ENGINEERING BIORETENTION FOR TREATMENT OF URBAN STORM WATER RUNOFF

Bioretention is an urban storm water best management practice developed in the early 1990's. Bioretention media can remove pollutants through several mechanisms, including sedimentation, filtration, sorption, and precipitation. However, the optimal design of bioretention media for pollutant removal, while maximizing infiltration characteristics has not been systematically investigated. In this study, pollutant removals using bioretention media columns have been determined, along with corresponding infiltration rates, for a variety of bioretention media mixes.The water infiltration rate ranged from 0.28 to 0.84 cm/min in these 6-hr experiments. It was the highest with sand as the only medium and the lowest when soil was the dominant medium. For conditions where the media was composed of several layers, as the soil layer thickness increased, the infiltration rate decreased. For pollutant removal, the results show that every media mixture used in this series of experiments produced excellent removal efficiency (>98%) for suspended solids, oil/grease, and lead. For total P, the removal efficiency ranges from 47% to 85%, increasing as the sand ratio in the medium increased. For nitrate-N and ammonium-N, the removal efficiency ranges from 1% to 27% and from 2% to 26%, respectively.