Enhanced Organic Phosphorus Sorption from Urban Stormwater Using Modified Bioretention Media: Batch Studies

Abstract

Dissolved organic phosphorus (DOP) has been found to be a significant fraction of the urban runoff phosphorus load. To achieve enhanced DOP removal, bioretention soil media (BSM) amended with an aluminum-based water treatment residual (WTR) and montmorillonite (both 10% by mass) were additionally treated with aluminum sulfate (10% by mass) to improve sorption capacities. The sorption of myo-Inositol hexakisphosphate (IHP) and adenosine monophosphate (AMP), two forms of organic phosphorus, by modified BSM were studied using batch experiments. The sorption of AMP was increased by a factor of 17 and 21 for WTR- and montmorillonite-amended BSM with 10% alum, respectively. Similarly, the IHP removal capacity of these two modified media mixtures were increased by factors of 4 and 5, respectively. Scanning electron microscopy (SEM) and Brunauer, Emmett, and Teller (BET) surface area analyses were used to provide support for underlying sorption mechanisms for the enhanced DOP removal. The oxalate ratio (OR) was employed to provide an index for DOP sorption onto BSM. Generally, greater DOP sorption was observed with higher oxalate ratios.