Bioretention Media for Enhanced Permeability and Phosphorus Sorption from Synthetic Urban Stormwater

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Bioretention systems have been proven as effective urban stormwater control measures (SCMs), and are commonly used to improve both quantity and quality (pollutant removal) aspects of urban runoff. A promising media modification process is developed to simultaneously achieve both high infiltration rate and improved P removal in bioretention systems, Bioretention soil media (BSM) and a sandy ‘high flow medium’ (HFM) were modified with three Al-based amendments: water treatment residual (WTR), alum, and partially hydrolyzed aluminum (PHA), 10% by dry mass, respectively. The sorption of adenosine monophosphate (AMP) and myo-Inositol hexakisphosphate (IHP), two forms of organic phosphorus, and inorganic phosphate by modified media mixtures were studied. Compared with unmodified BSM and HFM, the sorption of AMP was increased by a factor of 26 and 80 for media with alum and PHA, respectively. Similarly, the IHP removal capacity were increased by factors of 7 and 8, respectively. Alum and PHA modified media mixtures can reduce P concentrations to <0.01 mg P/L within a contact time < 1 min. Adsorption and chemical precipitation are two predominated mechanisms for P removal using modified media mixtures. HFM modified with HFM and WTR showed high permeability and excellent P removal relative to other media mixtures and most importantly, it requires simplified modification conditions and is recommended for use in bioretention and related SCMs.