Nitrous oxide reductase (N₂OR) (EC 1.7.2.4) is the only enzyme that can catalyze nitrous oxide (N₂O) decomposition to nitrogen gas, which connects tightly with N₂O accumulation. But it is known little about N₂O metabolism based on the enzyme in biological nitrogen removal of wastewater, especially in aerobic conditions. This paper studies the biosynthesis and metabolism of N₂O through the analysis of the activity of the enzyme in aerobic conditions. It is revealed that the main metabolic mechanism of N₂O was heterotrophic denitrification, which was mainly affected by electron supply (the amount of organic matter) and the external environment (pH value), while the escaped N₂O mainly came from nitrifiers. This indicates that the primary reason for the emission of N₂O in the aerobic phase was that the N₂O consumption rate of heterotrophic denitrifiers was lower than the N₂O production rate of nitrifiers. Considering the removal efficiency of nitrogen, the enzyme activity and the reduction of N₂O emissions, it is feasible to keep the C/N ratio of inflowing around 6.5 in A/O SBR.

一氧化二氮还原酶（N ₂ OR）（EC 1.7.2.4）是唯一可以催化一氧化二氮（N ₂ O）分解为氮气的酶，该酶与N ₂ O的积聚紧密相连。但是，基于酶的N ₂ O代谢在废水的生物脱氮方面，尤其是在有氧条件下，还知之甚少。通过分析好氧条件下酶的活性，研究了N ₂ O的生物合成和代谢。结果表明，N ₂ O的主要代谢机制是异养反硝化作用，主要受电子供应（有机物含量）和外部环境（pH值）的影响，而逃逸的N₂ O主要来自硝化器。这表明在好氧阶段排放N ₂ O的主要原因是异养反硝化器的N ₂ O消耗速率低于硝化器的N ₂ O生成速率。考虑到氮的去除效率，酶活性和N ₂ O排放的减少，在A / O SBR中将流入的C / N比保持在6.5附近是可行的。