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Organohalide-respiring bacteria are generally sensitive to pH.  Reductive dechlorination of tetrachloroethene (PCE) to trichloroethene (TCE) and then to ''cis''-1,2-dichloroethene(cDCE) can occur at a pH as low as 5.5.  However, rates of cDCE reduction to vinyl chloride (VC) and then to ethene are reduced below a pH of 6.0.  For efficient dechlorination to non-toxic end products, aquifer pH should be maintained above 6.0 during enhanced reductive dechlorination.
  
 
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>
 
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>
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'''Related Article(s):'''
 
'''Related Article(s):'''
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*[[Bioremediation – Anaerobic | In Situ Anaerobic Bioremediation]]
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*[[Biodegradation - Reductive Processes]]
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*[[Design Tool for Estimating Base Required during ERD]]
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*[[pH Buffering in Aquifers]]
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*[[Chlorinated Solvents]]
  
  
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'''CONTRIBUTOR(S):''' [[   ]] and [[  ]]
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'''CONTRIBUTOR(S):''' [[Dr. Robert Borden, P.E.]]
  
  
 
'''Key Resource(s):'''
 
'''Key Resource(s):'''
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*[[media:2012-Li_yixuan-MASc_thesis_Adaptation_of_KB-1_to_Acidic_Environments.pdf| Li, J.J., 2012. Adaptation of a Dechlorinating Culture, KB-1, to Acidic Environments.  M.S. Thesis, University of Toronto, Toronto, ON, Canada]]<ref name= "Li2012">Li, Y.X., 2012. Adaptation of a Dechlorinating Culture, KB-1, to Acidic Environments. M.S. Thesis, University of Toronto, Toronto, ON, Canada. [[media:2012-Li_yixuan-MASc_thesis_Adaptation_of_KB-1_to_Acidic_Environments.pdf| Report.pdf]]</ref>
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*[https://doi.org/10.1021/acs.est.7b01510 doi: 10.1021/acs.est.7b01510 Yang et al. 2017a. Organohalide respiration with chlorinated ethenes under low pH conditions]]<ref name= "Yang2017a">Yang, Y., Cápiro, N.L., Marcet, T.F., Yan, J., Pennell, K.D. and Loffler, F.E., 2017. Organohalide respiration with chlorinated ethenes under low pH conditions. Environmental Science & Technology, 51(15), pp.8579-8588. [https://doi.org/10.1021/acs.est.7b01510 doi: 10.1021/acs.est.7b01510]</ref>.
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*[[media:2017b-Yang-Resilience_and_recovery_of_Dehalococcoides....pdf| Yang et al. 2017b. Resilience and recovery of Dehalococcoides mccartyi following low pH exposure]]<ref name= "Yang2017b">Yang, Y., Cápiro, N.L., Yan, J., Marcet, T.F., Pennell, K.D. and Löffler, F.E., 2017. Resilience and recovery of Dehalococcoides mccartyi following low pH exposure. FEMS microbiology ecology, 93(12), p.fix130. doi: 10.1093/femsec/fix130. [[media:2017b-Yang-Resilience_and_recovery_of_Dehalococcoides....pdf| Report.pdf]]</ref>
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==Introduction==
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[[Bioremediation - Anaerobic | Enhanced reductive dechlorination (ERD)]] is commonly used to treat chlorinated solvents and related contaminants in groundwater by providing a fermentable organic substrate to serve as both an electron donor and a carbon source to stimulate microbially mediated [[Biodegradation - Reductive Processes| reductive dechlorination]]<ref>AFCEE, NFESC, ESTCP, 2004. Principles and Practices of Enhanced Anaerobic Bioremediation of Chlorinated Solvents. Parsons Corporation. Air Force Center for Environmental Excellence, Naval Facilities Engineering Service Center, and Environmental Security Technology Certification Program. [[media:AFCEE_Principles_and_Practices.pdf| Report PDF]]</ref><ref>ITRC, 2008. Enhanced attenuation of chlorinated organics (EACO-1): A decision framework for site transition. Washington, D.C.: Interstate Technology & Regulatory Council, Enhanced Attenuation: Chlorinated Organics Team[[media:2008-ITRC-EACO_1.pdf| Report pdf]]</ref><ref>Stroo, H.F., West, M.R., Kueper, B.H., Borden, R.C., Major, D.W. and Ward, C.H., 2014. In Situ Bioremediation Of Chlorinated Ethene Source Zones. In Chlorinated Solvent Source Zone Remediation (pp. 395-457). Springer New York. [http://dx.doi.org/10.1007/978-1-4614-6922-3_12 doi:10.1007/978-1-4614-6922-3_12]</ref>.  During ERD, the pH may decline as hydrochloric acid (HCl) is produced during reductive dechlorination<ref>Vogel, T.M. and McCarty, P.L., 1985. Biotransformation of tetrachloroethylene to trichloroethylene, dichloroethylene, vinyl chloride, and carbon dioxide under methanogenic conditions. Applied and Environmental Microbiology, 49(5), pp.1080-1083.</ref> <ref>Mohn, W.W. and Tiedje, J.M., 1992. Microbial reductive dehalogenation. Microbiological reviews, 56(3), pp.482-507.</ref> and carbonic acid and organic acids are produced by substrate fermentation.  However, dechlorinating bacteria appear to be particularly sensitive to pH changes with dechlorination of cDCE and VC to ethene completely inhibited at a pH of 5.5<ref name= "Rowlands2004">Rowlands, D., 2004.  Development of optimal pH for degradation of chlorinated solvents by the KB-1TM anaerobic bacterial culture.  M.S. Thesis, University of Guelph, Guelph, ON, Canada</ref><ref name= "Vainberg2006">Vainberg, S., Steffan, R.J., Rogers, R., Ladaa, T., Pohlmann, D. and Leigh, D., 2006.  Production and application of large-scale cultures for bioaugmentation. Proc 5th Internat Conf Remediation of Chlorinated and Recalcitrant Compounds, Monterey, CA, USA.  May 22-25.  Paper No. A-50.</ref><ref name= "Eaddy2008">Eaddy, A., 2008. Scale-up and characterization of an enrichment culture for bioaugmentation of the P-area chlorinated ethene plume at the Savannah River site. M.S. Thesis, Clemson University, Clemson, SC, USA. [[media:2008-Eaddy-Scale_Up_and_Characterization_Thesis_Final_pdf.pdf| Report.pdf]]</ref><ref name= "Yang2017a"/>, resulting in a significant decline in degradation rates<ref>Duhamel, M., Wehr, S.D., Yu, L., Rizvi, H., Seepersad, D., Dworatzek, S., Cox, E.E. and Edwards, E.A., 2002. Comparison of anaerobic dechlorinating enrichment cultures maintained on tetrachloroethene, trichloroethene, cis-dichloroethene and vinyl chloride. Water Research, 36(17), pp.4193-4202. [https://doi.org/10.1016/s0043-1354(02)00151-3 doi: 10.1016/S0043-1354(02)00151-3]</ref><ref>McCarty, P.L., Chu, M.Y. and Kitanidis, P.K., 2007. Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater. European Journal of Soil Biology, 43(5-6), pp.276-282. doi: 10.1016/j.ejsobi.2007.03.004. [[media: 2007-McCarty-Electron_donor_and_pH_relationships....pdf| Report.pdf]]</ref>. 
  
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==Effect of pH on Bioremediation Processes==
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Many biological processes are sensitive to pH.  Most microorganisms important for subsurface bioremediation function most efficiently in near neutral conditions<ref name= "Lowe1993">Lowe, S.E., Jain, M.K. and Zeikus, J.G., 1993. Biology, ecology, and biotechnological applications of anaerobic bacteria adapted to environmental stresses in temperature, pH, salinity, or substrates. Microbiological reviews, 57(2), pp.451-509</ref>. Low pH can interfere with pH homeostasis or increase the solubility of toxic metals<ref>Slonczewski, J.L., 2009 Stress Responses: pH, In Encyclopedia of Microbiology (3rd Ed.), Editor-in-Chief: Schaechter, M., Academic Press: Oxford Vol 5. pp. 477-484</ref>.  Microorganisms can expend cellular energy to maintain homeostasis, or conditions in the cytoplasm and periplasm may change in response to external changes in pH<ref>Foster, J.W., 1999. When protons attack: microbial strategies of acid adaptation. Current opinion in microbiology, 2(2), pp.170-174. [https://doi.org/10.1016/s1369-5274(99)80030-7 doi: 10.1016/S1369-5274(99)80030-7]</ref>.  Some anaerobes have adapted to low pH conditions through alterations in carbon and electron flow, cellular morphology, membrane structure, and protein synthesis<ref name= "Lowe1993"/>.
  
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==Introduction==
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There is some evidence that organohalide-respiring bacteria are particularly sensitive to changes in pH.  Pure cultures and consortia of organohalide-respiring microorganisms show highest dechlorination rates at circumneutral pH<ref name= "Yang2017a"/>.  Reduction of cDCE to VC to ethene is primarily carried out by strains of ''Dehalococcoides mccartyi (Dhc)''<ref name = "Löffler2013">Löffler, F.E., Yan, J., Ritalahti, K.M., Adrian, L., Edwards, E.A., Konstantinidis, K.T., Müller, J.A., Fullerton, H., Zinder, S.H. and Spormann, A.M., 2013. Dehalococcoides mccartyi gen. nov., sp. nov., obligately organohalide-respiring anaerobic bacteria relevant to halogen cycling and bioremediation, belong to a novel bacterial class, Dehalococcoidia classis nov., order Dehalococcoidales ord. nov. and family Dehalococcoidaceae fam. nov., within the phylum Chloroflexi. International journal of systematic and evolutionary Microbiology, 63(2), pp.625-635. doi: 10.1099/ijs.0.034926-0 [media: 2013-Loffler-Dehalococcoides_mccartyi_gen._nov....pdf| Report.pdf]</ref>.  Growth and dechlorination by ''Dhc'' occurs between pH 6 and 8, with highest activity measured between pH 6.9 and 7.5<ref name = "Löffler2013"/>
  
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Table 1 shows the range and optimum pH for growth of bacteria that reduce PCE to TCE and cDCE.  Zhuang and Pavlostathis (1995)<ref>Zhuang, P. and Pavlostathis, S.G., 1995. Effect of temperature, pH and electron donor on the microbial reductive dechlorination of chloroalkenes. Chemosphere, 31(6), pp.3537-3548. [https://doi.org/10.1016/0045-6535(95)00204-L doi:10.1016/0045-6535(95)00204-L]</ref> found that neutral pH was optimum for reductive dechlorination by a methanogenic mixed culture capable of dechlorinating PCE to VC.  Vainberg et al. (2006)<ref name= "Vainberg2006"/> reported an optimum pH of 6.0-6.8 for dechlorination of PCE by the SDC-9<sup>™</sup> bioaugmentation culture.  Dechlorination of PCE and TCE to cDCE can occur at pH down to 5.5<ref>Vainberg, S., Condee, C.W. and Steffan, R.J., 2009. Large-scale production of bacterial consortia for remediation of chlorinated solvent-contaminated groundwater. Journal of Industrial Microbiology & Biotechnology, 36(9), pp.1189-1197. [https://doi.org/10.1007/s10295-009-0600-5 doi: 10.1007/s10295-009-0600-5]</ref>. 
  
  
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'''Table 1. Summary of Key USEPA Documents Pertaining to TI Waivers'''
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'''Table 1. Range and optimum pH for growth of pure cultures reducing PCE '''
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{|- class="wikitable" style="float:left; margin: right; width: 100%;"
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{|- class="wikitable" style="float:left; margin: right; width: 75%;"  
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|-
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!style="background-color:#CEE0F2;" | Organism!!style="background-color:#CEE0F2;"|pH Range!!style="background-color:#CEE0F2;"| pH Optimum!!style="background-color:#CEE0F2;"|Reference
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|-
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|  ''Dehalobacter restrictus'' PER- K23 || 6.5 to 8.0 ||6.8 to 7.6 || Holliger et al., 1998<ref>Holliger, C., Hahn, D., Harmsen, H., Ludwig, W., Schumacher, W., Tindall, B., Vazquez, F., Weiss, N. and Zehnder, A.J., 1998. Dehalobacter restrictus gen. nov. and sp. nov., a strictly anaerobic bacterium that reductively dechlorinates tetra-and trichloroethene in an anaerobic respiration. Archives of Microbiology, 169(4), pp.313-321. [https://doi.org/10.1007/s002030050577  doi: 10.1007/s002030050577]</ref>
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|-
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| ''Sulfurospirillum multivorans'' || 5.5 to 8.0 || 7.0 to 7.5|| Neumann et al., 1994<ref>Neumann, A., Scholz-Muramatsu, H. and Diekert, G., 1994. Tetrachloroethene metabolism of Dehalospirillum multivorans. Archives of Microbiology, 162(4), pp.295-301. ISSN: 0302-8933, 1432-072X [https://doi.org/10.1007/bf00301854 doi: 10.1007/BF00301854]</ref>; Scholz-Muramatsu et al., 1995Scholz-Muramatsu et al., 1995 <ref>Scholz-Muramatsu, H., Neumann, A., Meßmer, M., Moore, E. and Diekert, G., 1995. Isolation and characterization of Dehalospirillum multivorans gen. nov., sp. nov., a tetrachloroethene-utilizing, strictly anaerobic bacterium. Archives of Microbiology, 163(1), pp.48-56. [https://doi.org/10.1007/bf00262203 doi: 10.1007/BF00262203]</ref>; Yang, 2017a<ref name= "Yang2017a"/>
 
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|-
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!style="background-color:#CEE0F2;" | DATE!!style="background-color:#CEE0F2;"| USEPA DOCUMENT!!style="background-color:#CEE0F2;"| DESCRIPTION
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| ''Desulfitobacterium dehalogenans'' JW/IU-DC-1 || 6.0 to 9.0 || 7.5 ||Utkin et al., 1994<ref>Utkin, I., Woese, C. and Wiegel, J., 1994. Isolation and characterization of Desulfitobacterium dehalogenans gen. nov., sp. nov., an anaerobic bacterium which reductively dechlorinates chlorophenolic compounds. International Journal of Systematic and Evolutionary Microbiology, 44(4), pp.612-619. [https://doi.org/10.1099/00207713-44-4-612 doi: 10.1099/00207713-44-4-612]</ref>
 
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|-
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| 1993 || Guidance for Evaluating the Technical Impracticability of Ground Water Restoration. EPA/540/R-93/080, OSWER Directive 9234.2-25<ref name= "USEPA_1993"/> || This is the primary USEPA guidance document on TI waivers that is still used today. It includes the definition of TI, summarizes technical challenges faced at remediation sites, describes what is and is not included in a TI waiver, outlines a consistent, site-specific approach for evaluating the TI of groundwater cleanup and establishing a protective alternative remedial strategy if restoration is determined to be technically impracticable within a reasonable timeframe.  
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| ''Desulfitobacterium'' sp. PCE-1 || 7.2 to 7.8 ||7.2 || Gerritse et al., 1996<ref>Gerritse, J., Renard, V., Gomes, T.P., Lawson, P.A., Collins, M.D. and Gottschal, J.C., 1996. Desulfitobacterium sp. strain PCE1, an anaerobic bacterium that can grow by reductive dechlorination of tetrachloroethene or ortho-chlorinated phenols. Archives of microbiology, 165(2), pp.132-140. [https://doi.org/10.1007/s002030050308 doi: 10.1007/s002030050308]</ref>
 
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|-
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| 1995 || Memorandum: Consistent Implementation of the FY 1993 Guidance on Technical Impracticability of Groundwater Restoration at Superfund Sites. OSWER Directive 9200.4-14<ref>U.S. Environmental Protection Agency (USEPA), 1995. Memorandum: Consistent Implementation of the FY 1993 Guidance on Technical Impracticability of Groundwater Restoration at Superfund sites. January. OSWER Directive 9200.4-14.[[media:USEPA-1995_EPA_Consistent_Implementation_of_1993_Guidance_9200.4-14.pdf| report.pdf]]</ref> || This memorandum specified a process for maintaining consistency for TI waiver implementation among different EPA regions. (The number of CERCLA sites conducting TI evaluations was reportedly far less than expected; therefore, the process outlined in this memorandum was not fully implemented)<ref name = "Deeb2011"/>.
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| ''Desulfitobacterium dichloroeliminans'' DCA1|| ||7.2 to 7.8 || Fogel et al., 2009<ref>Fogel, S., Findlay, M., Folsom, S. and Kozar, M., 2009. The importance of pH in reductive dechlorination of chlorinated solvents. In Proceedings Tenth International In Situ and On-Site Bioremediation Symposium, Baltimore, MD, USA, May(pp. 5-8)</ref>
 
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|-
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| 2007 || Recommendations from the EPA Ground Water Task Force. EPA/500/R-07/001<ref>U.S. Environmental Protection Agency (USEPA), 2007. Recommendations from the EPA Ground Water Task Force. December. EPA 500-R-07-001[[media:USEPA-2007_Recommendations_from_EPA_GW_Task_Force_500-R-07-001.pdf| Report.pdf]]</ref> || The task force identified and prioritized groundwater issues. They recommended developing supplemental guidance on TI and a fact sheet describing program flexibilities and alternative cleanup goals for DNAPL source zones. The report included an attachment describing cleanup goals that may be appropriate for DNAPL source zones.
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| ''Desulfuromonus chloroethenica TT4B''|| 6.5 to 7.4 || 7.4 ||Krumholz el al., 1996<ref>Krumholz, L.R., Sharp, R. and Fishbain, S.S., 1996. A freshwater anaerobe coupling acetate oxidation to tetrachloroethylene dehalogenation. Applied and Environmental Microbiology, 62(11), pp.4108-4113. [https://doi.org/10.1128/aem.01380-18 doi:10.1128/AEM.01380-18]</ref>;Krumholz, 1997<ref>Krumholz, L.R., 1997. Desulfuromonas chloroethenica sp. nov. uses tetrachloroethylene and trichloroethylene as electron acceptors. International Journal of Systematic and Evolutionary Microbiology, 47(4), pp.1262-1263. [https://doi.org/10.1099/00207713-47-4-1262 doi: 10.1099/00207713-47-4-1262]</ref>
 
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|-
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| 2009 || Summary of Key Existing EPA CERCLA Policies for Groundwater Restoration. OSWER Directive 9283.1-33<ref>U.S. Environmental Protection Agency (USEPA), 2009. Memorandum: Summary of Key Existing EPA CERCLA Policies for Groundwater Restoration. June. OSWER Directive 9283.1-33[[media:USEPA-2009_Summary_of_Key_EPA_CERCLA_Policies_9283.1-33.pdf| Report.pdf]]</ref> || This memorandum compiled key existing USEPA policies to enhance the transparency of USEPA decisions and to assist USEPA regions with making groundwater restoration decisions. The memo addressed expectations for groundwater restoration and TI waiver consideration in the context of principles for remediation. No new guidance or policy was included.
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|''Desulfomonile tiedjei'' DCB-1 ||6.5 to 7.8 ||6.8 to 7.0 ||DeWeerd et al., 1990<ref>DeWeerd, K.A., Mandelco, L., Tanner, R.S., Woese, C.R. and Suflita, J.M., 1990. Desulfomonile tiedjei gen. nov. and sp. nov., a novel anaerobic, dehalogenating, sulfate-reducing bacterium. Archives of Microbiology, 154(1), pp.23-30</ref>
 
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| 2011 || Groundwater Road Map: Recommended Process for Restoring Contaminated Groundwater at Superfund Sites. OSWER Directive 9283.1-34<ref name= "USEPA2011 "/> || The Groundwater Road Map compiled relevant highlights of existing USEPA laws, policy and guidance into a roadmap for groundwater restoration. Included is a discussion of TI waivers, institutional controls, wellhead treatment and other topics to the extent that these may be part of a comprehensive groundwater remedy.
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|''Desulfuromonas michiganensis'' sp. Nov || 6.8 to 8.0|| 7.0 to 7.5 ||Sung et al., 2003<ref>Sung, Y., Ritalahti, K.M., Sanford, R.A., Urbance, J.W., Flynn, S.J., Tiedje, J.M. and Löffler, F.E., 2003. Characterization of two tetrachloroethene-reducing, acetate-oxidizing anaerobic bacteria and their description as Desulfuromonas michiganensis sp. nov. Applied and Environmental Microbiology, 69(5), pp.2964-2974. doi 10.1128/AEM.69.5.2964–2974.2003.[[media:2003-Sung-characterization_of_two_tetrachloroethene-reducing....pdf| Report.pdf]]</ref>
 
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|-
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| 2012 || Summary of Technical Impracticability Waivers at National Priorities List Sites. Report with General Technical Impracticability Site Information Sheets. OSWER Directive 9230.2-24<ref name= "USEPA2012"/> || The report summarized TI waivers issued by USEPA regions, presented some summary statistics and included an appendix of brief site information sheets for each site where a TI waiver was adopted. A total of 91 waivers at 85 sites were identified.
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|''Geobacter lovleyi'' SZ|| || 6.5 to 7.2 Sung et al., 2006<ref>Sung, Y., Fletcher, K.E., Ritalahti, K.M., Apkarian, R.P., Ramos-Hernández, N., Sanford, R.A., Mesbah, N.M. and Löffler, F.E., 2006. Geobacter lovleyi sp. nov. strain SZ, a novel metal-reducing and tetrachloroethene-dechlorinating bacterium. Applied and Environmental Microbiology, 72(4), pp.2775-2782. [https://doi.org/10.1128/aem.72.4.2775-2782.2006 doi: 10.1128/AEM.72.4.2775-2782.2006]</ref>
 
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| 2016 || Clarification of the Consultation Process for Evaluating the Technical Impracticability of Groundwater Restoration at CERCLA Sites. OLEM Directive 9200.3-117<ref>U.S. Environmental Protection Agency (USEPA), 2016. Clarification of the Consultation Process for Evaluating the Technical Impracticability of Groundwater Restoration at CERCLA Sites. OLEM Directive 9200.3-117.[[media:USEPA-2016._Clarification_of_the_Consultation_Process_for_Eval._Tech._Imprac._of_GW_Rest..pdf| Report.pdf]]</ref> || The memo provides clarification of existing relevant Superfund policy and guidance and recommendations for planning and developing TI evaluation packages and describes the recommended process for EPA internal review and approval. The memo transmits five new recommended products, including a consultation process flowchart, TI evaluation flowchart, regional TI evaluation work planning spreadsheet, EPA review routing slip, and a summary checklist for the TI evaluation.
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|(adapted from Damborský, 1999; Yang et al. 2017a<ref name= "Yang2017a"/>)
 
|}
 
|}
  

Revision as of 16:01, 24 July 2018

Organohalide-respiring bacteria are generally sensitive to pH. Reductive dechlorination of tetrachloroethene (PCE) to trichloroethene (TCE) and then to cis-1,2-dichloroethene(cDCE) can occur at a pH as low as 5.5. However, rates of cDCE reduction to vinyl chloride (VC) and then to ethene are reduced below a pH of 6.0. For efficient dechlorination to non-toxic end products, aquifer pH should be maintained above 6.0 during enhanced reductive dechlorination.


Related Article(s):


CONTRIBUTOR(S): Dr. Robert Borden, P.E.


Key Resource(s):


Introduction

Enhanced reductive dechlorination (ERD) is commonly used to treat chlorinated solvents and related contaminants in groundwater by providing a fermentable organic substrate to serve as both an electron donor and a carbon source to stimulate microbially mediated reductive dechlorination[4][5][6]. During ERD, the pH may decline as hydrochloric acid (HCl) is produced during reductive dechlorination[7] [8] and carbonic acid and organic acids are produced by substrate fermentation. However, dechlorinating bacteria appear to be particularly sensitive to pH changes with dechlorination of cDCE and VC to ethene completely inhibited at a pH of 5.5[9][10][11][2], resulting in a significant decline in degradation rates[12][13].

Effect of pH on Bioremediation Processes

Many biological processes are sensitive to pH. Most microorganisms important for subsurface bioremediation function most efficiently in near neutral conditions[14]. Low pH can interfere with pH homeostasis or increase the solubility of toxic metals[15]. Microorganisms can expend cellular energy to maintain homeostasis, or conditions in the cytoplasm and periplasm may change in response to external changes in pH[16]. Some anaerobes have adapted to low pH conditions through alterations in carbon and electron flow, cellular morphology, membrane structure, and protein synthesis[14].

There is some evidence that organohalide-respiring bacteria are particularly sensitive to changes in pH. Pure cultures and consortia of organohalide-respiring microorganisms show highest dechlorination rates at circumneutral pH[2]. Reduction of cDCE to VC to ethene is primarily carried out by strains of Dehalococcoides mccartyi (Dhc)[17]. Growth and dechlorination by Dhc occurs between pH 6 and 8, with highest activity measured between pH 6.9 and 7.5[17]

Table 1 shows the range and optimum pH for growth of bacteria that reduce PCE to TCE and cDCE. Zhuang and Pavlostathis (1995)[18] found that neutral pH was optimum for reductive dechlorination by a methanogenic mixed culture capable of dechlorinating PCE to VC. Vainberg et al. (2006)[10] reported an optimum pH of 6.0-6.8 for dechlorination of PCE by the SDC-9™ bioaugmentation culture. Dechlorination of PCE and TCE to cDCE can occur at pH down to 5.5[19].


Table 1. Range and optimum pH for growth of pure cultures reducing PCE

Organism pH Range pH Optimum Reference
Dehalobacter restrictus PER- K23 6.5 to 8.0 6.8 to 7.6 Holliger et al., 1998[20]
Sulfurospirillum multivorans 5.5 to 8.0 7.0 to 7.5 Neumann et al., 1994[21]; Scholz-Muramatsu et al., 1995Scholz-Muramatsu et al., 1995 [22]; Yang, 2017a[2]
Desulfitobacterium dehalogenans JW/IU-DC-1 6.0 to 9.0 7.5 Utkin et al., 1994[23]
Desulfitobacterium sp. PCE-1 7.2 to 7.8 7.2 Gerritse et al., 1996[24]
Desulfitobacterium dichloroeliminans DCA1 7.2 to 7.8 Fogel et al., 2009[25]
Desulfuromonus chloroethenica TT4B 6.5 to 7.4 7.4 Krumholz el al., 1996[26];Krumholz, 1997[27]
Desulfomonile tiedjei DCB-1 6.5 to 7.8 6.8 to 7.0 DeWeerd et al., 1990[28]
Desulfuromonas michiganensis sp. Nov 6.8 to 8.0 7.0 to 7.5 Sung et al., 2003[29]
Geobacter lovleyi SZ 6.5 to 7.2 Sung et al., 2006[30]
(adapted from Damborský, 1999; Yang et al. 2017a[2])


References

  1. ^ Li, Y.X., 2012. Adaptation of a Dechlorinating Culture, KB-1, to Acidic Environments. M.S. Thesis, University of Toronto, Toronto, ON, Canada. Report.pdf
  2. ^ 2.0 2.1 2.2 2.3 2.4 Yang, Y., Cápiro, N.L., Marcet, T.F., Yan, J., Pennell, K.D. and Loffler, F.E., 2017. Organohalide respiration with chlorinated ethenes under low pH conditions. Environmental Science & Technology, 51(15), pp.8579-8588. doi: 10.1021/acs.est.7b01510
  3. ^ Yang, Y., Cápiro, N.L., Yan, J., Marcet, T.F., Pennell, K.D. and Löffler, F.E., 2017. Resilience and recovery of Dehalococcoides mccartyi following low pH exposure. FEMS microbiology ecology, 93(12), p.fix130. doi: 10.1093/femsec/fix130. Report.pdf
  4. ^ AFCEE, NFESC, ESTCP, 2004. Principles and Practices of Enhanced Anaerobic Bioremediation of Chlorinated Solvents. Parsons Corporation. Air Force Center for Environmental Excellence, Naval Facilities Engineering Service Center, and Environmental Security Technology Certification Program. Report PDF
  5. ^ ITRC, 2008. Enhanced attenuation of chlorinated organics (EACO-1): A decision framework for site transition. Washington, D.C.: Interstate Technology & Regulatory Council, Enhanced Attenuation: Chlorinated Organics Team Report pdf
  6. ^ Stroo, H.F., West, M.R., Kueper, B.H., Borden, R.C., Major, D.W. and Ward, C.H., 2014. In Situ Bioremediation Of Chlorinated Ethene Source Zones. In Chlorinated Solvent Source Zone Remediation (pp. 395-457). Springer New York. doi:10.1007/978-1-4614-6922-3_12
  7. ^ Vogel, T.M. and McCarty, P.L., 1985. Biotransformation of tetrachloroethylene to trichloroethylene, dichloroethylene, vinyl chloride, and carbon dioxide under methanogenic conditions. Applied and Environmental Microbiology, 49(5), pp.1080-1083.
  8. ^ Mohn, W.W. and Tiedje, J.M., 1992. Microbial reductive dehalogenation. Microbiological reviews, 56(3), pp.482-507.
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