Evaluation of Biofiltration Media for Optimum Stormwater Treatment Under Controlled Outflow Conditions

Geosyntec conducted a column study to develop and evaluate candidate media blends and assess the impact of outlet hydraulic control on pollutant removal performance for a land development project which is required to meet strict NPDES requirements based on outfall monitoring. The components of the biofiltration media tested included various combinations of sand, coconut coir pith, activated carbon, compost, peat, biochar, and zeolite. Composite influent and effluent samples were analyzed for E. coli, nutrients, total and dissolved metals, total suspended solids (TSS), and total organic carbon (TOC). Each media mix provided TSS removal below the lab detection limit, 80-90% E. coli removal, substantial metals removal, and moderate removal of nitrogen. Some phosphorus export was observed for mixes containing compost, but phosphorus export was not observed for mixes containing peat and/or coco coir. Beyond the specific project goals, these results are expected to provide valuable information for developing specifications for biofiltration media in the future.