EFFECTS OF BIOGENIC POLLUTANT-BIOAVAILABILITY ENHANCING AGENTS AND OF EXOGENOUS ELECTRON DONORS ON THE REDUCTIVE DECHLORINATION OF POLYCHLORINATED BIPHENYLS (PCBs) IN AN ANAEROBIC SEDIMENT OF THE VENICE LAGOON (ITALY)

The possibility of intensifying the dechlorination activity towards spiked Aroclor 1242 in a sediment of Venice lagoon by adding humic substances (HS), hydroxypropil--cyclodextrins (CDs), methanol plus ethanol or formate plus acetate was investigated. No PCB dechlorination was observed in untreated slurry microcosms, where sulfate-reduction slowly occurred, and in formate plus acetate fed slurry microcosms, where sulfate-reducers, that quickly used all available sulfate, were rapidly outcompeted by methanogens. On the contrary, the onset of the process was stimulated by the presence of exogenous methanol and ethanol, able to improve sulfate-reduction activity, and of CDs or HS, able to enhance the same process but also the water solubility of PCBs. These data also support previous observations according to which sulfate-reducing bacteria are responsible for PCB-dechlorination in the Venice Lagoon sediments.