Metabolism of 2,4,6‐trinitrotoluene by mixed microbial populations in digested sewage sludge under strict anaerobic conditions

Abstract

TNT (2,4,6‐trinitrotoluene) was degraded effectively by a mixed microbial population in digested sewage culture under strict anaerobic conditions. An initial concentration of 110 mg/L of TNT was reduced to a non‐detectable amount (> 99 % removal) in 6 days of incubation. One remarkable intermediate, originating from TNT metabolism was eluted on HPLC chromatogram, and many transformed metabolites were detected by using mass spectrometry during metabolism. Four main metabolites were identified: 2‐hydroxylamino‐4,6‐dinitrotoluene and its isomer, 4‐hydroxylamino‐2,6‐dinitrotoluene; and 2‐amino‐4,6‐diinitrotoluene and its isomer, 4‐amino‐2,6‐dinitrotoluene. In the major reduction pathway, TNT transformed to 2‐amino‐4,6‐dinitrotoluene via 2‐hydroxylamino‐4,6‐dinitrotoluene by mixed microbial populations under strict anaerobic conditions. Due to the resistance of the transformed inhibitors, further stepwise deamination and subsequent mineralization by ring cleavage occurred by mixed specific reductase which is created by many of the nitro‐reducing, sulfate‐reducing, methanogenous bacteria predominantly in digested sewage culture in low redox potentials.