Establishment of a denitrification phosphorus removal system under anaerobic-anoxic operation: Key factors, performance, and microbial community

Abstract

Denitrification phosphorus removal (DPR) technology has received much attention due to its high utilisation of carbon sources, and the relative abundance of denitrifying phosphate accumulating organisms (DPAOs) and phosphate accumulating organisms (PAOs) as a percentage of a DPR system can significantly affect system performance. In this study, two sets of parallel sequencing batch reactors (SBR) were constructed and operated in anaerobic/anoxic (R1) and anaerobic/aerobic/anoxic (R2) modes to enrich DPR systems with different relative abundances of DPAOs, to investigate the interactions between DPAOs and PAOs when they coexist, and the effects of nitrate, carbon source, free ammonia (FA) key factors on the phosphorus removal performance of DPR systems. The findings indicated that R1 and R2 reached maximum phosphorus release at 1.0 mgFA/L and 0.6 mgFA/L, respectively. According to data from scanning electron microscopy and microbial high-throughput analysis, globular bacteria predominated on the surface of the granular sludge that developed, and there was a high relative abundance of DPAOs in R1. In addition to confirming the DPR system's operational effectiveness in both anaerobic/anoxic and anaerobic/aerobic/anoxic modes, as well as the associated genetic variations in nitrogen and phosphorus metabolism, and the optimal organic matter dosing concentration of 240 mg/L and the optimal nitrate (NO₃^-) concentration of 12 mg/L in the system prior to anoxia were derived for the DPR system.