specific gravity significantly greater than water and therefore can create a distinct,
sinking layer of the compound, or DNAPL. Descriptions of the chemical and physical properties
of DNAPL chemicals are provided in ITRC's DNAPL-4 document An Introduction to
Characterizing Sites Contaminated with DNAPL (2003b). The physical and chemical properties
of the chlorinated ethenes relevant to the discussion in this document are summarized in Table 2-
1.
Table 2-1. Chemical and physical properties of chlorinated ethenes
Chemical
PCE
TCE
cis-DCE
Trans-DCE
DCE
VC
Molecular
Weight
165.834
131.3889
96.9439
96.9439
96.9439
62.4988
Molecular
Formula
C12C=CC12
C1CH=CC12
C1CH=CHC1
C1CH=CHC1
CH2=CC12
CH2=CHC1
Specific
Gravity
1.6230
1.4694
1.2837
1.2565
1.218
0.9106
Log
Kow
2.88
2.29
1.86
2.09
2.13
1.38
Koc
665
160
35
59
65
8.2
Color /
Form
Colorless
Liquid
Colorless
Liquid
Colorless
Liquid
Colorless
Liquid
Colorless
Liquid
Colorless
Gas
Boiling
Point
°C
121
86.7
60.3
47.5
31.9
13.37
Solubility
mg/L
150
1,550
3,500
6,300
2,250
1,100
In general, the chlorinated ethenes have low solubility in water, but still result in dissolved phase
concentrations well above groundwater standards. Due to the difficulty of directly determining
the presence of DNAPL in the subsurface, its presence is typically inferred from dissolved
concentrations of DNAPL constituents.
2.1.2 Sources of Chlorinated Ethene DNAPLs
Most releases of chlorinated ethenes occurred in the 1950's through the 1970's, before the
potential health effects of chlorinated ethenes were fully understood and major environmental
laws and regulations were passed. Due to their lower solubility limits, chlorinated ethenes can
persist in the subsurface for long periods of time, causing plumes of dissolved material to remain
at concentrations that are many orders of magnitude above the level of concern. Additionally,
there are inherent technical difficulties in discovering and measuring DNAPLs in groundwater,
so the numbers of DNAPL source areas are probably underestimated.
The operational history of a site may reveal important information about the duration and
intensity of operations that led to the subsurface contamination. Historical knowledge of the site
may provide anecdotal evidence that leads investigators to DNAPL source areas. Information on
historical production, raw materials, chemical products, and use, handling, and disposal practices
may also help determine the pervasiveness and scope of the problem (ITRC 2002, ISB-8). Rather
than being released as pure or neat chemicals, DNAPLs have often been discharged as spent
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones
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solvents or wastes that contain appreciable fractions of other chemicals which may, in turn,
impact ISB (ITRC 2002, DNAPLs-2). If the site has used or stored DNAPLs, a high potential
exists that a DNAPL release has occurred.
Numerous industries and facilities have used chlorinated ethenes during manufacturing. Two
major uses of chlorinated ethene solvents since the 1930s have been for degreasing machinery
and for dry cleaning. There are approximately 36,000 active dry cleaning facilities in the United
States, and soil and groundwater are contaminated by dry cleaning solvents at about 75% of
these facilities (Linn et al. 2004). In addition to the active dry cleaning facilities, an unknown
number of former dry cleaning sites are also contaminated (Linn et al. 2004). In 1930, TCE was
introduced as a dry cleaning solvent in the United States (Martin 1958), but since TCE causes
bleeding of some acetate dyes it is no longer used as a primary dry cleaning solvent. In 1934,
PCE was introduced as a dry cleaning solvent in the United States. The superior cleaning ability
of PCE, coupled with petroleum shortages during World War II and municipal fire codes
prohibiting the use of petroleum solvents resulted in increased use of non-flammable PCE. In
1948, PCE surpassed carbon tetrachloride use in dry cleaning operations, and by the early 1960s,
PCE had become the predominant dry cleaning solvent in the United States. It is estimated that
over 80% of the commercial dry cleaners in the United States today use PCE (Linn et al. 2004).
Table 2-2 lists some industries and industrial processes that are often, but not always, associated
with the presence of DNAPLs in the subsurface (Kueper et al. 2003).
Table 2-2. Industries associated with the presence of DNAPLs in the subsurface
Industries
timber treatment
coal gasification
electronics manufacturing
solvent or paint production
pesticide/herbicide manufacturing
airplane maintenance and engine manufacturing
military bases and rocket fuel production
dry cleaning
instrument manufacturing
transformer oil production
vehicle manufacturing
transformer reprocessing
steel industry cooking
pipeline compressor stations
Industrial Processes
metal cleaning and degreasing
metal machining and plating
tool and die operations
paint removing
solvent storage above and below ground
solvent transmission through pipeline
solvent loading and unloading
mixed waste disposal in landfills
storage of liquid waste in lagoons
2.1.3 DNAPLs and the HydrogeoloRJc Environment
As discussed in Section 2.1.1, the contaminants that can generate DNAPLs in aquifers' are
hydrophobic organic chemicals. These are compounds with low water solubility and with
An aquifer is a geologic unit composed of porous granular or fractured massive solids with the interstitial spaces filled with water In most
aquifers, the water is a transient component migrating through the aquifer matrix along a hydraulic head or pressure gradient The cross-sectional
dimensions of the interstitial spaces, their volume relative to the total aquifer volume, and their interconncctedness are key characteristics that
determine the behavior of water moving through the matrix.
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
principal fluid characteristics (density, viscosity, and surface tension) so distinct from those of
water that their respective fluid masses are immiscible. Many of the hydrophobic organics, such
as the chlorinated alkene and alkane solvents, are denser than water. In situations where DNAPL
is present in the saturated subsurface, the aquifer contains two fluids that act mostly
independently of each other: the wetting fluid (normally water) and the non-wetting fluid
(normally the organic phase).
An understanding of partitioning processes is essential in predicting the behavior of
contaminants released as a DNAPL. In addition to the contaminant mass in the pure phase,
contaminant may partition through
• dissolution from the DNAPL into groundwater (either static or flowing);
• sorption to the organic and mineral constituents of the geologic materials;
• formation of a continuous fluid mass of pure phase, drainable DNAPL;
• entrapment of residual pure phase DNAPL within pores as discontinuous globules or ganglia.
These partitioning processes are described below.
2.1.3.1 Dissolution
Chlorinated ethenes have a low solubility in water. However, for modeling purposes, the water
cannot be treated as a homogeneous medium because contaminant distribution and migration
patterns are significantly affected by the heterogeneities of actual formations. Aquifer water
mobility is a key variable in developing an improved understanding of contaminant distribution.
Though in reality groundwater displays a continuous distribution of velocities, the overall
movement may be modeled effectively, if simplistically, as consisting of two components:
migratory and static water.
For migratory water, groundwater movement is dominated by advective processes (i.e.,
processes related directly to the velocity of the fluid as opposed to non-advective processes, such
as diffusion). The migratory water is the contaminant mass transfer carrier, distributing
contamination along the aquifer flow path. Groundwater pumping increases the velocity of the
migratory water, decreasing its contact time in the contaminant source areas.
In static water, some fraction of the aquifer water is present in lower permeability materials
which may be a significant fraction of the aquifer material in some geologic settings. At the
extreme, this water mass is essentially static and may contain a significant contaminant mass.
This static water can act as a long-term source of contamination to the migratory water, similar
to the sorbed phases discussed below.
2.1.3.2 Sorption and Adsorption
Hydrophobic organic compounds often partition strongly into the soil organic matter typically
present in an aquifer matrix through a variety of partition reactions. Recent studies have
introduced the concept of "dual equilibrium" partitioning to explain the behavior of contaminants
in aquifer matrices. This concept allows the range of partition reactions to be organized into two
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones
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modes: sorption and adsorption.
The conventional approach to estimation of sorption uses the concept of organic carbon partition
coefficient (KoC) for each contaminant. Published values of KOC (see Table 2-1) are used in
calculation of a distribution coefficient that expresses the equilibrium partitioning of the
contaminant between the aqueous and sorbed phases. As the aqueous-phase concentration (CAQ)
increases, the sorbed-phase mass increases steadily until the aqueous-phase concentration
reaches its maximum value, CSAT- CSAT is thus the contaminant concentration at which the
groundwater and surface sorption sites are saturated with contaminant. Above this concentration,
contaminant may be present as a pure phase (drainable or residual) within the aquifer matrix.
CSAT concentrations are an indication, but not a confirmation of saturation.
In adsorption the contaminant is physically bound to a substrate. An aquifer contains mineral
surfaces and, in some cases, organic matter that serve as sites of adsorption (i.e., an exothermic
binding of a contaminant molecule to a binding site). The binding of hydrophobic organic
molecules to granular activated carbon is an example of the adsorption process. Adsorbed
contaminants are bound tightly to the sorbing matrix, and desorption is extremely slow in
comparison. Consequently, adsorption is often referred to as "irreversible" sorption, though
technically this is not correct. Figure 2-1 is an idealized schematic showing the different DNAPL
constituent states that are likely to occur in a plume. Site specific characteristics, such as
porosity, flow, clay content, and lithology, can significantly affect the contaminant distribution
among the various states.
Hydrophobic Organic Contaminant Mass Distribution
NAPL mass
drainable
residual
Total
non-aqueous-phase
mass
Migrating aqueous-phase mass
Static aqueous-phase mass
source zone
downgradient zone
groundwater flow
Total Aqueous-Phase Mass - g/m3
Total Aquifer Mass - g/m3
Figure 2-1. Idealized schematic of the distribution of DNAPL constituent mass among the
various physical states in a typical plume (redrawn from Suthersan and Payne 2005)
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
2.1.3.3 Drainable and Residual DNAPL Fractions
There are two fractions of DNAPL that may exist in an aquifer matrix: drainable and residual. If
a drainable DNAPL fraction is large, it may occupy sufficient pore space to form a continuous
fluid mass under positive nonaqueous phase fluid pressure. A residual DNAPL fraction consists
of smaller masses of DNAPL that become disconnected from the main fluid body and held in
capillary tension. This material becomes trapped in place because it can not generate the entry
pressures needed to drive its movement through the water-wetted porous or fractured medium,
except under circumstances where the surface tension is affected, such as a change in
temperature, the addition of cosolvents or surfactants, or the existence of an acceleration force
(e.g., seismic shocks).
A DNAPL travels through the vadose zone leaving behind residual accumulations until it reaches
the water table. In the saturated zone, it displaces water and moves deeper into the aquifer
leaving behind dissolved and trapped residuals in the soil pores in its wake. Strong capillary
forces result in capture of residual DNAPL accumulations in the soil pores. The DNAPLs have
very low solubility and the dissolved phase has strong affinity for organics that bind them tightly
to the soil. The small amounts of DNAPLs that partition into the groundwater are quickly
adsorbed to soil particles. Hence, the dissolved phase plume moves very slowly, constantly
releasing small amounts of contaminant into the groundwater (see Figure 2-2). Figure 2-2
highlights migratory water movement within the saturated media (not vadose zone conditions).
Upon reaching an impermeable barrier or hydraulic contrast, the DNAPL pools in depressions on
top of this barrier. Once these depressions are filled, the DNAPL may spread laterally, spill over
the edge, and travel downgradient and through cracks in the barrier, sometimes in a direction
different from the groundwater flow. The pool may also develop sufficient head to exceed the
entry pressure and force a finger through the barrier layer, after which much of the rest of the
pool may then drain more readily. Because the slope and cracks in the subsurface are not
generally known, these transport phenomena make detecting DNAPL difficult.
Residual DNAPL may be a significant portion of the contaminant mass in the source area. It may
reside in contact with migratory groundwater, where it dissolves directly into the moving water.
The surface area to volume ratio for residual DNAPL is much higher than for pools, so the mass
flux into the aqueous phase is usually higher, and over time, the residual DNAPL will generally
dissolve long before any drainable pools dissolve. Residual DNAPL may also reside in the static
groundwater, where it is linked to the migratory groundwater through diffusion.
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones
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Soil Particle
Soil Organic Matter
Resident Water
Residual NAPL
Figure 2-2. Miscible organic contaminant mass distribution (redrawn from Suthersan and
Payne 2005)
To be successful, a remedy applied to any aquifer zone may be required to remove or destroy a
significant portion of the nonaqueous-phase, sorbed phase, and static water mass of contaminant.
To achieve this, the remedial mechanism must reach beyond the migratory fraction of the
groundwater mass, which is the fraction that is available to most injected fluids. Technologies
that are limited because of the difficulty of accessing the non-migratory mass pools include
groundwater pumping and in situ oxidation. ISB also shares this fundamental limitation to a
certain extent, although microorganisms can grow in situ, colonizing less accessible areas, and
their activities in more accessible zones may enhance dissolution of the DNAPL constituents in
those areas that are less accessible.
For further discussion on DNAPL fate and transport, please refer to An Illustrated Handbook of
DNAPL on Transport and Fate in the Subsurface, published by the United Kingdom's
Environment Agency (Kueper et al. 2003).
2.1.4 Site Conceptual Model of DNAPL Contamination
An accurate site conceptual model (SCM) is a critical tool for considering and implementing ISB
at a contaminated site. An SCM includes a description of the site hydrogeologic setting, release
mechanism(s), flow directions, and locations of receptors. For a site where sufficient published
information is available, an SCM can be developed. Professional judgments are made based
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
upon what is known, what is unknown, and what is reasonably accurate to formulate an SCM.
SCM development is a dynamic process and is refined as more subsurface information becomes
available during site investigation. Site investigation is then planned to bridge data gaps and
further refine the uncertainties in the SCM.
Characterization of groundwater contamination in an aquifer, especially in a fractured or karst
aquifer, is a challenge for the remediation industry, and the characteristics of DNAPLs in the
hydrological setting pose real problems in formulating an SCM. The retention capacity of
geologic media for DNAPLs in the vadose zone is low, so even a small release over a period of
time can reach groundwater. Lateral movement from the input location can be large. Low
permeability layers do not preclude migration due to the presence of fissures and fractures
through which DNAPLs can move. SCMs involving DNAPLs are complex also due to the
nonaqueous nature and higher specific gravity of the contaminants, which make it difficult to
describe migration pathways. Pore geometry in fractured and sandy aquifers causes hysteresis
effects. The entry pressure in a pore depends upon the interfacial tension between DNAPL and
water and is inversely proportional to the pore size and shape. Drilling into or through a DNAPL
zone can cause remobilization of DNAPL, making contaminant distribution even more complex.
Two examples of SCMs for DNAPL contamination are shown in Figures 2-3 and 2-4. Figure 2-3
depicts an SCM of DNAPL release in karst regions in Tennessee. Figure 2-4 shows a generalized
SCM of DNAPL which has migrated through unconsolidated material, then pooled on and
migrated into fractured bedrock.
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones
October 2005
ff\ Regolith
Water table
> liil
EXPLANATION
1 TRAPPING IN REGOLITH 3 POOLING IN BEDROCK
1A - RESIDUAL DNAPL DIFFUSE-FLOW ZONE
IB-POOLING ON LOW
PERMEABILTY LAYER 4 POOLING IN CONDUIT
2 POOLING ATTOP OF ROCK 5 POOLING IN FRACTURES
ISOLATED FROM FLOW
rra CAVERNOUS CARBONATE fj REGOLITH
EflJ ROCK
WT( LOW-PERMEABILITY
O FRACTURED CARBONATE "^ REGOLITH LAYER
^ ROCK iwt
Kg POOLED DNAPL
..^ DISSOLVED CONTAMINANT
RESIDUAL DNAPL
Figure 2-3. SCM of chlorinated solvents in karst regions of Tennessee (from USGS 1997)
source
low
permeability
clay lens
DNAPL plume
ground
flow dlf
penetration ^
of fractures
vapours
dissolved plume • abstraction well
<-water table
soil
unconsolidated
sand aquifer
(cross-bedded)
fractured
bedrock
DNAPL pool DNAPL residual
Figure 2-4. SCM of DNAPL in fractured bedrock system (from Kueper et al. 2003)
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DN APL Source Zones October 2005
2.2 Background Biogeochemistry of ISB
Since current information concerning ISB and DNAPLs shows that reductive dechlorination is
the common biological process for degradation of chlorinated ethenes, an understanding of the
reduction-oxidation (redox) conditions in groundwater is critical to the design of an ISB system.
This section describes redox reactions, biotic chemical contaminant transformations, the
reductive dechlorination pathway of PCE to ethene, the impact of site reducing conditions on
electron acceptor use by microbes, secondary reactions associated with reductive dechlorination,
and environmental pH considerations common to ISB applications. The rate of biotransformation
is also a function of temperature, but temperature effects are not discussed in this document.
2.2.1 Redox Reactions
In general, redox reactions involve the transfer of electrons between two chemical species. In the
case of ISB the oxidized compound provides electrons (i.e., the electron donor). The oxidation of
a simple carbohydrate (CF^O) electron donor is represented by
2CH2O + 2H2O -» 2CO2 + 8H+ + 8e-
The electrons are transferred to the species undergoing reduction (i.e., the electron acceptor).
Multiple electron acceptors are present in most groundwater environments including oxygen,
ferric iron, and sulfate. However, the electron acceptors of particular interest are the
contaminants undergoing reductive dechlorination. For example, the reduction of PCE to ethene
is given by
C2C14 + 8H+ + 8e~ -» C2H4 + 4H+ + 4C1"
The net stoichiometry of these redox reactions indicates that two moles of the simple
carbohydrate electron donor are required to dechlorinate one mole of PCE to ethene. The
stoichiometry of these redox processes may be used to calculate the quantity of electron donor
required to meet the total electron donor demand exerted by all electron acceptors (AFCEE,
2004).
2.2.2 Biotic Chemical Contaminant Transformations
Some chemical species, including many organic species, can act as either an oxidizing agent or a
reducing agent depending upon external electrochemical conditions. Scientists use the concept of
an oxidation-reduction potential (ORP) to measure these oxidizing or reducing conditions. ORP
is typically measured in millivolts (mV) and can be used to infer the type of biotic chemical
contaminant transformation reactions that are possible. In most aquifers, bacteria are present that
can mediate many contaminant transformations requiring electron transfers. The most oxidizing
electron acceptor in groundwater is dissolved oxygen.
Contaminants that are degraded by anaerobic bacteria require the absence of dissolved oxygen.
In some cases, contaminants can act as electron acceptors and therefore can be degraded only
after dissolved oxygen has been depleted. Figure 2-5 shows an ORP scale with calculated ORP
values in mV for commonly monitored redox couples. The ORP values were calculated for
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones
October 2005
thermodynamic equilibrium at pH 7 (i.e., equal concentrations of oxidizing and reducing species
in each redox couple shown). Site-to-site variation in pH and differing reactants/products affect
the calculated ORP couples. In some cases, reaction ranges may overlap with more oxidizing or
more reducing reactions.
O2/H2O
Denitrification: NO3/N2
Manganese Reduction: MnO2/Mn*2
V
1000
Iron Reduction: Fe(OH)3/Fe+2
Alcohol Fermentation: CH2O/CH3OH
Sulfate Reduction: SO4"/H,S
Methanogenesis: CO,/CH4
Acetogenesis: CO2/CH3COOH (Acetic Acid)
H+/H,
Aerobic
(Oxygen as
Electron Acceptor)
V
Typical Primary
Substrates
(Electron Donors)
Figure 2-5. Estimated ORP of commonly monitored chemical species
Further discussion on ORP and idealized terminal electron acceptor processes is provided in A
Systematic Approach to In Situ Bioremediation in Groundwater: Decision Trees on In Situ
Bioremediation for Nitrates, Carbon Tetrachloride, and Perchlorate (ITRC 2002, ISB-8).
Furthermore, Table 3-1 of this document provides a list of suggested analytes (i.e., chemical
compounds that are the subject of chemical analysis and can be indicators of what reactions are
occurring) and the rationale for their use in bioremediation. These analytes also apply to ISB and
DNAPL source zones, and should be evaluated as secondary parameters to determine ISB
activity.
2.2.3 Reductive Dechlorination of Chlorinated Ethenes
During anaerobic reductive dechlorination, the chlorinated ethenes act as electron acceptors. The
anaerobic reductive pathway removes one chloride ion at a time and replaces it with a hydrogen
ion. The final step is the reduction of ethene to ethane. PCE is oxidized, and the byproducts are
successively more reduced, so that the ORP required for each successive dechlorination step
becomes increasingly negative. Reductive dechlorination typically requires ORP values in the
range needed for sulfate reduction or methanogenesis (i.e., below -200 mV).
The stoichiometry of chlorinated ethene DNAPL reductive dechlorination is well-known, and is
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
shown in Figure 2-6 (from AFCEE, 2004).
CCI2 = CCI 2 s *N»CHCI =CCI 2 s %» CHCI =CHCI
N = 2 s %
PCE ' * TCE ' * cDCE
H2 HCI H2 HCI
2 = CHCI x* V» CH2 = CH2
' * VC Ethene
H2 HCI H2 HCI
Figure 2-6. Reductive dechlorination pathway for chlorinated ethenes (Freedman and
Gossett 1989)
In each case, one mole of parent compound produces one mole of daughter product. The
reactions, as they are written above, infer the availability of a carbon source that donates
electrons (assumed to be in the form of molecular hydrogen). However many other reactions
consume electrons so, at a minimum, electron donor dosing must be based on reducing all the
electron acceptors, including common inorganic acceptors such as oxygen, nitrate, and sulfate, in
addition to the chloroethenes. Dosing strategies range from providing a minimal donor
concentration exceeding the stoichiometric demand by a small safety factor (e.g., two to four) to
account for donor incorporation into new biomass and loss through secondary reactions (e.g.,
methanogenesis), to the injection of donor doses that may exceed the minimum stoichiometric
donor requirements by an order of magnitude or more.
2.2.4 Effect of Half-Reaction Potentials on Contaminant Transformation
In Figure 2-7, the energy released from the reduction of electron acceptors increases to the right.
Microorganisms preferentially use electron acceptors that provide the most energy. As site
conditions become more reducing (i.e., lower redox potential), the more energetically favorable
acceptors are depleted. As can be seen, reductive dechlorination of the chloroethenes is
associated with half-reaction potentials greater than 360 mV; however, under typical field
conditions reductive dechlorination typically occurs at half-reaction potentials more commonly
associated with sulfate reduction and methanogenesis (i.e., between -100 to -300 mV; AFCEE,
2004).
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones
October 2005
-0.5 0 E01 (V)
i
-5 0 pE' +
I>~ Vitamin B-12 (reduced to oxidized)
C>- Acetate to CO2
r^^^»^ H to H*
P>- NADH to IV
Fe++ to Fe(OH)3[>-
Oxidations C>-
(electron donors)
-*
-«
-O H+to
H,
I
IAD+
PC
C
+0.5 +1 .0
I I
5 +10 +15
HCAtoPCE-=d
EDB to E-^^ 1 favora
Dichloro-
elimination
favorable
leno lysis
lie
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
During the site characterization phase, a sufficiently detailed understanding of critical factors,
such as the microbiology, chemistry, and hydrogeology of the site, must be obtained to properly
apply ISB as a remediation strategy. Following adequate site characterization and development
of an SCM, the next step is to identify the biogeochemistry (redox conditions) present in the
subsurface and establish whether the primary ISB pathway for chlorinated ethenes (reductive
dechlorination) can proceed. Since reductive dechlorination is the primary pathway, reducing
conditions are required. This typically occurs when an electron donor (carbon source) is present
to reduce the ORP to the desired level. Many options for electron donor exist, and selection
should be based on site-specific considerations. ISB-8 Sections 4.4.4 and 9.4.3.2 provide further
discussion of laboratory treatability tests and their importance (ITRC 2000b).
Other site issues to consider when determining the feasibility of ISB application include the
DNAPL architecture at the site (i.e., whether the DNAPL is present in pools or as residual), the
potential for biofouling, and the adequacy of mixing of any added amendment. These
considerations are described in detail below.
2.3.1 DNAPL A rchitecture
DNAPL architecture is critical to ISB efficacy. Bioremediation does not make sense for sites
where the DNAPL is largely located in pools. It makes much more sense for sites dominated by
ganglia (residual phase) DNAPL because the surface to volume ratio is much larger, leading to
much greater potential for dissolution and biodegradation at and near the nonaqueous phase
liquid (NAPL)-water interfaces. Modeling evidence by Christ et al. (2003) shows that the
ganglia-to-pool ratio is important to the potential efficacy of bioremediation alone or
bioremediaiton following surfactant-enhanced extraction. This point is discussed further in
Section 3.5, but the important conclusion is that bioremediation will be far more effective at sites
where most of the DNAPL occurs as ganglia.
2.3.2 Biofouling
As described in ISB-8 (ITRC 2002), biofouling
is attributed to the increase in microbial populations and perhaps more importantly, to the
creation by cells of extra cellular polysaccharides. These slimy polysaccharides are
important for the accumulation of microorganisms on surfaces or within porous media
and can contribute significantly to biofouling of a formation or injection well. A portion
of amendment goes to the creation of new bacteria (biomass). Eventually, continued
unchecked bacterial growth is likely to reduce circulation and injection of the
amendment, and may lead to a plugged formation or injection well (i.e.,
biofouling)...Various operating strategies have been devised to minimize this potentially
undesirable outcome. These methods are not formalized, but rather various engineering
approaches have been used over the years. No one approach is a clear winner. However,
it is an issue that must be considered in system design and operation.
ISB-8 Section 4.4.7 includes a more complete discussion of options to reduce biofouling.
Biofouling increases substantially under aerobic conditions, and therefore it is important to
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
maintain anaerobic conditions to minimize biofouling problems. Certain techniques (i.e., use of
hydrogen peroxide) to decrease biofouling may increase aerobic conditions and should be
managed appropriately to ensure anaerobic conditions are maintained.
2.3.3 Mixing
As noted in ISB-8 (ITRC 2002), ISB systems require the presence of contaminant-degrading
bacteria, plus appropriate concentrations of electron acceptors, electron donors, and microbial
nutrients. If a required component is absent, the biodegradation process slows and even stops.
Consequently, the focus of a successful remediation system is to design an effective delivery
process that will produce adequate amendment mixing in the subsurface treatment area (see ISB-
8 Section 4.4.8 for further discussion).
Widespread presence of DNAPLs in low permeability media poses significant challenges for
assessment of their behavior and implementation of effective remediation technologies (Siegrist
and Slack 2000). Most remedial methods that involve fluid flow perform poorly in low
permeability media. In fractures or tight formations, amendment mixing can be a problem. The
two major issues regarding geologic fractures and tight formations are the difficulty of locating
and delineating these features and the problem of providing adequate distribution of a particular
ISB amendment into the targeted geological environment. Formations containing clay, silt, and
rock impede mass transfer rates and thus limit the desired effect of the ISB amendment. While
geologic fractures represent "open" channels for the movement of fluids, these fractures can also
cause inadequate distribution of ISB amendment within the entire subsurface environment.
Hydraulic and pneumatic fracturing are two technologies that can enhance the remediation of
subsurface contaminants. Fracturing is the injection of either air or another gas into a tight
geologic formation at sufficient pressure to create artificial small fractures. These fractures
increase permeability and provide an enhanced, homogeneous environment for remediation
treatment. Hydraulic fracturing can improve the performance of other remediation methods, such
as oxidation, reductive dechlorination, and bioaugmentation, by enhancing delivery of reactive
agents to the subsurface.
3. TECHNICAL CONSIDERATIONS FOR ISB OF CHLORINATED ETHENE
DNAPL SOURCE ZONES
As noted in Section 1.1, the potential for biodegradation of chlorinated organic solvents has been
recognized since the early 1980's. Both co-metabolic and anaerobic biodegradation pathways
have been known for almost two decades (Vogel et al. 1987). Anaerobic biodegradation in
particular has been used commercially for natural and enhanced remediation of dissolved phase
plumes (AFCEE 2004, USEPA 1998). The documents referenced in this overview provide
excellent background on the use of ISB for dissolved plumes and include in-depth discussions of
the microbiology, biochemistry, and engineering considerations involved in ISB for chlorinated
ethenes; however, these documents do not address source zone treatment. The discussion in this
section provides background information on ISB and, in particular, focuses on source zone issues
related to ISB of chlorinated ethene DNAPLs.
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Discussed in the following sections are issues related to: definition and location of DNAPL
source areas (Section 3.1); functional site remediation objectives that may be applied to 1SB
application for chlorinated ethene DNAPL source zones (Section 3.2); geochemical and
biological mechanisms used by ISB for removal of chlorinated ethene DNAPL contamination
(Section 3.3); geochemical and biological environmental requirements for successful application
of ISB (Section 3.4); and design implications based on modeling ISB of source zones (Section
3.5).
The key points made in this section are as follows:
• Since delineation of DNAPL source zones is difficult, remediation technologies that can
cost-effectively treat a zone of the aquifer without exact delineation (such as ISB) are
preferred for these sites.
• Several mechanisms, including biological and abiotic, contribute to enhanced mass removal
during ISB of DNAPL source areas.
• ISB promises to cost-effectively shorten remediation time frames for DNAPL source areas
comprised primarily of residual or sorbed mass, but probably will not affect the time frame
for sites with significant drainable DNAPL mass.
3.1 Identifying DNAPL Source Zones
Treating a DNAPL source zone effectively requires that the source zone be indentified. The
National Research Council panel on Source Zone Remediation defined a source zone as a
subsurface zone "that acts as a reservoir that sustains a contaminant plume in groundwater,
surface water, or air, or acts as a source for direct exposure. This volume is or has been in contact
with separate phase contaminant (NAPL or solid)" (NRC, 2005). The typical rule of thumb for
identifying a DNAPL source area is the observation of DNAPL-forming compounds at more
than 1% of their aqueous-phase solubility. However, such rules of thumb should not be rigidly
applied for reasons discussed elsewhere (ITRC 2003a). Finding the location of a DNAPL source
area is challenging because of the non-uniform and unpredictable behavior of DNAPL in the
subsurface. The pattern of DNAPL movement is highly site dependent and is influenced by soil
lithology, pore size distribution, and structure. Due to these difficulties in exactly locating
DNAPL contamination, the presence of DNAPL and especially residual DNAPL is usually
inferred by high dissolved-phase concentrations. If DNAPL is present, its location is typically
known at best only within a few meters to tens of meters. Thus, treatment methods that can
remediate DNAPL on a broad scale without requiring the exact location of the DNAPL are
desirable.
Not all significant subsurface sources of chlorinated ethene contamination will appear the same.
The formation of a separate-phase liquid in a monitoring well, for instance, is evidence of the
presence of drainable NAPL which may be most effectively treated through direct extraction.
Similarly, substantial nonaqueous-phase mass may be present in a sorbed phase without
generating an aqueous-phase concentration indicative of DNAPL. Large sorbed-phase sources
may also serve as long-term sources of aquifer contamination, and the challenges in locating and
treating these materials in aquifers are similar to those associated with DNAPLs.
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
3.2 Functional Site Remediation Objectives for ISB Application
ISB of DNAPLs was not considered feasible until the 1990s, primarily because the chlorinated
ethene concentrations within source areas were considered potentially toxic (Pankow and Cherry
1996). Since that time, however, the use of ISB has increased based on three separate lines of
evidence that point to the viability of ISB for source areas. First, multiple, comprehensive studies
clearly identified the limitations of active pump-and-treat remediation programs. Second, as
highly aggressive treatment technologies, such as in situ thermal treatment or in situ chemical
oxidation, were applied to source zones, it was noted that large contaminant mass removals
attributed to these aggressive technologies would not necessarily result in large decreases in
subsurface contaminant concentrations and compliance with regulatory criteria. Third, emerging
laboratory and field evidence demonstrated that dechlorinating organisms can tolerate very high
chlorinated ethene concentrations and can potentially enhance the rate of DNAPL dissolution.
(USEPA 1989, Doty and Travis 1991, USEPA 1992, Bartow and Davenport 1992, NRC 1994,
USEPA 1996, USEPA 1999).
While all three of these lines of evidence were important, the experience with pump-and-treat
programs was pivotal in that it drew a sharp distinction between source removal and plume
containment. This distinction forced industry and the regulatory community to reexamine the
definition of remediation success. As studies indicated that rates of pump-and-treat contaminant
mass removal gradually declined over time, they also demonstrated that plume concentrations
would rebound following shut-down of the pump-and-treat systems. Therefore, it became
evident that these systems might require indefinite operation and that their primary value was in
containing the spread of contamination within their capture zone.
The principal lesson for remediation stakeholders from this experience was the critical need to
unambiguously define the objectives of site remediation (USEPA 1996, NRC 2004). While it is
clear that the absolute objective of remediation should be the protection of human health and the
environment, there is substantial uncertainty in the means to achieve this result. Accordingly,
given the difficulty of developing quantitative, well-defined metrics for this objective (ITRC
2004, NRC 2004), a range of functional site remediation objectives are commonly used. Some
possible objectives for remediation of a DNAPL-contaminated site, listed here and discussed in
more detail in Section 5.1, are as follows:
• removal of contaminant mass
• reduction of contaminant mass flux/concentration
• reduction of contaminant plume life
• reduction of project life-cycle cost
The critical issue in selecting ISB is determining whether it can be effective at meeting or
helping to meet the defined site remediation objectives within the time frame desired. While the
overall effectiveness of ISB for chlorinated ethene DNAPL source zone applications is still
relatively poorly understood, emerging evidence from a limited number of laboratory and field
studies indicate that ISB has the potential to address many DNAPL sites. For instance, a recent
Navy survey indicates an increase in the use of ISB for DNAPLs at sites where some sort of
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source zone treatment has been attempted. The survey found that ISB had been used at 20% of
the sites, only slightly less than the number of sites at which in situ thermal treatment and
chemical oxidation were applied (GeoSyntec 2004). ISB may also be less costly than other
treatment alternatives. A recent survey of field-scale source zone treatment projects conducted
by Groundwater Services, Inc., found that the reported average costs for the three dominant
technologies were $6I/yd3 for thermal treatment, $26/yd3 for in situ chemical oxidation, and
$16/yd3 for ISB (McDade et al. 2005). Please note that these costs are taken from a single
published survey and are provided for information only, not as an endorsement of their validity.
3.3 Geochemical and Biological Mechanisms of ISB for Removal of Chlorinated Ethene
DNAPL Sources
As discussed in Section 1, enhanced ISB in the context of this document is the introduction of an
electron donor and possibly nonindigenous microbes to enhance the removal of DNAPLs and the
sorbed phase mass through reductive dechlorination. Enhanced removal may be accomplished by
inducing a steep concentration gradient between the DNAPL and dissolved phases, but a separate
phase donor such as vegetable oil may also be added to sequester the DNAPL in situ and foster
biodegradation of DNAPL constituents as they solubilize over time. Note that bioremediation
does not work directly on the free-phase DNAPL. Instead, the technology reduces contaminants
through degradation and solubilization processes that occur near the water-DNAPL interface.
The contaminant mass stored in the nonaqueous phase must transfer into the aqueous phase
before it can be subjected to the dechlorination processes. This nonaqueous phase dominates the
contaminant mass in sites where DNAPL is present and, in many cases, where there is a sorbed-
phase mass component (see Section 2.1.3).
As described in Section 2, enhanced reductive dechlorination occurs through addition of an
organic electron donor to facilitate the sequential transformation of chlorinated ethenes as
follows:
PCE -> TCE -> cis-DCE -> VC -» ethene
The partitioning coefficients (Koc) of degradation products decrease with each step in the
transformation, thus each degradation product will be less sorptive than the previous degradation
product (see Table 2-1 for contaminant specific KOC values). In addition, aqueous solubility
increases from PCE to TCE to DCE. Using these properties, the mechanisms that are currently
understood to enhance DNAPL mass removal during bioremediation of DNAPL source zones
can be divided into the three types briefly described below (Sorenson 2002).
3.3.1 Increased Concentration Gradient
The first and most widely described mechanism discussed in the literature is enhancement of the
mass transfer rate during ISB resulting from an increase in concentration gradient due to
contaminant degradation in the aqueous phase (Seagren et al.1993, Seagren et al. 1994; Carr et
al. 2000, Cope and Hughes 2001; Yang and McCarty 2000, 2002). The initial prediction of this
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effect was based solely on modeling and is discussed further in Section 3.5. of Carr et al. (2000).
Cope and Hughes (2001) and Carr et al. (2000) demonstrated this effect using columns and batch
reactors, respectively. In the columns, PCE removal from a NAPL in biotic systems was 6.3
times greater than that observed in an abiotic "washout." This result was similar to the
observation of about a 3-fold increase in PCE removal rates from a NAPL in the continuous-flow
stirred-tank reactor. The total chlorinated ethene removal rate was 5 to 6 times greater for some
of the biotic columns compared to the abiotic. Similarly, Yang and McCarty (2000, 2002) found
that biological dechlorination activity increased aqueous phase total chlorinated ethene
concentrations by about a factor of 5 compared to abiotic controls with PCE DNAPL. This work
showed that dechlorinating organisms can withstand concentrations of total chlorinated ethenes
in solution that exceed saturation concentrations of PCE on a molar basis. In fact, the high
concentrations very near DNAPL inhibited the activity of other organisms, such as methanogens,
that could potentially compete with dechlorinators for hydrogen, leading to speculation that the
high concentrations might increase the efficiency of the bioremediation process.
3.3.2 Increased Solubility of Degradation Products
The second mechanism is enhanced mass transfer into the aqueous phase due to the changes in
properties of the degradation products relative to the parent compounds. Specifically, the
increased solubility of degradation products (especially DCE) has been indicated as affecting
enhanced mass transfer by facilitating more total moles of contaminant in solution than would be
possible for the parent compounds alone. Carr et al. (2000) found that the enhanced mass
removal in the batch reactors discussed above could be modeled using this mechanism and the
first. The decreased K<,c values of the degradation products have also been implicated because of
the decrease in sorbed mass relative to the parent compounds. This "enhanced desorption" effect
is inferred based on the contaminant properties, but it has not been well documented or
quantified to date.
3.3.3 Abiotic Electron Donor Interactions
The third mechanism proposed is abiotic interaction of electron donor solutions with the
contaminant mass. The impact of surfactants and cosolvents on chlorinated ethene NAPL
dissolution has been known for several years (Deitsch and Smith 1995, ITRC 2003b DNAPLs-3)
and is the basis of several enhanced flushing technologies (e.g., AATDF 1998, Jawitz et al.
2000). However, the impact of solubilization by an electron donor solution has only recently
been investigated. When high concentrations of soluble substrate are injected into CVOC source
areas, some increase in the effective solubility of the contaminant may occur. Sorenson (2002)
and Payne et al. (2001) report apparent increased dissolution of CVOCs from source areas when
organic substrates were injected to stimulate anaerobic biodegradation, which is partially
attributed to increases in CVOC solubility or perhaps increased desorption. It has been proposed
that the observed enhanced mass transfer through either dissolution or desorption might be
related to measured decreases in interfacial tension at high electron donor concentrations (e.g.,
30% sodium lactate), or surfactant/cosolvent effects resulting from electron donor fermentation
into alcohols, ketones, rhamnolipids, and other solubilizing agents. Although there is indirect
evidence for this third mechanism (Sorenson, 2002, ARCADIS 2002, Bury and Miller 1993), its
quantitative impact and practical importance under field conditions remain controversial.
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The complete dissolution of nonaqueous phase contaminant mass is limited by several factors,
including the typically large amount of nonaqueous phase mass present, as compared to the
aqueous phase, and the slow rate of dissolution. At some sites, significant destruction of
contaminant mass in the source area can be achieved by increasing the rate of contaminant
dissolution. However, even with dissolution rate increases, source areas at other sites are
expected to persist for many decades, due to the large amount of nonaqueous phase mass present.
Despite variation in source area characteristics, enhancing the contaminant dissolution rate
remains a key process objective for bioremediation of source areas.
3.4 Geochemical and Biological Environmental Requirements for ISB Application
Although the activities of numerous organisms are required for successful anaerobic
biodegradation, the key process is the stepwise reductive dechlorination of PCE ultimately to
ethene (Section 2.2.3). The basic geochemical and biological requirements for successful ISB of
chlorinated ethene DNAPL source zones are apparent from a consideration of the background
material described in Section 2.2. Appropriate redox conditions for complete reductive
dechlorination and a capable microbial community, as introduced in Section 2, are two
requirements for facilitating complete reductive dechlorination. A sufficient electron donor
distribution to stimulate biological activity is another requirement that can be manipulated. These
three requirements are discussed below.
3.4.1 Electron Donor Distribution
Without an electron donor, reductive dechlorination cannot occur. Therefore, distributing an
appropriate electron donor, often a fermentable carbon source, is key for successful ISB of
chlorinated ethenes. An electron donor is needed not only for reduction of the contaminants, but
also for reduction of competing electron acceptors (see Section 2.2). The electron donor addition
strategy depends in part on the concentrations of competing electron acceptors, but probably
depends more on the contaminant mass in the target treatment zone. In high concentration
chlorinated ethene source zones, relatively high concentrations of electron donor are generally
required to achieve adequate mass removal rates. Achieving sufficient electron donor distribution
can be challenging at low permeability sites.
Generally, two strategies have been used for introducing an electron donor to a site. The first
strategy is a more passive approach in which a long-lasting solid or semi-solid electron donor,
such as HRC-X™ or vegetable oil, is added directly to the DNAPL source area, generally
through multiple Geoprobe points. This approach is relatively slow, and it relies almost entirely
on the biological mechanisms for contaminant mass transfer and destruction. The second strategy
is a more active approach based on more frequent injections of aqueous electron donors, such as
lactate or molasses, in some cases with recirculation of the donor solution through the target
zone. In this approach, the donor can be more thoroughly distributed throughout the subsurface
and in addition to the biological mechanisms for removing DNAPL mass, the donor itself or its
metabolites may directly solubilize DNAPL, presumably through cosolvent and surfactant
properties. The longevity of the donor used can also affect the distribution. Various donors can
persist in the subsurface for periods ranging from a few weeks to several years (see AFCEE,
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2004), and this longevity can impact how far downgradient the donor may be transported.
3.4.2 Redox Conditions
Redox conditions are closely related to the electron donor distribution. When electron donor
distribution is insufficient, conditions often will not be sufficiently reducing to achieve complete
dechlorination, causing the process to stall at DCE. Wood and Sorenson (2004) provided several
case study examples of incomplete dechlorination resulting from inadequate electron donor
distribution. Incomplete dechlorination can often be overcome through improved distribution,
which in some cases simply means introducing higher electron donor concentrations, or in other
cases, more frequent injections.
As alluded to in Section 2.2, the dominant microbial community in a groundwater system is
largely dependent upon the distribution of electron acceptors. While PCE and TCE reduction
might occur under iron-reducing conditions, reduction of DCE and VC to ethene generally
requires at least sulfate reducing conditions, or preferably, methanogenic conditions (McCarty
1997, Freedman and Gossett 1989).
There is some debate regarding the theoretical performance of dechlorination reactions under
methanogenic conditions. Thermodynamic calculations and laboratory studies have been cited to
suggest that methanogens should out-compete dechlorinators in the presence of high electron
donor concentrations, implying that redox conditions should not be fully methanogenic (e.g.,
Smatlak et al. 1996, Fennell and Gossett 1998). These studies have generally been performed at
temperatures that are elevated relative to groundwater, and have used reactant concentrations that
are more typical of laboratory than field conditions. However, longer-term laboratory and field
studies suggest that the competition between dechlorinators and methanogens is not a significant
factor (e.g., Fennell and Gossett 1998). In fact, under field conditions, methanogenic activity
appears to have little detrimental impact on dechlorination activity, perhaps because the
predominant methanogens are those that use acetate instead of the hydrogenotrophic
methanogens that would compete with dechlorinators (Macbeth et al. 2004).
3.4.3 Microbial Community
While it is widely accepted that bacteria capable of anaerobic reductive dechlorination are vital
to biological dehalogenation processes in anoxic environments (Smidt et al. 2000), recent
advances in molecular techniques now allow scientists to characterize microbial communities,
including dechlorinators, more fully. These advances have led to the discovery of many
organisms capable of dechlorinating various compounds (Holliger et al. 1999).
Many bacteria are capable of reducing PCE and TCE to DCE (McCarty 1997), but only
Dehalococcoides spp. have been found to be capable of complete dechlorination of PCE and
TCE to ethene in a pure culture (e.g., Maymo-Gatell et al. 1997). In fact, an increasing body of
evidence suggests that complete biological reductive dechlorination of PCE and TCE to ethene
requires certain strains of the bacteria Dehalococcoides spp. (Loffler et al. 2003). Multiple
Dehalococcoides organisms, including strains KB-l/VC (Duhamel et al. 2004), BAV1 (He et al.
2003), and VS (Cupples et al. 2003), mediate dechlorination of cis-DCE and VC to ethene.
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Of particular importance is a recent study of 24 field sites in North America and Europe
(Hendricksen et al. 2002). This study found that strains of Dehalococcoides were present at all
21 sites that exhibited complete dechlorination to ethene. None of these organisms were found at
the three sites examined where dechlorination stopped at cis-DCE. This fact suggests that, while
Dehalococcoides spp. are relatively common and widely distributed, their absence at a site might
prevent complete dechlorination.
Site data have not been published to date to refute the importance of Dehalococcoides spp. for
complete biological reductive dechlorination. However, the inability to detect them at a site does
not necessarily mean that complete dechlorination will not occur. Their numbers may be very
low at some sites and their distribution sufficiently patchy that detection can be very difficult.
Environmental conditions may change and Dehalococcoides spp. may become established at a
later time, given the appropriate conditions. Moreover, other factors may complete the
dechlorination process, including co-metabolic destruction of DCE or VC by other organisms,
abiotic reactions that destroy incomplete dechlorination products, or dechlorination by some yet-
to-be-discovered organism or process. In addition, it should be noted that the detection of the
Dehalococcoides genus does not guarantee that complete dechlorination of PCE or TCE will
occur at a site. Some strains of the Dehalococcoides genus are not capable of dechlorinating PCE
and TCE, though they may degrade other chlorinated contaminants (e.g., Bunge et al. 2003).
Due to the apparent stalling of reductive dechlorination at intermediate degradation products
such as cis-DCE at some sites, many argue that selected mixed or pure cultures should be added
to sites to facilitate complete dechlorination of chlorinated ethenes. Although Dehalococcoides
spp. are found at many sites, they are not ubiquitous (Hendricksen et al. 2002). Further, their
numbers are often low and their growth rates in situ may be very slow, leading to long
acclimation times. Therefore, researchers have begun to test several mixed cultures containing
Dehalococcoides spp. for use in bioaugmentation. Initial results have been promising (e.g., Ellis
et al. 2000, Major et al. 2002), and the demonstrated success at some sites has led to the
introduction of several commercially available cultures.
3.5 Modeling of Bioremediation Removal Mechanisms for Chlorinated Ethene DNAPL
Sources
The first publications suggesting that bioremediation could be useful for source zone treatment
focused on mechanism type 1 (described in Section 3.3), the potential to enhance dissolution of
DNAPL (actually NAPL in general) within a source area by increasing the concentration
gradients (Seagren et al. 1993, Seagren et al. 1994). These modeling studies showed that
biodegradation near a source can enhance mass transfer rates by decreasing the aqueous
concentrations near the interface, thereby significantly accelerating mass transfer from a NAPL
to the aqueous phase and subsequent mass removal. The degree to which mass transfer was
enhanced was determined to be a function of the relative rates of advection and biodegradation.
As noted in Section 3.3, Carr et al. (2000) were among the first to document enhanced
dissolution of NAPL due to biodegradation experimentally. They also developed an analytical
model that adequately reproduced the experimental results based on mechanism types 1 and 2
(described in Section 3.3). Seagren et al. (2002) performed column studies to evaluate their
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earlier theoretical predictions of enhanced mass transfer, and observed up to a two-fold increase
in dissolution rates. However, they were evaluating toluene as a NAPL and it was speculated that
the toxicity of high toluene concentrations might have limited the dissolution enhancement due
to biodegradation. Chu et al. (2003) developed a two-dimensional advection-dispersion model
for enhanced dissolution of PCE from a pool due to biodegradation. Interestingly, they
demonstrated that enhanced dissolution increased with electron donor concentration because the
model predicted that unlimited electron donor allowed bacteria to grow closest to the DNAPL-
water interface, thereby maximizing the concentration gradient. It was also noted that
bioclogging of pore spaces could also impact long-term effects.
Recently, Christ et al. (2005) investigated a theoretical combination of aggressive mass removal
via surfactant flooding with bioremediation through numerical modeling. Based on the literature
reviewed in this document, the authors assumed bioremediation enhanced dissolution rates by a
factor of 5 compared to natural gradient dissolution. A key parameter in the cleanup timeframe
was found to be the "ganglia-to-pool ratio" (G:P ratio), which describes the amount of DNAPL
mass in the residual phase compared to the amount in the drainable free phase. Simulations with
low G:P ratios had the longest remediation timeframes, while those with high ratios had the
shortest timeframes. This result reiterates the fact that bioremediation is probably not well-suited
for sites with a large amount of drainable (pooled) DNAPL. Not surprisingly, given the model
assumptions, bioremediation alone was projected to shorten remediation timeframes by about a
factor of 5 relative to natural gradient dissolution. When combined with aggressive mass removal
through surfactant flushing, remediation timeframes were projected to be reduced by one to two
orders of magnitude.
Finally, it should be noted that Groundwater Services, Inc. has recently developed screening
tools for DNAPL remediation timeframe estimation for the ESTCP and the AFCEE (see the
Source DK Model website at http://www.gsi-net.com/Software/SourceDK.htm). These tools are
used to estimate dissolved phase concentrations downgradient from a DNAPL source and to
estimate the longevity of that source under various scenarios, including flushing (pump and
treat), active treatment, and natural biodegradation. Preliminary results suggest that enhanced
biodegradation might shorten DNAPL remediation timeframes considerably as compared to
natural gradient dissolution, though the magnitude of the decreases is estimated to be less than
that predicted by Christ et al. (2005).
4. THE STATE OF ISB TECHNOLOGY APPLICATIONS
This section discusses the current state of ISB technology applications for chlorinated ethene
DNAPL source zones. An overview is provided on ISB strategies for designing and applying an
ISB treatment system for either mass removal of chlorinated ethene DNAPLs or for source
containment (Section 4.1). The requirements for successful implementation of ISB as a primary
mode of treatment for chlorinated ethene DNAPL sources are briefly described (Section 4.2).
Several laboratory and field examples are presented regarding different ISB applications and
how they relate to site-specific characteristics (Sections 4.2.1 and 4.2.2). Injection strategies for
ISB applications under different site conditions (Sections 4.2.3 and 4.2.4), and bioaugmentation
for ISB of chlorinated ethene DNAPLs (Section 4.3) are discussed. Applications of ISB as a
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secondary treatment in combination with other treatment alternatives are also provided (Section
4.4). Finally, the strengths and limitations of applying ISB for chlorinated ethene DNAPL
sources are discussed (Section 4.5).
The key points made in this section are as follows:
• ISB is a flexible technology that can have different functional objectives and can be
implemented in a wide variety of ways, as a sole treatment technology or as part of a
treatment train.
• ISB can be used to enhance mass removal from a source area, to contain the source area, or
both, and it can be implemented using active systems that often employ recirculation or
passive approaches relying more on natural hydraulic gradients.
• Bioaugmentation is a viable approach for achieving complete dechlorination at sites that do
not have a capable indigenous microbial community.
• ISB's strengths for source treatment include its flexibility, its compatibility with other
technologies, its low cost relative to other technologies, its relative ease of implementation,
and the lack of process wastes generated during treatment.
• ISB's limitations include that it is relatively slow, it is generally not suitable for sources with
drainable DNAPL, it may be inhibited by other contaminants, it can impact secondary water
quality parameters, and it is still not well-understood or widely accepted for source treatment.
4.1 ISB Strategy Overview
As discussed in Section 3.2, the design of a bioremediation system for DNAPLs may have
several goals. Most commonly, ISB is deployed to enhance the rate of removal of chlorinated
ethene compounds, and thereby decrease the plume longevity and/or source loading to the
dissolved plume after treatment. However, ISB may also be used to provide biological
containment of the source, thereby, cutting off or reducing the plume loading. Finally, ISB may
be used to sequester the source and potentially degrade contaminants in place, effectively a
combination of the first two objectives. The appropriate metrics and criteria for stopping active
treatment must be chosen with these goals clearly defined and agreed-upon.
ISB may be applied as a primary or secondary treatment technology. In either case, there are two
general strategies based on electron donor type that have been used, and the responsible parties
need to make a conscious choice between these strategies. The first strategy is more passive in
that a long-lasting solid, semi-solid, or nonaqueous electron donor (e.g., chitin, HRC, or
vegetable oil) is added directly to the source area, generally through multiple direct-push
injection points. This approach is slower because of the passive electron donor distribution and
relies almost entirely on the biological enhancement mechanisms for mass removal (i.e.,
depleting the aqueous phase and conversion to less-chlorinated metabolites that partition into
water more readily). The second strategy is a more aggressive, active approach based on frequent
injections of aqueous donors, like lactate or molasses. In this approach, the donor can be more
thoroughly distributed throughout the target zone, and the donor itself or its metabolites can
directly enhance mass removal by solubilizing or desorbing DNAPL, as well as enhancing
biodegradation.
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When bioremediation is used as a secondary treatment, it may be coupled with any of several
other more aggressive technologies. For example, thermal treatment may be used for hot spots or
for a limited time, and bioremediation can be used for less contaminated areas or as a polishing
step. Similar uses in conjunction with chemical oxidation and surfactant or cosolvent flushing
have also been demonstrated. In these cases, it is important to plan ahead to take advantage of
positive synergies, such as the use of cosolvents as an electron donor or the positive impacts of
higher temperature on biological degradation rates, and avoid potential negative effects, such as
temporary sterilization by heating.
The optimum approach to implementing bioremediation for DNAPLs is not yet known, and site-
specific factors are critical in designing and operating a source zone bioremediation system. The
choice of electron donor will depend on a variety of site-specific environmental factors, as well
as the specific remedial objectives. The method for delivery of electron donors needs to be
carefully designed, as this is often the limiting factor in the success of in situ remediation, and
ongoing operational monitoring can be crucial.
4.2 ISB as the Primary Mode of Chlorinated Ethene DNAPL Source Treatment
There are two basic approaches to ISB as a mode of treatment:
• groundwater recirculating systems that extract, amend, and re-inject groundwater to establish
a dechlorination zone in the aquifer
• systems that rely on periodic injections of electron donor (can be slow-release or aqueous)
and distribution by natural groundwater flows
Figure 4-1 shows the layout for published examples of each type of system. The left side of the
figure represents the extraction/injection recirculation strategy deployed at the Brooks Air Force
Base bioaugmentation study, reported by Major et al. (2002). The system on the right side of the
figure represents the distribution of injected carbon using existing natural gradient groundwater
flow patterns, as implemented at the Midwestern U.S. full-scale biostimulation site, reported by
Payne et al. (2001). Each system achieved complete dechlorination of chlorinated ethenes in less
than 12 months. The recirculation system exchanged groundwater in the treated volume
approximately once every seven days. The natural gradient system received electron donor
injections on a monthly basis, and the injected electron donor was consumed in the first 100 days
of groundwater travel (approximately 100 feet downgradient from the injection wells). The
treatment cost for the natural gradient system closely matched the ISB estimate of $16/yd
(reported by McDade et al. 2005 and cited previously in Section 3.2).
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October 2005
background TOC
Key: EW = extraction well; IW = injection well; MW = monitoring well
Figure 4-1. Examples of carbon loading strategies for enhanced reductive dechlorination
of PCE and TCE (to-scale)
As noted in Section 4.1, ISB technology can be considered for two primary strategies at
DNAPL-contaminated sites. The first strategy is to use ISB for mass removal in the DNAPL
source zone. The second strategy is to use ISB for containment of the DNAPL source zone. Once
the remediation objectives have been defined (as introduced in Section 3.2 and discussed in
detail in Section 5.1), the effects of site-specific considerations on the application of ISB must be
considered. Table 4-1 illustrates the impact of some important site-specific characteristics on the
effectiveness of the ISB application for mass removal and source containment for DNAPL sites.
One of the key differences between the applications that is revealed in the table is that source
containment using ISB is probably applicable at a wider variety of sites than is mass removal.
This is as true for ISB as it is for many other technologies because many site-specific
characteristics that can make mass removal very difficult (e.g., low permeability, mass diffused
in secondary porosity, and complex DNAPL architecture) are less problematic for containment.
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Table 4-1. The effect of site specific characteristics on ISB application
Site-Specific
Characteristics
Application
Mass Removal
Source Containment*
Permeability
electron donor delivery can be more readily
achieved in permeable (e.g., sands, gravels)
formations
delivery can be achieved in low permeability
materials using techniques such as hydraulic
fracturing, but delivery costs are higher
dissolved mass in matrix might be very
difficult to remove in low permeability
in either high or low permeability media,
electron donor delivery schemes can be
optimized to minimize the amount of electron
donor utilized
low permeability still limits electron donor
distribution, but this can be more easily
overcome if the containment requires
treatment of a much smaller volume of
aquifer
dissolved mass in low permeability matrix is
less problematic because flux can be kept low
Volume of
DNAPL
effectiveness of ISB is highly dependent
upon DNAPL volume and "architecture"
low volume or a lack of pooled DNAPL
favors ISB, while large volumes of drainable
DNAPL limit effectiveness
effectiveness of ISB is independent of
DNAPL volume
Heterogeneity
high geologic heterogeneity implies highly
heterogeneous DNAPL distribution, which is
more difficult to remove completely
while high geologic heterogeneity implies
highly heterogeneous DNAPL distribution,
significant concentration/flux reductions in
the plume may be achieved without complete
mass removal in the source
Geochemistry
the presence of alternate electron acceptors
(e.g., sulfate, nitrate, manganese and iron
oxides) increases the electron donor dosing
requirements
high rates of electron donor amendment are
required to maintain high rates of mass
removal
the presence of alternate electron acceptors
(e.g., sulfate, nitrate, manganese and iron
oxides) increases the electron donor dosing
requirements
the rate of electron donor amendment can be
reduced to the minimum required to promote
biodegradation sufficient for the aqueous
phase in the plume.
Co-Contaminants
the presence of DNAPL co-contaminants that
serve as electron donors (i.e., fuels) might
favor mass removal
specific contaminants (e.g., chloroform) are
known to inhibit biodegradation in some
circumstances
some co-contaminants might not be readily
biodegraded
specific contaminants (e.g., chloroform) are
known to inhibit biodegradation in some
circumstances
some co-contaminants might not be readily
biodegraded
Microbiology
microorganisms capable of even partial
dechlorination can promote significant mass
removal
bioaugmentation can be used to expedite
complete dechlorination
a secondary technology may be required
depending on DAN PL volume and
architecture
high rates of mass removal might create
inhibitory concentrations of degradation
products (e.g., cis-DCE)
if the indigenous microbial population is not
capable of sustaining adequate rates of
complete dechlorination to ethane,
bioaugmentation might be required to stop
mass flux in a timely fashion
*Mass Flux/Concentration Reduction, Plume Size Reduction
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DN APL Source Zones October 2005
4.2.1 ISB for Mass Removal
Chlorinated solvent contamination is often associated with a DNAPL source area that
continuously supplies chlorinated compounds to the dissolved phase. Elimination or reduction of
these source areas can result in swifter contaminant plume remediation and a quicker path to site
closure. Engineered bioremediation is one approach that can be used to effectively treat a large-
scale zone of aquifer. With a properly designed amendment delivery system, any of the
substrates can be used to completely surround the discontinuously-located DNAPL mass.
Traditional schools of thought held that bioremediation in high concentration zones typical of
source areas would be infeasible because of two reasons. First, it was thought that contaminants
would be toxic to the microorganisms of interest. Second, it was thought that the impact on
nonaqueous sources would be no more effective using ISB than using pump-and-treat
remediation. However, recent research in both laboratory and field settings has shown that
enhanced bioremediation can be extremely effective for chlorinated ethene source areas, and that
dechlorinators actually may have an ecological niche in high concentration source areas.
The mechanisms currently identified for enhanced mass removal in chlorinated ethene DNAPL
source zones during ISB were discussed in Section 3. Several laboratory and modeling studies
were briefly described, along with some field examples. In this section, empirical results from
the laboratory and the field are provided in more detail to provide more insight into potential
applications and as illustrations of what might be expected of the technology.
4.2.1.1 Laboratory Studies
As mentioned in Section 3, Carr et al. (2000) conducted a laboratory study on the influence of
dechlorinating microorganisms and their degradation products in the presence of a PCE DNAPL.
The study was conducted in biotic and abiotic continuous-flow stir-tank reactors. Results showed
that dechlorination resulted in a significant increase in the PCE removal rates from the NAPL.
The authors noted that "the combined effects of dissolution and dechlorination on the removal of
chlorinated ethenes from the NAPL were described using a mathematical model that
approximated dechlorination as a pseudo-first-order process. It was determined that total
chlorinated ethenes removal from the NAPL would be achieved in 13 days in biotic reactors, as
compared to 77 days in the abiotic reactors, corresponding to an 83% reduction in longevity of
the chlorinated ethenes component of the NAPL."
In a similar study, Yang and McCarty (2000) evaluated the possibility of biological reductive
dechlorination of high concentrations of PCE. Their study showed that a bacterial culture was
able to transform PCE at saturated conditions and that an increase in PCE DNAPL dissolution of
up to 5-fold occurred under biologically reducing conditions. In a follow-up study concerning
biologically induced dissolution of PCE DNAPL conducted by Yang and McCarty (2002), the
substrate (electron donor) selection was deemed important for reductive dechlorination. This
study evaluated pentanol, calcium oleate, and olive oil for bioenhanced DNAPL dissolution.
Results from the study showed all substrates increased DNAPL dissolution, and methanogenesis
was extensive in the pentanol and oleate study columns. The study suggested that methanogens
can efficiently use the electron donor, and may produce considerable biomass that has the
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potential to clog flow paths. However, the presence of high PCE concentrations near DNAPL
accumulations can be toxic to methanogens. "Substrate near PCE ganglia would be used
primarily by dehalogenators because of PCE toxicity there, but methanogens could use the oleate
that was not near DNAPL" (Yang and McCarty 2002).
Another study, conducted by Cope and Hughes (2001), used upflow glass bead-filled columns to
study the influence of dechlorinating microorganisms on PCE and its reduction products in a
residual NAPL source zone. Their results showed that dechlorination resulted in an increase in
total PCE removal by a factor of up to 16 greater than ambient dissolution. Reductive
dechlorination degradation products were observed, and total chlorinated ethene removal was
enhanced from 5.0 to 6.5 times greater than the removal that would have resulted from
dissolution alone.
4.2.1.2 Field Studies
ISB has also been successfully demonstrated under field conditions, at both pilot- and full-scale
implementations. Several of the more controlled and well-monitored field studies are briefly
described below. In general, the results demonstrate that complete dechlorination can occur in a
source zone, enhanced mass removal can occur as a result of ISB within the source, and the
enhancement factor as compared to dissolution only is significant, though more modest than that
suggested by the laboratory studies described above.
One of the higher-visibility full-scale applications of ISB has been at the Idaho National
Engineering and Environmental Laboratory (INEEL) Test Area North (TAN), where TCE, PCE
and 1,2-DCE were detected in drinking water supply wells above risk based concentrations. The
groundwater contaminant plume was about two miles long, at a depth of 200^150 feet, and
concentrations of TCE in groundwater ranged from historical highs of over 300 mg/L in the
source zone (approximately 100-foot radius) to 5 |ag/L at the distal end of the plume. Enhanced
reductive dechlorination was used in the source zone, and food-grade sodium lactate with potable
water was injected into the aquifer. Periodic lactate injections accelerated the dechlorination in
the source zone, degrading contaminants in the aqueous phase near the source and accelerating
degradation of the source material itself (separate-phase DNAPL), as evidenced by large (near
20-fold) but temporary increases in aqueous TCE concentrations (Sorenson 2002). A reduction
of TCE to non-detectable levels has been shown in a number of wells, including the original
injection (disposal) well and the three monitoring wells where TCE concentrations had been the
highest. Continued groundwater monitoring has shown no rebound while the system continues to
operate. Analysis of stable carbon isotopes in the TCE showed that the signature of the TCE
changed, suggesting that the process directly impacted the source material (Song et al. 2002,
USDOE 2002).
Another field study of ISB was conducted at Naval Weapons Station Seal Beach in California.
This study demonstrated enhanced mass transfer using ISB in a source zone, apparently
comprised primarily of sorbed PCE mass (French et al. 2003). Although the highest
concentrations in the plume, located in a shallow coastal aquifer, were only on the order of one
to a few mg/L, they persisted in one area for several years. Sodium lactate was injected into the
area as a 3% solution periodically over several months. Enhanced mass transfer caused PCE
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DN APL Source Zones October 2005
concentrations to increase by 2.5- to over 10-fold in monitoring wells near the injection well, and
stoichiometric conversion to DCE was observed in all of them. The site was later bioaugmented
successfully to achieve complete dechlorination of the contaminants (French et al. 2004).
At Dover Air Force Base in Delaware, historic spills of chlorinated solvents contaminated
ground water with TCE, cis-1,2 DCE, and PCE with average concentrations of 4800 u.g/L, 1200
ug/L, and 3 (J.g/L, respectively. An accelerated ISB demonstration system was installed that
included the extraction of contaminated water and additions of nutrients, substrate, and
microorganisms prior to reinjection. The system showed complete in situ degradation of
chlorinated organic solvents to ethane, using groundwater recirculation and amendment through
augmentation of the native microbial community with a culture from Largo, Florida (Ellis et al.
2000).
A more recent demonstration has been conducted at Dover AFB to more thoroughly investigate
the potential for ISB to enhance DNAPL dissolution rates in source zones. In this pilot test, PCE
was added to enclosed test cells, and electron donor (lactic acid) was added after an initial
baseline equilibration phase. The test cells were then bioaugmented (with the KB-1™ culture)
The phases include a groundwater flush to determine baseline dissolution, biostimulation to
determine the impact of nutrient addition, and bioaugmentation to determine the impact of the
addition of PCE degrading microorganisms. The results to date demonstrate that ISB can
increase mass removal, by a factor of approximately 2, and that bioaugmentation was necessary
to promote complete dechlorination of the PCE to ethene. Again, stable carbon isotope analysis
has been valuable in demonstrating biological degradation has occurred, and microbial analyses
have shown that significant levels of dechlorinating organisms (over 107 cells per L) have been
maintained within the source area for over a year.
At the Kennedy Space Center, groundwater amended with ethanol was recirculated through a test
plot constructed within a TCE DNAPL source area (Battelle, 2004). Prior to ethanol amendment,
groundwater concentrations of TCE as high as the solubility were initially observed in some
locations. The TCE concentration in the recirculated groundwater was 160 mg/L. The addition of
ethanol at a concentration equivalent to a 4-fold stoichiometric excess to that required to reduce
all electron acceptor in groundwater (primarily TCE and sulfate), resulted in an increase in TCE
biodegradation and significant accumulation of 1,2-cis-DCE and VC. Electron donor addition
and groundwater recirculation continued for 107 days. Subsequently, the test plot was
bioaugmented with 40 L of KB-1™, a commercially-available dechlorinating microbial
consortium (Duhamel et al. 2002). After bioaugmentation, ethene was the dominant degradation
product and concentrations as high as 96 mg/L were observed. An increase in total chloroethene
concentrations following bioaugmentation suggested that there was an increase in the rate of
TCE mass removal from the test plot.
The examples discussed for using ISB for mass removal are all similar in the context of the
remediation objectives in Sections 3.2 and 5.1. They all showed good results in terms of mass
removal, reduction in local aqueous concentrations, and reduction in toxicity. None of them were
operated in such a way as to demonstrate a decrease in mass flux. Conditions at all of the field
sites were somewhat favorable for ISB. In terms of Tables 4-1 and 5-1, all of the examples had
moderate to high permeability and low DNAPL volumes. The heterogeneity was variable for the
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
field sites, with two being relatively homogeneous, while the INEEL TAN site is quite
heterogeneous, but highly transmissive. Alternate electron acceptors were not prohibitively high
at any of the sites, although sulfate was as high as 500 mg/L at Naval Weapons Station Seal
Beach. Bioaugmentation was performed at two of the field sites to facilitate complete reductive
dechlorination.
4.2.2 ISB for Source Containment
As shown in Table 4-1, some site conditions make mass removal using ISB very difficult, but are
more tractable when containment is the primary goal. Besides demonstrating enhanced mass
removal, the examples discussed in Section 4.2.1 demonstrate that complete dechlorination can
be stimulated.
The use of ISB for source containment is defined as stimulating a biological treatment zone
within or immediately downgradient of the DNAPL source zone to stop or minimize the flux of
contaminants leaving the source zone. Containment is most typically achieved by establishing a
reactive barrier downgradient of the source, through injection of an electron donor into wells or
injection points along a transect perpendicular to the groundwater flow path (see Figure 4-2).
Alternatively, physical barriers may be established, with biological treatment in defined areas
(so-called funnel-and-gate applications). Finally, electron donors, such as vegetable oil, may be
injected into and near the source area to sequester the DNAPL and degrade DNAPL constituents
as they solubilize. In any application, achieving containment requires facilitating complete
reductive dechlorination of contaminants in the aqueous phase.
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones
October 2005
Extraction Welt
DNAPL
Injection Well
Figure 4-2. Schematic for ISB applications for source containment
Source containment is applicable at a wider variety of sites than is mass removal because all of
the conditions that made the sites in the previous examples good candidates for using ISB for
mass removal in the source zone do not necessarily have to be met to use ISB for containment.
For example, low permeability might preclude ISB from being used for mass removal in a
spatially large source zone because the cost of closely spaced wells is too high. It might be
possible, however, to achieve containment with just a fraction of the wells required for
enhancing mass transfer, thereby making containment feasible. As another example, contacting
the DNAPL source mass is not important for containment because containment can occur
downgradient, so DNAPL architecture may be much less important for containment than for
mass removal. Another characteristic that might make containment more widely applicable than
mass removal is that injection strategies that could be appropriate for containment, such as
trenching, might not be appropriate for mass removal (see Section 4.2.4).
4.2.3 Electron Donor Injection Strategies
Several different techniques are available to inject electron donors into groundwater, and the
appropriate technique depends not only on the strategic objectives, but also on the electron
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
donor. The most common strategy is to inundate the source zone with electron donor to make the
entire source zone sufficiently anaerobic for complete dechlorination and to distribute donor
throughout the source zone. Less commonly, donor is distributed in a barrier along the
downgradient edge of the source zone. In either case, the donor can be distributed in relatively
passive or active delivery modes.
The most common approach used is a relatively passive delivery, involving direct injection of
the electron donor throughout the contaminated zone. The donor addition may include some
dispersive mixing, such as pressure pulsing or water chases, but for the most part practitioners
rely on ambient groundwater flow to distribute the electron donor throughout the subsurface. In
this approach, groundwater monitoring is used to judge the need for further electron donor
injections. This approach is used almost exclusively when adding insoluble or semi-soluble
donors, such as chitin, vegetable oil, or HRC™, and is often used with soluble donors as well.
Often, this approach is associated with the addition of an excess concentration of electron donor.
There are relatively low ongoing costs associated with passive electron donor delivery.
An active electron donor delivery approach is one that uses continuous recirculation of electron
donor-amended groundwater through the contaminated zone. Active delivery may be employed
to provide electron donor throughout the source zone or within a barrier configuration. While
there is an ongoing cost associated with operation of the recirculation system, this approach
provides better mixing of the electron donor and the groundwater, and can provide some ability
to optimize electron donor dosing based on monitoring data. Between these two approaches,
there are a number of semi-passive electron donor injection strategies that try to balance the cost
of additional injection locations against the operating costs of groundwater recirculation.
4.2.4 Electron Donor Injection Techniques
Different techniques are available to inject electron donors into groundwater, and the appropriate
technique depends not only on the relevant application (mass removal or plume containment) but
also on the electron donor selected. The following sections describe five different techniques for
distributing electron donors. A brief description of each is provided, along with the strengths and
weaknesses in terms of the site-specific characteristics in Table 4-1. None of the injection
techniques provide unique advantages for the last two characteristics in the table, so these are not
discussed.
4.2.4.1 Semi-passive, large injection point spacing
This technique relies on pulsed injection of significant volumes of electron donor solution to
achieve a large radius of influence around a single injection point. Examples of this include the
INEEL TAN site, where a radius of influence of approximately 100 feet from a single injection
well was achieved (Martin and Sorenson 2004), and the California Seal Beach site, where a
radius of influence of over 20 feet was achieved (French et al. 2003). This approach works best
under moderate to high permeability conditions. It can be highly effective for enhancing mass
transfer because of the volumes of high-concentration electron donor provided. It can work in
heterogeneous systems, although the electron donor will follow the advective flow paths. The
high volumes of electron donor solution are also well suited for removal of competing electron
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
acceptors.
4.2.4.2 Passive, small injection point spacing
This technique relies on either single injections or very infrequent injections of electron donor in
closely spaced injection points on a grid that covers the DNAPL source zone. This approach is
also effective at moderate to reasonably high permeability sites, although groundwater velocities
that are very high can be problematic because little to no cross-gradient distribution of the
electron donor occurs. It is also best in shallow sites where drilling costs are low, and it tends to
be cost-prohibitive when direct-push techniques cannot be used. It can be somewhat effective for
enhancing mass transfer, although concentrations that can be distributed away from the injection
points tend to be lower than some other methods. Highly heterogeneous sites are problematic for
this approach because the electron donor is not widely distributed from individual injection
points. Relatively homogeneous sites with low to medium advection to dispersion ratios are best.
Subject to the distribution limitations mentioned, concentrations of electron donor can generally
be high enough to handle competing electron acceptors, except when acceptor concentrations are
very high, as can be true for sulfate at some sites.
4.2.4.3 Forced advection
This technique uses continuous pumping and re-injection to control groundwater flow and
electron donor distribution. This approach provides the greatest engineering control, and it has
been used to distribute electron donor and bacteria successfully in several published
bioaugmentation demonstrations for treatment zones on the scale of approximately 10-30 feet
long (Ellis et al. 2000, Major et al. 2002, Lendvay et al. 2003). The strengths of this approach are
essentially the same as for the semi-passive approach, except that forced advection is somewhat
more robust for slightly lower permeability sites or more heterogeneous sites because of the
control over hydraulic gradients that is afforded. The hydraulic control can also be an advantage
in bio-barrier applications where it is desirable to maximize well spacing.
4.2.4.4 Trenching
This technique involves the installation of electron donor into the subsurface in a trench. This
approach has limited applicability for inundation of source areas because of the nearly two-
dimensional nature of a trench. It is most typically used to install permeable reactive biobarriers
(or "biowalls"), though one or a series of trenches may be used to treat a source in a relatively
permeable medium with a high groundwater velocity. As with the passive electron donor
addition, lower concentrations of electron donor are likely to migrate downgradient from the
barrier. Heterogeneity is less problematic for a permeable reactive barrier than other techniques
because it allows distribution across an entire cross-section of the source zone, regardless of the
heterogeneity.
4.2.4.5 Hydraulic Fracturing
This technique emplaces electron donor during hydraulic fracturing of the formation. It has been
successfully applied for facilitating ISB of a source zone in a low permeability formation at the
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Distler Brickyard Superfund Site (Martin et al. 2001, Bures et al. 2004a, 2004b). A radius of
influence of approximately 15-20 feet was achieved for individual fractures at the site. This
technique is probably best-suited to low permeability sites, although it can be used at higher-
permeability sites as well. Mass transfer limitations are similar to the passive and trenching
approaches, although the hydraulic fractures tend to cut across the heterogeneous units in a
formation, helping to overcome some of the difficulties in distributing the donor effectively.
4.3 Bioaugmentation
As noted in Section 3.4.3, an increasing body of evidence supports the notion that efficient,
complete reductive dechlorination of chlorinated ethenes is best facilitated in the presence of
Dehalococcoides spp. bacteria. At many sites, it might not be necessary to introduce these
bacteria, but at several sites, the addition of an exogenous culture containing Dehalococcoides
spp. has been shown to expedite cleanup. Several Dehalococcoides-containing bioaugmentation
cultures have now been used in the field and are commercially available. Individual vendors
often have specific protocols for implementing bioaugmentation, but the fundamental steps are
essentially universal.
1. Preconditioning. The first step before injecting a Dehalococcoides-conteming culture into site
groundwater is to add sufficient quantities of donor to achieve anoxic conditions. This pre-
conditioning will maximize the potential for survival of the strictly anaerobic Dehalococcoides
and will minimize the lag time before the onset of complete dechlorination.
2. Inoculation. Care should be taken during inoculation to prevent exposure of the culture to
oxygen, either during the transfer or in the receiving groundwater. Best results have been
obtained using enriched cultures containing approximately 107 to 109 Dehalococcoides cells per
milliliter. There are several studies in which large volumes of far less concentrated inoculants
have been used (typically groundwater containing an active dechlorinating microbial population
at densities 10-1000 lower than those cited above). However, the most common practice is the
use of highly-enriched cultures.
3. Distribution. Bacterial distribution is more complex than electron donor distribution, and there
are many factors that affect bacterial transport in groundwater. Nevertheless, transport on a scale
of several tens of feet has been demonstrated in the field at several sites (Ellis et al. 2000, Major
et al. 2002, Lendvay et al. 2003). Forced advection has been used successfully at these sites,
although a semi-passive system was used successfully at the California Seal Beach site (French
et al. 2004).
Given the necessary preconditioning and appropriate care during inoculation, evidence of
complete dechlorination is generally fairly rapid. Detections of VC and ethene usually occur
within weeks to at most a few months. Distribution of bacteria can take longer depending on the
scale of transport. The extent to which Dehalococcoides is retarded relative to groundwater
velocity appears to vary significantly in the demonstrations published to date. In all cases,
transport distances of tens of feet have been achieved in a few months.
Some limitations for bioaugmentation to expedite ISB in DNAPL source zones might exist. For
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
example, some strains of Dehalococcoides are inhibited by common co-contaminants, notably
1,1,1-trichloroethane (1,1,1-TCA), and research in this area is ongoing. Another example is that
Dehalococcoides activity in some studies appears to be inhibited to some extent when DCE
concentrations are extremely high, which can occur due to enhanced dissolution and
biodegradation in DNAPL source zones. This is also an area of active research. These issues
should be noted when considering bioaugmentation to ensure that expectations are realistic.
4.4 Using ISB in Combination with Other Treatment Technologies
When bioremediation is used as a secondary treatment, it may be coupled with any of several
other more aggressive technologies. For example, thermal treatment may be used for hot spots or
for a limited time, and bioremediation can be used for less contaminated areas or as a polishing
step. Similar uses in conjunction with chemical oxidation and surfactant or cosolvent flushing
have also been demonstrated. In these cases, it is important to plan ahead to take advantage of
positive synergies, such as the use of cosolvents as an electron donor or the positive impacts of
higher temperature on biological degradation rates. It is also important to avoid potentially
negative effects, such as temporary sterilization or unfavorable geochemical changes resulting
from other treatment technologies.
Despite anecdotal evidence that bioremediation has been employed as a secondary or polishing
treatment technology, there has been limited research to date examining the performance of
coupled bioremediation approaches. However, there are reasonable grounds for considering this
approach and ongoing research is likely to increase its relevance. The following sections describe
some of the possible coupled approaches, with examples of past applications.
4.4.1 ISB and Thermal Technologies
Thermal technologies, including steam injection and electrical heating, work by volatilizing and
mobilizing contaminants. Volatile components enter the vapor phase and migrate away from the
injection wells toward cooler regions. Condensation occurs at the thermal front, creating a bank
of contaminant in front of the advancing steam. DNAPL mobilization may also occur as a result
of the decreased interfacial tension and lowered viscosity accompanying the increase in
temperature (National Academy of Sciences 1999). Although only limited data are available,
thermal technologies have several potential impacts on ISB. The high temperatures involved can
reduce the population of viable microorganisms, with unforeseen results on the microbial
community and reductive dechlorination. The residual heat is likely to increase the rate of
biochemical reactions in the treated zone. Further, heating may result in geochemical changes. In
each of these areas, only limited information is available on the potential relevance of these
impacts to ISB.
In a recent study at a polyaromatic hydrocarbon NAPL source zone, the effects of steam
injection on soil microbial activity, community structure, and the potential for biodegradation of
contaminants following steam treatment were evaluated (Richardson et al. 2002). Findings
showed that samples collected while the subsurface was still hot were below detectable limits for
microbial activity. However, soils that were slowly cooled showed microbial activity comparable
to initial conditions. The study also showed that organisms capable of biodegradation were
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among the mesophilic populations that survived steam treatment. Similarly, in an EPA
groundwater issues paper, Davis (1998) indicated that increased biological activity occurred at a
steam injection site at Naval Air Station Lamoore, where in situ temperatures were as high as
100°C.
A pilot study of six-phase heating (SPH) was conducted as part of a multiple technology
demonstration for the in situ remediation of TCE present as DNAPL at Cape Canaveral in
Florida. Average soil temperatures in the heated area ranged between 80°C and 120°C. The
duration of the heating lasted 11 months, from August 18, 1999, to July 12, 2000. Soil sample
analysis suggested that a rise in microbial activity after heating was responsible for
biodegradation observed following the thermal study (Dettmer 2002). Subsequent laboratory
experiments performed by Pacific Northwest National Laboratories (PNNL) confirmed the
ability of indigenous microbial populations to degrade TCE at elevated temperatures (i.e., 70°C)
and under anaerobic conditions similar to those during SPH operations. Further microbial
analyses of samples from the SPH demonstration at Cape Canaveral suggested that thermal
treatment reduced the numbers and diversity of the indigenous bacterial populations, but that the
reduction was temporary (Battelle, 2001).
A pilot field demonstration study conducted at West Quartermaster's Fueling System in
Operable Unit 5 at Fort Wainwright, Alaska, used radio-frequency heating (RFH) and SPH.
Subsurface temperatures were elevated sequentially to above 30°C. Laboratory studies showed
that the optimum temperature for microbial consortia existing in the soil was about 20°C, and
biodegradation rates declined at temperatures above 30°C. Respiration tests were performed at
the unheated control site, the RFH site, and the SPH site. Results showed a varying increase in
biodegradation rates for the RFH and SPH sites heated to 10°C to 25°C. Interpretation of these
results showed that biodegradation rates increased with an increase in soil temperature above
5°C, up to about 30°C (Dettmer 2002).
There has also been some recent microcosm evidence that temperature increases comparable to
those observed during thermal treatment (e.g., 100° C for 10 days) inhibit the activity of both
hydrocarbon-degrading and dechlorinating organisms (Friis et al. 2004). Further, temperature
increases appear to increase the solubility of natural organic carbon present in the soil, which
appears to be readily utilized as an electron donor by survivor organisms to create reducing
conditions. However, it is clear that further research is needed to determine the effects of thermal
treatments on geochemistry, redox conditions, and biodegradation capacity.
In general, it appears the dechlorinating activity may be temporarily inhibited by the high
temperature associated with thermal treatment although this activity appears to recover. In
reviewing the available data on thermal treatment impacts on bioremediation, Dettmer (2002)
concluded that
bioremediation can be implemented as a polishing technique. It is apparent that
bioremediation has potential to follow thermal treatment, and that thermal treatment may
even enhance the biodegradation rates of contaminants. The combination of thermal
treatment for source removal and bioremediation for dissolved phase reduction could
significantly reduce remediation costs and energy consumption at a contaminated site.
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
[However], [IJittle is known about the thermal effects on dechlorinating microorganisms.
Dechlorinating microorganisms are typically known to be mesophilic and non-spore
forming, which means they do not possess the capability to survive high temperatures.
No research was found, however, on the possible existence of thermophilic
dechlorinating bacteria. Clearly, more research on the effects of elevated temperatures on
dechlorinating bacteria is needed. The combination of thermal treatment for source
removal and bioremediation as a polishing technique has potential to be used as an
effective treatment train in the near future. Before this combination can be implemented,
however, a better knowledge of the degradation processes affected by thermal activity
must be acquired.
4.4.2 ISB and Electrokinetic Bioremediation
Electrokinetic bioremediation (bioelectric remediation) technology for continuous in situ
treatment of groundwater or soil uses electro-osmosis or electrochemical migration to initiate or
enhance ISB (GWRTC 1997). In theory, it may provide improved amendment distribution in the
DNAPL source zones for increased biodissolution and biodegradation. Electro-osmosis applies a
direct current to the subsurface to accelerate groundwater flow. This process is applied to ISB to
increase amendment mixing and may be most applicable in low permeability areas.
Electrochemical migration occurs when an electrical field is applied primarily to fine silty clays
and mixed clays and moves uniformly through the fine soils. It helps ions more readily move
through small pore spaces. This electrical field may disperse some simple organic ISB
amendments more uniformly through the contaminant zone.
In 1995, an industrial consortium implemented an electrokinetics pilot demonstration treatment
study at the DOE Paducah Gaseous Diffusion Plant through a treatment process termed
Lasagna™ by Monsanto (DOE 1996). This process used electrokinetics to move contaminants in
soil pore water into treatment zones where the contaminants could be captured or destroyed. The
pilot study was conducted in a 15 by 10 by 15-foot volume where TCE maximum concentrations
were at 1,760 ppm. DNAPL locations within the study cell were reduced to 1 ppm levels. The
demonstration did not include testing of bioremediation potential following treatment.
4.4.3 ISB and Surfactant or Cosolvent Floods
Surfactants and cosolvents are typically used to enhance the dissolution of DNAPL constituents
into the aqueous phase, thereby increasing the rate of source mass removal. Common cosolvents
include alcohols such as ethanol, ter-butanol, methanol, and isopropanol (ITRC 2003b). These
technologies are particularly relevant to ISB in that most surfactants and cosolvents can act as
electron donors and tend to promote the growth of indigenous microorganisms (including
dechlorinators). Further, these technologies mobilize VOCs adsorbed to soil particles.
Few studies have been completed to specifically examine the sequential application of these
technologies with ISB. The most significant demonstration of the potential for combining
enhanced flushing is a study completed at the Sages Dry Cleaning site in Jacksonville, Florida,
where a cosolvent pilot-scale field demonstration was conducted in August, 1998. PCE DNAPL
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DN APL Source Zones October 2005
was recovered from an existing on-site water supply well and maximum concentrations of PCE,
TCE, and cis-l,2-DCE in groundwater were 930 mg/1, 34 mg/1 and 19 mg/1, respectively. The
ethanol cosolvent consisted of 95% ethanol and 5% water. The residual ethanol then served as an
electron donor for reductive dechlorination. PCE concentrations were reduced 60%, and
increases in the concentration of PCE degradation products, the production of dissolved methane
and hydrogen, and the depletion of sulfate indicated that the ethanol flush resulted in highly
reducing conditions and increased the rate of reductive dechlorination. The Sages site results led
researchers to conclude that "residual ethanol remaining after cosolvent flushing has
significantly enhanced in situ biological dechlorination processes for natural attenuation of the
contaminant mass" (ITRC 2003b). Results from this demonstration also strongly suggest that
cosolvent flushing systems can be designed and used to aid in the enhancement of
biodegradation processes at DNAPL sites (Mravik et al. 2003).
4.4.4 ISB and In Situ Chemical Oxidation
One of the most widely applied source treatment technologies has been in situ chemical
oxidation (ISCO). Although there has been considerable speculation about the potential impact
of ISCO on bioremediation after treatment, research on the topic is still needed. Results from
ongoing laboratory-scale research suggest that ISCO does not result in complete sterilization,
and that dechlorinators can survive and remain active after ISCO treatment. In fact, ISCO may
result in a flush of biodegradation following treatment, as a consequence of the chemical
decomposition of more complex native organic matter.
The existing data characterizing the impacts of oxidants of anaerobic bioremediation processes
provide contradictory evidence for the feasibility of utilizing bioremediation following oxidation.
In the case of permanganate, oxidation of constituents of the aquifer matrix can produce soluble
products. For example, sulfide minerals may be oxidized to produce sulfate (Nelson et al. 2002),
while some of the natural insoluble organic carbon content of the soil is partially oxidized to
carboxylic acids and aldehydes (Hayes 1989). Increases in dissolved organic carbon
concentrations observed at some field sites (Droste et al. 2002) may promote reducing conditions
favoring reductive dechlorination. However, permanganate oxidation results in the deposition of
manganese oxide (MnO2). Under anoxic conditions, manganese is essentially insoluble, but the
anaerobic conditions typically associated with ISB of chlorinated ethenes also favor manganese
reduction.
As an oxidizing agent, contact with permanganate adversely impacts microorganisms present in
groundwater, although complete sterilization of the microbial population is generally considered
unlikely to occur. In a study evaluating the impact of permanganate addition on indigenous
microorganisms, reductions in the populations of aerobic and anaerobic heterotrophs, nitrate-,
nitrite-, and sulfate-reducers, and methanogens following treatment ranged from 47-99.95%
(Klens et al. 2001). Replicate samples collected six months after treatment suggested that the
population of heterotrophic aerobic microorganisms rebounded although enumeration of
anaerobic heterotrophic microorganisms indicated that only minimal recovery of these
microorganisms had occurred. While permanganate may result in large reductions in microbial
populations, there is at least limited microcosm evidence to suggest that ISCO does not
intrinsically inhibit the dechlorinating activity of the microbial population (Rowland et al. 2001).
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ITROOverview of In Situ Bioremediation of Chlorinated Ethene DN APL Source Zones October 2005
Achieving a transition to a microbial population dominated by dechlorinating microorganisms
(e.g., Dehalococcoides) requires a significant shift in redox conditions. Since manganese-
reducing organisms use hydrogen much more efficiently than dechlorinating organisms (AFCEE
2004), it may be the case that the establishment of dechlorinating populations may only be
possible in anaerobic niches where manganese dioxide has been completely depleted (Crimi and
Siegrist 2004). However, it has also been reported that TCE dechlorination at least to DCE might
occur under manganese-reducing conditions (Hrapovic et al. 2005).
A similar circumstance is expected to occur in the case of Fenton's reagent, which results in the
production of oxygen and significant increases in temperature. Oxygen gas, the ultimate product
of hydrogen peroxide decomposition, can be trapped in the pore spaces and act as a long-term
source of dissolved oxygen gas in groundwater. Application of the conventional Fenton's reagent
to a site resulted in highly acidic pH conditions and elevated concentrations of dissolved oxygen
(up to 24 mg/L) in the treatment zone relative to a background location seventeen months after
oxidant injection (Kastner et al. 1997, 2000). Dissolved oxygen is toxic to anaerobic
microorganisms, including Dehalococcoides, and increases the amount of electron donor
required to create reducing conditions suited to reductive dechlorination.
4.4.5 ISB and Nano-Scale Zero Valent Iron (ZVI)
Improvements in the ability to produce ZVI at a controlled particle size gave rise to the idea of
injecting nano-scale ZVI for treatment of chloroethene-contaminated groundwater (Elliot and
Zhang 2001). When combined with an electron donor formulation (e.g., vegetable oil), ZVI can
be incorporated into an amendment that offers the potential for rapid destruction of
chloroethenes (dissolved phase and NAPL), along with the capability for prolonged
biodegradation of residual contamination. Because ZVI is a reductant, there are obvious potential
synergies between use of ZVI in combination with ISB (i.e., ZVI and ISB both operate under
reducing conditions).
Recently an amendment formulation was developed that combines vegetable oil and nano-scale
ZVI (Geiger et al. 2003). This formulation, termed emulsified Zero-Valent Iron (EZVI), was first
tested in the field at the NASA Launch Complex 34 site, for treatment of TCE-containing
DNAPL (Quinn, et al. 2005). The emulsion droplets consist of an inner core of water and nano-
scale ZVI that is contained within an oil/surfactant membrane. This oil/surfactant membrane
provides protection of the ZVI particles and can cause the droplets to be attracted to deposits of
chloroethene-containing NAPL. It may also be effective in combination with ISB because the oil
and surfactant can serve as longer-term electron donors.
At the Launch Complex 34 site, soil and groundwater samples were collected before and after
the 5-day injection period to evaluate effectiveness. Within 90 days, decreases in soil
concentrations of TCE were greater than 80% at four of the six sampling locations. TCE levels in
groundwater were reduced from 57-100% at the depth intervals where EZVI was delivered. At
the downgradient transect, the average reduction in TCE concentration was 68%, and the mass
flux decreased by about 56% over a period of 6 months. Production of cis-DCE and VC was also
observed, suggesting that biodegradation was an important contributor to the performance
(Quinn, et al. 2005). Follow-on research with EZVI is being funded through ESTCP to document
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones
October 2005
the cost and performance under field conditions.
4.5 Strengths and Limitations of ISB Application
The research cited thus far has revealed some of the key issues that affect the applicability,
selection, and design of source zone ISB systems. The strengths and limitations of ISB
technology are summarized in Table 4-2.
Table 4-2. Strengths and limitations of ISB
Strengths
ISB can reduce the total contaminant mass in the
dissolved, sorbed, and nonaqueous phases typically
without creating process waste requiring further
treatment.
Under appropriate conditions, ISB can meet regulatory
criteria for target contaminants in groundwater.
ISB may be used in both short- and long-term
timeframes, either by itself or following a more
aggressive source zone treatment technology.
At sites where significant dechlorination takes place
under naturally occurring conditions, ISB is compatible
with and can accelerate existing attenuation processes.
Implementation of electron donor addition and
bioaugmentation appears to be relatively
straightforward.
ISB may be a cost-competitive containment technology.
ISB is almost always faster than baseline pump-and-treat
remediation
Limitations
ISB treatment will be slow in highly contaminated
source zones and may not be appropriate for areas with
drainable DNAPL. In some cases, complete contaminant
destruction is not achieved, leaving the risk of a residual
toxic intermediate.
Some contaminants are resistant to biodegradation or
may be toxic to the microorganisms, impeding or
preventing the bioremediation process.
Source zone ISB can cause significant changes in water
quality. Uncontrolled proliferation of the
microorganisms might reduce permeability.
It might be difficult to adequately characterize sources
and to deliver reagents to them, thereby preventing
enhanced DNAPL removal rates from equaling those
observed in the laboratory.
Performance assessment and engineering optimization of
ISB technologies are not well understood.
The use of low-cost electron donor amendment
strategies, passive or semi-passive, is probably required
for cost-effective containment.
The effectiveness of ISB will vary from site to site and
be largely dependent upon the site geology and the
distribution of DNAPL in the subsurface.
It has become clear that ISB may not be appropriate for all DNAPL sites, particularly those with
large accumulations of free-phase NAPL. Borden (2003) used a simple mass transfer
biodegradation model to determine that significant enhanced dissolution from pooled NAPL was
not likely. He concluded that containment of a source zone by ISB was possible, but that
"enhanced anaerobic bioremediation is not likely to be effective for rapid restoration of heavily
contaminated source areas." As discussed in Section 3.5, recent work by Christ et al. (2005) has
indicated that ISB may be very effective in reducing plume longevity in source zones with high
G:P ratios, especially following a primary treatment, such as surfactant flushing. However, in
source zones dominated by pooled accumulations of DNAPL, ISB would have much less impact
on the plume longevity because of the limited mass transfer that is possible from the DNAPL to
water phases.
It is important to note that these modeling efforts focused on "rapid restoration." However, it has
become clear that ISB may be cost-effective even when deployed over relatively long periods of
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
time. Given sufficient time, bioremediation may well achieve results equivalent to more
aggressive, but more expensive, technologies, particularly other mass transfer-limited
technologies such as ISCO and surfactant flushing. Thus, bioremediation may be favored where
limited capital is available for the initial phase of remedial action. However, bioremediation
might be less desirable at sites where rapid treatment is preferred, such as sites undergoing
property transfer.
Another consideration when selecting or designing ISB for a specific site is that it is often very
difficult to deliver the necessary reagents to the source zone. Rapid degradation near the water-
DNAPL interface is a key to biological enhancement of the mass transfer of chlorinated ethenes
to the aqueous phase. Therefore, finding and targeting the DNAPL areas are critical to the
efficient and successful use of ISB. The ability to target DNAPLs has improved somewhat over
time, though it remains a particularly challenging problem. Although not the focus of this
technology overview, the development of improved source characterization tools, such as
membrane interface probes and partitioning tracer tests (Meinardus et al. 2002, Jawitz et al.
2003), could prove significant in helping to make ISB even more effective.
Addition of electron donors can also cause changes that need to be recognized and monitored.
These include high biochemical oxygen demand or chemical oxygen demand in groundwater,
increases in dissolved metal concentrations, lower pH near injection points, production of gases
such as methane and hydrogen sulfide, increases in groundwater or in the vadose zone of
carcinogenic byproducts such as VC, possible blockage of pore spaces in the subsurface, and
possible increased mobility of DNAPL constituents in the subsurface.
These changes can impact downgradient groundwater quality, but in general, the alterations
should dissipate with time and distance and should not pose insurmountable problems.
Moreover, any technology designed to enhance mass transfer of DNAPL also involves some risk
that DNAPL accumulations will be mobilized and that they may migrate within the subsurface.
For that reason, ISB will often be applied in conjunction with hydraulic control of some type to
contain or recover the mobilized DNAPL and the expected flush of dissolved contaminants.
Finally, application of ISB alone is unlikely to be sufficient to reach maximum contaminant
levels (MCLs). ISB may be particularly limited in low-permeability or heterogeneous settings
(National Research Council 2004). There are fundamental constraints in situ that limit the ability
of microorganisms to access all of the residual DNAPL present, especially if a significant
fraction of the DNAPL diffuses into a surrounding low-permeability matrix (Parker et al. 1994)
or migrates into inaccessible areas. Other technologies depending on aqueous delivery of
reagents have demonstrated similar limitations (Stroo et al. 2003).
5. DEFINING AND MEASURING SYSTEM PERFORMANCE OF ISB
APPLICATIONS FOR CHLORINATED ETHENE DNAPL SOURCES
Identifying appropriate performance measures is an important aspect of determining the progress
and success of ISB activities. This section briefly defines several functional remediation
objectives for clean up of sites contaminated with chlorinated ethene DNAPLs and the potential
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
for ISB to achieve those objectives under various geological site conditions and DNAPL source
strengths (Section 5.1). The remainder of this section provides a conceptual look at how to define
the success of ISB system performance (Section 5.2) and some suggestions for measuring the
level of successful performance (Section 5.3).
Key points made in this section include the following:
• ISB will likely not achieve typical closure criteria, but can achieve functional remediation
objectives such as reducing mass flux from the source, site remediation timeframes, or life-
cycle site management costs.
• ISB will be most effective in relatively permeable, homogeneous aquifers in which the
DNAPL is distributed predominantly as "ganglia," or residual, non-pooled accumulations.
• Measuring the progress or success of ISB is an important issue that should be carefully
considered. Typical metrics important in evaluating ISB include molar mass balances of the
chlorinated ethenes and their degradation byproducts.
5.1 Potential for ISB to Achieve Functional Site Remediation Objectives
As discussed in Section 3.2, the absolute objective of site remediation should be the protection of
human health and the environment. However, a range of functional site remediation objectives
are commonly used at many chlorinated ethene DNAPL sites because there is substantial
uncertainty about the means to achieve the absolute objective and because there is difficulty
developing quantitative well-defined metrics for this absolute objective. Under most conditions,
ISB of chlorinated ethene DNAPL sources is unlikely to meet clean closure criteria across an
entire site. In fact, it is rare that any chlorinated ethene DNAPL source depletion technology will
meet this rigorous standard. Therefore, it may be necessary to develop less restrictive site-
specific, risk-based functional objectives for source depletion in the vast majority of cases
(Kavanaugh et al. 2003, NRC 2005). Following is a discussion of several possible functional site
remediation objectives that can be applied to ISB of chlorinated ethene DNAPL sources.
1. Mass Removal. The least restrictive functional objective is mass removal. This is probably the
most common stated metric of source depletion, i.e., how much total mass has been removed or
destroyed as a fraction of the estimated original mass. Although quantitative criteria are difficult
to develop or measure, ISB has been estimated to remove greater than 90% of the original mass
under favorable conditions (McDade et al. 2005, GeoSyntec 2004). In many cases, the goal is
simply to remove mass to the extent practicable, although many would argue that the goal should
be to remove sufficient DNAPL from the source zone to make a significant difference in the
future site care requirements.
2. Mass Flux/Concentration Reduction. In many other cases, the objective is to reduce the
contaminant concentrations in groundwater leaving the source area, or less commonly the mass
flux or mass discharge from the plume. Because the relationship between mass reduction and
mass flux or concentration is not necessarily strictly linear, the reduction can be more or less
than the mass removal estimate suggests (Enfield et al. 2002, Sale and McWhorter 2001, Stroo et
al. 2003). Typically, the reduction in concentration or flux (expressed as a fraction or percentage
of the pre-treatment levels) will be less than the mass removal in homogeneous hydrogeologies
46
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DN APL Source Zones October 2005
and greater than the mass removal in more heterogeneous ones (Stroo et al. 2003, Wood et al.
2003).
3. Plume Life Reduction. Often, the stated or assumed goal of source depletion is to reduce the
lifetime of the associated dissolved phase plume. It is often assumed that there will be some
relatively simple relationship between plume duration and mass removal. However, it is clear
that such a simple relationship is unlikely because concentrations tend to plateau following a
first-order decay kinetic pattern in which the majority of the life of a plume will be characterized
by relatively low source mass and relatively low dissolved phase concentrations (Newell and
Adamson, in press).
4. Life-Cycle Cost Reduction. Finally, the objective may be to reduce the life-cycle costs for site
management. This objective is also difficult to define or estimate, given the limited history of
any aggressive chlorinated ethene source depletion efforts. Since plumes will continue to require
some form of containment for long periods of time following most source depletion efforts and
the long-term operations and maintenance costs for these containment technologies can represent
a substantial fraction of the life-cycle costs, it may be very difficult to make significant
reductions in these costs at most sites unless relatively low-cost source depletion technologies
can be used. For example, implementing a source depletion technology that facilitates the use of
MNA following source treatment and mitigates the need for a pump and treat system would
substantially reduce life-cycle cost.
ISB of chlorinated ethene source zones remains a developing technology, but there is sufficient
experience to make some generalizations about its potential efficacy for meeting the previously
discussed functional remediation objectives for different types of sites. Table 5-1 summarizes the
current consensus of the authors regarding ISB potential for different hydrogeologic and source
conditions, although exceptions to these generalizations undoubtedly exist. In preparing this
summary, the NRC (2005) categorization of hydrogeologic settings has been used:
• Type I sites are characterized as granular, with mild heterogeneity and moderate to high
permeability.
• Type II sites are granular, with mild heterogeneity and low permeability.
• Type III sites have granular structure, with moderate to high heterogeneity.
• Type IV sites are fractured media with low matrix porosity.
• Type V sites are fractured with high matrix porosity.
These are idealized sites but, in general, the difficulty in addressing DNAPL sources within these
settings increases from Type I through Type V because it is increasingly difficult to deliver
remedial agents to the DNAPL.
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones
October 2005
Table 5-1. The ability of ISB to meet remediation objectives'1
.vass Removal
Co?K!entrafi&n
Redaction
Mtm Flux
Redaction
Reduction of
Source Migtahon
flume See
Redaction
changes in source
Taxieity or Mobtfity
Efinranalion cH dorrieis
to Subsequent
Remedial Action'
0
o
o
o
o
o
o
I) Granular Media wrt&
Mild heterogeneity and
Moderate to High
PermeabMifv
o — *
O
0
©
0
Q
0
O
it) Granular Medkr vrifh
,VfM Heterogeneity and
low fermeabtfity
O
O
O
o
0
o
o
IHJ Grammar t^edta
tigh Helerogenerty
Hydrogeotogsc Setting
O
o
0
o
o
o
o
0
0
O
Q
O
0
0
IV) Practiced taedki V) Proceed
with Low Matrix Porosity we^Jia
with High wafriK Porosity
\^_) ^nfcna^-i of r'i-itr'ed ra'L'c c"en.cnc-r
* 7%« /aAte represents the current consensus
generalizations undoubtedly exist.
v/ew q/ //^^ authors about ISB potential under different conditions,
although exceptions to these
For the purpose of evaluating ISB, it is necessary to further characterize sources as either low-
strength or high-strength. Low-strength sources are characterized by primarily residual and
discontinuous DNAPL distributions, or in the terminology of Christ et al. (2005), high "ganglia-
to-pool ratios" (i.e., G:P ratios of 1.0 or greater). That is, over half of the total DNAPL present
can be found in discontinuous ganglia or as material sorbed onto the aquifer particles. In
contrast, high-strength sources have G:P ratios below 0.3. That is, over 70% of the total DNAPL
mass is present as "pools" or accumulations of free product within the subsurface in which the
DNAPL content exceeds residual saturation.
In reality, most sources are more complex than this categorization suggests. In addition, it is
technically difficult to determine the average source strength at most DNAPL sites. Nevertheless,
this type of classification can be useful in evaluating the feasibility of ISB or other source
depletion technologies.
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DN APL Source Zones October 2005
It should be remembered that most experience with ISB has been over relatively short time
periods. This limited experience has two implications important to this analysis. First, it is
difficult to predict the long-term impacts of treatment, particularly on plume longevity or life-
cycle costs. Second, it is also difficult to predict the impacts of longer ISB treatment durations.
Continuing ISB treatment for a period of several years may well produce greater decreases in
mass and flux, even in difficult hydrogeologic environments or with high-strength sources, while
remaining cost-competitive. There is considerable interest in the potential for longer-term ISB
treatment, so this assessment must be viewed as the current consensus regarding a rapidly-
developing technology. The current understanding of the technology's potential is likely to
change as practitioners gain further experience.
5.2 Defining and Measuring Success of ISB Application for Chlorinated Ethene DNAPL
Source Treatment
The functional site remediation objectives often represent the scientific measure against which a
treatment technology is judged to be successful. Conceptually, there are essentially two ends of
the spectrum for measuring this success. The first end of the spectrum is to define success as a
measurable reduction in the cost of due care for the DNAPL source. For example, the ISB
treatment might result in partial source removal, thereby reducing mass transfer to the aquifer to
a level that allows natural attenuation of the remaining mass. This end of the success spectrum is
one that responsible parties can more easily support, and the question of whether it is achievable
is not so controversial. The other end of the spectrum for measuring success is to remove enough
of the DNAPL mass so that groundwater concentrations are compliant with applicable drinking
water standards at all possible points of measurement. Measuring success in this way often
generates a great deal of debate, especially because the likelihood of total elimination of a long-
standing DNAPL source from an aquifer is very low.
Meeting a functional site remediation objective or a series of functional objectives is, perhaps,
the most intuitive way to judge remediation activities. It is important to note that EPA often
views a site remediation strategy for complicated groundwater cleanups as a phased approach,
which may include intermediate performance objectives to demonstrate progress toward
achieving the final cleanup goals. EPA refers to these objectives as "intermediate" because
actions taken to meet these objectives will typically occur after a facility achieves its short-term
protection goals, but before it achieves all final cleanup goals. EPA encourages regulators and
facilities to establish intermediate objectives when they can use such goals to demonstrate
progress toward meeting the ultimate final cleanup goals (USEPA 2002, section 3.0).
To determine whether ISB has resulted in significant chlorinated ethene DNAPL source zone
treatment, at least two important measures can be considered: the contaminant molar balance and
increasing molarities of total alkenes. These two measures of success are discussed in the
following sections.
5.2.1 Contaminant Molar Balance
The dechlorination reaction sequence provides one mole of dechlorinated product molecules for
every mole of starting material. That is, if 1.0 mole of PCE is degraded and close to 1.0 mole of
49
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
dechlorination products (TCE, DCE, VC, and/or ethene) is observed, it could be concluded that
enhanced reductive dechlorination is the mechanism responsible for the decrease of PCE.
Alternatively, if 1.0 mole of PCE is degraded and only 0.1 mole of dechlorination products is
observed, it is more difficult to conclude that enhanced reductive dechlorination is the
mechanism responsible for the decrease of PCE. It is possible that anaerobic oxidation or abiotic
dechlorination reactions has caused the disappearance, but those mechanisms are not enhanced
reductive dechlorination in the sense of this discussion. This document is not meant to address
methods to design, control, or document those processes. Moreover, closing the mass balance to
1.0 or greater demonstrates that the displacement of aquifer water by injected fluids is not the
cause of any observed contaminant decrease.
5.2.2 IncreasinR Molarities of Total Alkenes
When enhanced reductive dechlorination and its related processes dechlorinate sorbed-phase
mass of PCE or TCE, the total molarity of chlorinated ethenes may increase significantly. In
other words, the sum in moles per liter of
PCE + TCE + cis-DCE + VC + ethene + ethane
may be larger than that which would have been estimated from the mass of the PCE or TCE
found in the dissolved phase. This characteristic can only occur if sorbed or nonaqueous-phase
mass is being dechlorinated.
5.3 Stakeholder Issues
One measure of success for any site remediation project is how well the remediation satisfies the
expectations of concerned stakeholders. As with any site remediation project, stakeholder
concerns must be addressed to successfully implement ISB. Stakeholder input is critical and
should be sought at the earliest opportunity for any site where ISB is being considered as a
remediation strategy. To allow the public to ask appropriate questions about the efficacy of the
various alternative remediation options and to provide useful input to the informed decisions
about whether ISB is the most viable remediation option, information should be provided to help
the public understand the various advantages and disadvantages of ISB, along with other
proposed alternative treatment methods.
Among other things, stakeholders should
• understand the various assumptions which will be used in the groundwater model;
• know if the ISB technology is to stand alone or if it is part of a treatment train to reach the
desired end;
• have a visual idea of what the ISB technology will require logistically, such as drill rigs,
power supply, and the number of truck trips required to transport materials;
• know the noise implications of the technology selected;
• understand what the mass balance implications are for each technology selected, as well as
the potential consequences of daughter products and ISB byproducts. For instance, if
hydrogen sulfide or methane might be generated by an ISB technology, will there be a gas
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
collection system installed? How long will it operate? Will any metals be mobilized due to
the reducing conditions?;
• know how each technology will affect water quality, water table levels, flow rates, and
directions of groundwater flow;
• know that a technology may push contaminants deeper into the aquifer or bedrock or
volatilize the contaminant and allow migration into the vadose zone;
• understand the length of time for remediation;
• understand the design and expected performance of the monitoring system, as well the
monitoring requirements for post closure.
6. CONCLUSIONS
ISB of chlorinated ethene DNAPL source areas is a viable, emerging technology that has been
tested at a few sites in the U.S. and abroad. Even though ongoing research to evaluate, document,
and develop ISB strategies for addressing chlorinated ethene DNAPLs is still limited, initial
modeling studies, laboratory treatability tests, and pilot-scale demonstrations are encouraging.
Based on the limited but growing number of studies to date about this technology, the following
conclusions can be made:
• Effectiveness of ISB will be site-specific and largely dependent on the site geology and the
distribution of DNAPL in the subsurface.
• Implementation of ISB will require sufficient dechlorinating activity by either indigenous or
bioaugmented microorganisms and will likely require the addition of an electron donor
(biostimulation).
• ISB can be used for source containment and/or source mass removal, although applications
for containment will likely be successful over a wider variety of sites and hydrogeologic
conditions.
• Adverse impacts of ISB on secondary water quality objectives will need to be carefully
balanced against the benefits accruing from the removal of the target contaminants.
• ISB may be a cost-competitive containment technology, although the use of low-cost
electron donor amendment strategies (i.e., passive or semi-passive) will be essential.
ISB is not "one size fits all." Like any technology, ISB is most effective when applied
appropriately. ISB should be applied only when site conditions and geology are favorable for its
deployment. The site conditions, nature of contamination, and site remediation objectives should
all be considered before applying ISB.
When applied appropriately, ISB can be an effective and relatively inexpensive technology for
the remediation of chlorinated ethene DNAPLs. As these remediation systems are becoming well
understood and implementation continues, ISB shows promise in having the potential to play a
significant role in the cleanup of highly problematic DNAPL plumes and source areas. However,
because the nature of DNAPL sources is complex and the possible definitions of successful
system performance are quite varied, it is difficult to establish common metrics by which to
judge results and measure performance. Because of these issues, it is possible that the efficacy of
ISB for DNAPL source zones will remain a controversial and unsettled issue for the foreseeable
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
future.
ISB systems for DNAPL treatment in groundwater may face significant regulatory issues that
require careful attention as multiple regulatory authorities may become involved in oversight and
permitting and the level of interaction needed with the regulatory agencies may be higher than
when applying more traditional remediation technologies. The introduction of chemicals to effect
remediation of recalcitrant compounds, particularly the chlorinated solvents in DNAPL source
zones, is occurring with increasing frequency. In situ treatments have been applied in many
states. Howsoever those injections were permitted, they provide a pathway to regulatory
approval for ISB. Many of the historical objections to the introduction of the electron donor
amendments for remediation were institutional in nature and resided in state drinking water and
water quality programs (ITRC 1998). Those objections have subsided, as evidenced by the
increase in the number of in situ remedies variously reported. Available guidance from EPA
provides an excellent framework and roadmap for the path to regulatory approval for injection
and re-injection associated with ISB.
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and Biodegradation for Enhancing In Situ Dissolution of Nonaqueous-Phase Liquids."
Journal Contam. Hydrology, Vol. 12, pp. 103-132.
Seagren, E.A., B.E. Rittmann, and A.J. Valocchi. 1994. "Quantitative Evaluation of the
Enhancement of NAPL-Pool Dissolution by Flushing and Biodegradation."
Environmental Science and Technology, 28:833-839.
Sewell, G.W., S.C. Mravik, and A.L. Wood. 2000. "Field Evaluation of Solvent Extraction
Residual Biotreatment (SERB)." In Proceedings of the 7th International FZK/TNO
Conference on Contaminated Soil, Thomas Telford Publishing. Contaminated Soil 2000,
2:982-988
http://www.epa.gov/tio/download/newsltrs/gwc0600.pdf)
Siegrist, R. and W. Slack. 2000. Remediation of DNAPLs in Low Permeability Soils, Innovative
Technology Summary Report - OST/TMS ID 163. Subsurface Contaminant Focus Area.
DOE/EM-0550.
http://apps. em.doe.gov/OST/pubs/itsrs/itsrl63.pdf
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
Smatlak, C.R., J.M. Gossett and S.H. Zinder. 1996 "Comparative Kinetics of Hydrogen
Utilization for Reductive Dechlorination of Tetrachloroethene and Methanogenesis in a
Anaerobic Enrichment Culture." Environmental Science and Technology, 30:2850-2858.
Smidt, H., A.D.L. Akkermans, J. van der Oost, and W.M. de Vos. 2000 "Halorespiring Bacteria-
Molecular Characterization and Detection." Enzyme and Microbial Technology,
27(10):812-820.
Song, D.L., M.E. Conrad, K.S. Sorenson and L. Alvarez-Cohen. 2002. "Stable Carbon Isotope
Fractionation during Enhanced In-Situ Bioremediation of Trichloroethene."
Environmental Science and Technology, 36(10):2262-2268.
Sorenson, K.S. 2002. "Enhanced Bioremediation for Treatment of Chlorinated Solvent Residual
Source Areas," Chlorinated Solvent and DNAPL Remediation - Innovative Strategies for
Subsurface Cleanup, ACS Symposium Series 837, American Chemical Society,
Washington, D.C., pp. 119-131.
http://www.clu-in.org/studio/napl 121002/59/3 2732bw.pdf
Stroo, H.F., M. Unger, C.H. Ward, M.C. Kavanaugh, C. Vogel, A. Leeson, J.A. Marqusee and
B.P. Smith. 2003. "Remediating Chlorinated Solvent Source Zones." Environmental
Science and Technology, 37:224A-230A.
Sutherson, S.S. and F.C. Payne. In Situ Bioremediation. CRC Press: Boca Raton, Florida. 2005.
U.S. DOE. 2002. Enhanced In Situ Bioremediation. Innovative Technology Summary Report.
U.S. DOE, Office of Science and Technology, Washington, DC. DOE/EM-0624.
http://apps.em.doe.gov/ost/pubs/itsrs/itsr2410.pdf
U. S. DOE. 1996. Lasagna ™ Soil Remediation: Innovative Technology Summary Report. U.S.
DOE, Office of Environmental Management, Office of Science and Technology.
DOE/EM-0308.
http://web.em.doe.gov/plumesfa/intech/lasagna/index.html
U.S. EPA (Keely, J.F.). 1989. Performance Evaluations of Pump-and-Treat Remediations.
EPA/5404-89/005.
U.S. EPA. 1992. Evaluation of Ground-water Extraction Remedies: Phase II, Volume 1 -
Summary Report. Office of Emergency and Remedial Response, Washington, D.C.,
Publication No. 9355.4-05.
U.S. EPA. 1995. In Situ Remediation Technology Status Report: Thermal Enhancements. Office
of Solid Waste and Emergency Response, Technology Innovation Office, Washington,
D.C., EPA/542-K-94-009. http://www.epa.gov/tio/download/remed/thermal.pdf
61
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ITRC-Overview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones October 2005
U.S. EPA. 1996. Pump-and-Treat Groundwater Remediation: A Guide for Decision Makers and
Practitioners. Office of Research and Development, Washington, D.C., EPA/625/R-
95/005.
U.S. EPA. 1998. Technical Protocol for Evaluating Natural Attenuation of Chlorinated Solvents
in Ground Water. Office of Research and Development, Washington, D.C., EPA/600/R-
98/128. http://www.epa.gov/ada/download/reports/protocol.pdf
U.S. EPA. 1999. Groundwater Cleanup: Overview of Operating Experience at 28 Sites.
Washington, D.C., EPA 542-R-99-006.
http://www.epa.gov/tio/download/remed/ovopex.pdf
U.S. EPA. 2000. Engineered Approaches to In Situ Bioremediation of Chlorinated Solvents:
Fundamentals and Field Applications. Office of Solid Waste and Emergency Response,
Washington, D.C., EPA 542/R/00/008.
http://www.epa.gov/tio/download/remed/engappinsitbio.pdf
U.S. EPA. 2002. Handbook of Groundwater Protection and Cleanup Policies for RCRA
Corrective Action. EPA/530/R-01/015.
http://www.epa.gov/epaoswer/hazwaste/ca/resource/guidance/gw/gwhandbk/gwhbfinl.pdf
U.S. Geological Survey. 1997. Preliminary Conceptual Models of the Occurrence, Fate, and
Transport of Chlorinated Solvents in Karst Regions of Tennessee. 97-4097.
http://water.usgs.gov/pubs/wri/wri974097/text/figure 12.html
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Compounds." Environmental Science and Technology, 21:722-736.
Weidemeier, T., H. Rifai, C. Newell, and J. Wilson. 1999. Natural Attenuation of Fuels and
Chlorinated Solvents in the Subsurface. John Wiley & Sons, Inc., New York, New York.
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2004. "Impact of DNAPL Source Treatment on Contaminant Mass Flux." In Proceedings
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of Enhanced Anaerobic Bioremediation of Chlorinated Solvents, pp. 397-409.
Yang, Y. and P.L. McCarty. 2000. "Biologically Enhanced Dissolution of Tetrachloroethene
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Enhanced Tetrachloroethene DNAPL Dissolution." Environmental Science and
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APPENDIX A
List of Acronyms
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LIST OF ACRONYMS
AFCEE Air Force Center for Environmental Excellence
CAQ aqueous phase concentration
CSAT saturation concentration
CMS Corrective Measures Study
COC contaminants of concern
DCE dichloroethene
DOE U.S. Department of Energy
DNAPL dense nonaqueous phase liquid
EACO enhanced attenuation: chlorinated organics
ECOS Environmental Council of the States
EPA U.S. Environmental Protection Agency
ERD enhanced reductive dechlorination
ERIS Environmental Research Institute of the States
ESTCP Environmental Security Technology Certification Program
G:P ratio ganglia-to-pool ratio
HRC Slow Release Electronic Donor HRC-X™
ISCO in situ chemical oxidation
INEEL Idaho National Engineering and Environmental Laboratory
ISB in situ bioremediation
ITRC Interstate Technology and Regulatory Council
KOC organic carbon partition coefficient
MCL maximum contaminant level
MNA monitored natural attenuation
mV millivolts
ORP oxidation reduction potential
PCE perchloroethene
pE -logic [e~]
PNNL Pacific Northwest National Laboratories
PRP potentially responsible party
RCRA Resource Conservation and Recovery Act
RFH radio frequency heating
RPM remedial program manager
SCM site conceptual model
SEE steam enhanced extraction
SERB solvent extraction residual biotreatment
SERDP Strategic Environmental Research & Development Program
SPH six-phase heating
SVE soil vapor extraction
TAN Test Area North
TCA trichloroethane
TCE trichloroethene
VC vinyl chloride
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APPENDIX B
Glossary of Terms
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GLOSSARY OF TERMS
abiotic. Occurring without the involvement of living microorganisms.
advection. Transport of a solute by the bulk motion of flowing groundwater.
aerobic. Conditions for growth or metabolism in which the organism is sufficiently supplied
with molecular oxygen.
aerobic respiration. Process whereby microorganisms use oxygen as an electron acceptor to
generate energy.
aliphatic compounds. Acyclic or cyclic, saturated or unsaturated carbon compounds, excluding
aromatic compounds.
anaerobic. Environmental conditions requiring the absence of molecular oxygen.
anaerobic respiration. Process whereby microorganisms use a chemical other than oxygen as
an electron acceptor. Common "substitutes" for oxygen are nitrate, sulfate, iron, carbon
dioxide, and other organic compounds (fermentation).
bacteria. Any of a group of prokaryotic unicellular round, spiral, or rod-shaped single-celled
microorganisms that are often aggregated into colonies or motile by means of flagella that live
in soil, water, organic matter, or the bodies of plants and animals, and that are autotrophic,
saprophytic, or parasitic in nutrition, and important because of their biochemical effects and
pathogenicity.
bioaugmentation. The addition of beneficial microorganisms into groundwater to increase the
rate and extent of anaerobic reductive dechlorination to ethene.
biodegradation. Breakdown of a contaminant by enzymes produced by bacteria.
biomass. Material produced by the growth of microorganisms.
bioremediation. Use of microorganisms to biodegrade contaminants in soil and groundwater.
biostimulation. The addition of an organic substrate into groundwater to stimulate anaerobic
reductive dechlorination.
biotransformation. Microbiologically catalyzed transformation of a chemical to some other
product.
chlorinated solvent. Organic compounds with chlorine substituents that commonly are used for
industrial degreasing and cleaning, dry cleaning, and other processes.
chlorinated ethene. Organic compounds containing two double-bonded carbons and possessing
at least one chlorine substituent.
co-metabolism. A reaction in which microorganisms transform a contaminant even though the
contaminant cannot serve as an energy source for growth, requiring the presence of other
compounds (primary substrates) to support growth.
dechlorination. The removal of chlorine atoms from a compound.
dense, nonaqueous phase liquid (DNAPL). An immiscible organic liquid that is denser than
water (e.g., tetrachloroethene).
DNAPL architecture. The spatial distribution of DNAPL mass in the subsurface.
desorption. The converse of sorption.
diffusion. The process net transport of solute molecules from a region of high concentration to a
region of low concentration caused by their molecular motion in the absence of turbulent
mixing.
dilution. A reduction in solute concentration caused by mixing with water at a lower solute
concentration.
dispersion. The spreading of a solute from the expected groundwater flow path as a result of
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mixing of groundwater.
electron. A negatively charged subatomic particle that may be transferred between chemical
species in chemical reactions.
electron acceptor. A compound to which an electron may be transferred (and is thereby
reduced). Common electron acceptors are oxygen, nitrate, sulfate, ferric iron, carbon dioxide
and chlorinated solvents, such as tetrachloroethene and its daughter products trichloroethene,
cis-l,2-dichloroethene, and vinyl chloride.
enhanced bioremediation. An engineered approach to increasing biodegradation rates in the
subsurface.
electron donor. A molecule that can transfer an electron to another molecule. Organic
compounds, such as lactate, ethanol, or glucose, are commonly used as electron donors for
bioremediation of chlorinated ethenes.
functional objectives. Measures of the performance of a remediation project with well-defined
and quantifiable metrics that are the means of achieving the absolute objective (i.e., the
protection of human health and the environment).
ganglia. Zones of porous media containing DNAPL that are cut off and disconnected from the
main continuous DNAPL body.
growth substrate. An organic compound upon which a bacteria can grow, usually as a sole
carbon and energy source.
hydraulic conductivity. A measure of the capability of a medium to transmit water.
hydraulic gradient. The change in hydraulic head (per unit distance in a given direction,
typically in the principal flow direction.
inorganic compound. A compound that is not based on covalent carbon bonds, including most
minerals, nitrate, phosphate, sulfate, and carbon dioxide.
in situ bioremediation. The use of biostimulation and bioaugmentation to create anaerobic
conditions in groundwater and promote contaminant biodegradation for the purposes of
minimizing contaminant migration and/or accelerating contaminant mass removal.
intrinsic bioremediation. A type of in situ bioremediation that uses the innate capabilities of
naturally occurring microbes to degrade contaminants without taking any engineering steps to
enhance the process (including the addition of any amendment).
mass transfer. The irreversible transport of solute mass from the nonaqueous phase (i.e.,
DNAPL) into the aqueous phase, the rate of which is proportional to the difference in
concentration.
metabolism. The chemical reactions in living cells that convert food sources to energy and new
cell mass.
methanogen. Strictly anaerobic Archaeabacteria, able to use only a very limited substrate
spectrum (e.g., molecular hydrogen, formate, methanol, carbon monoxide, or acetate) as
electron donors for the reduction of carbon dioxide to methane.
microcosm. A batch reactor used in a bench-scale experiment designed to resemble the
conditions present in the groundwater environment.
microorganism. An organism of microscopic or submicroscopic size including bacteria.
mineralization. The complete degradation of an organic compound to carbon dioxide.
natural attenuation. Naturally-occurring processes in soil and groundwater environments that
act without human intervention to reduce the mass, toxicity, mobility, volume, or concentration
of contaminants in those media.
oxidation. Loss of electrons from a compound. During anaerobic reductive dechlorination, the
B-2
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electron donor (e.g., lactate) is oxidized.
petroleum hydrocarbon. A chemical derived from petroleum by various refining processes.
Examples include gasoline, fuel oil, and a wide range of chemicals used in manufacturing and
industry.
plume. A zone of dissolved contaminants. A plume usually originates from a source and extends
in the direction of ground water flow.
pool. An accumulation of DNAPL above a capillary barrier.
reduction transfer of electrons to a compound. During anaerobic reductive dechlorination, the
electron acceptor (i.e., the chlorinated ethene) is reduced.
reductive dechlorination. The removal of chlorine from an organic compound and its
replacement with hydrogen (see reductive dehalogenation).
saturated zone. Subsurface environments in which the pore spaces are filled with water.
site conceptual model. A hypothesis about how releases occurred, the current state of the source
zone, and current plume characteristics (plume stability).
sorption. The uptake of a solute by a solid.
source zone. The subsurface zone containing a contaminant reservoir sustaining a plume in
groundwater. The subsurface zone is or was in contact with DNAPL. Source zone mass can
include sorbed and aqueous-phase contaminant mass as well as DNAPL.
substrate. A compound that microorganisms use in the chemical reactions catalyzed by their
enzymes.
sulfate reducer. A microorganism that exists in anaerobic environments and reduces sulfate to
sulfide.
volatilization. The transfer of a chemical from its liquid phase to the gas phase.
B-3
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APPENDIX C
ITRC Contacts, Fact Sheet, and Product List
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ITRC CONTACTS
Naji Akladiss, P.E. (Team Leader)
Maine Dept. of Environmental Protection
P: 207-287-7709
F: 207-287-7826
Naji.n.akladiss@maine.gov
Smita Siddhanti, Ph.D. (Program Advisor)
EnDyna, Inc.
2230 Gallows Rd. Suite 380
Vienna, VA 22027
P: 703-289-0000x201
F: 703-289-9950
siddhanti@endyna.com
Patricia Harrington, Ph.D.
EnDyna, Inc.
2230 Gallows Rd. Suite 380
Vienna, VA 22027
P: 703-289-0000 x202
F: 703-289-9950
pharrington@endyna.com
Douglas Bradford
Louisiana Dept. of Environmental Quality
P: 225-219-3408
F: 225-219-3474
Douglas.Bradford@la.gov
James Brannon, P.E., C.S.P.
Northern New Mexico Citizens Advisory
Board
P: 505-661-4820
F: 505-661-4821
Jbrannon@prsmcorp.com
Anne W. Callison
Barbour Comm. Inc.
Lowry AFB RAB
P: 303-331-0704
F: 303-331-0704 hit *2 while ringing for fax
Awbarbour@aol.com
Ronald F. Carper, Jr., P.G.
New Jersey Schools Construction Corp.
P: 609-777-1805
F: 609-278-9508
Rcarper@niscc.com
James Cashwell
MACTEC Engineering and Consulting, Inc.
P: 770-421-3433
F: 770-421-3486
jmcashwell@mactec.com
Charles G. Coyle, P.E.
U. S. Army Corps of Engineers
P: 402-697-2578
F: 402-697-2595
charles.g.coyle@usace.army.mil
William De Valle-Gonzalez
U.S. EPA Region VII
P: 913-551-7115
F: 913-551-9115
Delvalle-Gonzalez.William@epa.gov
Linda Fiedler
U.S. EPA Technology Innovation Office
(5102G)
1200 Pennsylvania Avenue, NW
Washington, DC 20460
P: 703-603-7194
F: 703-603-9135
fiedler.linda@epa.gov
David L. Fleming
Thermal Remediation Services, Inc.
P: 425-396-4266
F: 425-396-5266
Dfleming@thermalrs.com
Joseph E. Gillespie
North Wind, Inc.
P: 208-557-7898
F: 208-528-8714
Jgillespie@nwindenv.com
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Dibakar (Dib) Goswami, Ph.D.
Washington Dept. of Ecology
P: 509-372-7902
F: 509-372-7971
dgos461 @ecy.wa.gov
Paul Hadley
California-EPA, Dept. of Toxic Substances
Control
P: 916-324-3823
F: 916-327-4494
phadley@dtsc.ca.gov
Eric Hausamann, P.E.
New York State Dept. of Environmental
Conservation
P: 518-402-9759
eghausam@gw.dec.state.ny.us
Chris Hawkins
Mississippi Dept. of Environmental Quality
P: 601-961-5775
F: 601-961-5300
Chris_hawkins@deq.stat.ms.us
Eric Hood, Ph.D., P.E.
GeoSyntec Consultants
130 Research Lane Suite 2
Guelph, Ontario
N1G5G3
Canada
P: 519-822-2230 (ext. 225)
F: 519-822-3151
ehood@geosyntec.com
Judie A. Kean
Florida Dept. of Environmental Protection
2600 Blairstone Road
MS 4520
Tallahassee, FL 32399
P: 850-245-8973
F: 850-245-8976
Judie.Kean@dep.state.fl.us
Mark Kluger
Dajak, LLC
P: 302-665-6651
F: 302-655-0912
Mkluger@dajak.com
Stephen Koenigsberg, Ph.D.
Regenesis Bioremediation Products
P: 949-366-8000
F: 949-366-8090
Skoenigsberg@regenesis. com
Konstantinos Kostarelos, Ph.D.
Polytechnic University
P: 718-260-3260
F: 718-260-3433
dino@poly.edu
James Langenbach, P.E.
GeoSyntec Consultants, Inc
P: 321-269-5880
C: 321-403-3784
F: 321-269-5813
Jlangenbach@GeoSyntec. com
Carmen Lebron
U. S. Naval Facilities Engineering Service
Center ESC411 1
100 23rd. Ave.
Port Hueneme, CA 93043
P: 805-982-1616
F: 805-982-4304
carmen.lebron@navy.mil
Kira Pyatt Lynch
U.S. Army Corps of Engineers
P: 206-764-6918
F: 206-764-3706
Kira.P.Lynch@NWS02.usace.army.mil
Tamzen Macbeth
Northwind, Inc.
P: 208-528-8714
Tmacbeth@northwind-inc.com
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Dave Major, Ph.D.
GeoSyntec Consultants, Inc
P: 519-822-2230x232
F: 519-822-3151
dmaj or@geosyntec. com
Susan C. Mravik
U.S. EPA ORD / NRMRL / GWERD / SRB
P: 580-436-8553
F: 580-436-8703
mravik.susan@epa.gov
Todd Mullins
Kentucky Dept. of Environmental Protection
P: 502-564-6717x338
F: 502-564-2705
Todd.mullins@ky.gov
Michael Nelson
Texas Dept. of Environmental Quality
P: 512-239-5361
F: 512-239-1212
minelson@tceq.state.tx.us
Ian T. Osgerby, Ph.D.
U.S. Army Corps of Engineers
New England District
P: 978-318-8631
F: 978-318-8614
Ian.t.osgerby@usace.army.mil
Kalpesh Patel, P.E.
U.S. Air Force
P: 210-671-5344
F: 210-671-0335
Kalpesh.Patel@lackland.af.mil
Frederick C. Payne, Ph.D.
ARCADIS, Inc.
25200 Telegraph Road
Southfield, MI 48034
P: (248) 936-8730
F: (248) 936-8731
FPayne@arcadis-us.com
Robert Pierce
Georgia Environmental Protection Division
P: 404-656-2833
F: 404-651-9425
Bob_pierce@dnr.state.ga.us
Gail L. Pringle
U.S. Naval Facilities Engineering Service
Center
P: 805-982-1411
F: 805-982-4304
gail.pringle@navy.mil
Suresh Puppala
PMK Group
P: 908-497-8900x137
F: 908-497-8943
Spuppala@pmkgroup.com
David Rathke
US EPA Region 8
P: 303-312-6016
F: 303-312-6067
Rathke.david@epa.gov
Rey Rodriguez
H2O-R1 Consulting Engineers, Inc.
P: 626-852-1235
F: 626-852-1285
Reyrhzorz@aol. com
Guy W. Sewell
East Central University
PMB S-78
1100E. 14th St.
Ada, OK 74820
P: 580-310-5547
F: 680-310-5606
guy_sewell@cs.ecok.edu
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Travis Shaw
U.S. Army Corps of Engineers
Seattle District
4735 E. Marginal Way
S. Seattle, WA 98134
P: 206-764-3527
F: 206-764-3706
travis.c.shaw@NWS02.usace.army.mil
G.A. (Jim) Shirzi, Ph.D., P.O.
Oklahoma Dept. of Agriculture, Food, and
Forestry
2800 N. Lincoln
Oklahoma City, OK 73105
P: (405)522-6144
F: 405-522-6357
Gashirazi@cox.net
Donovan Smith
JRW Bioremediation, LLC
P: 913-438-5544x113
F: 913-438-5554
dsmith@jrwbiorem.com
Michael B. Smith
Vermont Dept. of Environmental
Conservation
P: 802-241-3879
F: 802-241-3296
Michael.smith@anr.state.vt.us
Kent S. Sorenson, Jr., Ph.D., P.E.
Camp Dresser & McKee
1331 17th Street, Suite 1200
Denver, CO 80202
P: 303-383-2430
M: 303-298-1311
F: 303-293-8236
SorensonKS@cdm.com
Hans Stroo, Ph.D.
HydroGeoLogic, Inc./SERDP
300 Skycrest Drive
Ashland, OR 97520
P: 541-482-1404
C:541-301-3583
F: 541-552-1299
hstroo@hgl.com
Larry Syverson
Virginia Dept. of Environmental Quality
P: 804-698-4271
F: 804-698-4327
Iwsy verson@deq. Virginia, gov
Anna Willett
Regenesis Bioremediation Products
lOHCalleSombra
San Clemente, CA 92673
P: 949-366-8001 xl!4
F: 949-366-8090
anna@regenesis.com
Ryan A. Wymore, P.E.
Camp Dresser & McKee
P: 720-264-1110
F: 303-295-1895
wymorera@cdm. com
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The Interstate Technology &
Regulatory Council (ITRC) is a
state-led coalition of regulators,
industry experts, academic, citi-
zen stakeholders, and federal
partners working together to
increase regulatory acceptance
of state-of-the-art environmental
technologies and approaches.
With its diverse mix of environ-
mental experts and stakeholders
from both the public and private
sectors and official participation
of more than 40 states, ITRC
builds consensus to eliminate
barriers to the use of new tech-
nologies so that states can
reduce compliance costs and
maximize resources. Our net-
work of more than 1 1,000 peo-
ple from all aspects of the envi-
ronmental community is a unique
catalyst for dialogue between
regulators and the regulated
community to build and share
technical knowledge about the
selection, approval, and appli-
cation of emerging technologies
Together, we're building the
stales' ability to expedite quality
environmental decision making
while protecting human health
and the environment.
Regulation is necessarily conservative
regarding deployment of new tech-
nologies, yet new technologies often
are key to achieving better results
sooner and at less cost. IIRC takes aim
squarely at this dilemma and, drawing
from the combined technical skills and
experience of participating state and
other agencies, makes the introduc-
tion and regulatory approval of new
technologies both quick and safe."
—Washington State Regulator
Shaping the future.
i / j i HP
Regulatory Acceptance
We create...
Guidance documents
ITRC's guidance documents include technology
overviews, case studies, and technical/
regulatory guidelines. These guidelines—
often incorporating decision trees—suggest
uniform data requirements for technology
demonstrations or appiovals State concur-
rence with ITRC guidance makes the permit-
ting process more uniform and efficient across
states, helping technology consultants and
vendors avoid the time and expense of meet-
ing different requirements in each state where
an innovative technology is proposed for use.
Training courses
ITRC develops and delivers free, live, interac-
tive, Internet-based training on emerging envi-
ronmental technologies and approaches We
also partner with industry and other organiza-
tions to develop inexpensive classroom courses
offered across the country Our cost-effective
training has successfully leached more than
15,000 state, federal, industry, and other
stakeholders When asked about the impact of
ITRC documents and training, 90% of respon-
dents indicate that the knowledge they've
gained will help them save lime or money—
usually both—and sometimes the savings
amount to millions.
Consensus in the
environmental community
Working in teams to cieale documents and
training, ITRC participants everage each
other's expertise The contentiousness that
often characterizes relations belween regula-
tors and the regulated community dissipates
as teams build understanding of the conditions
under which new technologies should be
applied, consensus about how they should be
regulated, and confidence in their merits
Sharing problems, information, and lessons
learned spreads news of successful solutions
and increases deployments of the most appro-
priate technologies and approaches.
-------
ITRC
is bringing about a culture change in environmental deci-
sion making, replacing long-standing adversarial relationships
with collaboration, consensus, and concurrence State regulators are
using ITRC guidance documents, training, and peer exchange to find
creative ways to reduce regulatory barriers to new environmental
technologies, cut approval time, and enhance their ability lo make
quality decisions As a result, regulated industries and contractors are
benefiting from reduced remediation costs and accelerated cleanup
schedules. ITRC's ultimate beneficiary is the public—through a
safer, healthier environment; redeveloped brownfields; and a better
return on lax dollars.
Finding better solutions
Lackland Air Force Base used the expertise, documents, and train-
ing of ITRC's Small Arms Firing Range Team to keep 3,500 truck-
loads of untreated soil off the highways and avoid the associated
transportation and disposal costs At base invitation, team member
Gary Beyer, RCRA Corrective Action specialist for the Texas
Commission on Environmental Quality, shared alternatives for dis-
posal of lead-contaminated soils examined during the development
of ITRC guidance. The soil was chemically stabilized and used to
shore up a failing ad|acent landfill, an alternative that saved well
over $1 0 million Beyer suggests that everyone involved with the
cleanup of hazardous waste sites "consider participating in the pro-
grams, attend Internet training courses, and use guidance docu-
ments developed by ITRC to examine using cutting-edge technolo-
gies and regulatory solutions developed and promoted by ITRC to
save time and money and promote the decreased risk from environ-
mental hazards "
Slashing remediation costs
ITRC guidance on enhanced in situ biodenitrification was used
extensively in developing the conceptual remedy for a New Jersey
industrial site and in preparing the pilot and treatability study plans
submitted to state regulators. "Use of the ITRC guidance saved our
client perhaps six months of time and about $10,000 in consulting
fees . on top of the remediation savings of between $250,000
and $1 5 million associated with the innovative alternative,"
according to the site's environmental consultant
ITRC guidance documents were also key to implementing a biore-
mediation remedy instead of a large pump-and-treat system at a
California chemical manufacturing facility The facility estimates
using ITRC guidance "saved at least a year of consulting time,
modeling costs, and other documentation that would have been
vl find the workshops extremely informative and
very valuable in gaining perspectives in the appli-
cation of new technologies. This includes both
remedial technologies and innovative characteri-
zation technologies such as the diffusion sampling
method. Ihc fact that the regulatory community
is involved helps to facilitate better acceptance of
certain technologies and allows the consultant to
understand what questions are important to the
regulators when proposing a new method."
—tnvironmental Consultant
We're mak ng
a difference
ITRC has documented hundreds of helpful applications of ITRC
documents and training beyond the examples presented here to
illustrate the range of benefits and beneficiaries. Credit is
shared, of course, with the developers of innovative technologies
and approaches and the project managers who blaze trails by
deploying them. More examples and aetails are available at
www. itrcweb. org.
needed to devel-
op an experimen-
tal design, con-
vince the agency,
and implement a
plan that would
have gotten us to
the same point.
ITRC protocols and
principles saved
our company at
least half a million
dollars " Further
savings of at least $14 million in capital costs and $3 million in
annual costs resulted because the facility was able to demonstrate,
with the help of ITRC documents, that in situ bioremediation could
work as the primary remedy.
ITRC guidance helped
with the installation of
permeable reactive
barriers in Colorado
and New Jersey, result-
ing in cost savings
measured in millions
Cutting approval time
ITRC's guidance and training for monitored natural attenuation
(MNA) of chlorinated solvents helped lead the Louisiana
Department of Environmental Quality to approve MNA at a
Monsanto plant Several potential remedies were examined for
addressing residual contamination near the soil-groundwater inter-
face ITRC information and training on implementing monitoring for
natural attenuation led to buy-in from LDEQ Although MNA does
require continued monitoring, overall savings of thousands of dol-
lars will occur over time as a result of the adoption of this remedy
"It takes ..energy to investigate new remedies and to break down
barriers to implement alternative technologies to cleanup ITRC infor-
mation and expertise gives confidence that solutions are good "
—Doug Bradford, LDEQ Environmental Technology Division
Results horn passive diffusion bag (PDB) sampling are being used to
determine additional removal or remediation steps to be taken at
Nebraska's Ogallala groundwater contamination site "It took some
time to determine if the PDBs were applicable, but the information
provided by ITRC allowed the decision to use PDBs to move for-
ward," says EPA's Diane Easley. The use of PDBs is anticipated to
save $20,000-$50,000 for this pro|ect alone The experience
gained at Ogallala also encouraged EPA to allow the use of PDBs
at other Nebraska Superfund sites contaminated with volatile
organic compounds
-------
Sharing expertise
ITRC documents and training helped consultant Mark Waltham
review a site remediation plan incorporating in situ chemical
oxidation "I was able to use knowledge gained from iSCO
training to confidently review the...plan The ITRC training got
me up the learning curve very quickly and the interactive nature
of the seminar allowed me to get quick answers to my concerns
aboul ihe technology from experts " The proposed strategy will
save severa hundred thousand dollars as well as reduce the
remediation time from 5-10 years down to 1-2 years.
"IIRC documents and training have helped South
Carolina regulators provide more effective and
efficient oversight at a multitude of sites. And in
sharing this common foundation of knowledge
with cleanup contractors and site owners, South
Carolina has streamlined the deployment of inno-
vative technologies and quickened the pace of
cleanup at contaminated sites.''
—R. Lewis Shaw, former Deputy Commissioner,
fouth Carolina Department of Health
and Environmental Control
Colorado wildland firefighters recently faced not only intense fires
but also potential encounters with unexploded ordnance (UXO) on
a former defense site ITRC UXO Team members from the state's
Department of Public Health and Environment helped staff from
the U S Army Corps of Engineers add local and fire manage-
ment protocol information to the team's UXO Basic Taming. Forty
firefighters attended the first course |ust one week after the need
for the training was recognized Subsequent iterations in other
states have delivered critical training that would have otherwise
been cost-prohibitive
Building stakeholder confidence
When community leaders learned that uranium had been on
a brownfield site in the San Francisco Bay area, they called
on members of the ITRC Radionudides Team to help deter-
mine the best protocol to ensure against subsurface contami-
nation ITRC expertise and synergy yielded a monitoring solu-
tion that increased public confidence and led to a quicker res-
olution of issues confronting site developers
Praise for
II products
I have worked on a number of very challenging DNAPL sites
around the world with some of the top researchers in the country,
many listed in your [DNAPL overview] document One of my largest
problems on these sites is finding a reference for the public and my
clients which is not too technical yet still thorough enough to explain
the many complications encountered on a DNAPL site. I have finally
found the right document! Thanks very much for this effort!"-—Michael
Moore, The Johnson Company, Montpelier, Vermont
The Diffusion Sampler Team's Resource CD contains nearly 70 arti-
ces and presentations on various diffusion samplers, as well as an
ITRC training video One consultant says, "to effectively coordinate
the PDB work performed by others at various remedial locations, I
needed a concise source of current information on diffusion sampling
procedures and results. The ITRC CD provided that information "
Another reports the CD "detailed enough to fully educate the user on
the key aspects associated with PDB sampling yet simple and inter-
esting enough to keep a captive audience We plan to [use] the CD
to educate our field staff."
"Substantial dollar savings were realized by using the phytotechnolo-
gies decision tree to determine the feasibility of using phytoextraction.
Classroom training and guidance documents were critical to the
design and implementation of a remediation plan."—Regulaloi with
the Central California Coast Regional Water Quality Control Board
"The ISCO training was very useful, timely, and presented in a pro-
fessional manner I am recommending that engineers in our organiza-
tion take the ITRC Internel training "—Ron Sanhni, Duke Energy
"ITRC instructors are the creme de la creme, the most knowledgeable
people covering the topics well known, lending credibility and inter-
est. The classes are good, solid material with a deep content. We
get to hear regulators and sub|ect matter experts discuss current,
ongoing issues outside our own backyard "—Teresa Feagin,
Weshnghouse Savannah River electronic training coordinator
The training was extremely cost-effective and provided a tremendous
amount of useful information No fluff!"—Industry participant
"The networking opportunity provided by ITRC classroom training is
great We're able to successfully bring new technologies into the
field more quickly as a result of the training and interaction with other
folks versed in chemical oxidation technology ITRGsponsored train-
ing, .has enhanced our ability to bring innovative, cost-effective solu-
tions to our clients "—Chuck Elmendorf, Panther Technologies, Inc
States recognize the value of ITRC, as shown by their growing support and participation
In 2003, states provided more than $2 million of in-kind support for ITRC
People fiom all 50 states and overseas participate in ITRC activities
The darker shaded states have designated official points of contact for ITRC
-------
We're organized for $ucce$$
learns focus on consensus priorities
The annual revision of ITRC's Five-Year Program Plan is an open
process for soliciting and reviewing proposed areas on which to
focus resources With representatives from state agencies, industry,
and citizen stakeholders and input from sponsoring federal agen-
cies, ITRC's seven-member Board of Advisors makes final decisions
on the technical areas and issues that ITRC's teams pursue. The 21
technical teams funded through this process in 2004 are address-
ing a diverse set of regulatory and technical issues related to many
of the nation's most pressing environmental problems (see table).
"IIRC resources and the industrywide dialogue
within IIRC are critical to ensure that innovative
technology is used and promoted appropriately."
—OoO Project Manager
One or more state regulators lead each team, and membership typ-
ically includes 15-25 representatives from state agencies, federal
agencies, industry, and other stakeholders Active members and the
organizations that they represent agree that they will spend 10% of
their professional time supporting team activities Most teams meet
regularly by conference call and three times a year in person
Teams are generally active for at least three years The firsl year is
devoted to deve oping a case study or technical overview docu-
ment that establishes the state of the practice for an emerging tech-
nology or addresses a specific problem area and identifies related
regulatory issues In their second year, teams develop a technica
and (egulatory guidance document, often with a flow chart to
guide decisions on technology selection, approval, and applica-
tion Finally, teams develop Internet-based and sometimes class-
room training to share and increase use of their guidance docu-
ments and to build consensus for their use. In some cases addition-
al documents and training topics are pursued
2ii(lu Ofrtflifil
UUT iCUiiiltU
Stale membership
More than 40 states and the District of Columbia are currently active
in ITRC. Every member state assigns a point of contact (POC) on the
State Engagement Team to help the state benefit from ITRC products
and activities and to raise its environmental technology priorities to a
national level Reaching out through its network of POCs, the State
Engagement Team works to transform the regulatory process by
encouraging state concurrence on ITRC guidance documents, helping
technical teams refine their training courses, and tracking where and
how ITRC's products and services are making a difference.
ITRC is hosted by the Environmental Council of the
States Experienced regulators' time contributed by
member states is the backbone of our program
Three federal agencies cosponsor and fund ITRC activities the
U.S. Department of Energy, the U.S. Department of Defense, and the
U S Environmental
Protection Agency.
Copyright 2004 by ITRC
' Alternative Landfill Technologies
Arsenic in Groundwater
Bioremediation of DNAPLs
Brownfields
Contaminated Sediments
Dense Nonaqueous Phase Liquids
Diffusion Samplers
| Ecological Enhancements
1 In Situ Chemical Oxidation
I Mitigation Wetlands
I MTBE and Other Fuel Oxygenates
1 Natural Attenuation and
Passive Bioremediation
Perchlorate
Permeable Reactive Barriers
Radionuclides
Remediation Process Optimization
Risk Assessment Resources
Sampling, Characterization,
and Monitoring
j Small Arms Firing Range
I Unexploded Ordnance
I Vapor Intrusion (Indoor Air)
Colorado
New Jersey
Maine
New York
New Jersey, Washington
New York
New Jersey
Colorado
Missouri, Louisiana
Washington, Minnesota
New Hampsfme
Florida, South Carolina
Nevada, California
New Jersey
Ohio, Colorado
New Jersey
California
New Jersey
New Jersey, Washington
Alaska, Colorado
Kansas, New Jersey
,
Environmental Technology and Reciprocity Partnership, In Situ Bioremediation, Low-
Temperature Thermal Desorption, Metals in Soils Phytotechnologies Plasma
Technologies, Policy, Six-State Memoiandum of Understanding, and Venfication
Join us!
ITRC is the only organization of its kind led by state regulators and
actively involving federal agencies, industry experts, and citizen
stakeholders Our network of environmental professiona s exceeds
1 1 ,000 and is still growing We we come your involvement in our
unique approach to tackling the issues facing the environmental
characterization, monitoring, and remediation fields There are
many ways you can participate with ITRC'
K Use ITRC guidance documents, and attend our training.
* If your state is not already a member, make participation in
ITRC official by appointing a POC to the State Engagement
Team.
•join a team — With just 1 0% of your time, you can have a posi-
tive impact on the regulatory process
* Be part of our annual conference, where you can learn the
most up-to-date information about regulatory issues surrounding
innovative technologies
"Submit proposals for new technical teams and pro|ects
• Fund ITRC's technica teams and other activities
h
wmihcweb.org to find out more
-------
* INTERS!)
* AHOiVin
iM I ^^^^^H^^^ 1 Zj
ff ^ ^ •
* ADO1ONHD3± *
INTERSTATE TECHNOLOGY 8
* REGULATORY COUNCIL
Product
List
October 2005
ITRC documents and other products listed
below are available on the ITRC Web site at
http://www.itrcweb.org.
Document types are shown using the following codes:
G Technical/Regulatory Guidelines
O Technical or Regulatory Overviews
C Case Studies
X Other
Accelerated Site Characterization (ASC)
Doc. #
Title
Description
Type
Partners
ASC-1
ITRC/ASTM Partnership for Accelerated
Site Characterization-FY-97 Summary
Report (December 1997)
ITRC review and input on ASTM Guide for
Expedited Site Characterization of Hazardous
Waste and report on the options for future
collaboration between ITRC and ASTM.
O
American Society for
Testing and Materials
(ASTM)
ASC-2
ITRC/USEPA Consortium for Site
Characterization Technology
Partnership-FY-97 Summary Report
(January 1998)
State participation in the USEPA verification of PCB
field analytical and well-head monitoring and soil
and soil-gas sampling technologies.
O
USEPA
ASC-3
Multi-State Evaluation of an Expedited
Site Characterization Technology: Site
Characterization and Analysis
Penetrometer System-Laser-Induced
Fluorescence (SCAPS-LIF) (May 1996)
California certification, USEPA verification, and
multi-state acceptance of the SCAPS sensor for in
situ subsurface field screening method for
polynuclear aromatic hydrocarbons (PAHs).
U.S. Navy, Army,
and Air Force
ASC-4
Multi-State Evaluation of the Site
Characterization and Analysis
Penetrometer System-Volatile Organic
Compounds (SCAPS-VOC) Sensing
Technoloqies (December 1997)
Evaluation and approval of SCAPS-deployed
hydrosparge VOC sensor for real-time in situ
detection of VOCs below the water table.
U.S. Army Corps of
Engineers,
Waterways
Experimental Station
Alternative Landfill Technologies (ALT)
ALT-1
Technology Overview Using Case
Studies of Alternative Landfill
Technologies and Associated
Regulatory Topics (March 2003)
Presents examples of flexibility in regulatory
approval of alternative landfill covers, research
about the use of alternative covers, and examples of
approved designs and constructed covers.
O
ALT-2
Technical and Regulatory Guidance for
Design, Installation, and Monitoring of
Alternative Final Landfill Covers
(December 2003)
Focuses on the decisions and facilitating the
decision processes related to design, evaluation,
construction, and post-closure care associated with
alternative final landfill covers.
Bioremediation of Dense Nonaqueous Phase Liquids
BIODNAPL-1
Overview of In Situ Bioremediation of
Chlorinated Ethene DNAPL Source Zones
(October 2005)
Brownfields (BRNFLD)
BRNFLD-1
Vapor Intrusion Issues at Brownfield
Sites (December 2003)
Overview of in situ bioremediation and some of the issues
to consider when selecting and designing an ISB system
for remediation of chlorinated ethene DNAPLs source
An overview of vapor intrusion, contaminant types
with vapor intrusion potential, brownfield sites'
potential for indoor air exposure from vapor
intrusion, and steps that can limit exposures.
Dense Nonaqueous Phase Liquids (DNAPLs)
DNAPLs-1
Dense Non-Aqueous Phase Liquids
(DNAPLs): Review of Emerging
Characterization and Remediation
Technologies (June 2000)
Reviews three types of emerging characterization
technologies—geophysical, cone penetrometer, and
in situ tracers—and two categories of emerging
remediation technologies—thermal enhanced
extraction and in situ chemical oxidation.
O
O
O
DNAPLs-2
DNAPL Source Reduction: Facing the
Challenge (April 2002)
Summarizes current regulatory attitudes regarding
DNAPL source zone remediation and outlines the
pros and cons of partial source removal.
O
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Page 2
ITRC Product List
DNAPLs-3
DNAPLs-4
Technical and Regulatory Guidance for
Surfactant/Cosolvent Flushing of
DNAPL Source Zones (April 2003)
An Introduction to Characterizing Sites
Contaminated with DNAPLs
(September 2003)
Summarizes information needed by regulators and
others in selecting and evaluating design and
implementation work plans for surfactant and
cosolvent flushing of DNAPLs.
Discusses scientific approaches and strategies used
to characterize sites that are known, or suspected,
to be contaminated with DNAPLs.
G
O
Dense Non-Aqueous Phase Liquids (DNAPLs) Continued
Doc. #
DNAPLs-5
Title
Strategies for Monitoring the
Performance of DNAPL Source Zone
Remedies (August 2004)
Description
Presents approaches to performance monitoring of
various in situ technologies for treating DNAPL
source zones
Type
G
Partners
Diffusion Sampler Protocol (DSP)
DSP-1
DSP-2
DSP-3
User's Guide for Polyethylene-Based
Passive Diffusion Bag Samplers to
Obtain Volatile Organic Compound
Concentrations in Wells (March 2001 )
ITRC Diffusion Sampler Resource CD,
Ver. 3 (July 2004)
Technical and Regulatory Guidance for
Using Polyethylene Diffusion Bag
Samplers to Monitor Volatile Organic
Compounds in Groundwater (February
2004)
A jointly developed protocol for determining when,
where, and how to use diffusion samplers for
groundwater sampling.
Contains DSP-3, nearly 80 articles and
presentations on various diffusion samplers, a two-
hour training video, and an AFCEE/Parsons field
sampling video.
Guidance for regulators, technology users, and
stakeholders to facilitate the use of polyethylene
diffusion bag sampling, particularly for long-term
monitoring, including applicability and regulatory
issues, a cost model, and case histories.
G
X
G
U.S. Geological
Survey, Navy,
Air Force, USEPA
Ecological Enhancements (ECO)
ECO-1
Making the Case for Ecological
Enhancements (January 2004)
Presents white paper and case studies on natural
alternatives to traditional remediation processes
C
Wildlife Habitat I
Council |
Enhanced In Situ Biodenitrification (EISBD)
EISBD-1
Emerging Technologies for Enhanced In
Situ Biodenitrification (EISBD) of Nitrate-
Contaminated Ground Water (June
2000)
Description of nitrate in the environment, sources of
nitrate, environmental and health effects of nitrate,
current nitrate remediation practices, and the
emerging technology of EISBD.
O
In Situ Bioremediation (ISB)
ISB-1
ISB-2
ISB-3
ISB-4
ISB-5
ISB-6
ISB-7
Case Studies of Regulatory Acceptance
of ISB Technologies (February 1996)
ISB Protocol Binder & Resource
Document for Hydrocarbons (June
1996) (re-released September 1998)
Natural Attenuation of Chlorinated
Solvents in Groundwater Principles and
Practices (reprinted September 1999)
ITRC/ISB Closure Criteria
Focus Group Report
(March 1998)
Cosf & Performance Reporting for In
Situ Bioremediation Technologies
(December 1997)
Technical and Regulatory
Requirements for Enhanced In Situ
Bioremediation of Chlorinated Solvents
in Groundwater (December 1998)
Five-Course Evaluation Summary for
the ITRC/RTDF Training Course:
Natural Attenuation of Chlorinated
Case studies of the regulatory barriers and
implementation of in situ bioremediation in six
states.
General protocol and outline for ISB and literature
review for natural attenuation and bioventing of
petroleum hydrocarbons.
Description of practices to be used to recognize and
evaluate the presence of natural attenuation of
chlorinated solvent contamination.
Evaluation of state practices for establishing and
implementing closure criteria for bioventing, vapor
extraction, and natural attenuation of petroleum
hydrocarbons and chlorinated solvents
Template for obtaining and reporting cost and
performance information about the use of in situ
bioremediation.
Presents and discusses regulatory processes
appropriate to a variety of active bioremediation
techniques for chlorinated solvents in groundwater.
Presents a summary of results of surveys returned
by people who took the natural attenuation course.
C
G
G
O
G
G
X
Colorado Center for
Environmental
Management
Industrial members
of the Remediation
Technology
Development Forum
(RTDF): Ciba
Specialty, Dow,
DuPont, GE,
GeoSyntec
Consultants, ICI,
Novartis, Zeneca
RTDF industrial
members
RTDF industrial
members
RTDF industrial
members, DOD
RTDF industrial
members
-------
ITRC Product List
Page 3
ISB-8
Solvents in Groundwater
(September 1999)
A Systematic Approach to In Situ
Bioremediation in Groundwater
(August 2002)
Presents flow paths for defining parameters and
criteria leading to decision points for deployment of
ISB. Includes decision trees for evaluating in situ
bioremediation for treating nitrates, carbon
tetrachloride, and perchlorate in groundwater.
G
In Situ Chemical Oxidation (ISCO)
Doc. #
ISCO-1
ISCO-2
Title
Technical and Regulatory Guidance for
In Situ Chemical Oxidation of
Contaminated Soil and Groundwater
(June 2001)
Technical and Regulatory Guidance for
In Situ Chemical Oxidation of
Contaminated Soil and Groundwater,
Second Edition (January 2005)
Description
Discusses the capabilities, limitations, costs,
regulatory concerns, and data requirements for
using ISCO to remove or destroy BTEX, chlorinated
volatile organics, polycychc aromatic hydrocarbon
compounds, and chlorinated semivolatile organic
compounds.
Provides a more comprehensive discussion on
chemical oxidants than the first edition, along with a
more detailed presentation of some of the key
concepts of remedial design.
Type
G
G
Partners
Metals in Soils (MIS)
MIS-1
MIS-2
MIS-3
MIS-4
MIS-5
MIS-6
Technical and Regulatory Guidelines for
Soil Washing (December 1 997)
Fixed Facilities for Soil Washing. A
Regulatory Analysis (December 1 997)
Emerging Technologies for the
Remediation of Metals in Soils:
In Situ Stabilization/lnplace Inactivation
(December 1997)
Electrokinetics (December 1997)
Phytoremediation (December 1 997)
Metals in Soils 1998 Technology Status
Report' Soil Washing and the Emerging
Technologies of Phytoremediation,
Electrokinetics, and In Situ
Stabilization/In Place Inactivation
(December 1998)
Technical requirements for using soil washing
technologies.
A case study of fixed facilities for soil washing in the
United States and in other countries for identifying
successful models of deployment.
Three separate status reports on technologies for
the treatment of metals in soils and the potential
regulatory issues associated with their use.
Updates the five previous documents.
G
C
0
0
DOE (Office of
Environmental
Restoration and the
Mixed Waste Focus
Area)
RTDF IINERT
Technology Team
RTDF, USEPA
MTBE and Other Fuel Oxygenates
Overview of Groundwater Remediation
Technologies for MTBE and TEA
(February 2005)
Describes established and emerging technologies
for remediating groundwater containing methyl fert-
butvl ether and tert-butvl alcohol.
Perchlorate
PERC-1
Perchlorate: Overview of Issues, Status,
and Remedial Options (September
2005)
Discussion of sources, contamination, analytical
methodologies, toxicological issues and research,
remediation technologies and regulatory status of
perchlorate.
O
Permeable Reactive Barriers (PRB, formerly PBW)
PBW-1
PBW-2
PRB-3
Regulatory Guidance for Permeable
Reactive Barriers Designed to
Remediate Chlorinated Solvents (2nd
Edition, December 1999)
Design Guidance for Application of
Permeable Reactive Barriers for
Groundwater Remediation (March
2000)
Regulatory Guidance for Permeable
Reactive Barriers Designed to
Remediate Inorganic and Radionuclide
Contamination (September 1999)
Review of regulatory issues associated with
permeable reactive barriers.
U.S. Air Force document revised with state input to
provide technical information for PRB installation.
Provides regulatory guidelines for the installation of
permeable reactive barriers for the remediation of
inorganics and radionuclides
G
G
G
RTDF
U.S. Air Force,
Environics
Directorate,
Armstrong Lab,
Battelle
RTDF
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Page 4
ITRC Product List
PRB-*
Permeable Reactive Barriers. Lessons
Learned/New Directions (February
2005)
Provides updated information on new developments
and innovative approaches in applying PRBs to treat
a variety of groundwater contaminants.
G
Phytotechnologies (PHYTO)
PHYTO-1
PHYTO-2
Phytoremediation Decision Tree
(December 1999)
Phytotechnology Technical and
Regulatory Guidance Document
(April 2001)
A tool for determining the applicability of
phytoremediation at a given site
Identifies key regulatory and technical issues
relevant to the implementation of phytoremediation.
X
G
USEPA
Plasma Technologies (PT)
A Regulatory Overview of Plasma
Technologies (June 1996)
Policy (POL)
Doc.#
Title
General descnption of plasma technology and
regulatory pathways for permitting.
Description
Type
Partners
POL-1
An Analysis of Performance-Based
Systems for Encouraging Innovative
Environmental Technologies
(December 1997)
Case studies of performance-based environmental
regulatory and contracting practices and an analysis
of activities that could encourage development and
deployment of innovative technologies.
U.S. Army Environ.
Policy Institute, DOD
(ES), Idaho National
Engineering and
Environmental Lab.
POL-2
Case Studies of Selected States'
Voluntary Cleanup/Brownfields
Programs (September 1997)
Radionuclides (RAD)
RAD-1
Radiation Reference Guide: Relevant
Organizations and Regulatory Terms
(December 1999)
In-depth case studies of selected states' voluntary
cleanup/brownfields programs and
recommendations for possible enhancements.
Resource of organizations, activities, and technical
terminology related to radioactive contamination.
Colorado Center for
Environ. Mgmt,.
Assoc. of State &
Territorial Solid
Waste Mqmt. Officials
RAD-2
Determining Cleanup Goals at
Radioactively Contaminated Sites:
Case Studies (April 2002)
Summarizes the various regulatory standards and
requirements dictating the cleanup of radioactively
contaminated sites, processes for developing
cleanup levels and, case studies from 12 sites.
RAD-3
Issues of Long-Term Stewardship:
State Regulators' Perspectives
(July 2004)
Presents the results of the survey of state regulator
perspectives on long-term stewardship.
O
Remediation Process Optimization (RPO)
RPO-1
Remediation Process Optimization:
Identifying Opportunities for Enhanced
and More Efficient Site Remediation
(September 2004)
Provides guidance on how to systematically
evaluate and manage uncertainty associated with
the remediation process by using RPO as a tool.
Sampling, Characterization and Monitoring (SCM)
SCM-1 Technical and Regulatory Guidance for
the Triad Approach. A New Paradigm
for Environmental Project Management
(December 2003)
Small Arms Firing Range (SMART)
SMART-1
Characterization and Remediation of
Soils at Closed Small Arms Firing
Ranges (January 2003)
Introduces the Triad approach to conducting
environmental work, which increases effectiveness
and quality and reduces project costs.
Provides decision diagram and guidance for
planning, evaluating, and approving lead soil
remediation systems.
SMART-2
Environmental Management at
Operating Outdoor Small Arms Firing
Ranges (February 2005)
Technology Acceptance &
Reciprocity Partnership (TARP)
Assists range operators in developing, using, and
monitoring environmental management plans to
minimize potential exposure to metals, especially
lead, at active outdoor small arms firinq ranqes.
www.dep.state.pa.us/dep/deputate/pollprev/techservices/tarp
Tier 1 Guidance (December 2000)
A protocol for defining the quality of information that
TARP states will accept for a field demonstration of
any technology
Massachusetts,
Pennsylvania, New
Jersey, New York,
California, Illinois
MOU-1
Strategy for Reciprocal State
Acceptance of Environmental
Technologies (December 2000)
The six-state strategy for reducing duplicative
demonstration and testing of technologies,
expediting multistate technology acceptance and
reducing costs for both vendors and state regulators
Massachusetts,
Pennsylvania, New
Jersey, New York,
California, Illinois
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ITRC Product List
J^age 5
Protocol for Stormwater Best
Management Practice Demonstrations
(July 2003)
Thermal Desorption (TD)
TD-1
TD-2
TD-3
Technical Requirements for On-Site
Low Temperature Thermal
Desorption of
Non-Hazardous Soils Contaminated
with Petroleum/Coal Tar/Gas Plant
Wastes (December 1997)
Solid Media Contaminated with
Hazardous Chlorinated Organics
(September 1997)
Solid Media and Low Level Mixed
Waste Contaminated with Mercury
and/or Hazardous Chlorinated Organics
(September 1998)
Provides a uniform method for demonstrating
Stormwater technologies and developing test quality
assurance plans for certification or verification of
performance claims.
^^^^^^•••^^^^^^^•^^^^^^^^••i^^^H^^^^^^^Hi
These three reports serve as the protocol for
minimum technical requirements and can be used
together when treating a mix of contaminants
Massachusetts,
Pennsylvania, New
Jersey, New York,
California, Illinois,
Virginia
•I __
DOE Mixed Waste
Focus Area
Unexploded Ordnance (UXO)
Doc. #
UXO-1
UXO-2
UXO-3
Title
Breaking Barriers to the Use of
Innovative Technologies: State
Regulatory Role in Unexploded
Ordnance Detection and
Characterization Technology Selection
(December 2000)
Technical/Regulatory Guideline for
Munitions Response Historical Records
Review (November 2003)
Geophysical Prove-Outs for Munitions
Response Projects (November 2004)
Description
Using case studies, this document recommends
including states in the selection of technologies for
detecting and characterizing unexploded ordnance.
A guide for regulators, stakeholders, and others
involved in oversight or review of munitions
response historical records review projects on
munitions response sites.
Introduces the purpose and scope of GPOs,
provides examples of associated goals and
objectives, and presents information needed to
understand and evaluate the design, construction,
implementation and reporting of GPOs.
Type
C
G
G
Partners
Verification (VT) Nancy Uziemblo (WA) • (509) 736-3014
VT-1
Multi-State Evaluation of Elements
Important to the Verification of
Remediation Technologies, 2nd Edition
(December 1999)
A matrix of data requirements for a technology
verification process to enhance states' confidence in
the technology verification and demonstration
results. Use of this matrix will allow verification
programs to modify their efforts and provide the data
most needed by states in their approval process.
This type of data collection will encourage states to
consider reciprocal state acceptance of verification
efforts Highlights of the verification programs are
also provided.
11 North American
verification
programs, DOE,
USEPA
Wetlands (WTLND)
WTLND-1
WTLND-2
Technical and Regulatory Guidance for
Constructed Treatment Wetlands
(December 2003)
Characterization, Design, Construction,
and Monitoring of Mitigation Wetlands
(February 2005)
A guide to help regulators, consultants, and
stakeholders make informed decisions about the use
of constructed treatment wetland systems for
remediating a variety of waste streams, including
acid mine water, remedial wastewaters, and
agriculture waste streams.
A guide to the appropriate characterization, design,
construction, and monitoring of compensatory
mitigation wetlands as part of a federal, state, or
local permitting requirement.
G
G
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