Sequential anaerobic-aerobic biodegradation of emerging insensitive munitions compound 3-nitro-1,2,4-triazol-5-one (NTO)

Abstract

Insensitive munitions, such as 3-nitro-1,2,4-triazol-5-one (NTO), are being considered by the U.S. Army as replacements for conventional explosives. Environmental emissions of NTO are expected to increase as its use becomes widespread; but only a few studies have considered the remediation of NTO-contaminated sites. In this study, sequential anaerobic-aerobic biodegradation of NTO was investigated in bioreactors using soil as inoculum. Batch bioassays confirmed microbial reduction of NTO under anaerobic conditions to 3-amino-1,2,4-triazol-5-one (ATO) using pyruvate as electron-donating cosubstrate. However, ATO biodegradation was only observed after the redox condition was switched to aerobic. This study also demonstrated that the high-rate removal of NTO in contaminated water can be attained in a continuous-flow aerated bioreactor. The reactor was first fed ATO as sole energy and nitrogen source prior to NTO addition. After few days, ATO was removed in a sustained fashion by 100%. When NTO was introduced together with electron-donor (pyruvate), NTO degradation increased progressively, reaching a removal efficiency of 93.5%. Mineralization of NTO was evidenced by the partial release of inorganic nitrogen species in the effluent and lack of ATO accumulation. A plausible hypothesis for these findings is that NTO reduction occurred in anaerobic zones of the biofilm whereas ATO was mineralized in the bulk aerobic zones of the reactor.

Evidence for Phytoremediation and Phytoexcretion of NTO from Industrial Wastewater by Vetiver Grass

“…No significant NTO reduction in NC treatments indicated that NTO reduction was caused by the vetiver plants. Microbiological transformation of NTO to ATO to urea, CO2, and N2 has been reported earlier [ 2 , 10 , 11 ]. For this study, no transformation products of NTO were detected in the NTO-wastewater in NV treatments, indicating that NTO had been taken up by vetiver over time.…”

“…Under anaerobic conditions, NTO is biotransformed into ATO (3-amino-1,2,4-triazol-5-one), which requires further treatment based on regulatory standards. In a sequential anaerobic-aerobic biodegradation study, while NTO biotransformed into ATO under anaerobic conditions, ATO later mineralized under aerobic conditions [ 10 , 11 ]. Sorbents such as granular activated carbon (GAC) are ineffective, as NTO carries an electrostatic charge in aqueous solutions and sorbs very poorly to GAC [ 1 , 12 ].…”

Ecotoxicity of the insensitive munitions compound 3-nitro-1,2,4-triazol-5-one (NTO) and its reduced metabolite 3-amino-1,2,4-triazol-5-one (ATO)

“…The concentrations of NTO and ATO were verified via HPLC-DAD analysis. The method was previously described by Madeira et al [5]. …”

“…Its nitro group is reduced to an amino group, yielding 3-amino-1,2,4-triazol-5-one (ATO, Figure 1), which was found to be persistent in the soil in the absence of oxygen [5–7]. The reductive transformation of NTO to ATO could alter the molecule’s toxicity.…”

Investigations of Structural Properties, Spectroscopic Aspects, Electronic and Thermodynamic Properties of 3-Benzyl-4-[3-(3-methoxybenzoxy)-benzylidenamino]-4,5-Dihydro-1H-1,2,4-Triazol-5-one with DFT/HF Basis Sets

“…4-Amino-1H-1,2,4-triazole and its derivatives play an essential function in numerous biological activities such as antitumor, antimicrobial, anticancer, anti-HIV, antifungal, anti-inflammatory, antiviral, antioxidant and analgesic etc. [1][2][3][4][5][6][7][8]. The synthetic chemistry of the 1,2,4-triazole derivatives is experiencing significant development because of the semiconduction properties of certain materials in this family and because the bioactivity and pharmaceutical application are continuously increasing.…”