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Created page with "Filtration is the process by which stormwater runoff is conveyed through a filter medium to remove solid particles and associated pollutants. Several stormwater practices use..."
Filtration is the process by which stormwater runoff is conveyed through a filter medium to remove solid particles and associated pollutants. Several stormwater practices use filtration through sand or gravel media as the primary mechanism for treatment of urban runoff.
Stormwater passes through a filter based on the pressure difference on either side of the filter. In most stormwater treatment applications, the pressure difference is created by gravity (or hydraulic head). As the filter becomes occluded, higher pressure is needed to drive stormwater through the filter, until a point is reached at which flow through the treatment system must be redirected to another flow path (usually a bypass within or upstream of the system).
==Types of filtration==
Two common types of filter media used in stormwater treatment are granular media, such as sand, and membranes:
'''Granular media''' is a multilayer lattice or matrix that traps solids as water flows through the tortuous channels in the media. Clogging may occur when solid particles form a film or cake on top of the filter or accumulate within the media channels to the point where the channels become occluded.
'''Membranes''' have very thin separation lattices with openings or pores that remove all particles larger than the nominal pore size of the filter at the surface, thereby acting much like a sieve. Membranes are often pleated to increase the surface area, allowing for more particles to be trapped prior to clogging.
Stormwater passes through a filter based on the pressure difference on either side of the filter. In most stormwater treatment applications, the pressure difference is created by gravity (or hydraulic head). As the filter becomes occluded, higher pressure is needed to drive stormwater through the filter, until a point is reached at which flow through the treatment system must be redirected to another flow path (usually a bypass within or upstream of the system).
==Types of filtration==
Two common types of filter media used in stormwater treatment are granular media, such as sand, and membranes:
'''Granular media''' is a multilayer lattice or matrix that traps solids as water flows through the tortuous channels in the media. Clogging may occur when solid particles form a film or cake on top of the filter or accumulate within the media channels to the point where the channels become occluded.
'''Membranes''' have very thin separation lattices with openings or pores that remove all particles larger than the nominal pore size of the filter at the surface, thereby acting much like a sieve. Membranes are often pleated to increase the surface area, allowing for more particles to be trapped prior to clogging.