Abstract: Novel nitrogen removal technologies via nitrite
pathway attract increasing interest in recent years. In this study,
batch experiments were performed to investigate nitrite accumulation
characteristics and shifts in nitrifying community structure at
different growth environments including ammonia concentration, pH
and alkalinity. It was found that nitrite accumulation ratios were
maintained at around 95% at studied conditions, and the optimum pH
and Alk/N (ratio between alkalinity and nitrogen) for ammonium
oxidization were 8.5 and 8.33, respectively. Fluorescence in situ
hybridization analysis of nitrifying bacteria showed that high free
ammonia (from influent ammonium or caused by high pH)
significantly altered the structure of nitrifying community, leading to
abundance of ammonia-oxidizing bacteria (AOB), especially
Nitrososmonas, and inhibition of nitrite-oxidizing bacteria (NOB).
The results suggest that free ammonia plays more important role than
other studied conditions on nitrite accumulation.