Media filtration has long been used in drinking water and wastewater treatment processes. This technology has proven effective at removing sediments, nutrients, heavy metals, and a wide variety of organic contaminants. The target pollutants, hydraulic retention time, filter media, pretreatment, and flow rate all affect the removal efficiency of the filter.
Mechanisms of Removal
BayFilter™ removes pollutants from water by two mechanisms: 1) interception/attachment and 2) adsorption. Interception occurs when a pollutant becomes trapped within the filter media. A sediment particle, for example, may be carried into the filter media by the water and become stuck in the interstices of the media. Such a particle will typically remain trapped within the media until the media is removed or the filter is backwashed.
Attachment occurs when pollutants bind themselves to the surface of the filter media, and this happens primarily through adsorption. Adsorption is a surface process by which dissolved ions are removed from a solution and chemically bind themselves to the surface of the media. This occurs when the surface of the filter media particle contains sites that are chemically attractive to the dissolved ions. The BayFilter™ system uses a proprietary media containing activated alumina to enhance adsorption of anions such as phosphates.
The BayFilter™ Cartridge
The main building block of the BayFilter™ stormwater filtration system is the BayFilter™ cartridge (BFC). The BFCs are housed in a structure which may be a vault, manhole or other structure. This structure contains the inlet and outlet pipes as well as an internal manifold that delivers treated water to the outlet of the BayFilter™ system.
Stormwater runoff enters the manhole or concrete structure via an inlet pipe and begins to fill the structure. An energy dissipator at the vault inlet slows the influent water and allows coarse sediments to settle within the structure. When the water surface elevation in the vault/manhole reaches operating level, water flows through the BFC driven by a hydrostatic head. Within the BFC, the water flows through a proprietary filter media and drains via a vertical pipe. The vertical drain is connected to the underdrain system which conveys filtered water to the outfall.