State-of-the-Art Review of Phosphorus Sorption Amendments in Bioretention Media: A Systematic Literature Review

AbstractThe ability of bioretention systems to treat phosphorus heavily depends on the filter media composition. Dissolved phosphorus is primarily removed from influent stormwater runoff through sorption processes, although the organic material contained within bioretention media can also leach phosphorus. Amendments containing sorptive metals such as aluminum, iron, and calcium have been introduced in recent years to increase the phosphorus sorption capacities and rates of bioretention media. This study is a state-of-the-art review that uses a systematic literature review process to identify, integrate, and critically evaluate the findings of all published column, mesocosm, and field studies identified from two database platforms that have provided quantitative analyses of phosphorus sorption amendments for bioretention systems. These amendment materials were grouped into four categories: (1) waste products, (2) natural materials, (3) processed materials, and (4) proprietary products. A total of 51 amendment materials or material combinations were evaluated across 59 studies, of which only four have been evaluated within a field setting (expanded slate, fly ash, Sorbtive Media, and aluminum-based water treatment residuals) and only one (fly ash) has been evaluated within an aged system. This study provides a detailed discussion on the performance, applicability, constructability, and operational challenges of phosphorus sorption amendments used in bioretention systems. Recommendations for amendment selection and installation methods are provided to support both engineering practice and future research on the topic.