Enhanced In-Situ Bioremediation: How to Assess if It Can Work at Your Site

Transcription

1 Enhanced In-Situ Bioremediation: How to Assess if It Can Work at Your Site Douglas Larson, Ph.D., P.E. Geosyntec Consultants October 5-6, 2010 Introduction Overview of key microbiological processes Applicable contaminants Implementation strategies for EISB Hydrogeology Typical remediation timeframes Slide 2 1

2 Important Microorganisms Bacteria are the most important Fungi may play a role in soil but are less important in ground water What do Microbes Need to Grow? Like all living things microorganisms need: Food To supply carbon To supply energy Respiratory substrate Something to breathe Mineral nutrients t Water Usually from the same source Some use oxygen as the electron acceptor, others can use alternatives, including chlorinated solvents 2

3 Terminology and Definitions Electron donor A compound that donates electrons during its oxidation Simple organic compounds such as sugars, alcohols, or methane can be oxidized to carbon dioxide (CO 2 ) 5 Terminology and Definitions Electron acceptor A compound that accepts electrons during its reduction Inorganic compounds like oxygen, nitrate, sulfate, oxidized metals, or CO 2 can be reduced d to water, dinitrogen gas, hydrogen sulfide, dissolved metals, or methane, respectively 6 3

4 Overview of Microbial Metabolism Electron Donor or Substrate (Reduced) Sugars, Proteins, Fats Toluene; H 2 ; Fe(II) Electron Acceptor (Oxidized) Oxygen Nitrate (NO 3 ) Sulfate (SO 4 ) Fe(III), CO 2 Enzymes in a microbe Electron Donor or Substrate (Oxidized) CO 2, H 2 O, Fe(III) Electron Acceptor (Reduced) Water N 2, H 2 S Fe(II), CH 4 Chlorinateds as Electron Acceptors Electron Donor or Substrate (Reduced) H 2 ; Acetate Electron Acceptor (Oxidized) PCE, TCE, cdce, VC Enzymes in a microbe Electron Donor or Substrate (Oxidized) CO 2, H 2 O Electron Acceptor (Reduced) TCE, cdce, VC, ethene 4

5 Key Microbiological Processes Oxidation Bacteria use the contaminant as a food source (electron donor) Need an electron acceptor (e.g., oxygen) Reduction Bacteria use the contaminant as an electron acceptor Need a food source (electron donor) Co-metabolism Bacteria fortuitously break down contaminant (e.g., by enzyme secretion) Slide 9 Example Biodegradation Pathways Direct oxidation: Contaminant as food Aerobic oxidation Anaerobic oxidation Aerobic co-metabolic biodegradation Anaerobic reductive dechlorination 10 5

6 Aerobic Oxidation R-Cl Cl - Bacteria More Bacteria! O 2 e.g., BTEX Compounds, VC SVE/Bioventing Airsparging/Biosparging ORC CO 2 +HO 2 11 Anaerobic Oxidation R-Cl Bacteria O 2 Cl - Mn 4+ Mn 2+ NO - 3 N 2 Fe 3+ Fe 2+ SO 2-4 S 2- CO 2 + H 2 CH

7 Aerobic Co-metabolism Food (CH 4 ) Bacteria O 2 R-Cl CO 2 + H 2 O + Cl - CO 2 + H 2 O 13 Introduction Overview of key microbiological processes Applicable contaminants Implementation strategies for EISB Hydrogeology Typical remediation timeframes Slide 14 7

8 Contaminant Types Volatile Organic Compounds (VOCs) Aromatic and aliphatic compounds Chlorinated compounds Semi-volatile Organic Compounds (SVOCs) Polynuclear aromatic hydrocarbons (PAHs) Phthalates Explosives (HMX, RDX, TNT) Polychlorinated biphenyls (PCBs) Pesticides Metals and Other Inorganics (e.g., As, rad, CN, ClO 4 ) 15 Oxidation-Reduction Potential Example Contaminants Petroleum Hydrocarbons, MTBE, Vinyl Chloride Perchlorate Chlorinated Ethenes ORP Probe Slide 16 8

9 Biodegradable Contaminants Volatile Organic Compounds (VOCs) Aromatic and aliphatic compounds Chlorinated compounds Semi-volatile Organic Compounds (SVOCs) Polynuclear aromatic hydrocarbons (PAHs) Phthalates Explosives (HMX, RDX, TNT) Polychlorinated biphenyls (PCBs) Pesticides (in some cases; e.g., dieldrin) Metals and Other Inorganics (e.g., As, rad, CN, ClO 4 ) 17 Chlorinated Solvent Concerns Most common contaminants other than petroleum hydrocarbons Carcinogenic at very low concentrations in drinking water Volatile: can pose significant vapor intrusion risk Persistent: they usually don t biodegrade on their own Slide 18 9

10 Rules of Thumb for Degradation of Chlorinated VOCs Fully-chlorinated VOCs (PCE, CT) cannot be oxidized biotically Highly chlorinated VOCs (PCE, TCE) are more susceptible to reductive dechlorination Less chlorinated VOCs are more susceptible to oxidation (aerobic or anaerobic) Biological Reductive Dechlorination Electron H 2 Donor (food) O 2 Dhc Dhc Dhc Cell Growth Dhc Dhc Dhc Dhc Dhc Dhc R-Cl Electron Acceptor R-H + Cl - Slide 20 10

11 Reductive Dechlorination Can accumulate if requisite bacteria are absent Dehalobacter Dehalospirillum Desulfitobacterium Desulfuromonas Dehalococcoides some strains of Dehalococcoides (Dhc) Slide 21 Dehalococcoides are Ecologically Widely Distributed Michigan Rivers Kitchener Red Cedar River Père Marquette River Ithaca Kent, WA Au Sable River Newark Niagara Falls Ft Lewis, WA Neeco Park (Niagara Falls) Textron (Niagara Falls) Alameda NAS Pompton Lakes Oakley Dover AFB LF 13 Lorenz Dover AFB Pilot Sacramento Jacksonville Winfield Cape Dordrecht Kelly AFB LF Canaveral Amsterdam Kelly AFB Pilot Victoria De Lisle Central Holland Beaumont Pinellas Berlin, GR Cheshire, Cornell Labs Tiedje s Lab N. England RTDF Sites* Geosyntec* Stuttgart, GR Du Pont s Sites* German Labs Compiled by Edwin R. Hendrickson, DuPont Company,CRD/CCER & CRG Detection by 16S rdna 11

12 You Need the Right Bugs Dehaloccoides (the Queen) has to be present for complete dechlorination to ethene Fermentative Bacteria Worker bees help the Queen Provide trace nutrients Ferment compounds, provide hydrogen Poise Eh, redox, buffer against other compounds Thin-section electron micrographs showing coccoid DHC cells PCE/TCE Degradation Pathways Aerobic Conditions Tetrachloroethene (PCE) reductive dechlorination Anaerobic Conditions CO 2 cometabolism Trichlorethene (TCE) CO 2 cometabolism reductive dechlorination Dichloroethene (1,2-DCE) Anaerobic oxidation CO 2 CO 2 cometabolism reductive dechlorination Vinyl Chloride (VC) Anaerobic oxidation CO 2 reductive dechlorination CO 2 oxidation Ethene Ethane 12

13 CT/CF/Degradation Pathways Aerobic Conditions CO 2 oxidation Carbon Tetrachloride (CF) reductive dechlorination Chloroform (CF) reductive dechlorination Dichloromethane (DCM) reductive dechlorination Chloromethane (CM) Methane (CH 4 ) reductive dechlorination Anaerobic Conditions denitrification Reduction/ co-metabolism/ sulfate -reduction CO 2 CO 2, CO, CSO, CS 2 acetate, formic acid CO 2 acetate, CO 2 methanethiol demethyl sulfide Inhibition of Dechlorination - TCA Inhibition TCE/cDCE starts ~1.5 mg/l Inhibition of VC to Ethene starts ~0.07 mg/l Inhibition is ~order of magnitude higher than CF (Duhamel et al. 2002) Other, Dhb, Dhc TCE Other, Dhb, Dhc 1,1,2-TCA cdce Other, Dhb Dhc 1,2-DCA VC Dhc DCM Other, Dhb, Dhc Ethene CF Dhc = Dehalococcoides Dhb = Dehalobacter CT Other = Desulflitobacterium, Sulfurosprillium, Clostridium Inhibition = PCE 1,1,1-TCA Dhb 1,1-DCA Dhb CA 13

14 Inhibition of Dechlorination - CF Inhibition starts ~ >0.07 mg/l (Duhamel et al, 2002 doi: /s (02) ) 1,1,2-TCA Other, Dhb 1,2-DCA Other, Dhb, Dhc Dhc VC Other, Dhb, Dhc TCE Other, Dhb, Dhc Dhc Ethene cdce DCM CF Dhc = Dehalococcoides Dhb = Dehalobacter CT Other = Desulflitobacterium, Sulfurosprillium, Clostridium Inhibition = PCE 1,1,1-TCA Dhb 1,1-DCA Dhb CA Inhibition of Dechlorination - DCM Inhibition starts ~ >30 mg/l (S. Dworatzek, Per Comm) Higher concentrations for TCE Other, Dhb, Dhc TCE Other, Dhb, Dhc 1,1,2-TCA cdce Other, Dhb Dhc 1,2-DCA VC Dhc DCM Other, Dhb, Dhc Ethene CF Dhc = Dehalococcoides Dhb = Dehalobacter CT Other = Desulflitobacterium, Sulfurosprillium, Clostridium Inhibition = PCE 1,1,1-TCA Dhb 1,1-DCA Dhb CA 14

15 Introduction Overview of key microbiological processes Applicable contaminants Implementation strategies for EISB Hydrogeology Typical remediation timeframes Slide 29 In Situ Bioremediation Natural Attenuation - biodegradation via natural processes Biostimulation addition of electron donor or acceptor to enhance natural processes Bioaugmentation increasing the activity of bacteria (sometimes through the addition of specific bacteria) that break down pollutants, a technique used in bioremediation. ( Slide 30 15

16 Oxygen Delivery (Air Sparging) Electron Donors for Chlorinateds Groups are developing/demonstrating various electron donors HRC Vegetable oils Molasses Chitin Etc., etc., etc. Injected oil Differ on how they ferment and encourage worker bee activities; all produce hydrogen for the Queen Choice is based on cost-effectiveness, ease of use/installation, objectives None will work if Dehaloccoides are absent 16

17 Reductive Dechlorination Involves A Complex Microbial Community "General" organics Fermenters Methanogens Simple Organics Acetogens Acetogens Acetate Methanogens Methane Hydrogen Methane PCE Ethene Dehalorespirers HCl Electron Donor Delivery Strategies Common methods for delivering electron donor Active Recirculation Semi-Passive Delivery Jet-Injection Pull-Push Biobarrier Selection depends in part on hydrogeology 17

18 Example Biobarrier Application Pump between wells at least until breakthrough of emulsified vegetable oil (EVO) Add bacterial culture during EVO injection In one week, a 300 biobarrier was constructed using 290 gallons of EVO and 40 liters of bacterial culture EEO Culture Overburden Bedrock Full-Scale Biobarrier 36 18

19 When to Bioaugment? At PCE and TCE sites that stall at cis-dce or VC during biostimulation To assure success and accelerate enhanced in situ bioremediation (EISB) To increase bioactivity and shorten remediation time frames At mixed chlorinated solvent sites At sites with DNAPL concentrations of chlorinated solvents KB-1/VC: Edwards, U of Toronto Slide 37 Important Design Factors Some Factors That Impact Doubling Time of Dhc and Observed Ranges for Successful Bioaugmentation Temperature 8-28ºC (20-30ºC probably bl ideal) Chloroethene concentrations (> 40 µg/l saturation) ph ( ) Co-contaminants (CF <50 µg/l/ 1,1,1-TCA 200 µg/l)* ORP -90 mv and lower Sulfate up to 400 mg/l Chloride up to 5500 mg/l *may be corrected with new cultures 19

20 Bioaugmentation Cultures Bioaugmentation cultures are now available for the following types of compounds: - Chlorinated ethenes (PCE, TCE, DCEs and VC) - Chlorinated ethanes (TeCA, 1,1,2-TCA, 1,1,1-TCA and 1,2- DCA) - Chlorinated methanes (carbon tetrachloride, chloroform) and mixtures of the above New molecular tests are available to better monitor new cultures in situ, and more are under development Not all DHC bacteria can dehalogenate completely vcra gene analysis Slide 39 Example Bioaugmentation Cultures KB-1 and SDC-9 TM culture chlorinated ethenes BCI Labs chlorinated ethenes and ethanes KB-1 Plus = KB-1 + ACT-3 chlorinated ethenes and ethanes WBC-2 chlorinated ethenes, ethanes and methanes (e.g., carbon tetrachloride, 1,1,2,2-TECA) 20

21 KB-1 Bioaugmentation Culture Anaerobic bioaugmentation culture enriched from TCE site in Ontario Used to introduce Dhc to sites Contains ~100 billion Dhc/Liter Not genetically engineered/pathogen free Added at ~1/35,000 dilution in groundwater Dehalococcoides KB-1/VC (SEM) SiREM Bioaugmentation Kit 21

22 Field Application of Bioaugmentation Cultures Culture Vessel Argon Argon blanket MW Microbial Growth TCE DNAPL Biodegrader positive TCE Plume DHC spread rates of ~ 0.1 to 0.2 feet per day typical Groundwater Flow Technology Limitations Typically requires nutrient delivery and mixing Potential for system fouling and associated operation and maintenance (O&M) Potential to form undesirable degradation intermediates Methane, hydrogen sulfide, daughter products, etc. 22

23 Technology Limitations (cont d) May not be feasible for large, dilute plumes Potential for undesirable geochemical changes (e.g., metals mobilization) Introduction Overview of key microbiological processes Applicable contaminants Implementation strategies for EISB Hydrogeology Typical remediation timeframes Slide 46 23

24 Heterogeneity Slide 47 Impacts of Stratigraphy Slide 48 24

25 Oxygen Delivery (Air Sparging) 25

26 Hydraulic Conductivity Both Scenarios: Extract and 20 gpm for 15 hours Contour interval on both maps = 0.2 ft Extract (20 gpm) - Inject (20 gpm) 15 hours (18000 gallons) K=100 ft/d Extract (20 gpm) - Inject (20 gpm) 15 hours (18000 gallons) K=300 ft/d MW HA MW HA UE A HA HA HA HA MW MW MW HA 10 HA HA-4 HA HA feet 6.72 HA-7 MW MW MW HA-10 HA HA-4 HA-6 HA-5 21 feet 6.84 K = 100 ft/d K = 300 ft/d Slide 52 26

27 Introduction Overview of key microbiological processes Applicable contaminants Implementation strategies for EISB Hydrogeology and geochemstry Typical remediation timeframes Slide 53 Some Factors Affecting Remediation Timeframe Contaminant type Complex molecules Simpler molecules Faster Contaminant concentrations Lower concentrations can sometimes lead to slower degradation rates Free product (LNAPL, DNAPL): Mass transfer limitations affect dissolution rates Bulk Groundwater Flow Film thickness, δ Water NAPL Slide 54 27

28 Some Factors Affecting Remediation Timeframe (cont d) Aggressiveness of approach MNA Biostimulation Bioaugmentation Geochemistry Faster Aerobic processes generally faster Generally slower reactions as you move down the RedOx scale Slide 55 Critical Cell Count 1x10 7 DHC/L is the target concentration for effective biodegradation The in-situ doubling rate for DHC is ~16 days In-Situ DHC Population 1.E+09 2 months 4 months 6 months C ells per Liter of roundwater DHC C G 1.E+08 1.E+07 1.E+06 1.E+05 Maximum DHC Population Threshold DHC Population 1.E Time (days) High Initial DHC Moderate Initial DHC Few Initial DHC Slide 56 28

29 Long Term Impact of Source Technologies From C.J. Newell et al., 2004 SERDP Poster, Temporal changes in chlorinated solvent concentrations at 59 source depletion sites. Some Factors Affecting Remediation Timeframe (cont d) Hydrogeology Ability to distribute electron donor or acceptor throughout treatment area Diffusion limitations (e.g., at clay interfaces) Slide 58 29

30 Questions? Overview of key microbiological processes Applicable contaminants Implementation strategies for EISB Hydrogeology Typical remediation timeframes Slide 59 Contact Information Douglas Larson, Ph.D., P.E. Geosyntec Consultants, t Inc. 289 Great Road, Suite 105 Acton, Massachusetts (978) dlarson@geosyntec.com Slide 60 30