Evaluation of Nutrients and Suspended Solids Removal by Stormwater Control Measures Using High-Flow Media

Abstract

High-flow media (HFM) are able to treat large runoff volumes using small-footprint systems. Four full-scale HFM stormwater control measures (SCMs) in a residential area were monitored over 11 months to assess the removal of total suspended solids (TSS), nitrogen, and phosphorus in first-flush (FF) stormwater runoff. Excellent removal of TSS and particulate-bound nutrients is noted, but, in most SCMs, removal of dissolved species is limited. Sorption of dissolved P occurs, although most likely on captured sediment and not on the HFM itself. N removal varies among the systems, but, in general, mineralization and nitrification of accumulated N species in the SCMs leads to nitrate export. FF is present in TSS (strongest), total nitrogen, and total phosphorous (weakest). HFM grain size and organic content do not significantly impact TSS or P removal, but higher organic content is associated with higher N removal. Optimal HFM SCM design incorporates sedimentation before filtration to minimize clogging concerns.