Polychlorinated biphenyls anaerobic dechlorination

The MBI anaerobic polychlorinated biphenyl (PCB) dechlorinating granular consortia technology is an in situ bioremediation technology that uses anaerobic microbial consortia in granular form to remediate PCBs in contaminated soils and sediments. 

Quensen, J.F., III, M.A. Mousa, S.A. Boyd, B.J.T. Sanderson, K.L. Froese, and J.P. Giesy. 1998. Reduction of aryl hydrocarbon receptor-mediated activity of polychlorinated biphenyl mixtures due to anaerobic microbial dechlorination. Environ. Toxicol. Chem. 17 806-813. 

Quensen et al. [69] showed that micro-organisms isolated from Hudson river sediment dechlorinated most polychlorinated biphenyls in Aroclor 1242 under anaerobic conditions in the laboratory. The higher the polychlorobiphenyl concentration, the more rapid the rate of dechlorination. The possible mechanisms involved are discussed. The products of dechlorination were less toxic than the original compounds and were more readily degraded by aerobic bacteria wastewater containing... 

Alder, A. C., Haggblom, M. M., Oppenheimer, S. R. Young, L. Y. (1993). Reductive dechlorination of polychlorinated biphenyls in anaerobic sediments. Environmental Science Technology, 27, 530-8. 

Boyle, A. W., Blake, C. K., Price, W. A. May, H. D. (1993). Effects of polychlorinated biphenyl congener concentration and sediment supplementation on rates of methano-genesis and 2,3,6-trichlorobiphenyl dechlorination in an anaerobic enrichment. Appliedand Environmental Microbiology, 59, 3027-31-... 

Quensen, J.F. Ill, Tiedje, J.M. Boyd, S. A. (1988). Reductive dechlorination of polychlorinated biphenyls by anaerobic microorganisms from sediments. Science, 242, 752-4. 

Van Dort, H. Bedard, D. L. (1991)- Reductive ortho and meta dechlorination of polychlorinated biphenyl congeners by anaerobic microorganisms. Applied and Environmental Microbiology, 57, 1576-8. 

In general, highly halogenated aliphatic compounds have high reduction potentials, so much so that hexachioroethane is a better electron acceptor than molecular oxygen The likelihood that such compounds will be reduced in anaerobic soils is high. There is evidence that polychlorinated biphenyls buried in anaerobic river sediments very slowly undergo reductive dechlorination, but this is believed to be a microbial process (Quensen et al, 1988). 

Possible Mechanism for Reductive Dechlorination by Anaerobic Microorganisms 6-5. 1998 Pish Advisories for Polychlorinated Biphenyls... 

Berkaw M, Sowers KR, May HD. 1996. Anaerobic ortho dechlorination of polychlorinated biphenyls by estuarine sediments from Baltimore harbor. Appl Environ Microbiol 62(7) 2534-2539. 

Quenson JF III, Boyd SA, Tiedje JM. 1990. Dechlorination of four commercial polychlorinated biphenyl mixtures (Aroclor) by anaerobic microoganisms from sediments. Appl Environ Microbiol 56(8) 2360-2369. 

Van Doit HM, Bedard DL. 1991. Reductive ortho and meta-dechlorination of a polychlorinated biphenyl congener by anaerobic microorganisms. Appl Environ Microbiol 57 1576-1578... 

Quensen, J. F., S. A. Boyd J. M. Tiedje, 1990. Dechlorination of four commerdal polychlorinated biphenyl mixtures (Aroclors) by anaerobic microorganisms from sediments. Appl. Environ. Microbiol. 56 2360-2369. 

Chlorinated benzoic acids have been shown to be intermediates in the biodegradation of several chlorinated aromatic compounds, for example, 4-chlorobenzoic acid is formed in the biodegradation of both polychlorinated biphenyls [103]. Mixed microbial cultures, which have been studied by a number of groups under aerobic conditions, can degrade a wide range of chlorinated benzoic acids, including 2-, 3- and 4-chlorobenzoic acid as well as 3,4-dichloro- and 2,4-dichlorobenzoic acid [104]. By contrast, under anaerobic conditions, only reductive dechlorination of meta-substituted benzoic acids has been observed [49,105,106]. Cometabolism of chlorobenzoic acids in the presence of unsubstituted benzoic adds leads to the formation of the corresponding... 

The aim of many of the described anaerobic bioreactors was only to test the potential use of this technology to remediate soil, water or air streams contaminated with organochlorines. In this regard, most of them were successful, even without reaching 100% removal. However, partial reductive dechlorination in other systems led to low removal rates (<30%) and to the formation of other, equally or more, toxic compounds like VC, biphenyl or monochlorobenzene, making the efficiency of these processes questionable, especially for extremely recalcitrant compounds like HCB, Polychlorinated Biphenyls or CF. Finally, it is important to note that all these reactors were designed and operated on lab-scale, where processes can be more easily... 

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