Abstract
Stormwater best management practices (BMPs) are installed to reduce the delivery of pollutants to surface waters. The objective of this study was to determine the stormwater NO3-N, PO4-P, and Escherichia coli (E. coli) reductions in a constructed wetland in Greenville, North Carolina. Water samples were collected at the inlet and outlet of the wetland before, during, and after 11 storms for NO3-N, PO4-P, and E. coli analysis. Treatment efficiencies for NO3-N (69%) and PO4-P (63%) exceeded the nutrient credit reductions assigned to stormwater wetlands (40% for both) in North Carolina. The E. coli (59%) and PO4-P (63%) concentration reductions in the wetland were similar to the reduction in specific conductivity (62%), possibly because of sedimentation in the wetland that reduced the suspended and dissolved solids with adsorbed E. coli and PO4-P. The relatively large size of the wetland (7% of drainage area), and below average rainfall likely contributed to the exceptional pollutant reduction efficencies.
Highlights
1.1 Urban StormwaterManagementStormwater runoff from urban areas can lead to impairment of adjacent receiving waterways via rapid transport of pollutants such as nutrients, sediment, and bacteria that accumulate on impervious surfaces between storms (Davis et al, 2001; Tilley & Brown, 1998)
Treatment efficiencies for NO3-N (69%) and PO4-P (63%) exceeded the nutrient credit reductions assigned to stormwater wetlands (40% for both) in North Carolina
The objective of this study was to determine if the NO3-N, PO4-P, and E. coli treatment efficiency of a constructed stormwater wetland was greater than or equal to the pollutant reduction credit established for the best management practices (BMPs) by North Carolina (NC) regulations
Summary
Stormwater runoff from urban areas can lead to impairment of adjacent receiving waterways via rapid transport of pollutants such as nutrients, sediment, and bacteria that accumulate on impervious surfaces between storms (Davis et al, 2001; Tilley & Brown, 1998). Best management practices (BMPs) such as stormwater wetlands are created to reduce the transport of runoff and pollutants from urban areas to natural waters, protecting water quality. Most stormwater wetlands consist of a forebay near the inlet, a shallow-water and shallow-land area, and another deep pool before the outlet (Hunt et al, 2007). Vegetation in the shallow water and shallow land areas uptake nutrients from runoff, and help slow the flow of influent, allowing sediment to settle (Gu & Dreschel, 2008). Constructed stormwater wetlands (CSWs) are often advantageous over other BMPs in that they tend to maintain a continuous flow, involving base flow and storm flow whereas other BMPs (retention ponds, etc.) may only be functioning as a treatment mechanism during and post storm events (Wadzuk et al, 2010)
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