Changes

Stormwater filtration is an essential component of urban runoff management. Filtration can improve water quality by removing suspended solids and pollutants which helps meet TSS removal targets and maintain watershed health. Filtration is the process by which stormwater [[Runoff volume control targets|runoff]] is conveyed through a medium to remove solid particles and associated pollutants. 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).

Stormwater filtration is an essential component of urban runoff management. Filtration can improve water quality by removing suspended solids and pollutants which helps meet TSS removal targets and maintain watershed health. Filtration is the process by which stormwater [[Runoff volume control targets|runoff]] is conveyed through a medium to remove solid particles and associated pollutants. 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).

==Types of filtration==

==Types of filter media==

Two common types of filter media used in stormwater treatment are granular media and membranes:   

Care should be taken when selecting the type of filter media used in an LID system. Two common types of [[Media filters|filter media]] used in stormwater treatment are granular media and membranes:   

*'''Granular media''' is a multilayer lattice or matrix that traps solids as water flows through the tortuous channels in the media. Examples of granular media include [[sand]] and [[Aggregates|gravel]].

*'''Granular media''' is a multilayer lattice or matrix that traps solids as water flows through the tortuous channels in the media. Examples of granular media include [[sand]] and [[Aggregates|gravel]].

*'''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. Care should be taken when selecting the type of [[Geotextiles|geotextile]] used in an LID system.

*'''[[Geotextiles|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.

Some filters include [[additives]] such as zeolite or iron to enhance the contaminant removal process for target water quality variables by increasing chemical adsorption and/or precipitation.

Some filters include [[additives]] such as zeolite or iron to enhance the contaminant removal process for target water quality variables by increasing chemical adsorption and/or precipitation.

==Maintenance Considerations==

==Maintenance Considerations==

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. As the filter becomes [[clogging|clogged]], 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 [[overflow|bypass]] within or upstream of the system).  

Clogging may occur when solid particles form a film on top of the filter or accumulate within the media channels to the point where the channels become occluded. Clogging can decrease the effectiveness of a filter. As the filter becomes [[clogging|clogged]], 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 [[overflow|bypass]] within or upstream of the system).  

*[[Permeable pavements]] can filter runoff through the surface pores or media between pavers, as well as through the bedding and base layers. Most of the [[sediment]] directed onto the pavements is trapped near the surface where it can be more easily accessed for cleaning.

*[[Permeable pavements]] can filter runoff through the surface pores or media between pavers, as well as through the bedding and base layers. Most of the [[sediment]] directed onto the pavements is trapped near the surface where it can be more easily accessed for cleaning.

*[[Filtration Manufactured Treatment Devices]]

*[[Filtration Manufactured Treatment Devices]]

*[[Media filters]]

*[[Stormwater planters]]

*[[Pretreatment]]

*[[Pretreatment]]

*[[Oil and grit separators]]

*[[Oil and grit separators]]