Sand Filtration Enhanced by Various Reactive Materials for Bioretention Cell Design Considerations

Abstract

Various reactive treatment materials were evaluated to enhance sand filtration of dissolved species common in stormwater runoff: NO3−, PO43−, Cu2+, Pb2+, and Zn2+. Fly ash and iron oxyhydroxide mine drainage residuals were blended with sand at 5% (FA5.0) and 7.5% (MDR7.5) by mass and packed into laboratory columns. Additionally, minus 30 mesh particle sizes of proprietary peat products APTsorb and bioAPT were each packed without blending with a succeeding sand layer (APT-S and BIO-S). Pollutant removal performance was evaluated by pumping synthetic stormwater (SS) through packed up-flow columns without recirculation. The control material was 100% sand (SAND). Target SS concentrations included 1.5 mg/L NO3− as N, 0.5 mg/L PO43− as P, 25 μg/L Cu2+, 30 μg/L Pb2+, and 100 μg/L Zn2+. FA5.0 and MDR7.5 both removed over 84% of P. SAND, APT-S, and BIO-S removed limited total P and total dissolved P, while BIO showed a net export of up to 30% P. All columns removed greater than 75% and 89% of Cu2+ and Zn2+, respectively. APT-S removed the greatest Pb2+, at over 84%. None of the columns exhibited consistent NO3− removal greater than 10%.