Continuous Phosphorus Removal From Retention Basin Water Using Modified Basic Oxygen Furnace Slag Under Controlled Superficial Velocity

ABSTRACT

To restore phosphorus (P) removal in aged basic oxygen furnace slag, the continuous P removal and breakthrough behaviors of thermally modified slag (TMS) and thermo‐alkali‐modified slag (TAMS) columns were evaluated across superficial velocities. In synthetic wastewater, both media exhibited kinetic breakthrough at 100 m/h from precipitate accumulation. At 50 m/h (1000 bed volumes; BV), TAMS (86.14% removal) maintained a 3.2‐fold lower effluent P concentration than TMS, mitigating precipitate‐induced kinetic breakthrough. In real urban retention basin water, a mixed bed (TMS:TAMS = 1:1) clogged prematurely at 50 m/h (333 BV). However, decreasing the velocity to 20 m/h (void hydraulic retention time = 17 s) restored effluent P below the limit of quantification under dry‐weather conditions and sustained over 92% removal (effluent P ≤ 0.11 mg/L) under a ninefold higher wet‐weather load (151.2 mg P). These findings provide superficial velocity guidelines to alleviate clogging during the treatment of urban retention basin water.