Mechanisms and differences of N2O emission characteristics in typical wastewater treatment processes
CHEN Hui-ling, QI Lu, CHEN Jia-bo, XIA Zhi-heng, LI Qian-gang, AO Zi-ding, JIANG Zhao, ZHANG Tong-tong, WANG Hong-chen, LIU Guo-hua
Research Center for Low Carbon Technology of Water Environment, School of chemistry and life resource, Renmin University of China, Beijing 100872, China
Abstract：This study mainly compared the emission characteristics of N2O in two typical wastewater treatment processes, SBR and AAO, and analyzed the mechanisms that cause the differences.. The results indicated that according to the total nitrogen removal efficiency of the SBR process, the N2O emission factor (EF) was 2.36%, which is 1.92 times higher than that of the AAO process. The aerobic phase was identified as the primary stage for N2O production in both processes, accounting for over 90% of the total N2O generated. Compared to the continuously AAO process, the sequencing SBR process exhibited a longer duration of low DO conditions. A sudden increase in NH4+-N concentration o and a high accumulation of NO2--N ccurred at the onset of the aerobic phase. Analysis of the microbial community structure and enzyme activity revealed that SBR process had a higher ratio of ammonia-oxidizing bacteria (AOB) to nitrite-oxidizing bacteria (NOB) and a higher nitrite reductase (NOR) activity, which were 1.7 and 1.4 times those of the AAO process, respectively. This further facilitated the production of more N2O through the AOB-mediated nitrification-denitrification pathway during the aerobic phase, which is the intrinsic mechanism for the high N2O emission factor of the SBR process.
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