In order to study the characteristics of nitrous oxide (N2O) production and hydroxylamine (NH2OH) variation under oxic conditions, concentrations of NH2OH and N2O were simultaneously monitored in a short-cut nitrification sequencing batch reactor (SBR) operated with different influent ammonia concentrations. In the short-cut nitrification process, N2O production was increased with the increasing of ammonia concentration in influent. The maximum concentrations of dissolved N2O-N in the reactor were 0.11 mg/L and 0.52 mg/L when ammonia concentrations in the influent were 50 mg/L and 70 mg/L respectively. Under the low and medium ammonia load phases, the concentrations of NH2OH-N in the reactor were remained at a low level which fluctuated around 0.06 mg/L in a small range, and did not change with the variation of influent NH4+-N concentration. Based on the determination results, the half-saturation of NH2OH in the biochemical conversion process of NH2OH to NO2-N was very small, and the value of 0.05 mg NH2OH-N/L proposed in the published literature was accurate. NH2OH is an important intermediate in the nitrification process, and the direct determination of NH2OH in the nitrification process was beneficial for revealing the kinetic process of NH2OH production and consumption as well as the effects of NH2OH on N2O production in the nitrification process.

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