Efficient manganese ammonia oxidation (Mnammox) and its influencing factors at low temperature: Metal oxide-mediated denitrification process in water bodies.

This study explores the metal oxide-mediated NH-N reduction process: manganese ammonia oxidation efficiency, influencing factors and its resistance to low-temperature environments in water bodies. After 177d of stabilized startup of an up-flow reactor, NH-N removal efficiency was 63.51 %, total nitrogen (TN) removal rate was 0.021 kg/(m.d), and effluent Mn concentration was 1.503 mg/L, which was in dynamic equilibrium. X-ray photoelectron spectroscopy exhibited manganese valence state 3.29, similar to biological manganese oxidation. High-throughput sequencing revealed that phyla's denitrification function increased relative abundance, and manganese-reducing bacterial genera appeared. The batch test showed that 5 mg MnO had NH-N removal at 85.01 %. After 44 days, NH-N removal efficiency was 77.47 %, effluent Mn concentration was 3.280 mg/L, TN removal rate was 0.063 kg/(m.d). The long-term effect of the influent load change on the denitrification and Mnammox efficiency at 25 ∼ 15 °C was examined. Effluent Mn concentration was 1.811 mg/L was relatively stable. Manganese valence decreased from 3.29 to 3.20, Mn decreased by 9.58 %, while Mn and Mn increased by 10.94 % and 1.37 %, respectively. A new phylum Thermotogota and genus SBR1031 appeared in the microbial community.