ENHANCED ANAEROBIC DEGRADATION OF BENZENE BY ENRICHMENT OF MIXED MICROBIAL CULTURE AND OPTIMIZATION OF THE CULTURE-MEDIUM

A heterogeneous mixed culture, originally collected from two different sources, namely cow-drug and sludge from the city waste-water treatme nt plant, was grown in mineral medium containing 1% glucose and then a dapted on benzene as the carbon and energy source. Under anaerobic con ditions benzene was degraded via benzoic acid as a major intermediate in the benzene degradation pathway. The degradation rate of benzene wa s improved stepwise by the number of enrichments and optimization of t he culture medium. The effects of microaerobic conditions and/or physi cochemical treatment with H2O2 prior to anaerobic degradation were stu died with respect to variations in benzene degradation rate, growth of biomass and gas composition. It was noticed that the amount of gas pr oduced is less than the theoretical value expected and the percentage of methane in the product gas was very small (3%-3.5%). The reason for this is not well understood but it is presumed that the major group o f benzene-degrading bacteria present in the culture medium are sulphat e reducers and the mixed consortium is unable to degrade certain compl ex aromatic intermediates in the benzene degradation pathway under the experimental conditions. For an actual explanation of the situation a rising in this study, further investigations must be carried out. Howe ver, the mixed culture is capable of oxidizing benzene more rapidly to intermediate compounds and also partly into gas under the culture con ditions, compared to the published data for the anaerobic degradation of benzene.