Nutrient and Escherichia coli Attentuation in a Constructed Stormwater Wetland in the North Carolina Coastal Plain

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.