Performance stability and adaptability of embedded phosphorus removal biofillers: insights from microbial community responses and regulatory mechanisms.

Given the typically low phosphorus (P) concentrations in municipal wastewater, this study established a reactor employing embedded P removal biofillers (EBPAOs). The P removal performance of the system was systematically evaluated under three aerobic-phase operating modes: high-P batch feeding (Experiment S), low-P batch feeding (Experiments T10-T2), and low-P continuous feeding (Phases A-E). The results exhibited that, under the low-P batch feeding mode, the aerobic P uptake rate (Pup-rate) of the EBPAOs followed the Michaelis-Menten equation (R2 = 0.940). Under the continuous feeding mode, the Pup-rate remained stable throughout the aerobic phase. When the influent PO43--P concentrations were sequentially adjusted to 10, 8, 6, 4, and 2 mg/L, with corresponding hydraulic retention times (HRTs) of 60, 50, 40, 30, and 25 min, respectively, the aerobic effluent PO43--P concentration remained below 0.3 mg/L in all cases. The volumes of wastewater treated per cycle were 2.5, 3, 3.75, 5, and 6 times the nominal reactor volume, respectively. Microbial community analysis revealed that Candidatus_Accumulibacter (48.59-58.82%) was the dominant genus in the EBPAOs. Metagenomic analysis further showed that, as the influent PO43--P concentration decreased, polyphosphate-accumulating organisms (PAOs) consumed more COD to synthesize additional polyhydroxyalkanoates (PHA), thereby providing the energy required for efficient P uptake under aerobic low-P conditions. Concurrently, the abundances of the PstS gene and genes associated with the Embden-Meyerhof-Parnas (EMP) pathway, the tricarboxylic acid (TCA) cycle, and PHA synthesis were significantly upregulated. In conclusion, EBPAOs enable efficient and stable P removal from low-P wastewater.