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Biodegradation performance of sequencing batch biofilm reactor for Polychlorinated biphenyls in transformer oil

Fahimeh Teimouri, Mahnaz Nikaeen, Mohammad Mehdi Amin

Department of Environmental Health Engineering, Environmental Research Center, Isfahan

University of Medical Science, Hezar Jerib Avenue, Isfahan, Iran

Key words: chlorobenzoic compound, Polychlorinated biphenyls (PCBs), sequencing batch biofilm reactor (SBBR), congeners.


pcbIn order that the biodegradability of oil contain PCBs (aroclor 1242 and 1254) from electrical transformer, two pilot – scale sequencing batch biofilm reactor were used with polyurethane foam as an inert and growth media. The reactors were operated for 238 days. During the operation, the effects of main operation parameters such as pH, organic loading rate, PCBs loading rate, co-substrate type and initial COD concentration were investigated. It was observed that microorganisms were able to utilize and degrade the oil containing PCBs. Optical density results showed that the increase of neutral pH resulted in the increase in cell number and optical density. The reactors showed PCBs removal efficiency more than 99%, with effluent PCBs concentration of lower than 3μg/l. COD removal efficiency and surface loading rate increased as the initial concentration of PCBs increased. The average of COD reduction by SBBRs was more than 85% corresponding to COD <100 mg/l in reactors effluent. The average of SLR in two reactors was more than 4 corresponding to PCBs removal efficiency which was more than 99% in two reactors. GC-MS chromatography analyses detected the chlorobenzoic compounds in reactors effluent as the byproduct of PCBs biodegradation. The results of 16s rDNA sequence analysis showed that Rodococcus, Pseudoxanthomonas, Agromycess and Pseudomonas were predominant bacteria in reactors. The study showed that SBBRs have a good potential for biodegradation of oil contain PCBs. Also, acetic acid could be recommended as a good co-substrate and alternative solvent because it is inexpensive, abundant and safe for environment.

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