Influence of pH, current and copper on the biological dechlorination of2,6-dichlorophenol in an electrochemical cell

This research investigates the stimulation of biological reduction of chlorinated organic compounds using an electric current and evaluates the influence of pH, current and heavy metals on the system. Copper and 2,6-dichlorophenol (2,6-DCP) were used as the test heavy metal and chlorinated organic compound, respectively. Microorganisms capable of dechlorinating 2,6-DCP were cultured in a completely-mixed recycle reactor. Serum bottle batch tests using this mixed culture showed that increasing the levels of H2 addition from 0 to 8 mL per day enhanced 2,6-DCP dechlorination, a pH of approximately 8.1 was optimum for 2,6-DCP dechlorination, and added copper concentrations of 0.05 to 0.2 mg/L showed inhibition of 2,6-DCP dechlorination. Suspended-growth batch tests performed in a divided electrochemical cell with the mixed culture in the cathode compartment showed that 2,6-DCP was rapidly dechlorinated at passed currents of −5 and −10 mA, an added copper concentration of 3 mg/L was the threshold copper level that caused the inhibition of 2,6-DCP dechlorination, and copper was removed from solution. Abiotic electrochemical tests showed minimal 2,6-DCP dechlorination. This study demonstrated that the formation of H2 on the cathode generated highly reducing conditions that induced the dechlorination of 2,6-DCP, and simultaneous heavy metal removal and biological reductive dechlorination can be obtained in bioelectrochemical systems.