Lab-Scale Column Studies for Enhanced Phosphorus Sorption from Synthetic Urban Stormwater Using Modified Bioretention Media

Building on previous batch studies, this study further investigated the removal of dissolved organic P (DOP) using small (15 cm) columns with water treatment residual (WTR) and alum as two promising amendments to bioretention soil media (BSM). BSM modified with alum and WTR exhibited higher sorption capacity. Compared with unmodified BSM, significant improvements were observed for adenosine monophosphate (AMP), myo-inositol hexakisphosphate (IHP), and inorganic P (SRP) removal using 10% alum-modified WTR-amended BSM (WTR-BSM), by factors of 26, 7, and 150, respectively. The 10% alum-modified WTR-BSM reduced DOP levels < 0.01 mg/L within 1 min of contact time, demonstrating more-rapid DOP sorption processes compared with unamended media. The oxalate ratio (OR), which is based on oxalate-extractable Al, Fe, and P, was employed to provide a criterion for BSM performance with respect to P sorption. Strong correlations (R-2 = 0.92, 0.96, and 0.65 for AMP, IHP, and SRP, respectively) between the media OR and P sorption capacity of media was observed, which supports the use of the OR to predict P sorption performance of BSM. (C) 2016 American Society of Civil Engineers.