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. (C) 2013 Elsevier Ltd. All rights reserved.