Characteristics of N₂O production and hydroxylamine variation in short-cut nitrification SBR process

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.