Halophilic Biodegradation of 3-nitro-1,2,4-triazol-5-one (NTO) in Brine

Abstract Production of insensitive munitions (IM) creates wastewater containing 3-nitro-1,2,4-triazol-5-one (NTO). As NTO is an anion in neutral pH wastewaters it can be removed via ion exchange (IX), released during IX brine recharge and may be subsequently degraded by halophiles. IX brine regeneration through halophilic NTO biotransformation was observed over 210 cycles in a sequencing batch reactor (SBR) and averaged 64.8 ± 20.2% NTO removal. NTO formed 3-amino-1,2,4-triazol-5-one (ATO) under sulfate- and nitrate-reducing conditions. Variable NTO reductions were observed over four phases including anaerobic enrichment (80.5 ± 7.7%, cycle 0 to 41); anaerobic followed by aerobic (42.2 ± 23.5%, cycle 42 to 81); anaerobic supplemented with nitrate (64.7 ± 21.5%, cycle 82 to 177); and anaerobic stress test with nitrate and perchlorate (91.0 ± 9.7%, cycle 178 to 210). Sequencing results show most of the genera to be halophiles and sulfate-reducing bacteria and archaea including Desulfovibrio and Halanaerobium. The results of these studies demonstrate that NTO biotransformation by halophiles in brine solutions is feasible.