Phosphorus-rich liquid extraction strategies to enhance phosphorus removal in aerobic granular sludge treating municipal wastewater

This study evaluates two aerobic phosphorus (P) starvation-based operational strategies, intermittent and continuous extraction of P-rich liquid at the end of the anaerobic phase, using aerobic granular sludge, to enhance P removal performance in municipal wastewater treatment while preserving granule stability. Three reactors were operated for 127 days: R1 with intermittent P-rich liquid extraction, R2 with continuous extraction, and a control (Rc). Results showed R1 had the highest P-uptake rate (1.42 mgP/gMLVSS·h) and P removal efficiency (≥ 90%), outperforming other reactors. While the extraction strategies affected granule stability, R1 successfully re-granulated, whereas R2 granules continued to disintegrate. The P-rich liquids extracted from R1 demonstrated high potential for P recovery via struvite precipitation. Sludge samples from R1 at the end of operation had the highest bacterial richness and diversity. Overall, intermittent extraction achieved consistently low effluent P and opened pathways for resource recovery, underscoring its value for future circular wastewater treatment strategies.