Degradation of 3-nitro-1,2,4-trizole-5-one (NTO) in wastewater with UV/H2O2 oxidation

Insensitive Munition (IM) formulations contain 3-nitro-1,2,4-trizole-5-one (NTO), an energetic compound with the highest aqueous solubility (16 g L−1) among all IM explosives, including 2,4-dinitroanisole (DNAN) and 1-nitroguanidine (NQ); as a result wastewater streams from IM processing facilities can be highly contaminated and potentially toxic. The removal of energetic compounds from wastewater streams prior to their discharge in the environment is imperative, and new technology must be developed to efficiently treat high levels of NTO and other IM compounds in these streams. In this study, the treatment of NTO wastewater by a UV/H2O2 oxidation process under acidic conditions (pH = 3.0 ± 0.1) and a hydrogen peroxide concentration of at least 1500 mg L−1 resulted in successful removal of the energetic compound. The organic carbon from the NTO ring was completely converted to inorganic carbon (CO2), as confirmed through TOC measurements and GC-MS analysis on the reactor headspace. Nitrate and ammonium ions were the major nitrogen by-products, as indicated by mass spectrometry. The results obtained in this work demonstrate that the UV/H2O2 oxidation process can effectively mineralize high concentrations of NTO in wastewater streams leading to recovery of valuable nutrients that can be used for supporting algal biomass growth for biofuel/biogas generation.