Dissolved Phosphorus Treatment in Stormwater Biofilters Enhanced with Media Amendments

Biofiltration systems are one type of vegetated sustainable drainage systems particularly suited for diffuse pollution control and with a relatively compact footprint that make them an ideal choice for retrofit in urban areas. Existing knowledge on dissolved pollutant fate in biofilters, the influence of their design and configuration on hydrological, pollutant removal and long term performance is limited. This paper focuses on investigating the influence of amended media on the removal performance of dissolved pollutants through a laboratory study using batch test and mesocosms under controlled condition. Duplicate control and three amended configurations comprising of Zeolite, Granular Activated Carbon, and a mix of both, were dosed with synthetic stormwater runoff simulating typical pollutants concentration of urban runoff areas. In this paper the results for phosphate removal are reported. Preliminary results suggested that there is significant difference between inlet and outlet phosphate concentration (P < 0.001) with the configurations with both the amendments and the zeolite resulting in highest average removal performance. Mean phosphate removal performance for the four configurations were lower than 27%. Batch test highlighted the occurrence of leaching from topsoil and woodchips used in the biofilters. Higher phosphate removal was observed after longer dry periods between runs.