Accumulation and isolation of simultaneous denitrifying polyphosphate-accumulating organisms in an improved sequencing batch reactor system at low temperature

The paper studied accumulation of denitrifying polyphosphate-accumulating organisms (DNPAOs) by using an improved sequencing batch reactor (SBR) system in which anaerobic-aerobic-anoxic (A-O-A) and anaerobic-anoxic (A-A) are at low temperature (15 °C). Results indicated that it was feasible to accumulate DNPAOs with nitrogen (N) and phosphorus (P) removals concurrently in an improved SBR system. Moreover, a DNPAOs strain was isolated from the accumulation and was identified as Acinetobacter sp. J6. Important factors that affect N and P removal efficiency of strain J6 were investigated, including temperature, pH and total phosphate (TP) concentration. Strain J6 had the highest N and P removal rates under original pH 8.0, TP concentration 4.16 mg L−1 and 15 °C. The purification culture of strain J6 contributed to the germplasm resources for a full-scale biological N and P removal system to denitrify and remove phosphate simultaneously.