Biological Transformation Of PCBs
In Hazardous Site Waste Sludge
Author(s)
J. Tharakan
Abstract
In this paper we review the use of biological technologies for the treatment of
PCB contaminated hazardous wastes and report on some results that have been
obtained from our laboratory on the utilization of two specific biological
technologies for PCB biotransformation, including a microbial amended
anaerobic-aerobic cycling bioreactor and an earthworm-inoculated vermicompost
bioreactor. Our review of PCB biological transformation research suggests a
large potential for biological transformation of PCBs using anaerobic reductive
dechlorination, with several mediating organisms and effective pathways
identified. The bulk of the research demonstrates reductive dechlorination of
higher chlorinated PCB congeners accompanied by the appearance of increased
levels of lower chlorinated congeners. Aerobic biodegradation using
cosubstrates demonstrated degradation of lower chlorinated PCBs, mostly as a
cometabolic function of cosubstrate oxidation. In our laboratories, actual
hazardous waste sludge contaminated with PCBs demonstrated reductions of as
much as 75% in an anaerobic-aerobic bioreactor amended with
PCB-dechlorinating anaerobic sediments. The addition of PCB cometabolizing
aerobic microbes did not reveal significant additional PCB reductions. Our
research with earthworms demonstrated PCB removals, mainly through
bioaccumulation in earthworm biomass, with little evidence of further PCB
biotransformation. However, these results do suggest high potential for
microbial or vermicompost systems and further research is warranted to establish
mechanisms and elucidate procedures for biological transformation of PCBs in
hazardous sludges.
Keywords: polychlorinated biphenyls (PCBs), biotransformation, microbial,
hazardous waste, earthworms.
Keywords
polychlorinated biphenyls (PCBs), biotransformation, microbial,
hazardous waste, earthworms.
Related Book
Other papers in this volume
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