Evaluating Nutrient Removal and Hydraulic Efficiency in a Free Water Surface Flow Constructed Stormwater Wetland.

摘要

Hydraulic efficiency and water quality treatment analyses were performed on Villanova University's current constructed stormwater wetland (CSW 2.0). The previous constructed wetland (CSW 1.0) was used as a baseline for comparison. It was found that CSW 2.0 significantly reduces storm peaks and volumes, while CSW 1.0 only reduced peaks. CSW 2.0 had an average peak flow reduction of 59% (n=15) and storm volume reduction of 25% (n=10). The average baseflow volume reduction was 41% (n=15), most likely as a result of increased residence time. CSW 1.0 had an average peak flow reduction of 39% (n=6) and insignificant storm volume reductions. Continuing research indicates greater efficiencies gained as CSW 2.0 plants become established. This includes peak flow reductions from 68% to 79%, and storm volume reductions from 16% to 56%. Trends indicate potential evapotranspiration as a result of fluxes in the hydrologic mass balance of the system. Data shows these evapotranspiration losses may be much more significant during growing seasons. Water quality analyses indicated significant CSW 2.0 reductions in nutrients, with sporadic chloride, TSS, and TDS results. Grab samples could be the reason for inconsistent solids and chlorides data. CSW 1.0 had slightly higher water quality treatment efficiencies, possibly because the data set from CSW 1.0 was taken after the system was established for at least four years. CSW 2.0 data was taken one to three years after its construction. Data monitoring and analysis will continue and further evaluations of CSW 2.0 performance will be completed. Future research will involve the use of autosamplers at all CSW 2.0 sampling locations, as well as expanded dissolved oxygen studies.