A novel approach for phosphorus removal and recovery using entrapped polyphosphate-accumulating organisms

Growing populations and stringent discharge limits are increasing pressure on wastewater treatment plants (WWTPs) to adopt process intensification strategies. Integrated biological phosphorus removal and recovery remains challenged by sludge handling and dewatering. Microbial entrapment enables biomass-liquid separation, offering a new approach for integrated nutrient management from low-P streams. This study evaluates entrapped activated sludge containing nitrifiers, denitrifiers, and PAOs in a sequencing-batch reactor over 18 weeks, investigating sustained nitrogen and phosphorus removal, production of a concentrated P-rich liquor and mechanical stability over 18 weeks. P- release–uptake cycles were conducted to assess P removal efficiency, with periodic release tests to evaluate recovery potential. Microbial community analysis tracked spatiotemporal changes in dominant taxa, while mechanical characterisation assessed bead stability through settling rate, mass and diameter changes, compression testing, and quantification of polyvinyl alcohol (PVA) dissociation. The entrapped system achieved a stable effluent concentration of 0.25 ± 0.18 mgP L -1 , with 95.7 ± 1.8% P removal. A P-rich liquor containing up to 96 mgP L -1 was recovered at a rate of 83 mgP L -1 h -1 . The dominant genera of PAOs and glycogen-accumulating organisms (GAOs) included Accumulibacter , Tetrasphaera , Micropruina , and Defluviicoccus , which showed distinct spatiotemporal dynamics. Mechanical testing revealed a 16% mass loss through initial attrition, with PVA dissociation stability after Week 7. A settling rate of 205 ± 6 m h -1 indicated rapid solid-liquid separation. These findings demonstrate that entrapped PAOs offer a robust and compact approach for intensified phosphorus removal and recovery, thereby supporting sustainable and circular wastewater treatment practices.