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

Abstract

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.