Continuous backwash media filtration for advanced primary treatment and resource recovery from wastewater

Advanced primary treatment diverts particulates from wastewater for resource recovery, reducing aeration energy demand and sludge production in secondary treatment. This study assessed the long-term performance of a pilot-scale (104-193 m³/d) high-rate primary treatment system integrating a rotating belt filter (RBF) for coarse solids capture, followed by a continuous backwash media filter (CBMF) for fine solids capture. The diverted solids formed a concentrated stream for resource recovery, while the filtrate enabled high-rate, energy-efficient secondary treatment. Conventional CBMF systems experience operational challenges under high and variable primary wastewater loading conditions, including solids clogging, elevated headloss, solids short-circuiting, and unstable filtration performance. To address these limitations, a novel CBMF system was developed that integrates dual airlift configurations for continuous media regeneration and solids capture, real-time process regulation, and coagulant-assisted process intensification. Under optimized operation with polyaluminum chloride dosing (43-78 mg/L), the CBMF attained hydraulic loading of 220-244 m³/m²/d, areal solids loading of 15-16 kg total suspended solids (TSS)/m²/d, and areal organic loading of 65-78 kg chemical oxygen demand (COD)/m²/d. Removal efficiencies of 67-71 % COD, 67-75 % TSS, 77 % total phosphorus (TP) were achieved at a solids rejection ratio of 3-4 %. These findings demonstrate that continuously regenerated deep-bed filtration with coagulation-assisted particle capture can serve as an intensified primary treatment platform and provide a compact alternative to conventional primary treatment systems, particularly for wastewater treatment facilities with limited footprint and increasing emphasis on resource recovery and energy-efficient operation.