Microbial Enrichment Culture Responsible for the Complete Oxidative Biodegradation of 3-Amino-1,2,4-triazol-5-one (ATO), the Reduced Daughter Product of the Insensitive Munitions Compound 3-Nitro-1,2,4-triazol-5-one (NTO)

Abstract

3-Nitro-1,2,4-triazol-5-one (NTO) is one of the main ingredients of many insensitive munitions, which are being used as replacements for conventional explosives. As its use becomes widespread, more research is needed to assess its environmental fate. Previous studies have shown that NTO is biologically reduced to 3-amino-1,2,4-triazol-5-one (ATO). However, the final degradation products of ATO are still unknown. We have studied the aerobic degradation of ATO by enrichment cultures derived from the soil. After multiple transfers, ATO degradation was monitored in closed bottles through measurements of inorganic carbon and nitrogen species. The results indicate that the members of the enrichment culture utilize ATO as the sole source of carbon and nitrogen. As ATO was mineralized to CO2, N2, and NH4 +, microbial growth was observed in the culture. Co-substrates addition did not increase the ATO degradation rate. Quantitative polymerase chain reaction analysis revealed that the organisms that enriched using ATO as carbon and nitrogen source were Terrimonas spp., Ramlibacter-related spp., Mesorhizobium spp., Hydrogenophaga spp., Ralstonia spp., Pseudomonas spp., Ectothiorhodospiraceae, and Sphingopyxis. This is the first study to report the complete mineralization of ATO by soil microorganisms, expanding our understanding of natural attenuation and bioremediation of the explosive NTO.

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].…”

Abiotic reduction of 3-nitro-1,2,4-triazol-5-one (NTO) and other munitions constituents by wood-derived biochar through its rechargeable electron storage capacity

“…Much research to date on the fate and treatment of NTO has focused on sorption 56–58 and biodegradation. 59–61 Because ATO can be readily mineralized to innocuous products such as CO 2 , NH 4 + , and N 2 , 62 reduction to ATO may be a first step to achieve complete NTO mineralization. Recent studies further showed that NTO can be abiotically reduced to ATO by geo-constituents including the hematite-Fe 2+ redox couple, 24 FeS minerals, 63 hydroquinones and humic acids.…”

A Synergistic Nano‐Zerovalent Iron‐Hydrogen Peroxide Technology for Insensitive Munitions Wastewater Treatment

“…Oxidative processes such as biological and chemical oxidation have been shown to remove DNAN and NTO [17,18], but they could not remove NQ [18]. Several studies showed microbial degradation of NTO, NQ, and DNAN, suggesting biological treatment may be a viable option [12,13,16,[19][20][21][22]. NTO could be microbially transformed to 3-amino-1,2,4triazol-5-one (ATO) by mixed cultures under anaerobic conditions [16,20,21].…”

“…NTO could be microbially transformed to 3-amino-1,2,4triazol-5-one (ATO) by mixed cultures under anaerobic conditions [16,20,21]. Madeira et al [22] reported that ATO was readily mineralized to CO 2 , N 2 , and NH 4…”