The U.S. Army is phasing out legacy munitions compounds that are prone to accidental detonation and replacing them with insensitive munitions compounds (IMCs). The major IMCs, namely 3-nitro-1,2,4-triazol-5-one (NTO), 2,4-dinitroanisole (DNAN), and nitroguanidine (NQ), are not compatible with existing munitions wastewater treatment technologies such as granular activated carbon due to their high water solubilities. In this study, a two-stage process employing nanoscale zero-valent iron (nZVI) and hydrogen peroxide (H 2 O 2 ) was evaluated as a potential technology for the destructive treatment of IMC wastewater. In the first stage, nZVI rapidly and completely degraded all three IMCs and generated dissolved Fe(II). NTO and DNAN were de-graded via nitro reduction to 3-amino-1,2,4-triazol-5-one and 2,4-diaminoanisole, respectively. In the second stage, H 2 O 2 was added to oxidize the IMC reduction products through Fenton reaction utilizing the dissolved Fe(II) from the first stage. nZVI-treated NTO and DNAN samples showed 66 % and 63 % TOC removal after oxidation, respectively. In contrast, NQ reduction products exhibited negligible mineralization. The results with individual IMCs were confirmed by an experiment using synthetic wastewater containing all three IMCs. This study illustrates the potential feasibility of a synergistic and destructive nZVIÀ H 2 O 2 technology for treating IMC-laden wastewaters at military facilities.

Advanced treated municipal wastewater is an important alternative water source for agricultural irrigation. However, the possible persistence of chemical and microbiological contaminants in these waters raise potential safety concerns with regard to reusing treated wastewater for food crop irrigation. Two low-cost and environmentally-friendly filter media, biochar (BC) and zero-valent iron (ZVI), have attracted great interest in terms of treating reused water. Here, we evaluated the efficacy of BC-, nanosilver-amended biochar- (Ag-BC) and ZVI-sand filters, in reducing contaminants of emerging concern (CECs), Escherichia coli (E. coli) and total bacterial diversity from wastewater effluent. Six experiments were conducted with control quartz sand and sand columns containing BC, Ag-BC, ZVI, BC with ZVI, or Ag-BC with ZVI. After filtration, Ag-BC, ZVI, BC with ZVI and Ag-BC with ZVI demonstrated more than 90% (> 1 log) removal of E. coli from wastewater samples, while BC, Ag-BC, BC with ZVI and Ag-BC with ZVI also demonstrated efficient removal of tested CECs. Lower bacterial diversity was also observed after filtration; however, differences were marginally significant. In addition, significantly (p < 0.05) higher bacterial diversity was observed in wastewater samples collected during warmer versus colder months. Leaching of silver ions occurred from Ag-BC columns; however, this was prevented through the addition of ZVI. In conclusion, our data suggest that the BC with ZVI and Ag-BC with ZVI sand filters, which demonstrated more than 99% removal of both CECs and E. coli without silver ion release, may be effective, low-cost options for decentralized treatment of reused wastewater. Graphical Abstract