Transformation of trinitrotoluene to triaminotoluene by mixed cultures incubated under methanogenic conditions

2,4,6-Trinitrotoluene (TNT) is an explosive widely used by the military. Al though it is no longer manufactured in the United States, large amounts of wastewater are generated annually from load, assembly, packing, and demilit arization operations Granular-activated carbon adsorption is the standard t echnology for treating wastewater containing TNT and maintaining discharges within the limits established under the National Pollutant Discharge Elimi nation System. Studies evaluating biological treatment of pink water with a n anaerobic fluidized-bed, granular-activated carbon bioreactor have been p romising, but the fate of TNT is unknown. We investigated the anaerobic tra nsformation of TNT by biofilm microorganisms obtained from a wastewater tre atment plant receiving explosive manufacturing wastewater. The TNT was tran sformed to a mixture of 2-amino-4,6-dinitrotolune; 4-amino-2,6-dinitrotolue ne; 2,4-diamino-6-nitrotoluene; and 2,6-diamino-4-nitrotoluene before culmi nating in the formation of triaminotoluene (TAT). Triaminotoluene was susce ptible to further degradation under anaerobic conditions, but its fate was not determined. Methane formation was inhibited but resumed after the deple tion of the diaminonitrotoluene isomers. These studies demonstrate near sto ichiometric formation of TAT from TNT and the transformation of 2-amino-4,6 -dinitrotoluene to 2,4-diamino-6-nitrotoluene and 2,6-diamino-4-nitrotoluen e by a mixed culture incubated under methanogenic conditions. This evidence indicates TAT is also a likely end-product of TNT biodegradation in the an aerobic fluidized bed bioreactor.