Nutrient, Metal, and Organics Removal from Stormwater Using a Range of Bioretention Soil Mixtures.

A column study was conducted to test the ability of bioretention soil mixtures (BSMs) to remove nutrients, metals, and polyaromatic hydrocarbons (PAHs) from stormwater collected from an urban highway. Infiltration rate, plant growth response, and turbidity of the effluent were also measured. The BSMs were made from a range of types and rates of composts and additional materials such as water treatment residuals, sawdust, and oyster shells. Sand was used as a control. Total N and P in stormwater measured 1.8 ± 1 and 0.08 ± 0.03 mg L. All treatments were a source of these nutrients. Metal concentrations in the stormwater were low, with mean Cu and Zn concentrations of 39.8 ± 19.1 and 173 ± 113 μg L, and Cd and Pb close to detection limits. All treatments absorbed Cu and Zn from stormwater with varying levels of removal efficiency. The three treatments tested removed 84 to 100% of the PAHs from the stormwater. In general, contaminant removal (N, P, and Zn) efficiency was not related to infiltration rate, with a slight decrease in Cu removal efficiency observed with increased infiltration rate ( = 0.32). These results indicate that the BSMs tested were a source of nutrients but were generally effective at removing metals and PAHs from stormwater.