| The purpose of this research was to evaluate the effectiveness of three variations of green infrastructure devices in the removal of stormwater contaminants for ten storm events along Nannie Helen Burroughs Avenue in Washington, D.C. This was done by collecting representative samples of stormwater from both the influent and the effluent of the bioretention cells for laboratory analysis. The three devices in this study are identified as: bioswale, swale-bioretention and bioretention. The general order of performance in descending order was: the bioretention, the bioswale and the swale-bioretention. For all three devices the effluent quality was significantly improved, in aggregate for all pollutants, than the influent stormwater.;The Swale-bioretention produced negative results for total dissolved solids, copper, cadmium, nitrite, nitrate and ammonia. The percentage removals for these pollutants were -564%, -24%, -10%, -50%, -9% and -8.33% respectively. The Bioswale produced negative results for total dissolved solids, lead and total phosphorus with percentage removals of -91%, -25% and -44% respectively. The Bioretention produced negative results for total dissolved solids, cadmium and zinc with -98%, -7% and -18% removals respectively. These poor results could be as a result of poor or lack of routine and periodic maintenance which includes; replacement of sub-soil mix, annual replacement of much layer and proper maintenance of plant material (Maryland Department of Environmental Resources (DER), 2007, Yu S. L et al., 2001). |
