EPA/600/A-96/092
Environmental Chemistry and Kinetics of
Biotransformation of Chlorinated Organic Compounds
in Ground Water
John T. Wilson, Don H. Kampbell, and Jim Weaver
Subsurface Protection and Remediation Division,
National Risk Management Research Laboratory, U.S. EPA,
R.S. Kerr Research Laboratory, Ada, Oklahoma
Introduction
Responsible management of the risk associated with chlorinated
solvents in ground water involves a realistic assessment of the
natural attenuation of these compounds in the subsurface before
they are captured by ground water production wells, or before
they discharge to sensitive ecological receptors. The reduction
in risk is largely controled by the rate of the biotransformation
of the chlorinated solvents and their metabolic daughter
products. These rates of biotransformation are sensitive
parameters in mathematical models describing the transport of
these compounds to environmental receptors.
Environmental Chemistry of Biodegradation of
Chlorinated Solvents
Please skip to the next section if you are familiar with
environmental chemistry. This section is designed specifically
for engineers and mathematical modelers that have no chemistry
background.
The initial metabolism of chlorinated solvents such a
tetrachloroethylene, trichloroethylene, and carbon tetrachloride
in ground water usually involves a biochemical process described
as a sequential reductive dechlorination. This process only
occurs in the absence of oxygen, and the chlorinated solvent
actually substitutes for oxygen in the physiology of the
microorganisms carrying out the process.
The chemical term "reduction" was originally derived from the
chemistry of smelting ores of metals. Ores are chemical
compounds of metal atoms coupled with other materials. As the
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ores are smelted to the pure element, the weight of the pure
metal was reduced compared to the weight of the ore. Chemically,
the positively charged metal ions received electrons to become
the electrically neutral pure metal. Chemists generalized the
term "reduction" to any chemical reaction that added electrons to
an element. In a similar manner, chemical reaction of pure
metals with oxygen results in the removal of electrons from the
neutral metal to produce an oxide. Chemists have generalized the
term "oxidation" to refer to any chemical reaction that removes
electrons from a material. For a material to be reduced, some
other material must be oxidized.
The electrons required for microbial reduction of chlorinated
solvents in ground water are extracted from native organic
matter, from other contaminants such as the BTEX compounds
released from fuel spills, or from volatile fatty acids in
landfill leachate, or from hydrogen produced by the fermentation
of these materials. The electrons pass through a complex series
of biochemical reactions that support the growth and function of
the microorganisms that carry out the process.
In order to function the microorganisms must pass the electrons
used in their metabolism over to some ultimate electron acceptor.
This ultimate electron acceptor can be dissolved oxygen,
dissolved nitrate, oxidized minerals in the aquifer, dissolved
sulfate, a dissolved chlorinated solvent, or carbon dioxide.
Important oxidized minerals used as electron acceptors include
iron and manganese. Oxygen is reduced to water, nitrate to
nitrogen gas or ammonia, Iron (III) or ferric iron to Iron (II)
or ferrous iron, Manganese (IV) to Manganese (II), sulfate to
sulfide ion, chlorinated solvents to a compound with one less
chlorine atom, and carbon dioxide to methane. These processes
are referred to as aerobic respiration, nitrate reduction, iron
and manganese reduction, sulfate reduction, reductive
dechlorination, and methanogenesis.
The energy gained by the microorganisms follows the sequence
listed above: oxygen and nitrate reduction provide a good deal of
energy, iron and manganese reduction somewhat less energy,
sulfate reduction and dechlorination a good deal less energy, and
methanogenesis a marginal amount of energy. The organisms
carrying out the more energetic reactions have a competitive
advantage; as a result they proliferate and exhaust the ultimate
electron acceptors in a sequence. Oxygen and then nitrate are
removed first. When their supply is exhausted, then other
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organism are able to proliferate, and manganese and iron
reduction begins. If electron donor supply is adequate, then
sulfate reduction begins, usually with concomitant iron
reduction, followed ultimately by methanogenesis. Ground water
where oxygen and nitrate are being consumed are usually referred
to as oxidized environments. Water where sulfate is being
consumed and methane is being produced are generally referred to
as reduced environments.
Reductive dechlorination usually occurs under sulfate reducing
and methanogenic conditions. Two electrons are transferred to the
chlorinated compound being reduced. A chlorine atom bonded with
a carbon receives one of the electrons to become a negatively
charged chloride ion. The second electron combines with a proton
(hydrogen ion) to become a hydrogen atom that replaces the
chlorine atom in the daughter compound. One chlorine is replaced
with hydrogen at a time; as a result, each transfer occurs in
sequence. As an example, tetrachloroethylene is reduced to
trichlorethylene, then any of the three dichloroethylenes, then
to monochloroethylene (commonly called vinyl chloride), then to
the chlorine-free carbon skeleton ethylene, then finally to
ethane.
Kinetics of Transformation in Ground Water
Table I lists rate constants for biotransformation of
tetrachloroethylene (P.E.), trichlorethylene (TCE), cis-
dichloroethylene (cis-DCE) and vinyl chloride that were
extrapolated from field scale investigations. In some cases a
mathematical model was used to extract a rate constant from field
data. However, many of the rate constants were calculated from
the published raw data of others by John Wilson. In several
cases the primary authors did not choose to calculate a rate
constant, or felt that their data could not distinguish
degradation from dilution or dispersion.
The data were collected or estimated to build a statistical
picture of the distribution of rate constants, in support of a
sensitivity analysis of a preliminary assessment using published
rate constants. They serve as a point of reference for
"reasonable" rates of attenuation. It is inappropriate to apply
them to other sites without proper site specific validation.
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The estimates of rates of attenuation tend to cluster within an
order of magnitude. Figure 1 compares the rates of removal of
TCE in those plumes where there was evidence of biodegradation.
Most of the first order rates are very close to 1.0 per year,
equivalent to a half life of 8 months. Table I also reveals that
the rate of removal of P.E., TCE and cis-DCE and Vinyl Chloride
are similar; they vary by little more than one order of
magnitude.
Table II lists first-order and zero-order rate constants
determined in laboratory microcosm studies. The rates of removal
in the laboratory microcosm studies are similar to estimates of
removal at field scale for TCE, cis-DCE, and Vinyl Chloride.
Rates of removal of 1,1,1-trichloroethane (1,1,1-TCA) are similar
to the rates of removal of the chlorinated alkenes.
Summary
The rates of attenuation of chlorinated solvents and their less
chlorinated daughter products in ground water are slow as humans
experience time. If concentrations of chlorinated organic
compounds near the source are in the range of 10,000 to 100,000
ug/liter, then a residence time in the plume on the order of a
decade or more will be required to bring initial concentrations
to current MCLs for drinking water. Biodegradation as a
component of natural attenuation can be protective of ground
water quality in those circumstances where the time of travel of
a plume to a receptor is long. In many cases, it will be
necessary to supplement the benefit of natural attenuation with
some sort of source control or plume management.
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DISCLAIMER
The U.S. Environmental Protection Agency through it's
Office of Research and Development partially funded and
collaborated in the research described here. It has been
subjected to the Agency's peer review and has been approved for
publication in an EPA document.
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Table I. Apparent attenuation rate constants (Field Scale Estimates).
Location
St . Joseph,
Michigan
Picatinny
Arsenal ,
New Jersey
Sacramento,
California
Necco Park
New York
Plattsburgh
AFB , New
York
Ref-
erence
15
16
19
8
13
4
12
21
Distance
from
source
(meters)
130 to 390
390 to 550
550 to 855
240 to 460
320 to 460
240 to 320
0 to 250
70 to 300
0 to 570
0 to 660
0 to 300
300 to 380
380 to 780
Time from
source
(years)
3.2 to 9.7
9.7 to 12.5
12.5 to 17.9
2.2 to 4.2
2.9 to 4.2
2.2 to 2.9
0.0 to 2.3
0.5 to 2.3
0.0 to 1.6
0.0 to 1.8
0.0 to 6.7
6.7 to 8.6
8.6 to 17.7
Residence
time
(years)
6.5
2.8
5.4
2.0
1.3
0.7
1.8
1.6
1.8
6 .7
1.9
9.1
TCE
cis-DCE
Vinyl
chloride
Apparent Loss Coefficient
(I/year)
0.38
1.3
0.93
1.4
1.2
1.1
0.7
0.7
1.3
0.23
absent
0.50
0.83
3.1
produced
produced
1.6
0.5
0.86
produced
0.6
0.07
0.18
0.88
2.2
produced
produced
3.1
produced
1.16
0.47
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Table I continued. Apparent attenuation rate constants (Field Scale Estimates).
Location
Tibbitt's
Road, New
Hampshire
San
Francisco
Bay Area,
California
Perth,
Australia
Eielson,
AFB, Alaska
Not
Identified
Cecil Field
NAS,
Florida
Ref-
erence
20
3
2
9
6
22
Distance
from
source
(meters)
0 to 24
0 to 40
0 to 55
0 to 600
0 to 140
Time from
source
(years)
0.0 to 2.4
0.0 to 6.4
0.0 to 10
0.0 to 14
0.0 to 1.2
Residence
time
(years)
2.4
6.4
10
1.2
P.E.
TCE
cis-DCE
Apparent Loss Coefficient
(I/year)
4 .4
0.8
3.3 to
7.3
0.21
0.42
0.73
5.11
0.32
0.73
2.3
0.8
produced
0.68
>0.73
0.8
3.3 to
7.3
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Table II. Apparent attenuation rate constants from laboratory microcosm studies.
Location of
material
Refer-
ence
Distance
from source
(meters)
Time from
source
(years)
Incubation
time
(years)
TCE
cis-DCE
Vinyl
Chloride
1,1,1-TCA
Apparent First Order Loss (I/year)
Apparent Zero Order Loss (ug/L*day)
Laboratory Microcosm Studies done on material from field scale plumes
Picatinny
Arsenal, NJ
St. Joseph,
MI
Traverse
City, MI
Tibbitts
Road, NH
7
17
10
18
14
240
320
460
300
At Source
2.2
2 .9
4.2
0.5
0.5
0.5
0.12, 0.077
1.8
0.64
0.42
0.21
1.8, 1.2
1.8
4.8
0. 52
9.4
3.1
Laboratory Microcosm Studies done on material not previously exposed to the chlorinated organic compound
Norman
Landfill, OK
Florida
5
11
14
1
Aerobic
Material
Sulfate
Reducing
Methan-
ogenic
Reducing
Reducing
4.2
10
0.012
1.28
1.20
1.65 1.42
3.6
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References
1. Barrio-Lage, G.A. , F.Z. Parsons, R.M. Narbaitz, and P.A.
Lorenzo. 1990. Enhanced anaerobic biodegradation of vinyl
chloride in ground water. Environmental Toxicology and
Chemistry. 9:403-415.
2. Benker, E., G.B. Davis, S. Appleyard, D.A. Berry, and T.R.
Power. 1994. Groundwater contamination by trichloroethene
(TCE) in a residential area of Perth: Distribution,
Mobility, and Implications for Management. Proceedings:
Water Down Under ^94, 25th Congress of IAH, Adelaide, south
Australia, November 21-25, 1994.
3. Buscheck, T. and K. O'Reilly. 1996. Intrinsic anaerobic
biodegradation of chlorinated solvents at a manufacturing
plant. Abstracts of the Conference on Intrinsic Remediation
of Chlorinated Solvents, Battelle Memorial Institute
(Columbus, Ohio), Salt Lake City, Utah, April 2, 1996.
4. Cox, E., E. Edwards, L. Lehmicke, and D. Major. 1995.
Intinsic biodegradation of trichloroethylene and
trichloroethane in a sequential anaerobic-aerobic aquifer.
In R.E. Hinchee, J.T. Wilson, and D.C. Downey (Eds)
Intrinsic Bioremediation pp.223-231. Battelle Press,
Columbus, Ohio.
5. Davis, J.W., and C.L. Carpenter. 1990. Aerobic
biodegradation of vinyl chloride in groundwater samples.
Applied and Environmenatal Microbiology. 56(12):3878-3880.
6. De, A. And D. Graves. 1996. Intrinsic bioremediation of
chlorinated aliphatics and aromatics at a complex industrial
site. Abstracts of the Conference on Intrinsic
Remediation of Chlorinated Solvents, Battelle Memorial
Institute (Columbus, Ohio), Salt Lake City, Utah, April 2,
1996.
7. Ehlke, T.A., T.E. Imbrigiotta, B.H. Wilson, and J.T. Wilson.
1991. Biotransformation of cis-1,2-dichloroethylene in
aquifer material from Picatinny Arsenal, Morris County, New
Jersey. U.S. Geological Survey Toxic Substances Hydrology
Program--proceedings of the technical meeting, Monterey, CA,
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March 11-15, 1991. Water- Resources Investigations Report
91-4034. pp. 689-697.
Ehlke, T.A., B.H. Wilson, J.T. Wilson, and T.E. Imbrigiotta.
1994. In-situ biotransformation of trichloroethylene and
cis-1,2-dichloroethylene at Picatinny Arsenal, New Jersey.
In: Morganwalp, D.W., and D.A. Aronson, (eds) Proceedings of
the U.S. Geological Survey Toxic Substances Hydrology
Program, Colorado Springs, Colorado (September 20-24, 1993).
Water Res. Invest. Rep. 94-4014. In Press
9. Gorder, K.A., R.R. Dupont, D.L. Sorensen, and M.W.
Kemblowski. 1996. Intrinsic remediation of TCE in cold
regions. Abstracts of the Conference on Intrinsic
Remediation of Chlorinated Solvents, Battelle Memorial
Institute (Columbus, Ohio), Salt Lake City, Utah, April 2,
1996.
10. Haston, Z.C., P.K. Sharma, J.N.P. Black, and P.L. McCarty.
1994. Enhanced Reductive Dechlorination of Chlorinated
Ethenes. Preceedings of the EPA Symposium on Bioremediation
of Hazardous Wastes: Research, Development, and Field
Evaluations, pp. 11-14. U.S. Environmental Protection
Agency, EPA/600/R-94/075.
11. Klecka, G.M., S.J. Gonsior, and D.A. Markham. 1990.
Biological transformations of 1,1,1-trichloroethane in
subsurface soils and ground water. Environmental Toxicology
and Chemistry 9:1437-1451.
12. Lee, M.D., P.F. Mazierski, R.J. Buchanan, Jr., D.E. Ellis,
and L.S. Sehayek. 1995. Intrinsic and in situ anaerobic
biodegradation of chlorinated solvents at an industrial
landfill. In R.E. Hinchee, J.T. Wilson, and B.C. Downey
(Eds) Intrinsic Bioremediation pp.205-222. Battelle Press,
Columbus, Ohio.
13. Martin, M., and T.E. Imbrigiotta. 1994. Contamination of
ground water with trichloroethylene at the building 24 site
at Picatinny Arsenal, New Jersey. Symposium on Natural
Attenuation of Ground Water. Denver, CO, August 30-September
1, 1994. EPA/600/R-94/162. pp. 109-115.
14. Parsons, F., G. Barrio Lage, and R. Rice. 1985.
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Biotransformation of chlorinated organic solvents in static
microcosms. Environmental Toxicology and Chemistry. 4:739-
742.
15. Semprini, L., Kitanidis, P.K., Kampbell, D.H., and J.T.
Wilson. Anaerobic Transformation of chlorinated aliphatic
hydrocarbons in a sand aquifer based on spatial chemical
distributions. Water Resources Research. 31 (4) :1051-1062 .
16. Weaver, J.W., J.T. Wilson, D.H. Kampbell, and M.E.
Randolph. 1995. Field derived transformation rates for
modeling natural bioattenuation of trichloroethene and its
degradation products. Proceedings: Next Generation
Environmental Models and Computational Methods. August
7-9, 1995. Bay City, Michigan.
17. Wilson, B.H., T.A. Ehlke, T.E. Imbigiotta, and J.T. Wilson.
1991. Reductive dechlorination of trichloroethylene in
anoxic aquifer material from Picatinny Arsenal, New Jersey.
U.S. Geological Survey Toxic Substances Hydrology
Program--proceedings of the technical meeting, Monterey, CA,
March 11-15, 1991. Water- Resources Investigations Report
91-4034. pp 704-707.
18. Wilson, B.H., J.T. Wilson, D.H. Kampbell, B.E. Bledsoe, and
J.M. Armstrong. 1990. Biotransformation of monoaromatic and
chlorinated hydrocarbons at an aviation gasoline spill site.
GeomicroJbiology Journal. 8:225-240.
19. Wilson, J.T., J.W. Weaver, D.H. Kampbell. 1994. Intrinsic
Bioremediation of TCE in Ground Water at an NPL Site in St.
Joseph, Michigan. Symposium on Natural Attenuation of
Ground Water. Denver, CO, August 30-September 1, 1994.
EPA/600/R-94/162. pp. 116-119.
20. Wilson, B.H. 1996. Design and interpretation of microcosm
studies. Symposium on Natural Attenuation of Chlorinated
Organics in Ground Water (U.S. EPA, USAF Armstrong
Laboratory, USAF Center for Environmental Excellence)
Dallas, Texas, September 11-13, 1996.
21. Wiedemeier, T. 1996. Plattsburgh Air Force Base, New York.
Symposium on Natural Attenuation of Chlorinated Organics in
Ground Water (U.S. EPA, USAF Armstrong Laboratory, USAF
Center for Environmental Excellence) Dallas, Texas,
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September 11-13, 1996.
22. Chapelle, F. 1996. Identifying redox conditions that favor
the natural attenuation of chlorinated ethenes in
contaminanted ground-water systems. Symposium on Natural
Attenuation of Chlorinated Organics in Ground Water (U.S.
EPA, USAF Armstrong Laboratory, USAF Center for
Environmental Excellence) Dallas, Texas, September 11-13,
1996.
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Figure 1. The first order rate constant for biotransformation of
TCE in a variety of plumes of contamination in ground water.
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Chart2
TCE Removal in Field
03
0
0
o
o
or
3
15
Of
i_
0
6
1234567
9 10 11 12 13 14 15 16 17
Page 1
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TECHNICAL REPORT DATA
(Please read fnstructforu on the reverse before completing/
2.
3, R6C
A, TITLE AND SUBTITLE
ENVIRONMENTAL CHEMISTRY AND KINETICS OF BIOTMNSFORMATION
OF CHLORINATED ORGANIC COMPOUNDS IN GROUND WATER
S. R6PC
6. PERFORMING ORGANIZATION COOE
7. AUTHOR(S)
JOHN T. WILSON, DON H. KAMPBELL, AND JIM W. WEAVER
8. PSRPOHMINO ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
U.S. EPA, NRML, SPRD
P.O. BOX 1198
ADA, OKLAHOMA 74820
10. PROGRAM 6C6M6NT NO.
1 1. CONTRACT/GRANT NO.
IN-HOUSE RPJW9
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. EPA, NRMRL, SPRD
P.O. BOX 1198
ADA, OKLAHOMA 74820
13. TYPE OF REPORT ANO PERIOD COVERED
BOOK CHAPTER
14. SPONSORING AGcNCY COOE
EPA/600/15
tS. SUPPLEMENTARY NOTES
IS. ABSTRACT
The rates of attenuation of chlorinated solvents and their less
chlorinated daughter products in ground water are slow as humans
experience time. If concentrations of chlorinated organic
compounds near the source are in the range of 10,000 to 100,000
ug/liter, then a residence time in the plume on the order of a
decade or more will be required to bring initial concentrations
to current MCLs for drinking water. Biodegradation as a
component of natural attenuation can be protective of ground
water quality in those circumstances where the time of travel of
a plume to a receptor is long. In many cases, it will be
necessary to supplement the benefit of natural attenuation with
some sort of source control or plume management.
KEY WORDS ANO DOCUMENT ANALYSIS
DESCRIPTORS
b. IDENTIFIERS/OPEN SNO60 TSPMS
COSATI Field.CfOup
8. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
SPA For*, 2220-1 (R«». 4-77) *«e«ious
19. SSCURITY CLASS iThis
UNCLASSIFIED
21. NO. O<= *»AG£S
14
20. SSCURITY CLASS iThtt pa
UNCLASSIFIED
72.
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