Prediction of Flow Rates through Various Stormwater Biofilter Media Mixtures

Stormwater bioinfiltration systems are widely used in urban areas to reduce stormwater runoff volume, peak flows, and stormwater pollutant loads reaching receiving waters. Appropriate hydraulic characteristics of the filter media, including treatment flow rate, and water contact time, are important considerations for the selection of the media. This paper describes a series of tests conducted using a variety of biofilter media to determine factors that affect their infiltration rates. Laboratory tests examined the infiltration rates of these materials subjected to various levels of compaction and sand amendments. A series of sand mixtures were also prepared and tested that represent a wide range of median particle sizes and uniformity coefficients and were also subjected to various levels of compaction. The effects on the infiltration rates by adding organic matter to selected media mixtures were also examined. 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.