Comparison of biochemical characteristics between PAO and DPAO sludges

A successful enhanced biological phosphorus removal (EBPR) was observed in both anaerobic-aerobic sequencing batch reactor (An-Ox SBR) to induce growth of phosphorus accumulating organism (PAO) and anaerobic-anoxic (An-Ax) SBR to induce growth of denitrifying PAO (DPAO). Although the EBPR performance of An-Ox SBR was higher by 11.3% than that of An-Ax SBR, specific phosphorus release rates in the An-Ax SBR (22.8 ± 3.5 mg P/(g VSS·hr)) and the An-Ox SBR (22.4 ± 4.8 mg P/(g VSS·hr)) were similar. Specific phosphorus uptake rates under anoxic and aerobic conditions were 26.3 ± 4.8 mg P/(g VSS·hr) (An-Ax SBR) and 25.6 ± 2.8 mg P/(g VSS·hr) (An-Ox SBR), respectively, which were also similar. In addition, an analysis of relationship of poly-β-hydroxyalkanoates (PHA) synthesized under anaerobic conditions with phosphorous release (P_released/PHA_synthesized) and of PHA utilized under anoxic and aerobic conditions with phosphorous uptake (P_uptaked/PHA_utilized) verified that biological activities of EBPR per unit biomass between DPAO and PAO were similar. An analysis of the specific denitrification rate of DPAO showed that NO^?₃-N can be denitrified at a rate that does not substantially differ from that of an ordinary denitrifier without additional consumption of organic carbon when the PHA stored inside the cell under anaerobic conditions is sufficiently secured.