DSHW-2007-002419 - 0901a0688013e0ac

Lauicl: Sysieois Gfcup
P.O. Box 98
"""'"'"""" HAND DELIVERED
wwvv.rilk.coiii
APR 1 8 2007
UTAH DIVISION OF
SOLID & HAZARDOUS WASTE
April 18,2007 _ ,.
Dennis R. Downs, Director
Department of Environmental Quality
Division ofSolid and Hazardous Waste
288 North 1460 West
P.O. Box 144880
Salt Lake City, Utah
84114-4880
RE: ATK Launch Systems Inc., EPA ID# UTD009081357
Flow Cell Treatability Study
Dear Mr. Downs,
ATK Launch Systems Inc. (ATK) is submitting a notification to the Division of Solid and
Hazardous Waste to conduct a Flow Cell Treatability Study (the Study). The purpose of the
Study is to investigate altemative electron donor sources and delivery practices for the ATK
Bacchus Bioremediation Pilot Plant. A copy of the Study is attached.
If you have questions or need additional information conceming this Study, please contact Paul
V. Hancock at [phone].
Sincerely,
David P. Gosen, P.E.
Director, Environmental Services
.ATK Launch SvsK'ins Envimnnicnliil Services
Bacchus Enhanced In Situ
Bioremediation Pilot Plant Biofilm
Control:
Flow Cell Treatability Study Design
Fourth Revision - Draft
J.E. Wells
ATK Launch Systems
Environmental Services
February, 2007
J.E.Wells Paee 1 4/18/2007
.AIK Luunch .Svsicin.s l.-.iiviionnii.-nuil ScrvicL-s
Abstract
A bench-scale flow cell reactor is being constructed to study microbial biofilm control. The
purpose of this study is to investigate altemative electron donor sources and delivery practices
that may alleviate biofouling. This study will also investigate which electron donor feed
methods work best to minimize biofouling.
Introduction
Well biofouling is a common concem when using enhanced in situ bioremediation (EISB)
technology to treat contaminated groundwater. Left uncontrolled, biofilm proliferation in
electron donor injection wells have the capability to upset the system by impeding (i.e.
generation of backpressure) groundwater recharge. Such a scenario has been encountered at the
Alliant Techsystems' Bacchus facility. An EISB pilot plant operating on the facility to
remediate perchlorate contaminated groundwater has been ineffective due to significani
biofouling. The purpose of this study is to investigate altemative electron donor sources and
delivery practices that may alleviate biofouling.
Ethanol and citric acid have previously been used in the Bacchus EISB plant as electron donors
with negligible success. In both cases, the recharge well was fouled with a stable biofilm
unaffected by chlorine dioxide injections used to kill or inhibit bacterial growth. Ethanol and
citric acid are readily metabolized by the microbial community either directly or indirectly;
leading to a significant portion ofthe community being stimulated. This leads to an environment
where rapid growth rates and survival mechanisms are essential for a particular population to
proliferate. Depending on the conditions, there is an opportunity for nondesirable or "weedy"
bacteria to outcompete more desirable populations. Therefore, as suggested by Coates et al,
utilizing compounds that are metabolized by limited populations in the community is expected to
be more effective.
Electron donor can be added to groundwater through a single injection batch feed or a
continuous feed. There is no clear answer as to which delivery regimen is the most beneficial to
prevent fouling. A strong batch delivery of an electron donor with biocide or biofilm dispersal
activity would seem to have the greatest effect in preventing biofilm foiTnation on the injection
well screen. However, depending on retention time in and around the well screen, a lagging
interface (as the concentrated "plug" of donor passes out of the screen) of electron donor that has
dropped below the inhibitory concentration might develop and lead to rapid biofilm foiTnation
over subsequent injections. Altematively, the theory of a continuous feed system is to maintain a
constant flow of electron donor at relatively low concentration to limit biomass production. The
success of this type of delivery may depend on keeping concentrations of electron donor and an
additional biocide amendment (i.e. chlorine) at levels necessary to prevent initial biofilm
formation. If biofilm formation becomes established, significant fouling could result. This study
will investigate which feed method works best for the electron donors under investigation.
J.F:. Wells .Paee 2 4/18/2007
.ATK l.;)uni.ii Svslciiis l:n\ iioniiK-riMl Scr\ ices
Hypothesis
The hypotheses tested by this study are stated below:
Null donors: No differences in biofilm formation are observed between altemative electron
donors and citric acid.
Null delivery: No differences exist between continuous delivery and batch delivery of
electron donor.
Bacchus Groundwater Chemistry
Table 1 shows the values for particular constituents of interest in the Bacchus groundwater.
These values have been used to calculate electron donor demand for microbial mediated
perchlorate reduction and determine water hardness.
TABLE 1. Bacchus Groundwater
Constituents of Interest
Constituent
Perchlorate
Calcium
Magnesium
Nitrate
Dissolved Oxygen
mg/L
0.3
35*
10*
18
8
Values from Magna Water Company "Water Quality Report for 2005"
Flow Cell Design
Figure 1 illustrates the schematics for the flow cell. The system is loosely a 1/16 scale model of
the Bacchus EISB plant. Tubing diameters and exit flow rate from the well screen are modeled
as accurately as possible. Unlike the EISB plant, the flow cell relies on continuous recirculation
through three 5 gallon reservoirs to model approximately 24 hours of retention time. The
retention time is obtained by circulating approximately 33 liters of groundwater from the
Bacchus EISB plant at a constant flow rate of 20 mL/min. The low flow rate models the outflow
of injected groundwater through the well screen's open surface area. To compensate for
groundwater constituent loss (i.e. nitrate, perchlorate) during recirculation, a concentrated
nitrate/perchlorate feed solution and oxygen will be pumped into a "recharge reservoir"
continuously. The following is a description for each component in the flow cell:
J.r-. Wells Paee 3 4/18/2007
.ATK l.uuncli ,S\sK'itis l-'.n\ n-i.jnuKMU.il .Sci\ici^s
Feed Reservoir: The reservoir is a 5 gallon polypropylene container with lid. This reservoir
contains the circulation pump and acts as a recharge reservoir. Perchlorate, nitrate and dissolved
oxygen (via an aquarium pump) will be added at the top of the reservoir to bring the water back
to pretreatment conditions.
Sample Reservoir: The reservoir is a 5 gallon polypropylene container with lid. Receives water
via gravity flow from the Holding Reservoir. Water will be collected from an oveiflow tube at
the top of the reservoir and analyzed for perchlorate and electron donor concentrations.
Holding Reservoir: The reservoir is a 5 gallon polypropylene container with lid. Receives water
that has been amended with electron donor and has flowed through the Biofilm Attachment
Surface and Groundwater Recirculation Line. The holding reservoir allows for extended
retention time for perchlorate reduction.
Circulation Pump: The circulation pump is a Dayton 1/100 hp compact submersible centrifugal
pump rated to 240 GPH at 1 foot of head. This will provide continuous flow through the system.
Donor Feed Reservoir: The donor feed reservoir is a 1 gallon aspirator bottle designed to deliver
electron donor to the flow cell. The flow from the Donor Feed Reservoir is controlled by a fluid
metering pump that pressurizes the aspirator bottle and displaces the appropriate volume. The
donor feed rate is calibrated to deliver the maximum per day donor requirements for each
treatment (0.170 L/day for each cell).
Biofilm Attachment Surface (BAS): This component is made of !^" Schedule 80 clear PVC
pipe. The pipe is 30 inches long to simulate the 40 foot well screen at the EISB plant. The clear
PVC allows for biofilm observations during flow cell operation.
Groundwater Feed/Recirculation Line: These lines are made of '/i" outer diameter (0.170" inner
diameter) polyethylene tubing rated to 150 psi. The lines are used to simulate the two inch lines
at the EISB plant that deliver water from the extraction wells to the recharge well. A valve
connected to the end of the Recirculation Line provides the 20 mL/min flow rate through the
system.
Nitrate / Perchlorate Feed Reservoir: This reservoir will be used to deliver a concentrated
perchlorate/nitrate feed solution to maintain a steady state concentration in the recirculated
groundwater. The concentrated solution recharges the recirculated groundwaler to simulate the
continuous flow of untreated water that comes into the EISB plant. One variable rate metering
pump will be used to deliver perchlorate/nitrate solution to the feed reservoir of all five flow
cells at 0.17 L/day (0.118 mL/min continuous delivery). The calculation is shown below:
Potassium Nitrate
18 mg/17day x 33 L = 594 mg/day x 21 days = 12474 mg x 5 cells = 62370 mg
0.17IVday flow rate x 5 cells = 0.85 L/day x 21 days = 17.85 L
J.il Wells Page 4 4/18/2007
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KJMO3 atomic mass/NOa' atomic mass = 101 grams per mole /62 grams per mole = 1.63
1.63 X 62370 mg NO3" = 101,663 mg KNO3/I7.85L
Note: 17.85 L is near container capacity for "5 gallon " reservoirs.
Ammonium Perchlorate
0.3 mg/I7day x 33 L =10 mg/day x 21 days = 210 mg x 5 cells = 1050 mg
0.17lVday flow rate X 5 cells = 0.85 Udayx 21 days = 17.85 L
NH4CIO4 atomic mass/C104' atomic mass =117 grams per mole/99 grams per mole =
1.18
1.18 X 1050 mg CIO4" = 1239 mg NH4CIO4/I7.85L
Note: 17.85 L is near container capacity for "5 gallon " reservoirs.
Figure 1. Flow Cell Schematic
Jr
\
t Flow Conlrol
Valve
Holding
Reservoir
To Overflow
Proledion
Reservoir
fc>n
Flow Conlrol
Valve
Overtlow
Perchlorale/Nilraic
Feed Reservoir
Overflow/sample
lube
Pressure
Groundwaler _f ^
Feed
t
Sample
Reservoir
T)M
Groundwater Recirculation Line
Donor Feed
Reservoir
w/pump
J.L. Wells Paee 5 4/18/2007
.A'l'K l.uunch Svslciiis •.ii\ iionnicnuil .Scr\ ices
Study Treatments
The Flow Cell study is comprised of three electron
donor treatments and a positive and negative
control. Each trealment will be studied for 21 days.
The treatments and controls are shown in Table 2.
Table 2. Flow Cell Treatments
Treatment
1
2
3
Positive Control
Negative Control
Electron Donor
Nitrilotriacetic Acid (NTA)
Socdium Benzoate (SB)
NTA/SB
Citric Acid
No Donor
Treatment 1: Nitrilotriacetic Acid
Nitrilotriacetic Acid (NTA) is a chelant similar lo elhylenediaminetelraacetic acid (EDTA).
Chelants have been used previously (specifically EDTA) in medical device research to
disperse P. aeruginosa biofilms (Banin et al, 2006). Additionally a calcium-specific chelant,
ethylene glycol-bis (P-aminoethyl ether)-A/,A^-tetraacetic acid (EGTA), was shown to
disperse mixed population biofilms derived from activated sludge (Turakhia et al, 1983).
The effectiveness of these chelants is related to their ability to remove free calcium and
magnesium cations which are known to affect "slime" formation. The significant advantage
of NTA is that it is readily biodegradable compared lo EDTA. In fact, a Pseudomonas sp.
was shown to utilize NTA as a sole carbon source (Bourquin et al, 1977). Furthermore, a
more recent report showed a denitrifying bacterium capable of using NTA as a sole carbon
source while using NO3" as the terminal electron acceptor in an anaerobic environmeni
(Jenal-Wanner et al). These findings beg the question of whether members of the
perchlorate reducing community in a groundwater environment may be able to use NTA as
an electron donor during perchlorate reduction.
NTA has two appealing properties as a candidate for biofouling control. As a chelant, it is
capable of reducing free calcium and magnesium cation concentralions. Therefore, NTA
should act as a deterrent to biofilm formation al suitable concenlralions. As an electron
donor, NTA is metabolized via specific pathways that are mosl likely nol preseni in all
members of the groundwater microbial community. Moreover, since some denitrifying
bacteria have been shown lo posses such pathways, it is hopeful that NTA would also be
metabolized directly by some perchlorate reducing bacteria. Thus, unlike ethanol or citrate
that are metabolized by a wide array of bacteria (eilher directly or indirectly); NTA may
provide the ability to better target desired populations in the communiiy.
The NTA demand for perchlorate reduction was calculated using the values for perchlorate,
nitrate and dissolved oxygen shown in Table 1. The balanced redox reaction and
stoichiometric ratio are shown below for each constituent:
Perchlorate
4C6H6N06Na + 9CIO4" -1- 12 H^ —• 24C02 + 9Cr -I- 12Na^ -1- 4NH3 -1-I2H2O
Stoichiometric ratio: Molecules NTA x atomic mass NTA = 4 x 257 = 1.15
J.F.. Wells Paee 6 4/18/2007
.ATK l.aunch S>slciiis Einiionnieni.il .Services
Molecules CIO4' x atomic mass CIO4" 9 x 99
Nitrate
5C6H6N06Na + 18NO3" + 33H^ • 3OCO2 -f- 9N2 -1- 15Na^ + 5NH3 + 24H2O
Stoichiometric ratio: Molecules NTA x atomic mass NTA = 5 x 257 = 1.15
Molecules NO3" x atomic mass NO3" 18 x 62
Dissolved Oxygen
2C6H6N06Na + 9O2 + 6H^ • 12CO2 + 6Na^ -1- 2NH3 + 6H2O
Stoichiometric ratio: Molecules NTA x atomic mass NTA = 2 x 257 = 1.78
Molecules O2 x atomic mass O2 9 x 32
Final stoichiometric demand using NTA as an electron donor is illustrated in Table 3:
Table 3. NTA Electron Donor Demand
Constituent Demand
Perchlorate
Nitrate
Dissolved
Oxygen
(0.300 ppm X 1.15 stoichiometric ratio) x 1.25 excess = 0.431 ppm NTA
(18 ppm X 1.15 stoichiometric ratio) x 1.25 excess = 26 ppm NTA
(8 ppm x 1.78 stoichiometric ratio) x 1.25 excess = 18 ppm NTA
Total 45 ppm NTA
The quantity of NTA needed for a 21 day study is calculated below:
45 mg/L NTA x 33 L Groundwater = 1485 mg NT A/day x 21 day = 31185 mg NTA
A 34 mM solution (8684 mg/L or 33g/3.8L) of NTA will deliver the required mass al a flow
rateof 0.17L/day:
45 mg/L NTA x 33 L Groundwater = 1485 mg NTA/day/8684 mg/L = 0.17 L/day
Note: The 45 ppm electron donor demand for NTA also creates a 1:1 chelator to
calcium/magnesium ion ratio.
Trealmenl 2: Sodium Benzoate
Sodium Benzoate (SB) is commonly used as an antimicrobial in processed foods. Generally,
SB becomes inhibitory al concentralions greater than 1000 ppm and pH values less lhan 5.
SB is readily degraded in bolh aerobic and anaerobic environments. Although SB has an
inhibitory effecl on bacteria, the ability lo maintain necessary concentrations and an effeclive
J.H. Wells Paee 7 4/18/2007
.\TK l.aiincli .Svslenis Hiuimrinicnial Services
pH while maintaining the proper levels for perchlorate reduction become limiting faclors.
Furthermore, SB may not have an inhibitory effecl on some organisms in a diverse
groundwaler microbial communiiy. Nevertheless, like NTA, SB is metabolized by bacteria
with specific enzymes that allow for the molecule lo be broken down inlo functional
intermediates. Therefore, a portion of the microbial communiiy is directly stimulated. This
can include the targei perchlorate reducers. A perchlorate reducing Dechloromonas strain
was found lo degrade benzene anaerobically wilh perchlorate as the terminal electron
acceptor (Chakraborty et al, 2005).
Perchlorate
4C7H502Na+15C104'-t-4H^ —• 28CO2-i-15Cr-f-4Na^-(-4NH3-1-I2H2O
Stoichiometric ratio: Molecules SB x atomic mass SB = 4 x 144 = 0.39
Molecules CIO4" x atomic mass CIO4" 15 x 99
Nitrate
C7H502Na-I-6NO3" + 7H^ • 7CO2-t-3N2-t-Na*-1-6H2O
Stoichiometric ratio: Molecules SB x atomic mass SB = 1 x 144 = 0.39
Molecules NO3' x atomic mass NO3" 6 x 62
Dissolved Oxygen
2C7H502Na + 15O2 -I- 2H* • 14CO2 -1- 2Na* + 6H2O
Stoichiometric ratio: Molecules SB x atomic mass SB = 2 x 144 = 0.6
Molecules O2 x atomic mass O2 15 x 32
Final stoichiometric demand using SB as an electron donor is illustrated in Table 4:
Table 4. Sodium Benzoate Electron Donor Demand
Constituent Demand
Perchlorate
Nitrate
Dissolved
Oxygen
(0.300 ppm x 0.39 stoichiometric ratio) x 1.25 excess = 0.146 ppm SB
(18 ppm X 0.39 stoichiometric ratio) x 1.25 excess = 8.8 ppm SB
(8 ppm X 0.6 stoichiometric ratio) x 1.25 excess - 6 ppm SB
Total 15 ppm SB
The quanlily of SB needed for a 21 day study is calculated below:
15 mg/L SB X 33 L Groundwater = 495 mg SB/day x 21 day = 10395 mg SB
J.E. Wells Paee 8 4/18/2007
.A TK Launch .Svsleins r.uviiunmcnial Seivues
A 20 mM solulion (2895 mg/L or llg/3.8L) of SB will deliver the required mass al a flow
rate of 0.17L/day:
15 mg/L SB X 33 L Groundwater = 495 mg SB/day/2895 mg/L = 0.17 L/day
Trealmenl 3: NTA/SB Mixture
A likely scenario is a mixlure of both SB and NTA. NTA's potenlial lo deter biofilm
formation by the reduction of free calcium and magnesium cations is a significant attribute.
However, il is unknown how well il might function as a sole electron donor or what
microbial populations might be specifically stimulated. SB's biocide properties are limiied
lo concentrations and pH levels that are mosl likely undesirable and difficult lo achieve (high
concentration to achieve biocidal properties in excess of demand). On the olher hand, SB
has been shown to be metabolized directly via perchlorate reduction; allowing for the hope
for specific stimulation of perchlorate reducers. A 50/50 combination of NTA and SB will
be used lo study the combined effects.
Positive Control: Citric Acid
Citric acid has previously been used as an electron donor at the EISB and generaied
significani biofouling in the recharge well (RW-1). Therefore, it is being used as the
positive conlrol in this study to evaluate if the flow cell design and the waler chemistry
support the same extent of biofouling previously observed.
Perchlorate
4C6H807-I-9C104' —• 24C02-l-9Cr+I6H2O
Stoichiometric ratio: Molecules Citric Acid x atomic mass Citric Acid = 4 x 192 = 0.86
Molecules CIO4" x atomic mass CIO4' 9 x 99
Nitrate
5C6H8O7 -I- I8NO3" -I- 18H* • 3OCO2 + 9N2 -I- 29H2O
Stoichiometric ratio: Molecules Citric Acid x atomic mass Citric Acid = 5 x 192 = 0.86
Molecules NO3" x atomic mass NO3" 18 x 62
Dissolved Oxygen
2C6H8O7 + 9O2 -I- 2H* • i2C02 + 8H2O
Stoichiometric ratio: Molecules Citric Acid x atomic mass Citric Acid = 2 x 192 = 1.33
Molecules O2 x atomic mass O2 9 x 32
J.F. Wells Paee 9 4/18/2007
.ATK l.aLincli Svslciiis P.iniinninenial Ser\ lee^
Final stoichiometric demand using SB as an electron donor is illustrated in Table 5:
Table 5. Citric Acid Electron Donor Demand
Constituent Demand
Perchlorate
Nitrate
Dissolved
Oxygen
(0.300 ppm x 0.86 stoichiometric ratio) x 1.25 excess - 0.332 ppm Citric
Acid
(18 ppm X 0.86 stoichiometric ratio) x 1.25 excess = 19.4 ppm Citric Acid
(8 ppm X 0.6 stoichiometric ratio) x 1.25 excess = 13.3 ppm Citric Acid
Total 33 ppm Citric Acid
The quanlily of citric acid (CA) needed for a 21 day study is calculated below:
33 mg/L CA X 33 L Groundwaler = 1089 mg CA/day x 21 day = 22869 mg CA
A 33 mM solulion (6315 mg/L or 24g/3.8L) of CA will deliver the required mass al a flow
rateof 0.17L/day:
33 mg/L CA X 33 L Groundwater = 1089 mg CA/day/6315 mg/L = 0.17 L/day
Negative conlrol: No Donor
This trealmenl allows for biofilm formation observations lo be laken when no donor is
preseni. The negative control provides a measure of biofilm formation due to intrinsic
groundwater properties.
Continuous vs Batch Delivery
To study the impacl of electron donor delivery rale on biofilm formation, the flow cell for each
treatment will be operated in both a continuous and batch delivery configuration. Continuous
delivery provides a low concentration environmeni in the BAS where electron donor is always
present. The electron donor feed pump will be calibrated to deliver donor al a consistent 0.118
mL/min feed rale lo achieve the 0.17 L/day donor requiremenl. Alternatively, a batch delivery
configuration provides an environmeni in the BAS where donor is preseni for only a short period
of time but at high concentrations. For this configuration, the electron donor feed pump will be
calibrated to inject the 0.17 L daily requiremenl in a single timed injeciion.
Sample Collection
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Water samples will be collected from the discharge hose that connects the Sample Reservoir to
the Feed Reservoir. Waler collected al this point will have been retained in the cell
approximaiely 24 hours afler electron donor addition. The first sample from each cell will be
taken circa 24 hours afler the study has been initiated. Dissolved oxygen and oxidation-
reduction potential (ORP) in the Sample Reservoir will be monitored daily to determine when
the second sampling should occur. Once Oxygen and ORP have reached suitable levels for
perchlorate reduction (DO < 2 mg/L and ORP < 100 mV), a second sample will be laken from
each cell. Subsequeni samples for laboratory analysis will be taken once per week or as deemed
necessary. Approximaiely 300 to 340 mLs of water will be sampled for perchlorate, nitraie and
electron donor.
Safety Requirements
Special care will be laken to ensure personnel working wilh or around the flow cells are nol
exposed lo hazardous conditions. Placards will be in place indicating the chemicals in use and
their concentrations as well as the HazCom Web MSDS number as shown in Table 6.
All personnel working wilh the flow cells
under experimental conditions will be
required lo wear safety glasses with side
shields, smock and natural rubber latex
gloves. In addilion, to prolecl againsi
electrical shock, all electrical devices will
be connected lo an appropriale ground
fault circuit interrupter (GFCI) as directed
by ATK Safely. Additional requirements
TABLE 6. Chemicals Planned for Flow Cell
Experiments: MSDS Information
Chemical Name
Ammonium Perchlorate
Citric Acid
Nitrilotriacetic Acid
Polassium Nitrate
Sodium Benzoate
HazComWeb MSDS #
6116
17449
17448
17450
17447
may be added as deemed necessary by ATK Safety.
Post Study Material Disposal
All waler and rinse water used in this study will be disposed of by processing ihrough the
perchlorate bioreactor al Promontory's M705 treatment facility. Conlainers, tubing and other
components ofthe flow cell will be triple rinsed before slorage or disposal.
Summary
Allemative electron donors that specifically largel the perchlorate reducing microbial population
should be preferred over more generalisl donors such as ethanol and citric acid. Also, electron
donors that inlerfere wilh biofilm formation are expected lo provide addilional advantages. NTA
and SB both have these attributes. In addition, their potential as a mixture is appealing. This
bench scale study evaluates the effectiveness of NTA, SB and SB/NTA lo limil biofouling while
also stimulating microbial perchlorate reduction. In addilion, the study will investigate the most
effeclive delivery means for each of the donor treatments. Finally, the flow cell reactor syslem
can be utilized for fulure evalualion of biofilm conlrol agenis as needed.
J.F. Wells Paee 1 1 4/18/2007
.ATK l.aunch Svslcms Hnvironiiicnial Services
Works Cited
Banin, E., K.M. Brady, E. P. Greenberg. 2006. Chelalor-Induced Dispersal and Killing of
Pseudomonas aeruginosa Cells in a Biofilm. Appl. Environ. Microbiology. 72: 2064-2069.
Turakhia, M.H., K.E. Cooksey, W.G. Characklis. 1983. Influence ofa Calcium-Specific Chelant
on Biofilm Removal. Appl. Environ. Microbiology. 46: 1236-1238.
Bourquin, A.W., V.A. Przybyszewski. 1977. Distribution of Bacteria with Nitrilotriacetale-
Degrading Potential in an Estuarine Environmeni. Appl. Environ. Microbiology. 34: 411-418.
Jenal-Wanner, U., T. Egli. 1993. Anaerobic Degradation of Nilrilotriacetate (NTA) in a
Denitrifying Bacterium: Purification and Characterization of the NTA Dehydrogenase-Niirate
Reductase Enzyme Complex. Appl. Environ. Microbiology. 59: 3350-3359.
Chakraborty, R., S.M. O' Connor, E. Chan, J. D. Coates. 2005. Anaerobic Degradation of
Benzene, Toluene, Elhylbenzene, and Xylene Compounds by Dechloromonas Strain RGB.
Appl. Environ. Microbiology. 71: 8649-8655.
Coates, J.D., L.A. Achenbach. Chapler 11. The Microbiology of Perchlorate Reduction and ils
Bioremedialive Application.
www.science.siu.edu/microbiology/achenbach/Chaplerl2_2005.pdf
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