The effect of chemical pretreatment on the aerobic microbial degradation of PCB congeners in aqueous systems

Abstract

A series of experiments was conducted to examine the effects of chemical pretreatment on biodegradation of 14C-labeled PCB congeners in aqueous systems. Fenton's reagent was used to generate hydroxyl radicals (OH) which were successful in partially oxidizing/transforming otherwise recalcitrant molecules of tetrachlorinated PCB, but had little or no impact on the biodegradation of a monochlorinated congener. Application of Fenton's reagent (1% H2O2, 1 mM FeSO4) followed by inoculation with pure cultures Pseudomonas sp, strain LB 400 and Alcaligenes eutrophus, strain H850 resulted in the removal of approximately 38% of 2-chlorobiphenyl and 51% of 2,2',4,4'-tetrachlorobiphenyl in the form of 14CO2. Comparison of the rate and extent of biodegradation of 2,2',4,4'-tetrachlorobiphenyl after the application of Fenton's reagent with the dynamic and final level of radioactivity in the aqueous phase of experimental system suggests two possible means of microbial utilization of tetrachlorinated PCB congener altered by chemical oxidation: (a) consumption of the partially oxidized chemical dissolved in the aqueous phase, and (b) direct microbial attack on the transformed compound, which may still be adhered to the solid surface.

Selected Chloro-Organic Detoxifications by Polychelate (Poly(acrylic acid)) and Citrate-Based Fenton Reaction at Neutral pH Environment

“…Polychlorinated biphenyls (PCBs) are highly toxic compounds and are present in groundwater and wastewater. − These compounds are difficult to biodegrade and can bioaccumulate to threaten animal and human health. A chemical reduction process (such as with zerovalent metals: Fe, Zn) can successfully dechlorinate PCBs. , However, one of its final products, biphenyl, is still toxic for the environment, , and it can only be detoxified by an oxidation reaction.…”

“…Polychlorinated biphenyls (PCBs) are highly toxic compounds and are present in groundwater and wastewater. [13][14][15][16][17] These compounds are difficult to biodegrade and can bioaccumulate to threaten animal and human health. A chemical reduction process (such as with zerovalent metals: Fe, Zn) can successfully dechlorinate PCBs.…”

Process for degradation of nitrobenzene: Combining electron beam irradiation with biotransformation

“…Combinations of AOP and biodegradation have been reported to remove priority pollutants with enhancement of biodegradation (Aronstein et al, 1995;Lee and Carberry, 1992;Martens and Frankenberger, 1995). Co 60 ␥-rays (Taghipour and Evans, 1996) or high-energy electron beam (Wang et al, 1994) irradiation improved the biodegradation of the recalcitrant chlorinated compounds in pulp and paper mill effluent.…”

“…Longer irradiation or reaction durations are needed to treat wastewater with high concentrations of pollutants and radical scavengers (Berge et al, 1994). AOP pretreatments have led to enhanced biodegradation of some aromatic compounds such as PCBs (polychlorinated biphenyls) and PAHs (polynuclear aromatic hydrocarbons) (Aronstein et al, 1995;Carberry et al, 1995;Martens et al, 1995).…”