Effect of different types of electron acceptors on the anoxic phosphorus uptake activity of denitrifying phosphorus removing bacteria

The effect of different types of electron acceptors (O2, NO 3 - and NO 2 - ) on anoxic phosphorus uptake was investigated to obtain a better understanding of the metabolic behavior of denitrifying phosphorus removing bacteria (DPB). Two sets of sequencing batch reactor (SBR) were used to enrich phosphorus accumulation organisms (PAOs) by alternative anaerobic and aerobic operations (oxygen was used as the electron acceptor), batch experiments under two different electron acceptor conditions, nitrate and nitrite, were performed by using activated sludge generated from the above-operated SBR reactors. Anoxic phosphorus uptake achieved successful both by using nitrate or nitrite as the electron acceptor. However, the relative small amount of anoxic phosphorus was taken up by microorganisms with nitrite used as the electron acceptor in comparison with nitrate. The optimal stoichiometric loading amount of electron acceptors of nitrate and nitrite to phosphorus (N/P ratio) were 0.89 and 0.60, respectively. If the initial concentration of electron acceptors was controlled below the optimal ratio, the amount of phosphorus taken up increased with the concentration, otherwise it would decrease. It was also found that DPB lost the ability of phosphorus release and uptake rapidly under continuous anaerobic–anoxic operation condition.