Influence of phosphorus concentration on denitrifying glycogen accumulating organisms in endogenous partial denitrification system

In endogenous partial denitrification System (EPD) systems, phosphorus concentration is a key factor regulating the community structure of denitrifying glycogen accumulating organisms (DGAOs) and denitrifying phosphorus accumulating organisms (DPAOs). Given that DPAOs form different phosphorus concentration environments through phosphorus release during the anaerobic phase, it is important to explore the response mechanism of DGAOs under different phosphorus concentration disturbances to optimize the microbial community structure in EPD systems. In this study, the performance of EPD system driven by DGAOs, sludge physicochemical characteristics and microbial community structure differences were systematically evaluated by simulating different phosphorus concentration conditions. The results showed that the appropriate phosphorus concentration (6.00 and 15.00 mg/L) environments stimulated the secretion of extracellular polymeric substance (EPS) by the DGAOs and removed phosphorus mainly by adsorption/desorption and inorganic precipitation/dissolution of PO4 3- and Cat+ via LB-EPS, thus maintaining the relative stability of the bacterial community, in which Defluviicoccus (DGAOs) relative abundance increased from 0.71 % to 4.17 % (6 mg/L PO43-) and 4.79 % (15 mg/L PO43-), respectively. In addition, the formation of inorganic kernel hydroxyapatite (HAP) promoted sludge granularity. However, the high phosphorus concentration (30 mg/L PO43-) environment induced algal proliferation in the EPD system leading to deterioration of performance. This study revealed the potential phosphorus removal capacity of the EPD system, and this EPS-mediated phosphorus removal not only reduced the carbon source consumption of the system, but also provided new perspectives on the microbial community collaboration between DGAOs and DPAOs.