Methanotrophic biodegradation of cis-1,2-dichloroethylene in a continuously fed fixed-film bioreactor

Co-metabolic biodegradation of cis-dichloroethylene (cis-DCE) was investigated in a bench-scale fixed-film bioreactor inoculated with a mixed culture of methane oxidising bacteria. The aim of this work was to identify factors that affect the cis-DCE biodegradation. It was observed that the presence of methane was necessary to enhance the biodegradation of cis-DCE, but an excess of methane inhibited the cis-DCE removal. cis-DCE did not inhibit the methane biodegradation at concentrations up to 300 microg/L. Maximum cis-DCE removal was observed with a methane bulk concentration ranging from 0.2 to 0.7 mg/L. It was found that the activity of the biofilm was located in the upper 100 microm of the biofilm. On the basis of this study it is concluded that careful control of the oxygen and methane concentrations as well as of the biofilm thickness is necessary in order to optimise the biodegradation of cis-DCE in fixed film bioreactors.