Evaluation Of A Parking Lot Bioretention Cell ForRemoval Of Stormwater Pollutants

Bioretention is used to retain and treat urban stormwater, which has been identified by the United States Environmental Protection Agency as one of the most significant forms of water pollution. In this study, the efficiency of a bioretention facility in terms of temperature, pH, dissolved oxygen, nutrients, and heavy metals removal over a period of 15 rain events was evaluated. This was performed by collecting representative samples of the stormwater runoff for laboratory analysis of both the influent to and the effluent from the bioretention cell. The bioretention was efficient in terms of pollutant removal in the following order: TSS (~ 98%) > Zn (~ 80%) > Cu (~ 75%) > Pb (~ 71%) > Cd (~ 70%) > NH3-N (~65%) > Fe (~ 51%) > Cr (~ 42%) > NO2-N (~ 27%) > Al (~ 17%) > PO4-P (~3%). From the field results Cu (II), Zn (II) and Pb (II) were removed significantly at 81%, 79% and 75%. The field results indicate that bioretention facilities can be effective for the removal of heavy metals in the following order: Cu > Zn > Pb > Cd > Fe > Cr > Al. Although the removal efficiency for this actual field bioretention cell was not has high as previously reported laboratory and field evaluations, removal of pollutants was significant. Organic matter and plants were believed to be the dominant bioretention elements for the removal of heavy metals.