Difference between revisions of "Pretreatment"

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<p>Oil and grit separators (OGS) are devices which use physical principles to improve water quality. Typically these are underground chambers installed in catchbasins or manholes. Many commercial and custom configurations exist.  
[[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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*One option employs a series of baffles within a tank or chamber:
==Overland sheet flow==
**The first baffle slows the incoming water flow, encouraging any larger, heavier particles to drop out of the water,
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:
**A second baffle skims the surface of the water, preventing floating debris, oils and grease from passing,  
*[[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!


*Another option is a hydrodynamic device, which forces the incoming water flow into a circular vortex:  
==Concentrated overland flow==
**This motion forces the larger, heavier particles are outwards and downwards into a lower chamber,  
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:
**Floating debris, oils and grease are trapped behind a baffle or in small tank area, towards the top of the main vortex chamber. </p>
* 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.


===External Links===
==Concentrated underground flow==
<ul>
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.
<li>[https://www.cmhc-schl.gc.ca/en/inpr/su/waho/waho_015.cfm CMHC OGS Effectiveness Study]</li>
</ul>
<h4>Proprietary Systems</h4>
Links are provided for information only. Inclusion of a company or product does not constitute endorsement. <br>
You may inform us of any omissions using the link below:
<ul>
<li>[http://www.imbriumsystems.com/stormwater-treatment-solutions/stormceptor-systems| Stormceptor]</li>
</ul>


{{:Feedback}}
{|class="wikitable"
[[category:pretreatment]]
|+ 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]]

Latest revision as of 14:13, 30 August 2021

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.

Overland sheet flow[edit]

The following pretreatement features are recommended where surface sheet flow is being directed to a BMP (e.g. a bioretention cell) receiving flow from the edge of an impermeable surface such as an asphalt parking lot or a paved plaza:

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[edit]

Where a curb cut, a disconnected roof downspout pipe, 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;
  • 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. Rain Guardian is one example of a proprietary sump device.

Concentrated underground flow[edit]

This type of pretreatement is dominated by proprietary systems, some of which have undergone verification under the Environmental Technology Verification (ETV) program.

Pretreatment options
Type Description ETV products Other products (not verified)
Catch basin inserts Great for improving water quality in retrofit situations
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.
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
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.
Membrane filters Uses advanced membrane technology adapted from water treatment plants.
Media filters A variety of proprietary designs and media mixes are available.
Overland flow sumps Collects and settles debris as overland flow passes through sump to treatment device.
  • 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: