Filtration pretreatment practices include proprietary and non-proprietary devices that remove particles by filtration or sieving through media (gravel, sand or other), vegetation, geotextile or fabric material, metal or plastic screen, or other material. The filtration devices presented in this table are classified as pretreatment due to the nature of the filtration, placement in the treatment train, or built-in additional pretreatment mechanisms. The filtration methods are widely varied from biological to mechanical. They seek to remove not only larger sediments and debris, but also heavy metals, nutrients, and other fine contaminants. The natural or engineered biological systems are, by nature, above ground.
Some filtration pretreatment methods require a larger footprint than other pretreatment options due to the slower flow through rate and surface-area-based effectiveness. Most drainage area references refer to impervious area.
Sizing is largely based on drainage area and estimated runoff volumes for different design storms or intensities. Most important for the sizing is the anticipated frequency of operation and maintenance as well as protection of downstream BMPs and receiving water. Some devices have “enhancements” that can provide treatment mechanisms beyond the primary pretreatment mechanism. These can provide an additional level of treatment such as filtration, skimming (in addition to settling or screening), chemical treatment/sorption, or biodegradation. This is denoted by the Y or N in the table indicating this ability to perform additional mechanisms.
Below are links to several tables containing information on filtration. To see all tables on a single page, link here. To see the information in a single spreadsheet click on the following link: [[File:]]