Nitrogen Removal and N2O Emission During Low Carbon Wastewater Treatment Using the Multiple A/O Process

With the organic carbon of acetate (SBR-A) and propionate (SBR-P), the effect of organic carbon sources on nitrogen removal and nitrous oxide (N2O) emission in the multiple anoxic and aerobic process was investigated. The nitrogen removal percentages in SBRA and SBR-P reactor were both 72%, and the phosphate removal percentages were 97 and 85.4%, respectively. During nitrification, both the NH4+-N oxidation rate in the SBR-A and SBR-P had a small change without the influence of the addition of nitrite nitrogen (NO2--N). With the addition of 10 mg/L NO2--N, the nitrate nitrogen (NO3--N) production rate, N2O accumulation rate and emission factor had increased. At the same time, the N2O emission factor of SBR-A and SBR-P reactors increased from 2.13 and 0.87% to 4.66 and 2.08%, respectively. During exogenous denitrification, when nitrite was used as electron acceptor, the N2O emission factors were 34.1 and 8.6 times more than those of NO3--N as electron acceptor in SBR-A and SBR-P. During endogenous denitrification with NO2--N as electron acceptor, the accumulation rate and emission factor of N2O were higher than those of NO3--N as electron acceptor. High-throughput sequencing test showed that the dominant bacteria were Proteobacteria and Bacteroidetes in both reactors at the phylum level, while the main denitrification functional bacteria were Thauera sp., Zoogloea sp. and Dechloromonas sp. at the genus level.