4 Conclusions
These studies demonstrated the complete reduction of TNT to a mixture of reduction products that converged to triaminotoluene. The ortho nitro group was preferentially reduced, forming 2-amino-4,6-dinitrotoluene, accounting for more than 80 percent of the two monoaminodinitrotoluene isomers. 2-Amino-4,6-dinitrotoluene was further reduced at both the ortho and para position, forming 2,6-diamino-4-nitrotoluene and 2,4-diamino-6-nitrotoluene, respectively. The reduction products converged to triaminotoluene, accounting for nearly 75 percent of the initial TNT concentration, before being further degraded to unknown products.
These findings suggest that TNT was not mineralized to CH4 and CO2, nor bound to the organic matter. Glucose and ethanol enhanced the TNT degradation rate, while acetate had little effect. The influence of cosubstrates on the degradation rates may be related to the cosubstrates' ability to serve as H2 donors. Glucose and ethanol are fermented by bacteria, producing H2, which becomes available to the TNT degrading bacteria. The metabolism of acetate does not result in the production of H2; therefore, it does not enhance TNT degradation rates. This study demonstrates, for the first time, near stoichiometric formation of triaminotoluene from TNT by a mixed culture incubated under methanogenic conditions.
