Urban stormwater treatment using biofilters is one of the leading economic, efficient and sustainable solutions to the worsening water crisis in California. In this study, the mechanisms that affect the transport of Cu, Zn, and Pb from urban storm water runoff through column experiments, and subsequent characterization using spectroscopy, microscopy and diffraction on biofilter sediments, was investigated. Limited studies have focused on understanding these mechanisms owing to their complexity. Therefore, column experiments were conducted using pure sand, iron-oxide coated sand (IOCS), manganese oxide coated sand (MOCS) and sand collected from a storm water basin in University of California, Riverside (UCRS). This is important to better understand the role of sand in biofilters in the transport of Cu, Zn, and Pb in urban stormwater runoff. A synthetic stormwater solution comprised of 0.75mM Ca+2, 0.075mM Mg+2, 1.75mM Na+, 0.072mM NH4+, 0.33mM SO4-2, 1mM HCO3-, 1.7mM Cl-, 0.0725mM NO3-, 4.87x10-4mM Pb+2, 1.57x10-3 mM Cu+2, 1.52x10-3 mM Zn, 4.67mM ionic strength and pH 7.1, was reacted continuously for a week with the sand packed in columns at 8ml/min flowrate. Results from X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) identified the presence of Cu+2, Zn+2 and Pb+2 on the surface of all sand media. SEM analysis showed higher concentrations Cu+2, Zn+2 and Pb+2 on MOCS surface which was likely associated with surface area and point zero charge of manganese oxides. Additionally, XAS analysis suggested precipitation of Pb, Zn and Cu carbonates at the sediment surface. Ongoing work is identifying the chemical composition of the precipitates. Lead (Pb) had the highest ability to be immobilized compared to other metals in urban stormwater runoff. Results from this investigation likely have substantial implications in stormwater treatment and metal recovery using biofilters.

Competing mechanisms affecting transport of copper, zinc, and lead in urban stormwater runoff: Column experiments

2019 Fall National Meeting

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