Nitrogen Removal and N 2 O 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 (N 2 O) emission in the multiple anoxic and aerobic process was investigated. The nitrogen removal percentages in SBR-A and SBR-P reactor were both 72%, and the phosphate removal percentages were 97 and 85.4%, respectively. During nitrification, both the NH 4 + -N oxidation rate in the SBR-A and SBR-P had a small change without the influence of the addition of nitrite nitrogen (NO 2 − -N). With the addition of 10 mg/L NO 2 − -N, the nitrate nitrogen (NO 3 − -N) production rate, N 2 O accumulation rate and emission factor had increased. At the same time, the N 2 O 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 N 2 O emission factors were 34.1 and 8.6 times more than those of NO 3 − -N as electron acceptor in SBR-A and SBR-P. During endogenous denitrification with NO 2 − -N as electron acceptor, the accumulation rate and emission factor of N 2 O were higher than those of NO 3 − -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.