Bioretention is an upland water quality and water quantity control practice that uses the chemical, biological and physical properties of plants, microbes and soils for removal of pollutants from storm water runoff. Some of the processes that may take place in a bioretention facility include: sedimentation, adsorption, filtration, volatilization, ion exchange, decomposition, phytoremediation, bioremediation, and storage capacity. This same principle of utilizing biological systems has been widely used in the retention and the transformation of pollutants and nutrients found in agricultural and wastewater treatment practices. Unlike various other practices that control only peak discharge, bioretention can be designed to mimic the pre-existing hydrologic conditions by treating the associated volumes of runoff (from bioretention.com).
A rain garden is a bowl-like depression in the ground, used to collect stormwater runoff from impervious surfaces, such as roofs and pavement, in order to infiltrate the ground rather than runoff into the stormwater system. Commonly, native plants are used to not only beautify this process, but also in combination with the mulch and soil, will assist in the natural processes to filter pollutants from runoff and break down in the soil over time (from Oklahoma Cooperative Extension Service).
