Difference between revisions of "Pretreatment"
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<li>[https://www.cmhc-schl.gc.ca/en/inpr/su/waho/waho_015.cfm CMHC OGS Effectiveness Study]</li> | <li>[https://www.cmhc-schl.gc.ca/en/inpr/su/waho/waho_015.cfm CMHC OGS Effectiveness Study]</li> |
Revision as of 20:40, 8 August 2017
Overland sheet flow[edit]
The following pretreatements are recommended where sheet flow is being directed to a BMP (typically a bioretention cell) 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 two designs can be used in combination to even greater effect!
Concentrated overland flow[edit]
Where a curb cut, a disconnected downspout or a swale directs surface water to a point, increasing the flow rate, one or more of the following pretreatments should be considered:
- Forebays (well suited for bioretention cells)
- Sand filters (well suited for underground infiltration)
- Screens and racks
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.
Type | Description | ETV products | Other products (not verified) |
---|---|---|---|
OGS 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 |
Hydrodynamic OGS | 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 | Stormceptor | |
Cartridge filters | Uses membrane technology adopted from water treatment plants. | - | Jellyfish filter |
Catchbasin inserts | Great for retrofitting situations, to improve water quality | CB Shield | Snout |
External resources[edit]
This article is particularly heavy on proprietary systems and information. Please inform us of any omissions or broken links using the box below: