Anaerobic dechlorination of PCB in marine sediments - Possibilities for enhancement

Marine sediments in several Norwegian harbours and fjords are in many cases contaminated with PCB. The aim of this work has been to study the influence of sulphate on anaerobic dechlorination of PCB. The application objective is to use this knowledge to evaluate the possibilities for bioremediation of PCB-contaminated marine sediments. Inocula from PCB contaminated and non-contaminated marine sediments, aquatic sediments and contaminated river sediments have been used. The cultures were added a mixture of defined congeners of PCB. Different carbon sources like methanol, acetate, propionate, butyrate, and malate were added to enhance dechlorination. After 5 months CC-analysis showed dechlorination and formation of new lower chlorinated congeners in cultures added freshwater and artificial seawater without sulphate. Reduction varied from 9 to 88% on mol basis. The highest reductions were observed in the lowest chlorinated congeners. No dechlorination was observed when the artificial seawater with sulphate was used. As far as we know, this is the first time where dechlorination of PCB have been demonstrated in laboratory experiments, using inocula from Norwegian sediments. The results of this work show that dechlorination of PCB in marine sediments may be enhanced by initial removal of surplus sulphate, acid by adding sediments containing PCB dechlorinating microorganisms.