Improvement of phosphorus and heavy metals retention in stormwater treatment

Scope and method of study. The objectives of this study were to find filter media with high phosphorus sorption and adequate hydraulic conductivity for use in bioretention cells, and to evaluate the improvement of heavy metals retention in sandy soil after amending with fly ash. The pollutant retention capacity of a filter media is an important consideration in stormwater infiltration systems. Batch sorption experiments were used to screen filter media. Column experiment and transport modeling allowed the evaluation of phosphorus and heavy metals sorption capacity of filter media in a dynamic condition.; Findings and conclusions. Soils had a low phosphorus sorption. Fly ash had the highest phosphorus sorption. The addition of fly ash in soils increased the phosphorus sorption, but decreased the hydraulic conductivity. Sandy soil amended with fly ash exhibited a high phosphorus sorption while maintaining adequate hydraulic conductivity. Sandy soil had the lowest heavy metals sorption while fly ash the highest. The addition of fly ash in sandy soil increased the heavy metals sorption. These results will provide valuable information for the practical use of fly ash in amending soils to improve phosphorus and heavy metals retention in stormwater infiltration systems such as bioretention cells.