Removal Kinetics of Heavy Metals and Nutrients from Stormwater by Different Filter Materials

During storm events, contaminants and sediments from roadways, curbside, parking lots, and lawns in urban environments are mobilized and transported by the stormwater runoff. These contaminants are finally discharged in waterbodies, such as rivers and lakes, with adverse effects on public health and ecosystems. Several studies have reported high levels of heavy metals and nutrients in urban stormwater runoff. Best management practices such as sedimentation and bioretention are not practical in urban environments due to the lack of adequate space; however, filtration systems, such as an in-ground permeable filter system, are being developed because they are practical and feasible. Four different filter materials (calcite, zeolite, sand, and iron filings) were effective in removing individual contaminants (Cd, Cu, Ni, Cr, Zn, nitrate, and phosphate) in tests at 24 h. The present investigation assessed the removal kinetics of contaminants from a simulated stormwater consisting of multiple heavy metals and nutrients by the four filter materials. Batch experiments were conducted to evaluate the removal kinetics of co-existing heavy metals and nutrients from the simulated stormwater. The rate of contaminant removal and overall removal efficiency was found to be dependent on the filter material and contaminant nature, as well as the induced pH changes caused by the filter media. The zero-order kinetic model best described the removal rate of Cu and Ni by sand. The first-order kinetic model was only applicable for nitrate removal by iron filings, and the second-order kinetic model described the removal rates of other contaminants and filter media combinations.