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Line 1: ===Overland sheet flow===<p>The following pretreatements are recommended where sheet flow is being directed to a BMP (typically a [[Bioretention cells| bioretention cell]]) from the edge of an impermeable surface such as an asphalt parking lot or a paved plaza:<ul><li>[[Gravel diaphragms]]</li><li>[[Vegetated filter strips]]</li></ul>A gravel diaphragm typically requires less setback between the catchment and the BMP. Where space permits, these two designs can be used in combination to even greater effect!</p>===Concentrated overland flow===Where a [[Curb cuts| curb cut]], [[Downspout disconnection| a disconnected downspout]] or a [[Swales| swale]] directs surface water to a point, increasing the flow rate, one or more of the following pretreatments should be considered:<ul><li>[[Forebays]] (well suited for bioretention cells)</li><li>[[Sand filters]] (well suited for underground infiltration)</li><li>[[Screens and racks]]</li></ul>===Concentrated underground flow===This type of pretreatement is dominated by proprietary systems, some of which have undergone verification under the [http://etvcanada.ca/| Environmental Technology Verification (ETV)] program. <table class = "table table-striped table-responsive"><caption><strong>Inline pretreatment options</strong></caption><tr class ='success'> <th width = 20%>Type</th> <th width = 40%>Description</th> <th width = 20%>ETV products</th> <th width = 20%>Other products (not verified)</th></tr><tr><td>OGS Baffles</td><td>Baffles slow flow, encouraging larger, heavier particles to drop out of the water column. A skimmer may also trap floating debris, oils and grease. </td><td>-</td><td>[http://upstreamtechnologies.us/products/safl.shtml| SAFL baffle]</td></tr><tr><td>Hydrodynamic OGS</td><td>The shape causes rapidly flowing water to form a vortex which forces the larger, heavier particles are outwards and downwards into a lower chamber. Floating debris, oils and grease are trapped behind a baffle or in small tank area, towards the top of the main vortex chamber</td><td>[http://www.conteches.com/Products/Stormwater-Management/Treatment/CDS.aspx| CDS]<br>[https://www.hydro-int.com/en/products/downstream-defender| Downstream defender]<br>[http://nextstorm.ca/sdd/| SDD]</td><td> [http://www.imbriumsystems.com/stormwater-treatment-solutions/stormceptor-systems| Stormceptor]</td></tr><tr><td>Cartridge filters</td><td>Uses membrane technology adopted from water treatment plants. </td><td>-</td><td>[http://www.imbriumsystems.com/stormwater-treatment-solutions/jellyfish-filter| Jellyfish]</td></tr><tr><td>Catchbasin inserts</td><td>Great for retrofitting situations, to improve water quality</td><td>[http://www.cbshield.com/| CB Shield]</td><td> [http://upstreamtechnologies.us/products/snout.shtml| Snout]</td></tr></table>
<ul><li>[https://www.cmhc-schl.gc.ca/en/inpr/su/waho/waho_015.cfm CMHC OGS Effectiveness Study]</li></ul>
This article is particularly heavy on proprietary systems and information. Please inform us of any omissions or broken links using the button below:
→Concentrated overland flow
[[File:Oil-grit separator USGS 2002.png|thumb|Example oil-grit separator USGS 2002 (Wikimedia commons)]]
Pretreatment devices may be constructed in close association association with one or more [[inlets]]. Different configurations of each exist to accommodate any design.
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===Resources===
==Overland sheet flow==
The following pretreatement features are recommended where surface sheet flow is being directed to a BMP (e.g. a [[Bioretention cells|bioretention cell]]) receiving flow from the edge of an impermeable surface such as an asphalt parking lot or a paved plaza:
*[[Level spreaders]]
*[[Gravel diaphragms]]
*[[Vegetated filter strips]]
A gravel diaphragm typically requires less setback between the catchment and the BMP. Where space permits, these designs can be used in combination to even greater effect!
==Concentrated overland flow==
Where a [[Curb cuts| curb cut]], [[Downspout disconnection| a disconnected roof downspout]] pipe, [[Swales| swale]], trench drain, side inlet catch basin or other pre-fabricated inlet structure collects and conveys runoff as concentrated overland flow, which increases the flow rate, one or more of the following pretreatment features should be considered:
* Catch basin or other pre-fabricated inlet structure sump;
* [[Level spreader]];
*[[Pretreatment features| Forebays]] (well suited for bioretention cells);
* [[Stone]] and [[geotextile]] filter: A shallow excavation on the filter media bed surface at the inlet, lined with geotextile and rip rap or decorative stone cover; and,
*[[Sand filters]] (well suited for underground [[infiltration]]);
*Concrete sump pretreatment device. [https://acfenvironmental.com/products/stormwater-management/filtration/rain-guardian/ Rain Guardian] is one example of a proprietary sump device.
{{:Feedback}}
==Concentrated underground flow==
This type of pretreatement is dominated by proprietary systems, some of which have undergone verification under the [http://etvcanada.ca/ Environmental Technology Verification (ETV)] program.
{|class="wikitable"
|+ Pretreatment options
|-
!style="width: 10%;"|Type
!style="width: 40%;"|Description
!style="width: 25%;"|ETV products
!style="width: 25%;"|Other products (not verified)
|-
!Catch basin inserts
|Great for improving water quality in retrofit situations
|
*[http://www.cbshield.com/ CB Shield]
|
*[https://www.enviropod.com/products/littatrap Littatrap]
*[http://www.bmpinc.com/ Snout]
|-
!Manhole baffles
|Baffles slow flow, encouraging larger, heavier particles to drop out of the water column. A skimmer may also trap floating debris, oils and grease.||
|
*[http://upstreamtechnologies.us/products/safl.shtml SAFL Baffle]
|-
!Oil and grit (hydrodynamic) separators
|The shape causes rapidly flowing water to form a vortex which forces the larger, heavier particles are outwards and downwards into a lower chamber. Floating debris, oils and grease are trapped behind a baffle or in small tank area, towards the top of the main vortex chamber
|
*[http://www.conteches.com/Products/Stormwater-Management/Treatment/CDS.aspx CDS]
*[https://www.hydro-int.com/en/products/downstream-defender Downstream Defender]
*[https://www.hydro-int.com/en/products/first-defense First Defense]
*[http://www.hydroworks.com/hydrostorm.html Hydrostorm]
*[http://nextstorm.ca/sdd/ SDD]
*[http://www.imbriumsystems.com/stormwater-treatment-solutions/stormceptor-ef Stormceptor EF]
|
|-
!Isolated chamber row filter
|Separate rows at inlets, not connected by pipes to the other chambers, that isolate the bulk of sediment and associated pollutants and designed for ease of access by jet flushing cleaning equipment.
|
*[https://cultec.com/products/separator-row/ Cultec Separator Row]
|
|-
!Membrane filters
|Uses advanced membrane technology adapted from water treatment plants.
|
*[http://www.imbriumsystems.com/stormwater-treatment-solutions/jellyfish-filter Jellyfish Filter]
*[https://biocleanenvironmental.com/kraken-filter Kraken Filter]
|
|-
!Media filters
|A variety of proprietary designs and media mixes are available.
|
*[http://www.imbriumsystems.com/stormwater-treatment-solutions/filterra Filterra]
*Nonproprietary concrete inlet sump
*[https://baysaver.com/products/bayfilter/ BayFilter]
*[https://www.conteches.com/stormwater-management/treatment/stormwater-management-stormfilter StormFilter]
|
|-
!Overland flow sumps
|Collects and settles debris as overland flow passes through sump to treatment device.||
|
*[http://www.rainguardian.biz/project-planing/chamber-selection Rain Guardian]
*Catch basin or other pre-fabricated inlet structure sump
*Nonproprietary concrete inlet sump
|-
|}
This article is particularly heavy on proprietary systems and information. Please inform us of any omissions or broken links using the box below:
[[category: Pretreatment]]
[[category: Pretreatment]]