[The nitrite accumulation in a biological aerobic filter (BAF) and the influences factors]

The nitrite accumulation in a bench-scale biological aerobic filter (BAF) for nitrogen removal was reported in this paper. The influences of operational variables on filter performance and nitrite accumulation were also investigated. The influent loading of NH4+(-)N and TN were 0.26-0.62 kg/(m3.d) and 0.28-0.63 kg/(m3.d) respectively, the hydraulic loading, gas/water ratio and temperature were 1-2 m/h, 3:1 and 20.5 degrees C-26.5 degrees C respectively, the nitrogen removal loading of NH4+(-)N, TN were among 0.15-0.52 kg/(m3.d) and 0.18-0.42 kg/(m3.d) respectively. The nitrite concentrations in the bulk and effluent, the profiles of inorganic nitrogen-compounds, the microbial populations in the reactor and their activity were investigated, suggesting that the nitrite accumulation and shortcut nitrification-denitrification took place in the bioreactor. The mechanism of nitrite accumulation and the influences of operational variables were analyzed. The backwash process was considered as the key influential factor of nitrite accumulation. It was believed that the structure feature and operational pattern were the principal factors that may result in the nitrite accumulation and shortcut nitrification-denitrification occurring in the BAF reactor.