Biotransformation and biodegradation of selected nitroaromatics under anaerobic conditions

The fate of four nitroaromatic compounds (5-nitrosalicylate, 5NSA; 4-nitrob enzoate, 4NBc; 2,4-dinitrotoluene, 2,4DNT; nitrobenzene, NE) was studied in 160 mL laboratory-scale upward-flow anaerobic sludge bed reactors supplied with a mixture of volatile fatty acids and/or glucose as electron donors. All the nitroaromatics were transformed stoichiometrically to their corresp onding aromatic amines. After prolonged reactor operation, 5NSA and 4NBc we re completely mineralized to CH4 and CO2, whereas 2,4DNT was partially tran sformed to a nonidentified and nondegradable metabolite. Batch nitro-reduct ion experiments indicated that the position of the nitro group in relation to the other substituents in the aromatic ring plays a key role in the rate of the nitro-group reduction. The results obtained indicate that certain n itroaromatic compounds can be completely mineralized and serve as a carbon and energy source for anaerobic bacteria.