REDUCTIVE DEHALOGENATION OF CHLORINATED H YDROCARBONS DURING ANAEROBIC STABILIZATION OF MUNICIPAL WASTES

During sequential anaerobic digestion of municipal wastes, distinct bi ogeochemical phases exist which show different capabilities to transfo rm halogenated hydrocarbons. Chlorophenols, tetrachloroethylene, and c hloroanilines codisposed together with organic-rich waste substrates a re reductively dehalogenated during methanogenic conditions. Lindane i s degraded during acidogenesis as well as during methanogenesis. Howev er, degradation in methanogenic leachates is faster by a factor of 10. The poor transformation potential during acidogenesis compared to sub sequent transient methanogenic and stabile methanogenic phases cannot be explained by inadequate acclimation of prevailing microorganisms to the codisposed organochlorines. Thus, observed transformation capabil ities are a pertinent feature of methanogenic leachates, probably due to prevailing low redox potential and/or presence of suitable microbia l activities (not necessarily methanogenis). Dehalogenation of 2,3,4,6 -tetrachlorophenol as a model compound is hampered in methanogenic lea chate by addition of a surplus of sulfate and is completely suppressed by addition of molybdate which selectively inhibits sulfate reducing microorganisms. Competition for common electron donators (e. g. H-2) i s discussed as an explanation of these results. The results point to s ulfate reducing microorganisms being involved in reductive dehalogenat ion of chlorophenols.