Innovative treatment materials and technologies are demanded to address urban stormwater pollutants that challenge traditional infrastructure. This study aimed to investigate adsorption behaviors of aluminum-based water treatment residual (WTR)coated mulch for capturing representative runoff pollutants (i.e., P, Cu, Zn, and Pb) and evaluate its treatment performance in a filtration bed. Data from batch studies were fit using the nonlinear least square optimization technique. Adsorption kinetic data followed the pseudo-2 nd -order reaction patterns, while the adsorption isotherm data obeyed the Freundlich models. Model fitting passed the chi-square tests, as a statistical goodness-of-fit criterion, at a 90% confidence level. Column studies indicate that the WTR-coated mulch with a bed depth of 5.1 or 10.2 cm could effectively alleviate flow-weighted mean concentrations of these pollutants, with a minimal aluminum release, during treatment of the equivalent annual runoff in a typical U.S. Northeastern catchment. This study demonstrates that WTR-coated mulch is an effective and safe adsorbent media to tackle urban stormwater pollution.
• Practitioner points• Aluminum-based WTR-coated wood mulch can simultaneously and effectively capture representative metals and phosphate in urban runoff. • The pollutant adsorption follows the pseudo-2 nd -order kinetic reaction patterns and the Freundlich isotherm model. • WTR-coated mulch (5.1-10.2 cm bed depth) sufficiently treats the runoff generated annually in a typical U.S. Northeastern catchment. • Higher and more reliable pollutant removals can be achieved with a greater bed depth of the coated mulch in a filtration bed. • Aluminium release is minimal during application of the WTR-coated wood mulch.
Low impact development (LID) practices, such as bioretention and sand filter basins, are stormwater control measures designed to mitigate the adverse impacts of urbanization on stormwater. LID treatment performance is highly dependent on the media characteristics. The literature suggests that bioretention media often leach nutrients in the stormwater effluent. The objective of this study was to analyze the treatment performance of different sand and bioretention soil mixtures. Specifically, this investigation aimed to answer whether the use of limestone and recycled glass could improve the treatment performance of bioretention systems. Column experiments were designed to assess (1) the removal efficiencies of different sand and bioretention soil mixtures and (2) the impact of plant uptake on removal rates. Enhanced pollutant removal was observed for the custom blends with addition of limestone sand, indicating mean dissolved and total phosphorus removal of 44.5% and 32.6% respectively, while the conventional bioretention soil mixtures leached phosphorus. Moreover, improved treatment of dissolved and total copper was achieved with mean removal rates of 70.7% and 93.4%, respectively. The results suggest that the nutrient effluent concentration decreased with the addition of plants, with mean phosphorus removal of 72.4%, and mean nitrogen removal of 22% for the limestone blend.
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