Mass Transfer Kinetics of Phosphorus to Filter Media from Wastewater, Storm Water, and Surrogate Matrices

Granular media are increasingly utilized for control of phosphorus (P), frequently indexed as total P (TP), which represents the sum of particulate (PP) and dissolved P (DP) fractions. The fate of PP notwithstanding, when such media are deployed for control of DP, the mass transfer kinetics from an aqueous matrix to the media is important for design and modeling tools. In this paper, the mass transfer of DP for a suite of common media are monitored and modeled with a focus on comparing the behavior of Al-oxide coated media (AOCM) subjected to synthetic and actual runoff (wet weather) as well as wastewater (dry weather) matrices. The media employed were AOCM(c) (clay based), AOCM(p) (pumice based), and AOCM(pcc) (Portland cement concrete based), and their corresponding media (UCM) substrates. A 2nd-order potential driving model is utilized for the overall total phosphorus (TP) transfer rate from aqueous solution to AOCM, whereas an intramedia diffusion model illustrates diffusion rates. In comparison with AOCM forms that demonstrate similar and rapid kinetics (lower for AOCM(p)), other media exhibited large variability, decreasing in order from Fe-coated perlite, activated alumina, expanded shale, and bio-retention media. In contrast, Zeolite-perlite-GAC (granular activated carbon) and tire-crumb (Black and Gold, B&G) displayed net adsorption not significantly different from 0 (p = 0.05). Comparing synthetic and actual runoff matrices demonstrated that actual runoff produced slower kinetics for AOCM(c) and AOCM(p), primarily attributable to the presence of competitive ions (SO42-), whereas elevated Ca2+ at the alkaline surface of AOCM(pcc) offset the effect of SO42- through surface precipitation. DOI: 10.1061/(ASCE)EE.1943-7870.0000558. (C) 2013 American Society of Civil Engineers.