Flow Rate and Sediment Trapping Laboratory Experiments using Various Biofilter Media

Appropriate hydraulic characteristics of the filter media, including treatment flow rate, clogging capacity, and water contact time are critical for optimal performance of stormwater biofiltration systems in urban areas. A series of controlled laboratory column flow tests were conducted using sand-peat mixture, Tuscaloosa surface and subsurface soils, along with media from current Kansas City, North Carolina, and Wisconsin biofilters. Besides the flow tests, sediment-trapping experiments were also performed for the sand-peat media mixtures and Tuscaloosa soils using challenge water. The laboratory tests indicated that compaction has a significant effect on the infiltration rates; however, amending the sand mixtures with peat reduced the degraded flow rate effects associated with compaction. The particle-trapping experiments indicated that significant particulate trapping occurred for most lab columns with little difference for the different column media mixtures. However, columns with local area soils had increased discharges of very small particle sizes compared with the influent water due to washing of the fines from the media.