Complete degradation of high concentrations of tetrachloroethylene by a methanogenic consortium in a fixed-bed reactor

Tetrachloroethylene (PCE) is a chlorinated aliphatic compound essentially used as a degreasing and dry-cleaning solvent. A methanogenic and sulfate-reducing consortium was obtained from anaerobic digested sludge from a waste water treatment plant (Bourg-en-Bresse, France). An ascending fixed-bed reactor inoculated with this mixed culture was fed semi-continuously with various PCE loading. The dechlorination of PCE was efficient and complete for high concentrations: 40-215 mu M of PCE. Indeed, 215 mu M PCE was degraded rapidly at the rate 3 mu mol l(-1) h(-1) and with 98% PCE removal. No chlorinated products were accumulated in the effluent. The tracer experiments with C-13-labeled PCE indicated that the PCE was completely degraded to carbon in the biomass and CO2. The inhibitor of methanogenesis stopped the PCE dechlorination. Methanogens had a deciding role in the dechlorination process after the enrichment period with high concentration of PCE. To our knowledge, this is the first methanogenic consortium which dechlorinated with this capability. This fixed-bed reactor is an attractive method with high dechlorination rates, and the absence of chlorinated products, for removal of PCE in bioremediation processes. (C) 1998 Elsevier Science B.V. All rights reserved.