title: 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.
authors.affiliation: Department of Chemical & Environmental Engineering, University of Arizona, P.O. Box 210011, Tucson, AZ 85721-0011, USA. Electronic address: cmadeira@email.arizona.edu.
authors.forename: Camila L
authors.initials: CL
authors.lastname: Madeira
authors.affiliation: Department of Chemical & Environmental Engineering, University of Arizona, P.O. Box 210011, Tucson, AZ 85721-0011, USA.
authors.forename: Samuel A
authors.initials: SA
authors.lastname: Speet
authors.affiliation: Department of Chemical & Environmental Engineering, University of Arizona, P.O. Box 210011, Tucson, AZ 85721-0011, USA.
authors.forename: Cristina A
authors.initials: CA
authors.lastname: Nieto
authors.affiliation: Department of Soil, Water & Environmental Science, University of Arizona, P.O. Box 210038, Tucson, AZ 85721-0038, USA; Departments of Chemistry & Biochemistry, University of Arizona, P.O. Box 210011, Tucson, AZ 85721-0041, USA.
authors.forename: Leif
authors.initials: L
authors.lastname: Abrell
authors.affiliation: Department of Soil, Water & Environmental Science, University of Arizona, P.O. Box 210038, Tucson, AZ 85721-0038, USA.
authors.forename: Jon
authors.initials: J
authors.lastname: Chorover
authors.affiliation: Department of Chemical & Environmental Engineering, University of Arizona, P.O. Box 210011, Tucson, AZ 85721-0011, USA.
authors.forename: Reyes
authors.initials: R
authors.lastname: Sierra-Alvarez
authors.affiliation: Department of Chemical & Environmental Engineering, University of Arizona, P.O. Box 210011, Tucson, AZ 85721-0011, USA.
authors.forename: Jim A
authors.initials: JA
authors.lastname: Field
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D019149:Bioreactors / Q000382:microbiology*; D053834:Explosive Agents / Q000032:analysis*; D008962:Models, Theoretical; D009574:Nitro Compounds / Q000032:analysis*; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis*; D014230:Triazoles / Q000032:analysis*
chemical_list: C505897:3-nitro-1,2,4-triazol-5-one; D053834:Explosive Agents; D009574:Nitro Compounds; D012989:Soil Pollutants; D014230:Triazoles
keywords: 3-Amino-1,2,4-triazol-5-one; 3-Nitro-1,2,4-triazol-5-one; Biodegradation; Insensitive munitions; Soil