Effectiveness of scrap tire chips for phosphorus removal in surface waters

Surface waters may transport organic and inorganic pollutants. Phosphorus is typically the limiting nutrient that contributes to the growth of nuisance aquatic plants and algae in freshwater systems. Excessive algal growth may adversely impact water supply agencies ability to comply with federal secondary drinking water standards. Traditional methods for nonpoint nutrient pollutant control typically focus on biological processes. Physical/chemical processes (i.e. iron salts for phosphorus) are widely practiced at point sources. Ferric ions react with dissolved phosphate to precipitate ferric phosphate, which is removable using filtration, settling or adsorption. Corrosion of steel can supply ferric ions (iron oxide).; This project examines the potential of using steel belted automobile tire chips as a source of ferric ions and therefore a treatment medium for phosphorus removal in surface waters. Simulated runoff solutions of various phosphorus concentrations were tested in laboratory-scale columns or "towers" filled with tire chips of various exposed metal volume. Both the starting solution P concentration and tire chip exposed metal volume were found to have a significant effect on the percent of phosphorus removed from solution. Average removal rates ranged from 11% to 73% depending on the treatment combination and exposure time. These results indicate exposing surface water runoff to tire chips with exposed steel is a potentially useful phosphorus treatment practice.