DCE/VC Stall at Natural Attenuation Sites

Transcription

1 RITS Fall 2003 DCE/VC Stall at Natural Attenuation Sites Strategies for Mitigation during Natural Attenuation or Bioremediation of Chlorinated Ethenes North Wind, Inc. Electron Acceptor O 2 Electron Donor Food Electron Donor + Electron Respiration Acceptor Products + Energy

2 Presentation Overview Reductive Dechlorination Primer Causes of DCE Stall Electron Donor Limitation Biological Limitation Solution Strategies No Action Monitored Natural Attenuation Monitored Natural Attenuation Wait for Complete Dechlorination to Ethene Biostimulation for Reductive Dechlorination Bioaugmentation for Reductive Dechlorination Biostimulation for Enhanced Biological Oxidation Summary 2

3 Microbial Metabolism Electron Acceptor O 2 Electron Donor Food Electron Donor + Electron Respiration Acceptor Products + Energy For example, glucose oxidation: C 6 H 12 O 6 + 8O 2 6CO H 2 O kcal 3 Reductive Dechlorination Primer

4 Bioremediation Metabolism Electron Acceptor O 2, NO, etc. 3 Electron Donor BTEX e.g., C 6 H O 2 6CO 2 + 3H 2 O Electron Acceptor Chlorinated Solvents Electron Donor Food (Organic Compound) e.g., C 2 Cl 4 (PCE) C 3 H 5 O 3- (lactate) +2.33H 2 O C 2 H 4 (ethene) + 4HCl CO HCO 3-4 Reductive Dechlorination Primer

5 Reductive Dechlorination of Chlorinated Ethenes In Situ Biodegradation of chlorinated solvents: Chlorinated organics utilized as electron acceptors by indigenous microorganisms Chlorine atoms sequentially replaced with hydrogen through reductive dechlorination 5 Reductive Dechlorination Primer

6 Reductive Dechlorination Pathway Cl Cl Cl Cl PCE C C TCE C C Cl Cl Cl H 1,1 -DCE cis - 1,2 - DCE trans - 1,2 -DCE Cl H Cl Cl H Cl C C C C C C Cl H H H Cl H Vinyl Chloride H Cl C C CI Chlorine Atom H H C H Carbon Atom Hydrogen Atom Single Chemical Bond Double Chemical Bond H H Ethene H C C H O C Complete Mineralization O O Cl H H H H Ethane H C C H Modified from Wiedemeier et al., Reductive Dechlorination Primer H H

7 Electron Donor, Redox Conditions, and Dechlorination O 2 NO - 3 When electron donor is very limited oxygen will be present, and only aerobic organisms will be active because they derive the most energy Fe +3 SO 4 CO 2 x. z z z z z. PCE/ TCE DCE/ VC Electron Donor 7 Reductive Dechlorination Primer Copyright North Wind, Inc., 2003

8 Electron Donor, Redox Conditions, and Dechlorination (cont.) NO - 3 If enough electron donor is present to deplete the oxygen, anaerobic organisms that can use nitrate will become active Fe +3 SO 4 CO 2 x. z z z z z. PCE/ TCE DCE/ VC Electron Donor 8 Reductive Dechlorination Primer Copyright North Wind, Inc., 2003

9 Electron Donor, Redox Conditions, and Dechlorination (cont.) Once nitrate is depleted due to higher levels of electron donor, ironreducing organisms become active; at this point the energy available from reducing PCE or TCE is still lower than the naturally occurring electron acceptors Electron Donor Fe +3 SO 4 CO 2 x. z z z z z. PCE/ TCE DCE/ VC 9 Reductive Dechlorination Primer Copyright North Wind, Inc., 2003

10 Electron Donor, Redox Conditions, and Dechlorination (cont.) When the electron donor is sufficient to deplete naturally occurring electron acceptors down to sulfate, organisms that reduce PCE and TCE can finally derive enough energy to compete, and become active Electron Donor SO 4 CO 2 PCE/ TCE DCE/ VC Copyright North Wind, Inc., Reductive Dechlorination Primer

11 Electron Donor, Redox Conditions, and Dechlorination (cont.) Due to the low energy available from reduction (dechlorination) of DCE and VC, organisms can generally only carry out this process when sufficient electron donor is present to create methanogenic conditions (carbon dioxide being the electron acceptor) Electron Donor CO 2 DCE/ VC Copyright North Wind, Inc., Reductive Dechlorination Primer

12 Presentation Overview Reductive Dechlorination Primer Causes of DCE Stall Electron Donor Limitation Biological Limitation Solution Strategies No Action Monitored Natural Attenuation Monitored Natural Attenuation Wait for Complete Dechlorination to Ethene Biostimulation for Reductive Dechlorination Bioaugmentation for Reductive Dechlorination Biostimulation for Enhanced Biological Oxidation Summary 12

13 DCE Stall Reductive dechlorination of PCE and TCE to DCE appears to be universal at sites where conditions are at least sulfate reducing At some sites, all of the necessary conditions for efficient, complete dechlorination of PCE or TCE to ethene are not present and degradation stalls at DCE The basic requirements are: Sufficient electron donor (usually derived from a carbon source) to achieve strongly reducing conditions Bacteria capable of efficient dechlorination of DCE to ethene It should be noted that biological activity can be hindered at some sites by extreme conditions that are not related to the above requirements, including extreme ph, presence of biotoxins, micronutrient limitations, etc. 13 Causes of DCE Stall

14 Presentation Overview Reductive Dechlorination Primer Causes of DCE Stall Electron Donor Limitation Biological Limitation Solution Strategies No Action Monitored Natural Attenuation Monitored Natural Attenuation Wait for Complete Dechlorination to Ethene Biostimulation for Reductive Dechlorination Bioaugmentation for Reductive Dechlorination Biostimulation for Enhanced Biological Oxidation Summary 14

15 Electron Donor Limitation The first potential reason for DCE stall is a lack of sufficient electron donor (usually a fermentable carbon source) to achieve the necessary strongly reducing conditions This occurs when either natural or introduced carbon sources are sufficient to achieve iron- or sulfate-reducing conditions, but are exhausted before the natural sulfate Some examples are presented for two cases: Pre-biostimulation Post-biostimulation 15 Causes of DCE Stall

16 Pre-Biostimulation: Test Area North TSF ppb TAN-37 TAN-26 TAN ppb Generally anoxic conditions, but no dissolved iron, and sulfate above background at 30 to 40 mg/l (Sorenson et al. 2000) 100 ppb Pre-biostimulation conditions at TAN (µg/l except COD in mg/l) 16 Summary point: Lack of electron donor results in DCE stall Causes of DCE Stall: Carbon Limitation Examples TSF-05 TAN-25 TAN-26 TAN-37 COD* 5 <5 <5 <5 PCE TCE cis-dce VC ND ND ND ND Ethene ND ND ND ND *Chemical Oxygen Demand (COD) is used as a surrogate for electron donor

17 Pre-Biostimulation: Naval Weapons Station Seal Beach Site 40 Locomotive maintenance shop where solvents were disposed to the ground with some petroleum hydrocarbons over a period of several years A natural attenuation evaluation previously concluded reductive dechlorination was occurring in isolated areas, but primarily to cis-dce. In July 2001, sulfate ranged from 160 to 480 mg/l, and ORP was approximately +150 mv. Summary point: Lack of electron donor results in DCE stall MW-22 MW-25 MW-23 MW-26 COD 28 <20 <20 36 PCE TCE cis-dce VC ND ND ND ND Ethene ND ND ND ND 17 Causes of DCE Stall: Carbon Limitation Examples

18 Post-Biostimulation: Ft. Lewis, WA, East Gate Disposal Yard Ft. Lewis Reductive Anaerobic Biological In Situ Treatment Technology (RABITT) Treatability Testing (Battelle et al. 2002) A pilot test was conducted using butyric acid as an electron donor in the TCE-contaminated site Initial TCE concentrations were about 5,200 µg/l, cis-dce concentrations were about 5,800 µg/l, and vinyl chloride concentrations were about 12 µg/l Butyric acid was injected continuously at approximately 550 mg/l at a rate of about 0.5 L/min into three injection wells and monitored at wells 10, 20, and 30 ft downgradient The results, as described in the RABITT final report, were that cis- DCE accumulated, VC was produced at low levels, and ethene was not observed in significant quantities. 18 Causes of DCE Stall: Carbon Limitation Examples

19 Post-Biostimulation: Ft. Lewis TCE Site Layout Monitoring Well Array Injection Wells MW-9 3 ft MW-8 MW-7 MW-5 10 ft MW-6 MW-4 MW-3 MW-2 MW-1 10 ft 10 ft IW-3 IW-2 IW-1 19

20 Post-Biostimulation: Ft. Lewis TCE 20 Causes of DCE Stall: Carbon Limitation Examples

21 Post-Biostimulation: Ft. Lewis cis-dce 21 Causes of DCE Stall: Carbon Limitation Examples

22 Post-Biostimulation: Ft. Lewis Vinyl Chloride 22 Causes of DCE Stall: Carbon Limitation Examples

23 Post-Biostimulation: Ft. Lewis Methane and ORP Average Methane Concentration (µg/l) Begin butyric acid injection Methane Ethene Ethane Time (Weeks) Average Methane, Ethane, and Ethene Concentrations at the EGDY, Fort Lewis, WA Ethene and Ethane (µg/l) Methane spiked and average ORP reached its lowest point in Week 17, coincident with VC production and following the injection of the high concentration butyric acid slug. Following the pump repair, things returned to Week 12 conditions. Summary point: DCE stall was only mitigated when electron donor was increased, and recurred when electron donor was limiting 23 Causes of DCE Stall: Carbon Limitation Examples

24 Post-Biostimulation: Ft. Lewis (cont.) In the discussion of these results in the RABITT final report it was acknowledged that the redox potential in situ may never have been depressed enough to achieve significant levels of cis-dce dechlorination. The methane and VC production following the injection of high-concentration butyric acid support this conclusion, and the fact that increased electron donor levels might have alleviated the problem. This issue is also discussed in the following excerpt from the Draft Tri-Services Bioremediation Guidance Document: An increased rate of hydrogen production will result in increased halorespiration without affecting the competition between various bacteria for the available hydrogen Attempts to limit hydrogen concentrations in practical heterotrophic field systems may result in significant portions of the targeted zone not reaching sufficiently reducing conditions for optimum treatment, which can then result in sites stalling at cis-dce and VC. 24 Causes of DCE Stall: Carbon Limitation Examples

25 Post-Biostimulation: New Jersey Superfund Site A bioaugmentation pilot study was performed (although Dehalococcoides ethenogenes was detected in background samples) A combination of lactate, acetate, and methanol was initially used as an electron donor (acetate was eventually dropped) The primary terminal electron accepting process after more than 1 year of electron donor injection appeared to be sulfate reduction Reductive dechlorination of TCE stalled at cis-dce at most wells; in one exception, significant VC was produced, but negligible ethene 25 Causes of DCE Stall: Carbon Limitation Examples

26 Post-Biostimulation: New Jersey Site (cont.) Summary Point: Stalled dechlorination likely due to insufficient carbon to generate strongly reducing conditions A decrease in ORP was accompanied by an increase in VC in samples collected in November Data courtesy of U.S. EPA Region 2 26 Causes of DCE Stall: Carbon Limitation Examples

27 Presentation Overview Reductive Dechlorination Primer Causes of DCE Stall Electron Donor Limitation Biological Limitation Solution Strategies No Action Monitored Natural Attenuation Monitored Natural Attenuation Wait for Complete Dechlorination to Ethene Biostimulation for Reductive Dechlorination Bioaugmentation for Reductive Dechlorination Biostimulation for Enhanced Biological Oxidation Summary 27

28 Biological Limitation The second possible reason for DCE stall is that no bacteria are present at the site that are capable of efficiently dechlorinating DCE to ethene Only one species of bacteria has been identified that is capable of complete dechlorination of PCE or TCE to ethene in a pure culture: Dehalococcoides ethenogenes Characterization of microbial communities at sites all over the world has revealed that D. ethenogenes is present in a wide variety of environments, but is not ubiquitous. For example, in a survey of dechlorinating sites in North America and Europe, it was observed that D. ethenogenes was detected at all 21 sites with complete dechlorination, and none of the 3 sites with DCE stall. 28 Causes of DCE Stall: Biological Limitation

29 Biological Limitation: Hendrickson et al Kent, WA Lorenz, CA Sacramento, CA Winfield, KS Kelly AFB, TX LF Kelly AFB, TX Kelly AFB, TX Pilot Victoria, TX Beaumont, TX Complete dechlorination Partial dechlorination Bioaugmentation plot Newark, OH DeLisle, MS Southern Ontario, Canada Niagara Falls, NY 1 Niagara Falls, NY 2 Niagara Falls, NY 3 Pompton Lakes, NJ Dover AFB, DE LF 13 Pinellas, FL Dover AFB, DE Dover AFB, DE Pilot Cheshire, England Central Holland Dordrecht, Holland Amsterdam, Holland 29 Locations of the chloroethene-contaminated sites in North America and Europe that were tested for Dehalococcoides group 16S rdna sequences Causes of DCE Stall: Biological Limitation

30 Biological Limitation: Dover AFB (EPA 2000) A biostimulation pilot test was conducted from September 1996 to May 1997 with lactate as an electron donor, resulting in conversion of TCE to cis-dce Process Diagram of Bioaugmentation at Dover AFB Injection Wells Substrate, Nutrients, and Nonindigenous Bacteria Recovery Wells In spite of complete removal of sulfate and production of methane, no degradation to VC or ethene was observed 30 Confining Layer Groundwater Flow Causes of DCE Stall: Biological Limitation Complete dechlorination to ethene was observed after a 3-month lag following addition of 350 L of culture containing D. ethenogenes after 9 months, TCE and DCE were absent Summary Point: electron donor was not limiting; biology apparently was

31 Biological Limitation: Kelly AFB (Major et al. 2002) After 87 days of acetate and methanol addition (beginning Day 89), dechlorination of TCE had only proceeded to cis-dce* On Day 176, a D. ethenogenes-containing culture was added and complete dechlorination to ethene was observed about 75 days later *Laboratory microcosm studies had also suggested that DCE stall might be an issue at the site; also D. ethenogenes DNA was not detected at the site prior to bioaugmentation Summary Point: electron donor was not limiting, but biology apparently was 31 Causes of DCE Stall: Biological Limitation

32 Biological Limitation: NWS Seal Beach (BEI 2002) A 6-month biostimulation pilot study was performed beginning in August 2001 to treat PCE using lactate as an electron donor At the end of the study, complete conversion of PCE to cis-dce was observed along with methanogenesis, but no VC or ethene Compound Concentrations (micromolar) /13/01 MW-22 Reductive Dechlorination Results ETH VC DCE TCE PCE 8/13/01 9/13/01 10/13/01 11/13/01 12/13/01 1/13/02 2/13/02 DNA analysis revealed that D. ethenogenes could not be detected at the site (a bioaugmentation pilot test is now under way) Electron donor was not limiting, but biology appears to be 32 Causes of DCE Stall: Biological Limitation

33 Example: Tennessee Air National Guard (Romer et al. 2003) A large-scale biostimulation pilot was begun in May 2002 using lactate to treat PCE, TCE, and DCE After 8 months of monitoring, complete conversion of PCE and TCE to cis-dce was observed, but almost no VC or ethene in spite of ample electron donor and methanogenic conditions DNA analysis revealed only trace detections of D. ethenogenes in 1 of 6 wells suggesting the limitation was biological 33 Causes of DCE Stall: Biological Limitation

34 Biological Limitation: Tennessee Air National Guard (cont.) DCE Stall: Well IW PCE TCE 1,1-DCE t-dce c-dce VC Ethene umol/l /4/2002 5/24/2002 7/13/2002 9/1/ /21/ /10/2002 1/29/2003 3/20/2003 5/9/2003 6/28/ Causes of DCE Stall: Biological Limitation

35 Biological Limitation: Naval Base Ventura County Pt. Mugu Biostimulation was performed beginning in December 1998 using lactic acid to treat TCE and DCE Complete and rapid conversion to VC was accomplished, with much slower conversion to ethene; in other words, VC stall was encountered rather than DCE stall Microcosm experiments suggested that the absence of TCE may have stalled dechlorination, implying that VC dechlorination was cometabolic and was induced or accelerated by the presence of TCE (L. Semprini, personal communication) 35 Causes of DCE Stall: Biological Limitation

36 Presentation Overview Reductive Dechlorination Primer Causes of DCE Stall Electron Donor Limitation Biological Limitation Solution Strategies No Action Monitored Natural Attenuation Monitored Natural Attenuation Wait for Complete Dechlorination to Ethene Biostimulation for Reductive Dechlorination Bioaugmentation for Reductive Dechlorination Biostimulation for Enhanced Biological Oxidation Summary 36

37 Potential DCE-Stall Solution Strategies A variety of potential solution strategies exist and the best strategy will be dependent on site-specific issues, including: Initial contaminant concentrations Acceptable cleanup time frame Travel time to receptors Course of events that led to DCE stall Attitude toward innovative technologies (risk tolerance) Budget As a number of potential strategies are discussed, an attempt will be made to indicate how they fit into the sitespecific considerations above 37 Solution Strategies

38 Presentation Overview Reductive Dechlorination Primer Causes of DCE Stall Electron Donor Limitation Biological Limitation Solution Strategies No Action Monitored Natural Attenuation Monitored Natural Attenuation Wait for Complete Dechlorination to Ethene Biostimulation for Reductive Dechlorination Bioaugmentation for Reductive Dechlorination Biostimulation for Enhanced Biological Oxidation Summary 38

39 No Action At sites with low parent compound concentrations, DCE stall may not prevent meeting cleanup standards because DCE is less toxic than PCE or TCE PCE MCL: 5 µg/l TCE MCL: 5 µg/l cis-dce MCL: 70 µg/l VC MCL: 2 µg/l For example, at one site at NAS Dallas, maximum observed TCE concentrations were about 30 µg/l without much evidence of natural attenuation. Biostimulation resulting in conversion to cis-dce would meet cleanup standards. 39 Solution Strategies: No Action

40 No Action Advantages and Limitations 40 Advantages Very fast because conversion from PCE or TCE can be stimulated in a few months Travel time to receptors is not important because cleanup standards can be met quickly Biological limitations are not a concern, and may even be preferable Conversion of PCE and TCE to cis-dce is almost universal in the presence of sufficient carbon Can be very inexpensive at moderate to high permeability sites Solution Strategies: No Action Limitations Concentration (ppb) Only applicable for low concentration PCE or TCE sites Requires good electron donor distribution, which may be more expensive at low permeability sites DCE Stall Not Always Bad Time (months) DCE MCL TCE (ppb) DCE (ppb) TCE MCL

41 Presentation Overview Reductive Dechlorination Primer Causes of DCE Stall Electron Donor Limitation Biological Limitation Solution Strategies No Action Monitored Natural Attenuation Monitored Natural Attenuation Wait for Complete Dechlorination to Ethene Biostimulation for Reductive Dechlorination Bioaugmentation for Reductive Dechlorination Biostimulation for Enhanced Biological Oxidation Summary 41

42 Monitored Natural Attenuation (MNA) 42 DCE is less toxic than PCE or TCE Conversion of PCE or TCE to DCE may improve possibilities for MNA as many more natural attenuation pathways exist for DCE than for PCE and TCE For PCE, only reported biological pathway is reductive dechlorination For TCE, in addition to reductive dechlorination, intrinsic cometabolic oxidation has been observed, but only at slow rates For DCE, in addition to those pathways for PCE and TCE, direct oxidation has been reported. In general, natural attenuation rates will be much higher under mildly reducing or aerobic conditions. Solution Strategies

43 Natural Attenuation Pathways for DCE: Dilution/Dispersion Given that DCE is less toxic and has a higher MCL than PCE and TCE, this mechanism of attenuation may be acceptable for much higher concentrations than would be acceptable for PCE and TCE, given sufficient distances from receptors TCE TCE after 4X reduction still 20X MCLs DCE Receptor For TCE converted to DCE, 4X reduction nearly achieves MCLs 43 Solution Strategies: MNA

44 Natural Attenuation Pathways for DCE: Cometabolic Oxidation PCE is not subject to any biological oxidation, direct or cometabolic. TCE, DCE, and VC can all undergo cometabolic oxidation, which is a chance oxidation of the contaminants that occurs while bacteria are producing enzymes for other purposes such as methane oxidation. TCE Methane DCE Enzyme Cell 44 Solution Strategies: MNA

45 Natural Attenuation Pathways for DCE: Cometabolic Oxidation (cont.) Although cometabolic oxidation is not often considered to be significant for MNA, it has been observed in at least one case to be important (Sorenson et al., 2000) TCE Degradation Half-Life = 13 years ln(tce/h 3 ) ln(dce/h 3 ) ksorenson: ksorenson: Insert Insert TAN TAN DCE DCE degradation degradation fig. fig. DCE Degradation Half-Life = 8 years Distance (ft) Distance (ft) Cometabolic oxidation may be especially important following generation of methane during biostimulation, though this has not been demonstrated in the field. Approach was included in a pilot test work plan for Naval Weapons Station Seal Beach, Site Solution Strategies: MNA High Methane, No DO, DCE No Methane, Some DO, Low PCE/TCE/DCE

46 Natural Attenuation Pathways for DCE: Direct Oxidation Neither PCE nor TCE can be used directly as a carbon source by any known biological process. DCE, however, has been shown in a few studies to undergo direct oxidation as a sole carbon source. Klier et al. (1999) and Bradley and Chapelle (2000) showed DCE mineralization (conversion to CO 2 ) by mixed laboratory cultures Coleman et al. (2002) were able to isolate a bacterium that used DCE as a sole carbon source It was noted that this activity appeared to be uncommon, even at sites contaminated with DCE (only 2 of 18 samples were positive) Electron Acceptor O, 2 NO 3, etc. Electron Donor DCE 46 Solution Strategies: MNA

47 Natural Attenuation Pathways for DCE: Abiotic Degradation An increasing amount of work is being performed to evaluate the degradation of chlorinated ethenes by iron sulfides and other reactive inorganics Iron sulfides are very common at sites with reducing conditions due to iron and sulfate reduction The Fe+2 acts as an abiotic electron donor like zero-valent iron, thereby reducing chlorinated ethenes This has been suggested as a potentially important degradation mechanism downgradient of a mulch biowall at Altus AFB where dechlorination appears to stop at DCE (Henry et al. 2003) 47 Solution Strategies: MNA

48 48 Natural Attenuation Pathways for DCE: Abiotic Degradation (cont.) A >90% reduction in total moles of VOCs without the accumulation of DCE, and without generation of VC or ethene are cited as evidence that DCE stall is being managed through natural processes Well Location OU1-1 (30 upgradient) PES-MP01 (biowall) PES-MP02 (5 down) PES-MP03 (10 ) PES-MP04 (30 ) PES-MP05 (100 ) TCE (ppb) 7,200 < ,000 Solution Strategies: MNA cdce (ppb) 1, ,200 1,500 VC (ppb) < <1.0 <1.0 <1.0 <1.0 Total Molar Concentration (nm/ 80,000 70,000 60,000 50,000 40,000 30,000 20,000 10,000 0 Biowall Direction of Groundwater Flow July 2002 Sept 2002 March Distance from the Biowall (feet) A combination of mechanisms including reactions with iron sulfide, which is abundant at the site, may be responsible for the observed contaminant behavior Data used are courtesy of B. Henry, Parsons

49 Natural Attenuation Advantages and Limitations Advantages Conversion of PCE and/or TCE to DCE removes some of the obstacles to MNA, including: slowly degraded sorbed contaminants, low MCLs, and slow aerobic degradation rates May be very useful in combination with biostimulation Relatively low cost as monitoring and reporting are the only major activities Limitations Generally not applicable for high concentrations Travel time to receptors still a consideration Lack of DO may limit degradation rates Some DCE degradation mechanisms have only been demonstrated recently and regulatory acceptance may require additional sampling and some education 49 Solution Strategies: MNA

50 Presentation Overview Reductive Dechlorination Primer Causes of DCE Stall Electron Donor Limitation Biological Limitation Solution Strategies No Action Monitored Natural Attenuation Monitored Natural Attenuation Wait for Complete Dechlorination to Ethene Biostimulation for Reductive Dechlorination Bioaugmentation for Reductive Dechlorination Biostimulation for Enhanced Biological Oxidation Summary 50

51 Natural Attenuation Pathways for DCE: Wait for Complete Dechlorination ( they will come ) In the case of biological limitation, it is possible that establishment of a viable D. ethenogenes population may just require sufficient time with the appropriate conditions for their growth This idea is currently based only on ecological principles, deductive reasoning, and some preliminary data These organisms have been found all over the world (Hendrickson et al., 2002) Most old sites contaminated with fuel hydrocarbons and chlorinated solvents exhibit dechlorination past DCE if they are not carbon limited At least one more recent example may illustrate this phenomenon 51 Solution Strategies: Wait for Complete Dechlorination

52 Natural Attenuation Pathways for DCE: Wait and See Example: Sages Cleaners Site The Sages Cleaners site in Florida initially had PCE contamination with only minor amounts of dechlorination degradation products. An ethanol flood was performed to remove DNAPL, leaving high concentrations of ethanol in the ground with residual PCE Conversion of PCE to cis-dce was significant after about 13.5 months, but no significant dechlorination to VC and ethene occurred until about 40 months post-flush Data used are courtesy of S. Mravik, EPA (Ada, OK) 52 Solution Strategies: Wait for Complete Dechlorination

53 Natural Attenuation Pathways for DCE: Wait and See Example: Sages Cleaners Site - Ethanol ~1 Month Post-Flush ~5.5 Months Post-Flush C7 C4 C3 C4 C3 MW-512 MW-512 MW-514 MW-513 MW-514 MW-513 C2 MW-505 C2 MW-505 C1 C1 C7 Ethanol MW-509 MW-510 MW-511 MW-507 MW-506 MW-509 MW-510 MW-511 MW-507 MW-506 ~13.5 Months Post-Flush C7 ~22 Months Post-Flush C7 350 mm 300 mm C4 MW-514 MW-513 C2 C3 C1 MW-512 MW-509 MW-510 MW-511 MW-505 MW-507 MW-506 C4 MW-514 MW-513 C2 C3 C1 MW-512 MW-509 MW-510 MW-511 MW-505 MW-507 MW mm 200 mm 150 mm ~31 Months Post-Flush C7 ~42 Months Post-Flush C7 100 mm 50 mm C4 MW-514 MW-513 C2 C3 C1 MW-512 MW-505 C4 MW-514 MW-513 C2 C3 C1 MW-512 MW mm MW-509 MW-510 MW-511 MW-507 MW-506 MW-509 MW-510 MW-511 MW-507 MW Solution Strategies: Wait for Complete Dechlorination

54 Natural Attenuation Pathways for DCE: Wait and See Example: Sages Cleaners Site PCE Pre-Ethanol Flush ~3.5 Months Post-Flush C7 C4 C3 C4 C3 MW-512 MW-512 MW-514 MW-513 MW-514 MW-513 C2 MW-505 C2 MW-505 C1 C1 C7 PCE MW-509 MW-510 MW-511 MW-507 MW-506 MW-509 MW-510 MW-511 MW-507 MW um C4 MW-514 MW-513 C2 ~13.5 Months Post-Flush C3 C1 MW-512 MW-509 MW-510 MW-511 MW-505 MW-507 MW-506 C7 C4 MW-514 MW-513 C2 ~22 Months Post-Flush C3 C1 MW-512 MW-509 MW-510 MW-511 MW-505 MW-507 MW-506 C7 450 um 400 um 350 um 300 um 250 um 200 um 150 um ~31 Months Post-Flush C7 ~42 Months Post-Flush C7 100 um 50 um C4 MW-514 MW-513 C2 C3 C1 MW-512 MW-505 C4 MW-514 MW-513 C2 C3 C1 MW-512 MW um 54 MW-509 MW-510 MW-511 MW-507 MW-506 Solution Strategies: Wait for Complete Dechlorination MW-509 MW-510 MW-511 MW-507 MW-506

55 Natural Attenuation Pathways for DCE: Wait and See Example: Sages Cleaners Site cis-dce Pre-Ethanol Flush C7 C4 C3 C4 C3 ~3.5 Months Post-Flush C7 cis-dce MW-514 MW-513 C2 C1 MW-512 MW-505 MW-514 MW-513 C2 C1 MW-512 MW-505 MW-509 MW-510 MW-511 MW-507 ~13.5 Months Post-Flush MW-506 C7 MW-509 MW-510 MW-511 MW-507 ~22 Months Post-Flush MW-506 C7 175 um 150 um C4 MW-514 MW-513 C2 C3 C1 MW-512 MW-505 C4 MW-514 MW-513 C2 C3 C1 MW-512 MW um 100 um MW-509 MW-510 MW-511 MW-507 ~31 Months Post-Flush MW-506 C7 MW-509 MW-510 MW-511 MW-507 ~42 Months Post-Flush MW-506 C7 75 um 50 um 25 um C4 MW-514 MW-513 C2 C3 C1 MW-512 MW-505 C4 MW-514 MW-513 C2 C3 C1 MW-512 MW um 55 MW-509 MW-510 MW-511 MW-507 MW-506 Solution Strategies: Wait for Complete Dechlorination MW-509 MW-510 MW-511 MW-507 MW-506

56 Natural Attenuation Pathways for DCE: Wait and See Example: Sages Cleaners Site - VC ~28 Months Post-Flush ~31 Months Post-Flush C7 C4 C3 C4 C3 MW-512 MW-512 MW-514 MW-513 MW-514 MW-513 C2 MW-505 C2 MW-505 C1 C1 C7 Vinyl Chloride MW-509 MW-510 MW-511 MW-507 MW-506 MW-509 MW-510 MW-511 MW-507 MW um 1.8 um ~35 Months Post-Flush ~40 Months Post-Flush 1.6 um C7 C7 1.4 um C4 MW-514 MW-513 C2 C3 C1 MW-512 MW-505 C4 MW-514 MW-513 C2 C3 C1 MW-512 MW um 1.0 um MW-509 MW-510 MW-511 MW-507 MW-506 MW-509 MW-510 MW-511 MW-507 MW um 0.6 um C4 ~42 Months Post-Flush C3 C7 0.4 um 0.2 um 0.0 um MW-514 MW-513 C2 C1 MW-512 MW-505 MW-509 MW-510 MW-511 MW-507 MW Solution Strategies: Wait for Complete Dechlorination

57 Natural Attenuation Pathways for DCE: Wait and See Example: Sages Cleaners Site - Ethene Pre-Ethanol Flush C7 C4 C3 C4 C3 ~5.5 Months Post-Flush C7 Ethene MW-514 MW-513 C2 C1 MW-512 MW-505 MW-514 MW-513 C2 C1 MW-512 MW-505 MW-510 MW-511 MW-509 MW-507 MW-506 MW-510 MW-511 MW-509 MW-507 MW-506 ~13.5 Months Post-Flush ~22 Months Post-Flush 0.5 um C4 C3 C7 C4 C3 C7 0.4 um MW-514 MW-513 C2 C1 MW-512 MW-505 MW-514 MW-513 C2 C1 MW-512 MW um MW-510 MW-511 MW-509 MW-507 MW-506 MW-510 MW-511 MW-509 MW-507 MW um ~31 Months Post-Flush ~42 Months Post-Flush 0.1 um C7 C7 C4 C3 MW-512 MW-514 MW-513 C2 C1 MW-505 C4 C3 MW-512 MW-514 MW-513 C2 C1 MW um MW-510 MW-511 MW-509 MW-507 MW-506 MW-509 MW-510 MW-511 MW-507 MW Solution Strategies: Wait for Complete Dechlorination

58 Wait for Complete Dechlorination Advantages and Limitations Advantages May be technically and costeffective at low risk sites, allowing resources to be focused on higher risk sites Applicable for relatively new natural attenuation sites (cocontaminated with nonchlorinated organics and chloroethenes) or biostimulated sites that are not carbon limited Limitations Probably only applicable at lowrisk sites because may require 3 to 4 years of waiting or more Site must not be carbon limited Has not been rigorously demonstrated at multiple sites May be perceived as a stall tactic, or an attempt to avoid taking cleanup action 58 Solution Strategies: Wait for Complete Dechlorination

59 Presentation Overview Reductive Dechlorination Primer Causes of DCE Stall Carbon Limitation Biological Limitation Solution Strategies No Action Monitored Natural Attenuation Monitored Natural Attenuation Wait for Complete Dechlorination to Ethene Biostimulation for Reductive Dechlorination Bioaugmentation for Reductive Dechlorination Biostimulation for Enhanced Biological Oxidation Summary 59

60 Biostimulation for Reductive Dechlorination Sites that appear to exhibit DCE stall under natural conditions, and are electron donor-limited, might only require biostimulation to mitigate the DCE stall In this case, biostimulation refers to electron donor addition for the purpose of creating strongly reducing conditions and facilitating complete reductive dechlorination Before After Electron Donor SO 4 CO 2 PCE/ TCE DCE/ VC Electron Donor CO 2 DCE/ VC Copyright North Wind, Inc., Solution Strategies: Biostimulation

61 Biostimulation for Reductive Dechlorination: DOE s Test Area North As discussed previously, the site was carbon limited and no dechlorination beyond DCE was apparent Biostimulation using sodium lactate as an electron donor was begun in January 1999 resulting in complete dechlorination of TCE to ethene 61 Solution Strategies: Biostimulation

62 Biostimulation for Reductive Dechlorination: Test Area North (cont.) Chemical Oxygen Demand Sept. 13, 1999 TSF ft Fractured Basalt Unsaturated Zone (Not to Scale) 200-ft Fractured Basalt Aquifer??? Impermeable Interbed Solution Strategies: Biostimulation Feet

63 Biostimulation for Reductive Dechlorination: Test Area North (cont.) 2.0E-05 TAN-25 Ethenes (mol/l) 1.6E E E-06 TCE cis-dce trans-dce VC Ethene 4.0E E+00 1/6/1999 3/6/1999 5/6/1999 7/6/1999 9/6/ /6/1999 1/6/2000 3/6/2000 Date 63 Solution Strategies: Biostimulation

64 Biostimulation for Reductive Dechlorination: Naval Weapons Station Seal Beach A previous natural attenuation evaluation concluded reductive dechlorination was occurring in isolated areas, but primarily to cis-dce In July 2001, very little organic carbon was observed prior to a biostimulation pilot test; sulfate ranged from 160 to 480 mg/l, and ORP was approximately +150 mv (BEI, 2002) Biostimulation via lactate addition began in August 2001 The treatment area was initially dominated by PCE and dechlorination proceeded to DCE within about 2 months, but DCE stall was encountered even after 6 months, and no D. ethenogenes could be detected at the site 64 Solution Strategies: Biostimulation

65 Biostimulation for Reductive Dechlorination: Naval Weapons Station Seal Beach (cont.) Sodium lactate was added as a 3% solution periodically for 6 months using a simple system with no electricity Potable Water Source Dosatron Product Injector Inline Flow Meter In-Line Filter Pressure Regulator Ball Valve In-Line Check Valve Tie Down Strap 55-Gallon Drum 60% Sodium Lactate Injection Well Source: Dosatron International, Inc. Not to Scale 65 Solution Strategies: Biostimulation

66 Biostimulation for Reductive Dechlorination: Naval Weapons Station Seal Beach (cont.) Significant carbon was distributed throughout the test area COD Concentrations, Site 40 COD Concentration (mg/l) MW MW MW MW MW MW Date 66 Solution Strategies: Biostimulation

67 Biostimulation for Reductive Dechlorination: Naval Weapons Station Seal Beach (cont.) Sulfate was depleted within 2 months and methanogenesis was significant within about 3 months Methane, Site 40 Sulfate Concentration (mg/l) /8/01 7/8/01 Sulfate Concentrations, Site 40 8/7/01 9/6/01 10/6/01 11/5/01 Date 12/5/01 1/4/02 2/3/02 3/5/02 4/4/02 MW MW MW MW MW MW Methane (mg/l) MW MW MW MW MW MW /4/02 2/13/02 12/25/01 11/5/01 9/16/01 7/28/01 6/8/01 67 Solution Strategies: Biostimulation

68 Biostimulation for Reductive Dechlorination: Naval Weapons Station Seal Beach (cont.) Dechlorination stalled at cis-dce and D. ethenogenes was not detected Compound Concentrations (micromolar) /13/01 MW-22 Reductive Dechlorination Results ETH VC DCE TCE PCE 8/13/01 9/13/01 10/13/01 11/13/01 12/13/01 1/13/02 2/13/02 Compound Concentrations (micromolar) /13/01 MW-23 Reductive Dechlorination Results ETH VC DCE TCE PCE 8/13/01 9/13/01 10/13/01 11/13/01 12/13/01 1/13/02 2/13/02 Compound Concentrations (micromolar) /13/01 ETH VC DCE TCE PCE MW-25 Reductive Dechlorination Results 8/13/01 9/13/01 10/13/01 11/13/01 12/13/01 1/13/02 2/13/02 Number of Copies/mL Real-Time PCR Results of Samples to Quantitate the Occurrence of Species D. ethenogenes Decreasing Degree of Impact from Lactate Addition Decreasing Degree of Impact from Lactate Addition 68 Solution Strategies: Biostimulation Well Name

69 Biostimulation for Reductive Dechlorination Advantages and Limitations 69 Advantages Can be effective from low concentrations up to residual DNAPL conditions Much faster than MNA (assuming carbon is limited) Treatment generally occurs within electron donor distribution area, so proximity of receptors less important than for MNA For sites that are already at least mildly reducing, works with tendencies of natural system Among least expensive active treatment technologies Solution Strategies: Biostimulation Limitations Only applicable at electron donorlimited sites Will require long cleanup times if large volumes of DNAPL are present Lag times are likely to be longer at aerobic sites both for the onset of dechlorination and for complete dechlorination Extremely high bioavailable iron, or high sulfate may present challenges Other environmental factors such as extreme ph, high sulfide, other chemical toxicity issues, and trace nutrient limitations may limit biostimulation, but are uncommon

70 Presentation Overview Reductive Dechlorination Primer Causes of DCE Stall Carbon Limitation Biological Limitation Solution Strategies No Action Monitored Natural Attenuation Monitored Natural Attenuation Wait for Complete Dechlorination to Ethene Biostimulation for Reductive Dechlorination Bioaugmentation for Reductive Dechlorination Biostimulation for Enhanced Biological Oxidation Summary 70

71 Bioaugmentation for Reductive Dechlorination Once it is determined a biological limitation exists at a site, bioaugmentation becomes a viable option This application involves the addition of a D. ethenogenescontaining microbial culture to site groundwater to facilitate complete dechlorination to ethene Before After Electron Donor CO 2 x DCE/ VC Electron Donor CO 2 DCE/ VC 71 Solution Strategies: Bioaugmentation

72 Bioaugmentation for Reductive Dechlorination: Dover Air Force Base (Ellis et al., 2000) Biostimulation was performed for 269 days by injecting lactate into a TCE-contaminated aquifer that was initially aerobic DCE stall was encountered, as observed in previous microcosm and column studies using site media Bioaugmentation was performed by injecting 351 L of D. ethenogenes-containing culture enriched from DOE s Pinellas site Following a 90-day lag period, dechlorination of DCE to ethene began After 509 days, only ethene was detected in the test area 72 Solution Strategies: Bioaugmentation

73 73 TCE cdce VC Ethene Solution Strategies: Bioaugmentation Bioaugmentation: Dover AFB (cont.) Dechlorination trends from Well 7D show complete dechlorination about 5 m from the injection well beginning about 112 days after inoculation In general, it took from 98 to 140 days for ethene to be detected at wells from 1 to 17 m from the injection wells Estimated travel time from the injection wells to the monitoring wells was from 1 to 58 days

74 74 Bioaugmentation for Reductive Dechlorination: Naval Weapons Station Seal Beach A 6-month biostimulation pilot at a PCE-contaminated site using lactate resulted in DCE-stall DNA analysis revealed an absence of D. ethenogenes Bioaugmentation was begun in April 2003 through addition of 20 L of D. ethenogenes-containing culture (KB-1) in each of two inoculation wells Monitoring of the inoculation wells and two downgradient wells revealed some conversion of DCE to VC within 1 month of inoculation, though DCE persisted D. ethenogenes DNA was detected in wells about 8 ft downgradient from the inoculation wells after 3 months, and about 16 ft downgradient in 4 months Solution Strategies: Bioaugmentation

75 75 Bioaugmentation for Reductive Dechlorination: Naval Weapons Station Seal Beach (cont.) Dechlorination Data MW Bioaugmentation on Bioaugmentation on 4/16/03 ETH VC DCE TCE PCE MW ETH VC DCE TCE PCE 7/13/01 8/13/01 9/13/01 10/13/01 11/13/01 12/13/01 1/13/02 2/13/02 3/13/02 4/13/02 5/13/02 6/13/02 7/13/02 8/13/02 9/13/02 10/13/02 11/13/02 12/13/02 1/13/03 2/13/03 3/13/03 4/13/03 5/13/03 6/13/03 7/13/03 07/13/01 08/13/01 09/13/01 10/13/01 11/13/01 12/13/01 01/13/02 02/13/02 03/13/02 04/13/02 05/13/02 06/13/02 07/13/02 08/13/02 09/13/02 10/13/02 11/13/02 12/13/02 01/13/03 02/13/03 03/13/03 04/13/03 05/13/03 06/13/03 07/13/03 Compound Concentrations (micromolar) Compound Concentrations (micromolar) MW Bioaugmentation on 4/16/03 ETH VC DCE TCE PCE MW ETH VC DCE TCE PCE 7/13/01 8/13/01 9/13/01 10/13/01 11/13/01 12/13/01 1/13/02 2/13/02 3/13/02 4/13/02 5/13/02 6/13/02 7/13/02 8/13/02 9/13/02 10/13/02 11/13/02 12/13/02 1/13/03 2/13/03 3/13/03 4/13/03 5/13/03 6/13/03 7/13/03 03/25/03 04/25/03 05/25/03 06/25/03 Compound Concentrations (micromolar) Compound Concentrations (micromolar) Bioaugmentation on 4/16/03 Solution Strategies: Bioaugmentation

76 Bioaugmentation for Reductive Dechlorination: Naval Weapons Station Seal Beach (cont.) DNA Analysis Real-time polymerase chain reaction (PCR) was performed at the University of California (Berkeley) to monitor the survival and proliferation of D. ethenogenes 1.E+09 Quantitative PCR Results for Dehalococcoides 16s Gene gene copies per liter 1.E+08 1.E+07 1.E+06 1.E+05 1.E+04 MW MW MW MW MW E+03 Mar-03 Apr-03 May-03 Jun-03 Jul-03 Aug Solution Strategies: Bioaugmentation

77 Bioaugmentation for Reductive Dechlorination: Bachman Road Site (Lendvay( et al. 2003) A side-by-side test of bioaugmentation and biostimulation was performed at a shallow PCE- and DCE-contaminated site in Michigan The bioaugmentation culture was enriched from the contaminated site, and 200 L was injected in an area that initially exhibited DCE stall As the area was also carbon limited, a biostimulation test was performed nearby using lactate as an electron donor The bioaugmentation plot showed nearly complete conversion of DCE to ethene in 43 days The biostimulation plot experienced a 3-month lag, but showed nearly complete conversion to ethene after 121 days 77 Solution Strategies: Bioaugmentation

78 Bachman Road Site (cont.) Layout of test plots at Bachman Road Dechlorination trends 78 Solution Strategies: Bioaugmentation

79 Considerations for Implementing Bioaugmentation Is biostimulation sufficient to meet site needs (including schedule)? Are redox conditions suitable for bioaugmentation? Is the site electron donor limited? Are environmental conditions suitable for bioaugmentation (e.g., ph, competing electron acceptors, biotoxins, etc.)? Can bacteria be distributed cost-effectively in a relevant time frame for site cleanup goals? 79

80 Bioaugmentation Advantages and Limitations Advantages Same as biostimulation except somewhat more expensive May overcome biological limitations at a site Potentially reduces lag times Limitations Same as biostimulation except may reduce lag times at aerobic sites Effective distribution of the bacteria is not trivial; may require either large volumes of culture in a few locations, small volumes in many locations, construction of a recirculation system, or a lot of time to achieve Cost of effective distribution may be significant 80 Solution Strategies: Bioaugmentation

81 Presentation Overview Reductive Dechlorination Primer Causes of DCE Stall Electron Donor Limitation Biological Limitation Solution Strategies No Action Monitored Natural Attenuation Monitored Natural Attenuation Wait for Complete Dechlorination to Ethene Biostimulation for Reductive Dechlorination Bioaugmentation for Reductive Dechlorination Biostimulation for Enhanced Biological Oxidation Summary 81

82 Enhanced Biological Oxidation An alternative approach to dealing with biological limitations is to switch from anaerobic biodegradation processes to aerobic degradation processes DCE and VC are both susceptible to cometabolic and catabolic (for growth) degradation under aerobic conditions The injection of oxygen into a zone already containing DCE and/or VC, along with methane, will result in the growth of methanotrophs, and ultimately cometabolic oxidation Electron Acceptor O 2 Electron Donor CH 4 CO 2 + Cl DCE/VC 82 MMO e.g., C 2 Cl 3 H C 2 Cl 3 HO CO 2 + Cl - + H 2 O Solution Strategies: Enhanced Biological Oxidation Oxygenase

83 Naval Base Ventura County Pt. Mugu* 83 Biostimulation was performed beginning in December 1998 using lactic acid to treat TCE and DCE Complete and rapid conversion to VC was accomplished, with much slower conversion to ethene Microcosm experiments suggested that the absence of TCE may have stalled dechlorination, implying that VC dechlorination was cometabolic and was induced or accelerated by the presence of TCE (L. Semprini, personal communication) A pulsed-flow strategy of oxygen and methane injection was undertaken for 3 months to induce cometabolic oxidation of VC (would work nearly the same for DCE); a brief scale-up was performed with similar results *Truex et al. 2003, Johnson et al Solution Strategies: Enhanced Biological Oxidation

84 Pt. Mugu (cont.) A 5-spot was used to distribute substrates, and two 4-ft by 8-ft pallets held the aboveground equipment Nutrient Amendments Building C L A/C Pad EW-2 MW EW m (25 ft) N Recirculated groundwater Recirculated groundwater Vadose Zone or Confining Layer IW-1 EW m Biofilter Biofilter Concrete Pad C L Tent EW-3 Extraction Well (EW) Groundwater Flow Injection Well (IW) Groundwater Flow Sediment Filter (with bypass) Nitrate Stock Solution Mixing Tank Methane Gas Mixing Tank Oxygen Gas From other Extraction Wells Flow Control Valve In-Line Static Mixer Methane Eductor Booster Pump Oxygen Eductor Flow Control Valve 84 Injection Well Solution Strategies: Enhanced Biological Oxidation Direction of Aboveground Flow Extraction Well

85 Pt. Mugu (cont.) Results showed that VC degradation performance increased with time as methanotrophic activity increased Vinyl Chloride (µg/l) Vinyl Chloride at monitoring well Vinyl Chloride at manifold Methane at monitoring well Dissolved Methane (µg/l) Solution Strategies: Enhanced Biological Oxidation Days from Start of Treatment Cycles 100 0

86 Enhanced Biological Oxidation Advantages and Limitations Advantages The bacteria involved in this process are ubiquitous Bacterial growth rates, and potentially degradation rates, are higher under aerobic conditions Much faster than MNA (assuming electron donor is limited) Treatment generally occurs within oxygen and methane distribution area, so proximity of receptors less important than for MNA Cometabolic oxidation is a fairly well established and accepted process Limitations Aboveground equipment requirements are greater than for other options Concentrations higher than a few mg/l can inhibit the reaction Reduced aquifers need to be preoxidized with oxygen Design effort may be more intensive than other options Biofouling can be a problem because of higher growth rates Probably more expensive than anaerobic options 86 Solution Strategies: Enhanced Biological Oxidation

87 Presentation Overview Reductive Dechlorination Primer Causes of DCE Stall Electron Donor Limitation Biological Limitation Solution Strategies No Action Monitored Natural Attenuation Monitored Natural Attenuation Wait for Complete Dechlorination to Ethene Biostimulation for Reductive Dechlorination Bioaugmentation for Reductive Dechlorination Biostimulation for Enhanced Biological Oxidation Summary 87

88 YES NO PROCEED DCE Stall Strategies Summary Flowchart NO ACTION Are concentrations < MCLs? Was stall reached under natural attenuation conditions? Are concentrations < MCLs? NO ACTION Does risk require immediate action? Is site carbon limited? GO TO PAGE 2 Is site carbon limited? Evaluate Biostimulation Have all DCE NA pathways been fully evaluated? Perform new MNA evaluation in light of new information on DCE Is action required in < 3-4 years? Is site carbon limited? Perform microcosms and field DNA sampling DCE Stall and absence of D. ethenogenes in the field? Ready to go straight to pilot test? Perform Biostimulation Pilot including DNA sampling 88 MNA Is MNA acceptable? WAIT FOR COMPLETE DECHLORINATION GO TO PAGE 2 Is site carbon limited? DCE Stall? BIOSTIMULATION

89 FROM PAGE 1 Summary Flowchart (page 2) Perform field DNA sampling if not already complete YES NO PROCEED Strain of D. ethenogenes with known dechlorination capability present in the field? Biological limitation may be due to environmental factors such as extreme ph, extremely high bioavailable iron, high sulfate, high sulfide, other toxicity issues, nutrient limitations, etc. Can geochemistry be adjusted to fix DCE stall? BIOSTIMULATION OR CONSIDER CHEMICAL OXIDATION Bioaugmentation approved by regulators? ENHANCED BIOLOGICAL OXIDATION Perform bioaugmentation pilot DCE stall fixed? BIOAUGMENTATION 89

90 Points of Contact Naval Facilities Engineering Service Center Web Site North Wind, Inc. Web Site 90

91 References Documents Wiedemeier, T.H., M.A. Swanson, D.E. Moutoux, E.K. Gordon, J. Wilson, B.H. Wilson, D.H. Kampbell, J.E. Hansen, P. Haas, and F.H. Chapelle Technical Protocol for Evaluating Natural Attenuation of Chlorinated Solvents in Groundwater, Draft - Revision 1. Air Force Center for Environmental Excellence, Technology Transfer Division, Brooks Air Force Base, San Antonio, TX. Battelle Memorial Institute, Cornell University, Air Force Research Laboratory, Reductive Anaerobic Biological In Situ Treatment Technology (RABITT) Treatability Testing. Final Technical Report for ESTCP. Bechtel Environmental, Inc. (BEI), Technical Memorandum on Pilot Test for In Situ Enhanced Bioremediation at IR Site 40. Southwest Division Naval Facilities Engineering Command, CTO-0002/0336. Bradley, P. M., and F. H. Chapelle, Environmental Science and Technology, 34: Coleman, N. V., T. E. Mattes, J. M. Gossett, and J. C. Spain, Applied and Environmental Microbiology, 68(6): Ellis, D. E., E. J. Lutz, J. M. Odom, R. J. Buchanan, C. L. Bartlett, M. D. Lee, M. R. Harkness, and K. A. DeWeerd, Environmental Science and Technology, 34: