Performance of Compost Filtration Practice for Green Infrastructure Stormwater Applications
Urban storm water runoff poses a substantial threat to receiving surface waters. Green infrastructure, low impact development, green building ordinances, National Pollutant Discharge Elimination System (NPDES) storm water permit compliance, and Total Maximum Daily Load (TMDL) implementation strategies have become national priorities; however designers need more sustainable, low cost solutions to meet these goals and guidelines. The objective of this study was to: i) determine the multiple event removal efficiency and capacity of compost filter socks (FS) and FS + natural sorbents (NS) to remove soluble phosphorus, ammonium-nitrogen, nitrate-nitrogen, E. coli, Enterococcus, and oil from urban storm water runoff. Treatments were exposed to simulated storm water pollutant concentrations consistent with urban runoff originating from impervious surfaces, such as parking lots and roadways. Treatments were exposed to a maximum of 25 runoff events or when removal efficiencies were u 25%, whichever occurred first. Experiments were conducted in triplicate. The FS+NS removed significantly greater soluble P than the FS, removing a total of 237 mg/linear m over 8 runoff events, or an average of 34%. The FS+NS removed 54% of ammonium-N over 25 runoff events, or 533 mg/linear m, and only 11% of nitrate-N, or 228 mg/linear m. The FS and FS+NS both removed 99% of oil over 25 runoff events, or a total load of 38,486 mg/linear m. Over 25 runoff events the FS+NS removed E. coli and Enteroccocus at 85% and 65%, or a total load of 3.14 CFUs x 108/linear m and 1.5 CFUs x 109/linear m, respectively; both were significantly greater than the FS treatment. Based on these experiments, this technique can be used to reduce soluble pollutants from storm water over multiple runoff events.