Nitrite effect on biological phosphorus removal process

In this study,phosphorus accumulating organisms(PAOs) were cultivated in two SBR systems,one operated as anaerobic/aerobic mode,the other as anaerobic/anoxic mode.The effects of nitrite on the two modes of phosphorus removal system were investigated.The results showed that presence of nitrite inhibits both aerobic and anoxic phosphorus uptake,but aerobic phosphorus uptake was more affected than anoxic phosphorus uptake.In this research,0.88 mg/gVSS and 6.72 mg/gVSS were observed as threshold for aerobic and anoxic phosphate uptake,respectively.With the aid of a stepwise elevation of NO2——N added in influent,denitrifying phosphorus accumulating organisms were gradually accommodated to resist and utilize NO2——N as electron acceptor,but the phosphorus removal efficiency was lower than O2 and NO3——N as electron acceptors.