Biotransformation of 2,4-dinitrotoluene under different electron acceptor conditions

An anaerobic/anoxic fluidized-bed granular activated carbon (GAC) bioreactor in series with an activated sludge reactor was used to treat 2,4-dinitrotoluene (DNT). During methanogenic operation of the GAC bioreactor ethanol was supplied as the primary substrate at 600 mg/l. Influent DNT (110 mg/l) was transformed stoichiometrically to 2,4-diaminotoluene (DAT) in this anaerobic stage. The DAT was subsequently mineralized in the activated sludge reactor, with complete recovery of DAT nitrogen. Under denitrifying conditions in the fluidized bed, 3% of influent DNT was transformed to 2-amino-4-nitrotoluene (2A4NT) and 4-amino-2-nitrotoluene (4A2NT), 52% was transformed to unknown products and the 45% remained as DNT. Although 3% of the DNT was transformed to 2A4NT or 4A2NT in the activated sludge reactor, aerobic mineralization of DNT or the aminonitrotoluenes was not observed.