1,647
edits
Changes
Jump to navigation
Jump to search
Line 8:
Line 8: − + − + − + − + − + Line 33:
Line 33: − [[Permeable pavements]] can also be considered to be a type of filter. In this case, runoff and+
no edit summary
Two common types of filter media used in stormwater treatment are granular media and membranes:
Two common types of 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.
*'''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.
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 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).
==Applications==
==Applications==
Stormwater practices use filtration through as the primary mechanism for treatment of runoff include:
Stormwater practices use filtration through as the primary mechanism for treatment of runoff include:
*[[Bioretention]] systems such as <ref>https://sustainabletechnologies.ca/app/uploads/2020/06/High-rate-treatment-bioretention-filter-tech-brief.pdf<ref>
*[[Bioretention]] technologies such as [https://sustainabletechnologies.ca/app/uploads/2020/06/High-rate-treatment-bioretention-filter-tech-brief.pdf the Filterra® bioretention system] have successfully used filtration to achieve 80% TSS removal for events with influent TSS concentrations above 100 mg/L.
*[[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]]
*[[Media filters]]
Non-proprietary [[bioretention]] systems are sized as filters much more conservatively based on design storms, surface ponding depth and [[Flow through media|minimum media infiltration rate]]. The ratio of drainage area imperviousness to the surface area of bioretention facilities (referred to as the impervious-to-pervious ratio) is often many times lower than that for filtration MTDs. This ensures longer intervals for sediment maintenance and significant reductions in stormwater volumes through infiltration.
Non-proprietary [[bioretention]] systems are sized as filters much more conservatively based on design storms, surface ponding depth and [[Flow through media|minimum media infiltration rate]]. The ratio of drainage area imperviousness to the surface area of bioretention facilities (referred to as the impervious-to-pervious ratio) is often many times lower than that for filtration MTDs. This ensures longer intervals for sediment maintenance and significant reductions in stormwater volumes through infiltration.
==References==