Characteristics of NO production and hydroxylamine variation in short-cut nitrification SBR process.

In order to study the characteristics of nitrous oxide (NO) production and hydroxylamine (NHOH) variation under oxic conditions, concentrations of NHOH and NO were simultaneously monitored in a short-cut nitrification sequencing batch reactor (SBR) operated with different influent ammonia concentrations. In the short-cut nitrification process, NO production was increased with the increasing of ammonia concentration in influent. The maximum concentrations of dissolved NO-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 NHOH-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 NH-N concentration. Based on the determination results, the half-saturation of NHOH in the biochemical conversion process of NHOH to NO-N was very small, and the value of 0.05 mg NHOH-N/L proposed in the published literature was accurate. NHOH is an important intermediate in the nitrification process, and the direct determination of NHOH in the nitrification process was beneficial for revealing the kinetic process of NHOH production and consumption as well as the effects of NHOH on NO production in the nitrification process.