Effects of direct electric current and electrode reactions on vinyl chloride degrading microorganisms

The use of electro-bioremediation has gained increasing interest during recent years. In these hybrid technologies bioremediation is stimulated by electrochemical or electrokinetic techniques to increase pollutant biodegradation efficiency. It is a pre-requisite for successful application of the bio-electro-processes that the microorganisms are not negatively affected by the electric fields or electrode reactions. In this study, for the first time microbial activity of aerobic vinyl chloride (VC) degrading microorganisms was assessed after exposure to constant currents ranging from 0.04 to 14 mA cm(-2). Viability and degradation kinetics were monitored during electrolysis for 4 h using two different types of electrodes: stainless steel and dimensionally stable electrodes (I)SA). When the mixed microbial culture was exposed in the electrode compartments, inhibiting effects were observed with stainless steel and DSA electrodes beyond doses of 100 and 50 kJ/L, respectively. Incubation of the VC degrading microorganisms in the mineral medium that was pretreated in the electrode compartments with similar doses, resulted in slower VC degradation kinetics thus demonstrating that the inhibition was due to electrochemical reaction products. When electrodes were separated from the microorganisms by bipolar membranes, no inhibition by the electric field was observed. (c) 2009 Elsevier Ltd. All rights reserved.