In order to investigate the peak concentrations when NO -3-N and DO are regarded respectively as electron acceptors during phosphorus uptaken process

sequencing batch reactors (SBRs) are used to do parallel experiments. In an enhanced biological phosphorus removal (EBPR) system operated as anaerobic/ aerobic mode

phosphorus uptaken processes were investigated when NO -3-N concentration is 50 mg·L -1

75 mg·L -1

100 mg·L -1 and aeration rate is 16 L·h -1

28 L·h -1

40 L·h -1

respectively. The results show that

when internal carbon source is sufficient

the key factor to determine phosphorus uptaken rate is not the electron acceptor concentration

but whether sufficient electron acceptor can be supplied to the system timely. Compared with DO

NO -3-N is a less efficient electron acceptor. Meanwhile

the amount of NO -3-N denitrified and the amount of PO 3-4-P uptaken show a linear relationship

which means that the denitrification and phosphorus removal bacterias can exist in EBPR operated as anaerobic/ aerobic mode

and the calculation shows that its proportion can reach up to 17.70% in the total phosphorus accumulating organisms (PAOs). It is less practical to use pH variation curves as a strategy to control phosphorus uptaken process. The peak concentrations of NO -3-N and DO as electron acceptor during phosphorus uptaken process are 50.00 mg·L -1 and 0.4 mg·L -1

respectively.