University of Vermont
Co-Authors: E. Roy, S. Hurley, E. Perkins, Y. Yuan, M. Voorhees
Green stormwater infrastructure, such as bioretention systems, are increasingly used to manage stormwater volumes and pollutant loads in urban landscapes. However, phosphorus (P) removal in bioretention field studies has been highly variable, prompting research into P-sorbing amendments for bioretention media. In this study, we investigated potential tradeoffs between hydraulic conductivity and P sorption capacity in drinking water treatment residuals (DWTRs). We quantified the maximum P sorption capacity (Smax) for three DWTR sources using batch isotherm and flow-through column experiments. A large column experiment was also used to determine how solid and mixed layers of DWTRs affect system hydraulics and P removal performance. Study results showed that Smax values vary greatly among DWTR sources and experimental methodologies, which has implications for regulatory standards. When applied to bioretention media, the impact of DWTRs on hydraulic conductivity and P removal depended on layering strategy. Although both the solid and mixed layer designs improved P removal relative to the control, the mixed layer exhibited higher flow rates and better P removal than the solid layer. It is therefore recommended that DWTRs be mixed with sand in bioretention media to simultaneously achieve hydraulic control and long-term P removal in bioretention systems.