HIGH-RATE CONTINUOUS BIODEGRADATION OF CONCENTRATED CHLORINATED ALIPHATICS BY A DURABLE ENRICHMENT OF METHANOGENIC ORIGIN UNDER CARRIER-DEPENDENT CONDITIONS

The simultaneous biodegradation of toxic compounds in mixtures is a ma jor current concern. To bioremediate a toxic mixture, we designed a st rategy combining an adsorbent carrier with an ecological and nutrition al system which allowed work close to heavily polluted conditions in n ature. Starting from a methanogenic community, we developed a microbia l consortium acclimated to a mixture of about 30 chlorinated aliphatic s in a fixed-film stationary-bed bioreactor. Prior to the establishmen t of a durable period of dechlorination, an interval of progressive de chlorination of the toxic mixture was observed during which the excess of the toxic compounds was stored on the carrier. The latter, consist ing of activated carbon in a polyurethane foam, allowed us to work at concentrations far above the solubility of the toxic compounds (appare nt concentrations of about 10 g/L). The complete disappearance of hexa chloroethane as well as its lower homologues, penta-, tetra-, and tric hloroethane, present in the toxic mixture, was observed. Additionally, octachlorocyclopentene, carbon tetrachloride, trichloroethylene, tetr achloroethylene, and hexachloro-1,3-butadiene also completely disappea red. For the four latter compounds, from mass balances in the bioreact or, degradation rates around 10 mu mol/L per day were determined with total dechlorination. The enrichment culture thus developed exhibited high degradation performances similar to those reported in the literat ure for pure or enriched anaerobic microbial cultures in contact with a single toxic compound. The results demonstrate the possibility of co ncurrent high-rate degradation of several highly chlorinated toxic com pounds, under conditions approximating field situations. (C) 1995 John Wiley and Sons, Inc.