The basic science of anaerobic bioremediation
Dan Leigh PG, CHG June 4, 2013 Introduction: Dan Leigh – Licensed geologist and hydrogeologist – Walnut Creek, CA – Applying bioremediation for > 25 yrs – Applying anaerobic bioremediation of chlorinated organics for >20 yrs – Currently working on development of biogeochemical processes occurring during anaerobic bioremediation – [email protected] – 925.984.9121
Basic Science of Anaerobic Bioremediation 2 FMC provides a wide range of products for application of anaerobic bioremediation, biogeochemical and abiotic degradation EHC® Solid organic substrate with microscale ZVI EHC-L ® Liquid organic substrate with soluble Fe(II) ® ® EHC with sulfur source for biogeochemical EHC-M metals treatment
® Emulsified Lecithin Substrate for ELS enhancement of anaerobic bioremediation
® Solid organic substrate with ZVI for Daramend treatment of contaminated soils http://environmental.fmc.com/solutions Basic Science of Anaerobic Bioremediation 3 Presentation outline • Basic concepts of biological and geochemical processes – Respiration, fermentation, co metabolism – Electron donors and acceptors – Biotic and abiotic anaerobic degradation pathways of chlorinated ethenes – Processes for stimulating anaerobic bioremediation of chlorinated organics • Significant site conditions not conducive to anaerobic bioremedation and how to overcome them – Inappropriate or insufficient bacteria – High dissolved oxygen – Low pH – High sulfate concentrations • Biogeochemical degradation • Summary Basic Science of Anaerobic Bioremediation 4 Contaminants that can be degraded by anaerobic processes • Chlorinated solvents such as PCE, TCE, TCA, DCA,
CCl4, chloroform and methylene chloride • Chlorobenzenes including di- and tri-chlorobenzene • Energetic compounds such as TNT, DNT, HMX, RDX, nitroglycerine and perchlorate. • Most pesticides including DDT, DDE, dieldrin, 2,4-D and 2,4,5-T • Nitrate compounds • Petroleum hydrocarbons This presentation focuses on biological and geochemical processes that occur during the in situ anaerobic degradation of chlorinated ethenes.
Basic Science of Anaerobic Bioremediation 5 Bioremediation is a natural and sustainable remediation process. Bioremediation utilizes the life processes of organisms to reduce the concentration, mass, mobility or toxicity of contaminants.
– Yeast, fungi, bacteria or plants are stimulated to degrade toxic substances. – The primary processes include respiration and fermentation. – Not a new technology – • e.g. wastewater treatment – Improvements to bioremediation approaches are being developed. Basic Science of Anaerobic Bioremediation 6 Basic concepts of biological and geochemical processes
• Several biological processes occur during anaerobic bioremediation including: – Respiration: Aerobic and Anaerobic – Fermentation – Co-metabolism
• Abiotic processes can be integrated, or occur naturally, which enhance biological degradation processes.
• Biotic and abiotic anaerobic degradation processes occur in distinct, identifiable pathways.
Basic Science of Anaerobic Bioremediation 7 Respiration processes Eating and breathing Electron Electron Organism Donor Acceptor Respiration
Aerobic Respiration
Aerobic Respiration
Basic Science of Anaerobic Bioremediation 8 Aerobic and anaerobic respiration • Aerobic respiration
– Molecular oxygen (O2) is the only electron acceptor used in the process
• Anaerobic respiration – Any inorganic electron acceptor (other than oxygen) is used in the respiration process
• NO3, Mn(IV), As(V), Fe(III), SO4, CO2
• Cr(VI), ClO4
Basic Science of Anaerobic Bioremediation 9
Respiration Biologically Mediated Oxidation - Reduction Work Growth Light bulb Protein Synthesis Motors Reproduction
Resistor Electron Donor Electron Acceptor Negative Positive Reduced Oxidized O CnHn Fe(II) 2 Fe (III) NO HNO2 3 H2S SO4 As(III) As(V) CO H2 2 Mn(II) Mn(IV)
Basic Science of Anaerobic Bioremediation 10 Eh range for various electron acceptors
2- + - 3+ 0 Chromium (VI ) Cr2O7 + 14H + 6e 2Cr +7H O (Eh = +1330)
1000 2 Transfer
Anaerobic
+ - 0 Aerobic Oxygen O2 + 4H + 4e 2H2O (Eh = +820)
- + - 0 Electron Anaerobic Nitrate 2NO3 + 12H +10e N2(g) + 6H2O (Eh = +740)
+ - 0 Arsenic (V) H3AsO4 + 2H +2e H3AsO3 + H2O (Eh = +559) + - Manganese (IV) MnO2(s) + HCO3 +3H + 2e MnCO3 (s) + 2H20 500 (Eh0 = +520)
Redox Potential (Eh0) in Millivolts @ pH = 7 and T = 250C 0
Iron - - 0 - FeOOH(s) +HCO3 + 2H+ e FeCO3 + 2H2O (Eh = 50)
Sulfate SO 2- + 9H+ + 8e- 0 -
4 HS- + 4H2O (Eh = 220) Decreasing Amount of Energy Released During During Released of Energy Amount Decreasing + - 0 - -250 Methanogenesis CO2 + 8H + 8e CH4 + 2H2O (Eh = 240) Basic Science of Anaerobic Bioremediation 11 Anaerobic respiration and chlororespiration
Electron Electron Biota Donor Acceptor Respiration
Mn(IV) NO3 AnaerobicAerobic Fe(III) RespirationRespiration SO4 CO2
Chlororespiration
Basic Science of Anaerobic Bioremediation 12
Eh range for cholorinated ethene degradation
2- + - 3+ 0 Chromium (VI ) Cr2O7 + 14H + 6e 2Cr +7H O (Eh = +1330)
1000 2 Transfer
Anaerobic
+ - 0 Aerobic Oxygen O2 + 4H + 4e 2H2O (Eh = +820)
- + - 0 Electron Anaerobic Nitrate 2NO3 + 12H +10e N2(g) + 6H2O (Eh = +740)
+ - 0 Arsenic (V) H3AsO4 + 2H +2e H3AsO3 + H2O (Eh = +559) + - Manganese (IV) MnO2(s) + HCO3 +3H + 2e MnCO3 (s) + 2H20 500 (Eh0 = +520)
Redox Potential (Eh0) in Millivolts @ pH = 7 and T = 250C 0
Iron FeOOH(s) +HCO - + 2H+ e- 0 - 3 FeCO3 + 2H2O (Eh = 50) Range for Effective PCE TCE Chlorinated Ethene Degradation TCE DCE (chlororespiration) DCE VC Sulfate SO 2- + 9H+ + 8e- 0 - 4 HS- + 4H2O (Eh = 220) VC Ethene Decreasing Amount of Energy Released During During Released of Energy Amount Decreasing ↓ -250 Methanogenesis CO + 8H+ + 8e- CH + 2H O (Eh0 = -240) 2 4 2 Basic Science of Anaerobic Bioremediation 13 Many organisms generate energy by fermentation rather than respiration • Fermentation refers to the conversion of sugar to acids, gases and/or alcohol using yeast or bacteria.
• Fermentation does not use an electron transport chain
(e.g. O2, NO3, Mn(IV), SO4, CO2) as does respiration.
• Fermentation uses a reduced carbon source (e.g., cellulose, lecithin, lactose, sugars). – to generate volatile fatty acids ((VFAs) e.g. lactic, acetic, propionic, valeric, butyric acids)
– and gases (e.g. H2, CO2, CH4)
• H2 is used by dechlorinating bacteria to generate energy by sequentially reducing chlorinated organics.
Basic Science of Anaerobic Bioremediation 14 A note about co-metabolic oxidation The microbial breakdown of a contaminant in which the contaminant is oxidized incidentally by an enzyme or cofactor that is produced during microbial metabolism of another compound is called aerobic/anaerobic co-metabolism. – Co-metabolic oxidation applies respiration processes: • Electron donor: (e.g., methane, ethane, ethene, propane, butane, toluene, phenol,
ammonia) PLUS: electron acceptor (e.g, O2, SO4) – Enzymes generated to degrade food source also fortuitously degrades CEs or other contaminants. – The degrading organism does not gain energy from the contaminant degradation. – The presence of electron donor may inhibit contaminant degradation. Co-metabolism can be a challenge to apply. – Often requires substantial engineering effort – It is difficult to identify co-metabolic degradation in the aquifer – May not be an efficient use of substrate
Basic Science of Anaerobic Bioremediation 15 Dechlorinating bacteria
• Several organisms capable of partially dechlorinating chlorinated organics.
• Only organism confirmed to dechlorinate DCE and VC to ethene is Dehalococcoides (Dhc).
• Dhc uses H2 as the electron donor in dechlorination process.
Basic Science of Anaerobic Bioremediation 16
Biological Reductive Dechlorination of Chlorinated Ethenes
ORP 0
- 50 H HCl HCl H H ClH HCl H H ClH HCl H C C C C C C H H H ClH H H H ClH - 150 Cl HCl H Cl HCl H cis Ethene1,2TCEPCEVC -DCE transEthenePCETCEVC 1,2 -DCE 1,1EthenePCETCEVC - DCE - 200
- 250
Basic Science of Anaerobic Bioremediation 17 β elimination (abiotic) pathway Fe Fe Fe 0 0 0
Hydrogenolysis Hydrogenation
II II II Cl Cl Cl H H H C C C C C C
Cl Cl Cl Cl Cl Cl
DichloroacetylenePCE ChloroacetyleneAcetyleneTCE AcetyleneDCEEtheneEthane
Basic Science of Anaerobic Bioremediation 18 Some Hypothesized Reaction Pathways Biotic Abiotic PCE PCE
TCE TCE Dichloroacetylene
Cis 1,2-DCE Trans 1,2-DCE 1,1-DCE, trans 1,2-DCE, cis1,2-DCE VC Chloroacetylene VC Ethene
Ethene Acetylene Ethane
Ethane CO2, CH4,H2O CO2 , CH4 , H2O α-elimination Hydrogenolysis β-elimination Hydrogenation Basic Science of Anaerobic Bioremediation 19 different when measuring standard analyticalparameters Biological and Concentration PCE Biological Degradation
Time (Chlororespiration)
Anticipated change in CE molar concentration TCE
abiotic DCE
Basic Science of Anaerobic of Basic Science Bioremediation degradationappear processes
VC
Concentration Abiotic Degradation Ethene Time
( β
elimination) 20
Total
Generating anaerobic bioremediation processes Enhanced anaerobic bioremediation is conducted by providing whatever is limiting the complete degradation process.
Electron Electron Organism Chlororespiration Donor Acceptor
Need appropriate organism and electron donor (H2) to degrade CEs
Other supplements can be made to further enhance the anaerobic process. – Chemical reductants (e.g. ZVI, ferrous iron) – Nutrients Additional supplements can be made to enhance synergistic effects. – Sulfate – Iron
Basic Science of Anaerobic Bioremediation 21 Anaerobic reductive dechlorination is stimulated by providing an electron donor to the organisms
Various substrates used to generate H2 for dechlorination:
Molasses Acetic acid and its salts Only H2 has been Starch Lactic acid and its salts shown to be an Cheese whey Propionic acid and its salts electron donor for Emulsified vegetable oil Citric acid and its salts cis 1,2-DCE and Corn syrup vinyl chloride Various Bean Oils (soy, guar) Lactose conversion to Benzoic acid and its salts Glucose ethene Oleic acid and its salts Ethanol Methanol Polylactate esters of fatty acids (e.g.., Glycerol tripolylactate) Propanol Food process byproducts including milk whey or yeast extract Lecithin Complex organic material such as wood chips (cellulose)
Glycerol, xylitol, sorbitol Complex sugars Draft General Waste Discharge Requirements for In Situ Groundwater Remediation – Molecular Hydrogen (H ) Santa Ana Water Quality Control 2 Board CA, 2013
Basic Science of Anaerobic Bioremediation 22 Substrate requirements partially determined by amount of hydrogen required to reduce electron acceptors and contaminants
Electron Acceptor Electron equivalents per mole Oxygen (dissolved) 4 Nitrate (dissolved) 4 Sulfate (dissolved/solid) 8 Maybe carbon dioxide (dissolved) 8 Manganese (IV) (solid) 2 Ferric iron (III) (Solid) 1 PCE – tetrachloroethene (dissolved + adsorbed + NAPL) 8 TCE – trichloroethene (dissolved adsorbed + NAPL) 6 DCE – dichloroethene (dissolved + adsorbed) 4 VC – vinyl chloride (dissolved + adsorbed) 2 Most of the contaminant mass may be adsorbed to aquifer matrix Basic Science of Anaerobic Bioremediation 23 Some electron acceptors may be in solid form • Solid electron acceptors Some mineral electron acceptors occur as: Barite • oxides (BaSO4) • salts • minerals
• Solid electron • Barite – BaSO4 • Gypsum – CaSO ·2H O acceptors are not 4 2 • Anhydrite – CaSO4
accounted for by • Hannebachite – CaSO3 ·0.5H2O • Anglesite (PbSO ) dissolved phase 4 2+ 3+ • Magnetite (Fe Fe 2O4 or Fe3O4)
analysis. • Hematite (Fe2O3)
Basic Science of Anaerobic Bioremediation 24 Substrate requirements partially determined by amount of hydrogen generated during fermentation Hydrogen equivalents produced by various electron donors
Electron Donor Electron equivalent per mole
acetate 4 proprionate 3 lactate 2 fructose/glucose 12 sucrose/lactose 24 cellulose 24 linoleic acid 50 glycerol 7 lecithin 122 Most data derived from Fennel & Gossett (1998) and He, et al (2002) Basic Science of Anaerobic Bioremediation 25 Reducing/reductive degradation enhancement compounds
Ferrous Chloride Sodium Dithionite
Calcium Polysulfide Ferrous Carbonate
Ferrous Gluconate Zero-Valent Iron Granular Sorbitol Cysteinate Emulsified Draft General Waste Discharge Requirements for In Situ Groundwater Remediation – Santa Micro-scale Ana Water Quality Control Board CA, 2013 Sodium Sulfide Nano-scale
Basic Science of Anaerobic Bioremediation 26 Undesired and unexpected results
Incomplete degradation (e.g. cis DCE or VC stall)
• No, or insufficient Dhc population • Insufficient /too much substrate • Inefficient distribution of substrate and culture • Geochemical issues (e.g., sulfide toxicity) • pH outside appropriate range
Contaminants disappear without generation of daughter products • May be partitioning into substrate • May be biogeochemical/abiotic degradation
Contaminants disappear but come back after substrate is gone. • Other source of contaminants • DNAPL possible • High adsorbed phase • Matrix diffusion
Basic Science of Anaerobic Bioremediation 27 Anaerobic bioremediation may be applicable at more sites than previously considered.
Some sites may not initially appear to be appropriate for anaerobic bioremediation. Some of these conditions include: • Inappropriate or insufficient dechlorinating bacteria • High dissolved oxygen concentration • Low pH • Very high sulfate concentrations
Modifications may be made to alleviate these conditions and allow use of anaerobic bioremediation.
Basic Science of Anaerobic Bioremediation 28
At some sites biostimulation is sufficient, at other sites bioaugmentation is required.
• Biostimulation is the • Bioaugmentation is the modification of the introduction of a group of environment to stimulate natural microbial strains existing bacteria capable or genetically engineered of bioremediation. variants to achieve – Nutrients – e.g. nitrogen, bioremediation. phosphorous, potassium – Indigenous – native to site – Electron acceptors – e.g. – Exogenous - introduced oxygen, nitrate, manganese, ferric iron, sulfate carbon dioxide – Electron donors – e.g. lactate, vegetable oil, lecithin, cellulose, lactose
Basic Science of Anaerobic Bioremediation 29
Is bioaugmentation necessary?
• Dechlorinating organisms may not be present at sufficient concentrations at many sites. – > 1x107 Dhc cells/L considered necessary for dechlorination • The indigenous organism may not be efficient at dechlorination. – Final step may be co-metabolic, which is slow • Indigenous organisms (e.g. methanogenic bacteria) may
outcompete dechlorinators such as (Dhc) for H2.
www.mdsg.umd.edu/CQ/v05n1/main/ Basic Science of Anaerobic Bioremediation 30 Various organisms approved for bioaugmentation
Dehalococcoides (Dhc) Geobacter
Dehalobacter Corynebacterium
Dehalogenimonas Nitrosomonas
Desulfuromonas Nitrobacter
Desulfitobacterium Rhodococcus
Desulfovbrio Pseudomonas fluorescens
Sulfurospirillum Methylibium petroleiphilum
Alcaligenes faecalis Methanotrophs
Arthrobacter Methylosinus
Basic Science of Anaerobic Bioremediation 31 Bioaugmentation can increase degradation rates ETHENES LOOPBiostimulation 3 (BIOSTIMULATION, only LACTATE ONLY) 200 Tetrachloroethene Trichloroethene 1,2-Dichloroethene (total) 150
Vinyl Chloride mol/L)
m Ethene Total umol/L 100
Concentration ( 50
0 0 30 60 90 120 150 180 210 240 270 300 330 360 Days
Basic Science of Anaerobic Bioremediation 32 Comparison of bioaugmentation to biostimulation
BiostimulationETHENES LOOP 2 (BIOAUGMENTATION, with Bioaugmentation LACTATE ) 400 Tetrachloroethene 350 Trichloroethene
High total molar concentration 1,2-Dichloroethene (total) 300
Vinyl Chloride mol/L)
m 250 Ethene Total umol/L 200
150
Concentration ( Concentration 100
50
0 0 30 60 90 120 150 180 210 240 270 300 330 360 Days
Basic Science of Anaerobic Bioremediation 33 Can anaerobic processes be applied in aerobic aquifers? • Aerobic aquifers are often not considered appropriate for the application of anaerobic biological processes.
• Bioaugmentation is necessary to treat CE’s biologically in aerobic aquifers.
• Substantial effort is considered necessary to bioaugment in aerobic aquifers (i.e., several injection events required to establish reducing conditions). – Suggests anaerobic bio treatment not cost effective.
Basic Science of Anaerobic Bioremediation 34 Bioaugmentation methods applied to overcome aerobic conditions
Plan View Inject Anaerobic25%BioaugmentationChase75% Substrate Water Chase CultureWater
Cross Section
Basic Science of Anaerobic Bioremediation 35 Sites with high dissolved oxygen can be appropriate for anaerobic bioremediation • Dhc is an obligate anaerobe – Anaerobes are organisms that are not able to use (consume) molecular oxygen. – Obligate: those that cannot grow in the presence of molecular oxygen. • Anaerobic bacteria can be: – Oxyduric: those that are not killed by (i.e. tolerant of) molecular oxygen. – Oxylabile: Those killed in the presence of molecular oxygen. – Aerotolerant: those able to grow in the presence of molecular oxygen even though they do not use it.
Basic Science of Anaerobic Bioremediation 36
Bioaugmentation methods applied to overcome aerobic conditions
Dhc exposed to oxygen in GW
Basic Science of Anaerobic Bioremediation 37 DO depletion in closed system after addition of SDC-9* and e- donor
7
6 Temperature 15 ± °C TSS 0.1 g/L DHC Concentration 9E10 cells/L 5
4
3 DO Concentration (mg/L) Concentration DO 2
1 0 100 200 300 400 500 Time (minutes) *SDC-9 is a trademark of the CB&I/Shaw Corporation Basic Science of Anaerobic Bioremediation 38 cDCE and VC degradation rates by SDC-9 exposed to air (with & without e- donor) DHC 5E10 copies/L Temperature 15±°C 25 cDCE - Anaerobic Control No Air Exposure
VC - Anaerobic Control No Air Exposure cDCE – e- donor - Air Exposure 20 VC – e- donor - Air Exposure cDCE - Air Exposure VC - Air Exposure 15
10
Degradation Rate (mg/Lxh) Rate Degradation 5
0 0 10 20 30 40 50 60 70 80 Leigh, D.P., S. Vainberg, and R.Steffan, R., 2013, Can Anaerobic Bioaugmentation Cultures be Applied Directly to Aerobic Aquifers?: In situ and on Site Bioremediation Air Exposure Time (Hours) Symposium, 2013. Basic Science of Anaerobic Bioremediation 39 Field analytical results
DissolvedCNWS - Dissolved Oxygen Oxygen
8
7
6
5
4 mg/L 3
2
1
0 -100 -50 0 50 100 150 200 250 300
Days (Day 0 = June 6, 2011)
Basic Science of Anaerobic Bioremediation 40 Groundwater analytical results after bioaugmentation of anaerobic culture into an aerobic aquifer
Trichloroethene (TCE) Total Dichloroethene (DCE)
10000 1200
1000 1000
800 100
µg/L 600 10
400 Concentration (µg/L) Concentration 1 200
0 0 -100 0 100 200 300 400 500 -100 0 100 200 300 400 500
Days (Day 0 = June 6, 2011) Days (Day 0 = June 6, 2011)
Vinyl Chloride (VC) Ethene
1000 120
100 100 80
10 60
40
1 Concentration( µg/L) Concentration( Concentration( µg/L) Concentration( 20
0 0 -100 0 100 200 300 400 500 -100 0 100 200 300 400 500
Days (Day 0 = June 6, 2011) Days (Day 0 = June 6, 2011) Basic Science of Anaerobic Bioremediation 41 Anerobic biodegradation can be conducted only in a defined range of pH
• Dhc species are very sensitive to pH.
• Some other organisms (e.g. methanogens/SRBs) are not as sensitive to pH.
• SRB’s and methanogens outcompete
dechlorinators for available H2.
• Addition of organic substrates can generate organic acids which cause pH drop.
• Addition of ZVI/buffers raises pH. Basic Science of Anaerobic Bioremediation 42 Dechlorination rates by Dhc are affected by pH
1.5
1.0
Dhc do not recover the 0.5 ability to dechlorinate after extended exposure to low pH water.
0 5 6 7 8 9 10 pH
Vainberg, S., C.W. Condee, R.J. Steffan. 2009. Large scale production of Dehalococcoides sp.- containing cultures for bioaugmentation. J. Indust. Microbiol. Biotechnol. 36:1189-1197.
Basic Science of Anaerobic Bioremediation 43 Elevated concentrations of sulfide can inhibit anaerobic biodegradation • Sulfate reduction stimulated during anaerobic bioremediation • Sulfate converted into HS- • If ferrous iron is present, it will precipitate as ferrous sulfide species such as pyrite and mackinawite • If iron is insufficient, toxic levels of HS- may accumulate.
Addition of iron can solve sulfide toxicity issues. Basic Science of Anaerobic Bioremediation 44
Example of sulfide toxicity Bench tests – ambient conditions
1000 1200 Bioaugmentation Week 17
100 1000
10 800
1 600
0.1 e- donor 400 e- donor Concentration (mg/L) Concentration Addition Addition 0.01 Week 8 200
Week 20 Sulfate & Sulfide Concentration (mg/L) Concentration Sulfide & Sulfate 0.001 0 0 4 8 12 16 20 24 28 32 Time (weeks)
TCE DCE VC Ethene Sulfate Sulfide Basic Science of Anaerobic Bioremediation 45 Example of sulfide toxicity Bench tests – Fe-sulfide precipitation
1000 1200 Bioaugmentation Week 17
100 1000
10 800
1 600
0.1 e- donor 400
Concentration (mg/L) Concentration Addition e- donor 0.01 Week 8 Addition 200
Week 20 Sulfate & Sulfide & Sulfide Sulfate Concentration (mg/L) 0.001 0 0 4 8 12 16 20 24 28 32 Time (weeks)
TCE DCE VC Ethene Sulfate Sulfide Basic Science of Anaerobic Bioremediation 46 Anaerobic biogeochemical degradation Biogeochemical degradation includes processes where contaminants are degraded by abiotic reactions with naturally occurring and biogenically-formed minerals in the subsurface.
• Reactive iron sulfide minerals are produced at sites containing bioavailble iron and sulfate during anaerobic bioremediation.
• Degradation occurs by contact with reactive minerals
• Biogeochemical degradation pathway are the same as for ZVI (β elimination).
Basic Science of Anaerobic Bioremediation 47
Reactive iron sulfides minerals are formed during anaerobic bioremediation processes
Pyrite (FeS2) Mackinawite (Fe(1+x)S
Framboidal Mackinawite Pyrite coating
(FeS2) Pyrite Framboids
Euhedral pyrite (FeS2) Mackinawite (FeS) pore coatings Basic Science of Anaerobic Bioremediation 48 Other potential applications of anaerobic bioremediation
• Sequential anaerobic/aerobic bioremediation can be applied to treat some contaminants (i.e, chlorobenzenes/CEs). • Sulfate generated during activated persulfate treatment can be reduced to generate reactive iron sulfides. • Biogeochemical processes occuring with anaerobic bioremediation can be enhanced to sequester metals. • Enhanced anaerobic bioremediation can be applied following thermal treatment. • Anaerobic bioremediation can be applied to supplement or replace existing pump and treat systems.
Basic Science of Anaerobic Bioremediation 49 Presentation Summary
• Bioremediation uses natural and sustainable processes to destroy contaminants rather than transfer to other media. • The bioremediation process is effective because it enhances the life processes of the organisms. • Because this technology uses life processes organisms it can be applied at sites with very high contaminant concentrations. • Anaerobic bioremediation can be enhanced by adding abiotic substrates (ZVI, soluble iron) and biogeochemical amendments (sulfur sources) depending on site conditions. • Anaerobic bioremediation can be conducted in aquifers exhibiting low pH, high DO or high sulfate concentrations. • Combined anaerobic biological, abiotic and biogeochemical processes effectively treats a wide range of contaminants in soil and groundwater. Basic Science of Anaerobic Bioremediation 50 [email protected] 925.984.9121
Basic Science of Anaerobic Bioremediation 51