Enhancement of PCB congener biodegradation by pre-oxidation with Fenton's reagent

Abstract

Polychlorinated biphenyls (PCBs) were widely used in a number of industrial applications for about 60 years and became distributed extensively in the environment due to their insolubility and persistence. Biodegradability of some PCB congeners has been confirmed by previous work, indicating degradation mechanisms involving dechlorination and cometabolism. Slow microbial conversions can be enhanced by pre-oxidation with Fenton's reagent (FR) to assist microbial decomposition of PCB congeners. In this study two model PCB congeners, 4,4′-dichlorobiphenyl (DCB) and 2,2′,4,4′,6,6′-hexachlorobiphenyl (HCB) were used as model PCBs. Bioremediation of artificially PCB-contaminated soil was measured by gas chromotography using an electron capture detector. Soil samples, both treated with FR and untreated, were subjected to constant temperature degradation tests using a selected microbial consortium for PCBs. Statistically different biodegradation rate constants were obtained for the two model PCB congeners when FR pre-oxidation was carried out at an optimum pH of 3, compared with an unpretreated comparable system. The rate constant for HCB was 5 times greater for the pretreated system, and up to 3 times greater for DCB.