STUDY OF THE REDUCTIVE DECHLORINATION OF PENTACHLOROPHENOL BY A METHANOGENIC CONSORTIUM

Pentachlorophenol (PCP) dechlorination by a methanogenic consortium wa s observed when glucose, formate, lactate, or yeast extract was presen t in the mineral medium as a secondary carbon source. Acetate was not a good substrate to sustain dechlorination. The consortium was able to dechlorinate the different monochlorophenols, although the chlorine i n position ortho and meta was removed more readily than in para positi on. Dechlorination was most efficient at 37 degrees C. At 45 degrees C , the first PCP dechlorination steps were very rapid, but 3,5-dichloro phenol (3,5-DCP) was not further dechlorinated. At 15 and 4 degrees C, dechlorination was very slow. The dechlorination of PCP to 3-chloroph enol (3-CP) was still observed after the consortium had been subjected to heat treatment (80 degrees C, 60 min), suggesting that spore-formi ng bacteria were responsible. The dechlorinating activity of the conso rtium was significantly reduced by the presence of hydrogen, 2-bromoet hanosulfonic acid (BESA), or sulfate but not of nitrate. The dechlorin ation of 3-CP was completely inhibited by heat treatment or the presen ce of BESA, suggesting that a syntrophic microorganism would be involv ed. Vigorous agitation of the consortium stopped the dechlorination, b ut the presence of DEAE-Sephacel acting as a support was very efficien t in restoring the activity, suggesting that association between certa in members of the consortium was important.