The basic science of anaerobic bioremediation - …

1 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 2 basic science of anaerobic bioremediation FMC provides a wide range of products for application of anaerobic bioremediation , biogeochemical and abiotic degradation basic science of anaerobic bioremediation 3 EHC-L EHC EHC-M ELS Daramend Solid organic substrate with microscale ZVI Liquid organic substrate with soluble Fe(II)

2 EHC with sulfur source for biogeochemical metals treatment Emulsified Lecithin Substrate for enhancement of anaerobic bioremediation Solid organic substrate with ZVI for treatment of contaminated soils 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 4 basic science of anaerobic bioremediation Contaminants that can be degraded by anaerobic processes Chlorinated solvents

3 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. 5 basic science of anaerobic bioremediation bioremediation is a natural and sustainable remediation process.

4 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 wastewater treatment Improvements to bioremediation approaches are being developed. 6 basic science of anaerobic bioremediation 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.

5 Biotic and abiotic anaerobic degradation processes occur in distinct, identifiable pathways. 7 basic science of anaerobic bioremediation Respiration processes Aerobic Respiration Aerobic Respiration Eating and breathing Electron Donor Electron Acceptor Organism Respiration 8 basic science of anaerobic bioremediation 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)

6 , ClO4 9 basic science of anaerobic bioremediation Respiration Biologically Mediated Oxidation - Reduction Electron Donor Electron Acceptor Resistor Positive Negative Growth Protein Synthesis Reproduction CnHn Fe(II) H2S H2 O2 NO3 As(V) Mn(IV) SO4 CO2 Work Light bulb Motors As(III) Mn(II) Fe (III) Reduced Oxidized HNO2 10 basic science of anaerobic bioremediation Oxygen O2 + 4H+ + 4e- 2H2O (Eh0 = +820) Nitrate 2NO3- + 12H+ +10e- N2(g) + 6H2O (Eh0 = +740) Decreasing Amount of Energy Released During Electron Transfer Manganese (IV) MnO2(s) + HCO3 +3H + + 2e - MnCO3 (s) + 2H20 (Eh0 = +520) Iron FeOOH(s) +HCO3 - + 2H+ e- FeCO3 + 2H2O (Eh0 = -50) 500 Aerobic anaerobic 1000 0 -250 Arsenic (V) H3 AsO4 + 2H+ +2e- H3 AsO3 + H2O (Eh0 = +559) Chromium (VI ) Cr2O72- + 14H+ + 6e- 2Cr3++7H2O (Eh0 = +1330) anaerobic Eh range for various electron acceptors Redox Potential (Eh0) in Millivolts @ pH = 7 and T = 250C Methanogenesis CO2 + 8H+ + 8e- CH4 + 2H2O (Eh0 = -240) Sulfate SO4 2- + 9H+ + 8e- HS- + 4H2O (Eh0 = -220)

7 11 basic science of anaerobic bioremediation anaerobic respiration and chlororespiration anaerobic Respiration Chlororespiration Electron Donor Electron Acceptor Biota Respiration Aerobic Respiration NO3 SO4 Fe(III) CO2 Mn(IV) 12 basic science of anaerobic bioremediation Range for Effective Chlorinated Ethene Degradation (chlororespiration) Methanogenesis CO2 + 8H+ + 8e- CH4 + 2H2O (Eh0 = -240) Sulfate SO4 2- + 9H+ + 8e- HS- + 4H2O (Eh0 = -220) Iron FeOOH(s) +HCO3 - + 2H+ e- FeCO3 + 2H2O (Eh0 = -50) Oxygen O2 + 4H+ + 4e- 2H2O (Eh0 = +820) Nitrate 2NO3- + 12H+ +10e- N2(g) + 6H2O (Eh0 = +740) Decreasing Amount of Energy Released During Electron Transfer Manganese (IV) MnO2(s) + HCO3 +3H + + 2e - MnCO3 (s) + 2H20 (Eh0 = +520) Redox Potential (Eh0) in Millivolts @ pH = 7 and T = 250C 500 Aerobic anaerobic 1000 0 -250 Arsenic (V) H3 AsO4 + 2H+ +2e- H3 AsO3 + H2O (Eh0 = +559) Chromium (VI ) Cr2O72- + 14H+ + 6e- 2Cr3++7H2O (Eh0 = +1330)

8 anaerobic Eh range for cholorinated ethene degradation PCE TCE TCE DCE DCE VC VC Ethene 13 basic science of anaerobic bioremediation 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 ( O2, NO3, Mn(IV), SO4, CO2) as does respiration. fermentation uses a reduced carbon source ( , cellulose, lecithin, lactose, sugars). to generate volatile fatty acids ((VFAs) lactic, acetic, propionic, valeric, butyric acids) and gases ( H2, CO2, CH4) H2 is used by dechlorinating bacteria to generate energy by sequentially reducing chlorinated organics.

9 14 basic science of anaerobic bioremediation 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: ( , methane, ethane, ethene, propane, butane, toluene, phenol, ammonia) PLUS: electron acceptor ( , O2, SO4) Enzymes generated to degrade food source also fortuitously degrades CEs or other contaminants.

10 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 15 basic science of anaerobic bioremediation Dechlorinating bacteria Several organisms capable of partially dechlorinating chlorinated organics. Only organism confirmed to dechlorinate DCE and VC to ethene is Dehalococcoides (Dhc).