Biological treatment of polychlorinated biphenyls (PCBs) contaminated transformer oil by anaerobic-aerobic sequencing batch biofilm reactors

Concern about the environmental fate of PCBs contaminated transformer oils has increased recently. Therefore, there is a real need to develop and improve treatment methods of transformer oils to minimize their environmental side effects. This study was carried out to evaluate the efficiency of sequential anaerobic-aerobic batch biofilm reactors for the biological treatment of transformer oil containing PCBs. The process performance was studied by increasing the organic loading rate (OLR) in the range of 0.9-32.2 g COD/L.d. Average chemical oxygen demand (COD) removal efficiencies of 99.8% were achieved in the system at OLR of 21.5 g COD/L.d. Also, high PCBs biodegradation percentages 96.5 were observed. Analysis of common indicators for the monitoring of anaerobic and aerobic processes confirmed the high ability of the anaerobic-aerobic process for treatment of PCBs contaminated transformer oil, characterized by high COD concentration and by highly chlorinated biphenyls content. The Stover-Kincannon model found to be the most appropriate model for predicting transformer oil biodegradation in anaerobic-aerobic SBBR. This biological system as an environmentally friendly and cost effective method has proved to be a suitable technology for treatment of PCB contaminated transformer oil with high efficiency in organic matter and PCBs removal.