Pretreatment

thumb|650px|This non-proprietary pre-treatment device, known as a "Sediment Pad" that is used by the City of Toronto to capture coarse sediment, trash and debris in runoff before water drains into bioretention or other similar green stormwater infrastructure practices. Centralizing sediment and debris capture in a small area near the inlet to the bioretention feature helps simplify maintenance (City of Toronto, 2021City of Toronto. 2021. Curb Cut Inlet with Sediment Pad – Layout and Section. ENGINEERING & CONSTRUCTION SERVICES STANDARD DRAWING. Accessed. https://www.toronto.ca/wp-content/uploads/2021/08/9598-ecs-specs-gi-dwgs-T-850.102-Rev0-Sep2021.pdf.
Pretreatment devices may be constructed in close association association with one or more inlets. Different configurations of each exist to accommodate any design.
thumb|450px|Another example of the City of Toronto's non-proprietary pre-treatment device, known as a "Sediment Pad" shown being used at the curb inlet of a bioretention cell on Danforth Av. to capture coarse sediment, trash and debris in influent entering the BMP. 
==Overland sheet flow==
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:
*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 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). See Pretreatment features for guidance on sizing.;
* 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==
This type of pretreatment is dominated by proprietary systems, some of which have undergone verification under the Environmental Technology Verification (ETV) Canada program. Pretreatment devices suited to concentrated underground flow, or pipe flow include the following:
* Oil and grit (hydrodynamic) separators
* Manhole baffles
* Isolated chamber row filters
* Membrane filters
* Media filters
Membrane and media filters are more commonly used as "stand alone" water quality treatment practices when space for surface practices is not available, but may also be used downstream of LID facilities or treatment trains to enhance removal of sediment and other targeted pollutants (e.g., nutrients, metals) where warranted by receiving water sensitivity.
 Pretreatment options
Type 	Description 	Canadian ETV verified products	Other products (not verified)
Overland flow sumps 	Collects and settles debris as overland flow passes through sump to treatment practice. 	
*EnviroBasin 	
*Catchbasin or other non-proprietary pre-fabricated inlet structure sump. Small forebays may also be used for treatments systems receiving concentrated overland flow’
*Rain Guardian
Catchbasin inserts 	Great for improving water quality in retrofit situations 	
*CB Shield 	
*Snout
*Littatrap
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	
*CDS
*Downstream Defender
*First Defense
*Hydrostorm
*SCICLONE HDS
*SDD
*Stormceptor EF
*StormTrap Storm Settler	
*SAFL Baffle
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.| 	 	
*SAFL Baffle
Isolated chamber row 	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. 	
*Cultec Separator Row
*StormTech Isolator Row Plus®	
*ChamberMaxx®
Membrane filters 	Uses advanced membrane technology adapted from water treatment plants. 	
*Jellyfish Filter (TARP)
*Jellyfish Filter (TAPE)
*Kraken Membrane Filtration (TAPE)	
Media filters 	A variety of proprietary designs and media mixes are available. 	
*Filterra
*BaySaver BayFilter
*The Stormwater Management StormFilter (TAPE)
*Up-Flo Filter	
*Sorbtive Media
*Bioretention Filter Media
*Sand FiltersStormwater Manager's Resource Center. n.d. Stormwater Management Fact Sheet: Sand and Organic Filter. Accessed: https://www.stormwatercenter.net/Assorted%20Fact%20Sheets/Tool6_Stormwater_Practices/Filtering%20Practice/Sand%20and%20Organic%20Filter%20Strip.htm
*Gutter Guards/Filters
*Downspout Filters
*Media filters
*High Performance Soil Media MixesHowie, D., and Lubliner, B. 2021. Guidance on using new high performance bioretention soil mixes. "Water Quality Program",
Washington State Department of Ecology. Olympia, Washington. May 2021 - Publication 21-10-023.
This table and page are particularly heavy on proprietary systems and information. Please inform us of any omissions or broken links using the box below:
==Gallery==
==References==
category: Pretreatment