Quantifying, tracing and mitigating N2O production by ammonia-oxidizing archaea during mainstream nitrogen removal
Shengjun Li1, Yifeng Xu2, Mengwen Jia1
1Key Laboratory of Green Utilization of Critical Non-metallic Mineral Resources, Ministry of Education, Wuhan University of Technology, Wuhan 430070, China; Shenzhen Research Institute of Wuhan University of Technology, Shenzhen 518000 Guangdong, China.
Abstract:
Ammonia-oxidizing archaea (AOA) in wastewater systems remain underexplored for their roles in nitrogen removal and nitrous oxide (N2O) production. This study investigated ammonia oxidation and N2O production by a wastewater-derived AOA enrichment (>42 % Candidatus Nitrosocosmicus, cultivated using antibiotics) under varying oxygen and substrate (organic carbon, nitrite) availabilities. N2O production was first precisely quantified by retracting the portion (49-56 %) consumed by endogenous denitrification. Biomass-specific N2O production (5.08 × 10-5 to 2.38 × 10-4 μmol N/105 copies, 0.4-21 % O2) were 90-97 % lower than that of ammonia-oxidizing bacteria. The negative correlation between N2O production and oxygen in AOA was driven by hybrid formation and abiotic hydroxylamine oxidation. Candidatus Nitrosocosmicus was inhibited by exogenous nitrite as free nitrous acid at 0.11-0.15 μM, whereas organic carbon alleviated inhibition via heterotrophic nitrite reduction, elevating N2O emission factors to 0.77-1.09 % in ammonium- and nitrite-amended cultures (0.4-4.2 % O2). The findings will help updating N2O quantitative statistics and developing carbon-neutral nitrogen removal process.
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