Munition wastes containing high diverse energetics have posed serious environmental problems associated with soil and water contamination. Efficient methods of biodegradation have been the focus of recent studies. In the past, single microorganism cultures have been used in the partial mineralization of these energetics into their metabolites. However, their efficacy has been severely constrained due to the fact that mono species cultures contain fewer reductase enzymes that can degrade both the high energetics and their metabolites within a reasonably short period of time.; The high energetics, ammonium dinitramide (ADN), 2,4,6-trinitrotoluene (TNT), and octohydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocone (HMX) were used in this study. Starting with ADN at 250 mg/L, TNT at 110 mg/L, and HMX at 110 mg/L, these compounds and their transformation metabolites were mineralized to non-detectable quantities in periods of 5, 6, and 8 days, respectively, using probably a variety of nitroreductase enzymes created by the many nitro-reducing, sulfate-reducing, and methanogenous bacteria, etc, found in the anaerobic sewage culture. These results were shown to be a significant improvement upon the performance of either the separately cultured aerobic and/or facultative species--Pseudomonas aeruginosa, Bacillus subtilis, and Phanerochaete chrysosporium--or the anaerobe, Desulfovibrio desulfuricans.; Our study found that digested sewage sludge containg mixed specialized nitroreductase produced by nitro-reducing and sulfate-reducing bacteria bring about a successive stepwise reduction of nitro groups to amino groups. Whereas, the single bacteria and single fungal cultures were shown to be either only partially successful or not as effective as the mixed bacteria cultures in the degradation of munition wastes. They were also found to be metabolically inhibited by transformation metabolites formed as a result of incomplete degradation. In all cases we cannot rule out the possibility of cometabolism by the multiple bacterial species in the activated sludge. Our conclusions are that the anaerobic mixed culture, compared to the pure mono culture, is superior in the degradative efficiency of various energetics. These results point to potential applications in the degradation of other organo-nitro wastes, such as pesticide, dyes, and plastics in a number of media at various environments.
展开▼
