Technosols Offer a Suitable Replacement for Sand-Based Filter Media in Rain Garden Design

The sustainability of sand is becoming more uncertain; therefore, a critical need exists to identify alternative materials for green infrastructure that meet desirable, site-specific functions. Technosol rain gardens (glass, shale, and shell) were tested for their ability to infiltrate and filter stormwater of chemical pollutants. Technosols had similar infiltration rates as sand, while large particle sizes of technogenic materials led to significantly higher saturated hydraulic conductivities (111-211 cm h^-1) compared to sand (37.3 cm h^-1). Technosols decreased all pollutant concentrations, except Zn, compared with the synthetic stormwater. Shale (0.0461 mg L^-1), shell (0.0544 mg L^-1), and sand (0.0306 mg L^-1) had comparable effluent NH₄-N. Compared with sand, shale removed 27.8% more Cu, while glass, shale, and shell removed 58.9%, 85.3%, and 57.7% more Pb, respectively. Glass and shell demonstrate potential for increasing long-term runoff capture under saturated conditions while removing > 50% of chemical pollutants like NH₄-N, P, Cu, and Pb.