Performance comparison of stormwater biofiltration designs
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A biofiltration system is a stormwater Best Management Practice (BMP) that uses a biologically active filtration bed to remove contaminants. This type of BMP is preferred because it provides the opportunity for pollutant uptake (particularly nutrients) by vegetation in an aesthetically pleasing design. The goals of this research, proposed by the City of Austin, Texas, are to assess the role of plants in nutrient removal and to compare the pollutant removal effectiveness of biofiltration systems containing different media, plant species and designs. A laboratory column study was conducted with nineteen experiments using synthetic stormwater and one experiment using real stormwater. The results of this study show a significant improvement in nutrient removal with the presence of plants and a submerged zone with a carbon source in the filter. The columns without plants were found to export up to twice the nitrate/nitrite input, whereas the columns with plants showed significant removal of all nutrients (Nitrate 30-50%, Total Kjeldhal Nitrogen 65-85%, Total Phosphorus 80-90%). The difference between the two biofiltration media was not significant. Metals (Copper, Lead, Zinc) removal by all columns was very high (>95%) compared to similar field studies. Total Suspended Solids removal remained high through the whole set of experiments for all the columns (85- 95%).