School of Environment, Key Laboratory for Yellow River and Huai River Water Environment and Pollution Control, Ministry of Education, Henan Key Laboratory for Environmental Pollution Control, Henan Normal University, Xinxiang, Henan, 453007, China.
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China.
Environ Sci Pollut Res Int. 2017 Oct;24(30):23714-23724. doi: 10.1007/s11356-017-0019-x. Epub 2017 Sep 1.
The problem of producing strong greenhouse gas of nitrous oxide (NO) from biological nitrogen removal (BNR) process in wastewater treatment plants (WWTP) has elicited great concern from various sectors. In this study, three laboratory-scale wastewater treatment systems, with influent C/N ratios of 3.4, 5.4, and 7.5, were set up to study the effect of influent C/N ratio on NO generation in anaerobic/anoxic/oxic (AO) process. Results showed, with the increased influent C/N ratio, NO generation from both nitrification and denitrification process was decreased, and the NO-N conversion ratio of the process was obviously reduced from 2.23 to 0.05%. Nitrification rate in oxic section was reduced, while denitrification rate in anaerobic and anoxic section was elevated and the removal efficiency of COD, NH-N, TN, and TP was enhanced in different extent. As the C/N ratio increased from 3.4 to 7.5, activities of three key denitrifying enzymes of nitrate reductase, nitrite reductase, and nitrous oxide reductase were increased. Moreover, microorganism analysis indicated that the relative abundance of ammonium-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were positively correlated with NO generation, which was reduced from (8.42 ± 3.65) to (3.61 ± 1.66)% and (10.38 ± 4.12) to (4.67 ± 1.62)%, respectively. NosZ gene copy numbers of the AO system were increased from (1.19 ± 0.49) × 10 to (2.84 ± 0.54) × 10 copies/g MLSS with the influent C/N ratio elevated from 3.4 to 7.5. Hence, appropriate influent C/N condition of AO process could optimize the microbial community structure that simultaneously improve treatment efficiency and decrease the NO generation.
污水处理厂生物脱氮（BNR）过程产生强温室气体氧化亚氮（NO）的问题引起了各界的极大关注。本研究设置了三个实验室规模的污水处理系统，进水 C/N 比分别为 3.4、5.4 和 7.5，研究了进水 C/N 比对 AO 工艺中 NO 生成的影响。结果表明，随着进水 C/N 比的增加，硝化和反硝化过程中的 NO 生成均减少，过程中 NO-N 的转化率明显从 2.23 降低至 0.05%。好氧段硝化速率降低，而厌氧段和缺氧段反硝化速率提高，COD、NH-N、TN 和 TP 的去除效率在不同程度上提高。随着 C/N 比从 3.4 增加到 7.5，硝酸盐还原酶、亚硝酸盐还原酶和氧化亚氮还原酶三种关键反硝化酶的活性增加。此外，微生物分析表明，氨氧化菌（AOB）和亚硝酸盐氧化菌（NOB）的相对丰度与 NO 生成呈正相关，分别从（8.42±3.65）%降低至（3.61±1.66）%和从（10.38±4.12）%降低至（4.67±1.62）%。随着进水 C/N 比从 3.4 升高至 7.5，AO 系统中的 NosZ 基因拷贝数从（1.19±0.49）×10 增加至（2.84±0.54）×10 拷贝/g MLSS。因此，适当的 AO 工艺进水 C/N 条件可以优化微生物群落结构，同时提高处理效率，减少 NO 的生成。
