INFLUENCE OF NITRITE ON PHOSPHORUS UPTAKE BY ACTIVATED SLUDGE FROM ANAEROBIC-AEROBIC SEQUENCING BATCH REACTOR

The effect of nitrite on anoxic phosphorus uptake was investigated in detail to obtain a better insight into denitrifying phosphorus removing bacteria (DPB). Batch experimental tests under different nitrite concentrations were carried out using activated sludge cultivated in a sequencing batch reactor (SBR) under anaerobic-aerobic condition. The experimental results confirmed that nitrite could be used as electron acceptor for anoxic phosphorus uptake. However, for nitrite a relatively small amount of phosphorus was taken up compared to aerobic phosphorus uptake. The result also confirmed that the activity of anoxic phosphorus uptake is associated with the initial loading amount of nitrite. There was an optimal nitrite concentration at the beginning of experiment (in this study was 20mg·L~ -1 ). If the initial concentration were below the optimal one, the amount of anoxic phosphorus uptake increased with an increase in the nitrite concentration, otherwise it would decrease. It was suggested that nitrite was not an inhibitor to phosphorus removal process even the concentration was 80mg·L~ -1 high. Instead, it was an alternative electron acceptor to oxygen or nitrate. However, under continuous anaerobic-anoxic condition DPB lost the abilities of phosphorus release and uptake rapidly.