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Line 180: + + + − Kennedy, G., and T. Mayer. 2002. Natural and Constructed Wetlands in Canada: An Overview. Water Qual. Res. J. Canada 37(2): 295–325. doi: 10.2166/wqrj.2002.020.
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[[File:Kortright-farm-june-2011.jpg|thumb|Wetlands fed by stormwater at Kortright Farm, Vaughan ON]]
[[File:Kortright-farm-june-2011.jpg|thumb|500px|Wetlands fed by stormwater at Kortright Farm, Vaughan ON]]
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==Overview==
==Overview==
Free-water surface flow wetlands are most commonly employed for stormwater treatment and are similar to [[SWM ponds]] in function and design The most significant difference is the extent to which they are designed to incorporate shallow zones for wetland [[plants]]. A facility is normally characterized as a wetland if shallow zones (<0.5 m deep) make up more than 70 % of its volume.
Free-water surface flow wetlands are most commonly employed for stormwater treatment and are similar to [[SWM ponds]] in function and design The most significant difference is the extent to which they are designed to incorporate shallow zones for wetland [[plants]]. A facility is normally characterized as a wetland if shallow zones (<0.5 m deep) make up more than 70 % of its volume.
==Planning considerations==
==Planning considerations==
{|class="wikitable"
{|class="wikitable"
|+ Types of Constructed Wetland<ref>Grant, N., M. Moodie, and C. Weedon. 2000. Sewage Treatment Solutions. p. 35–67. In Sewage Solutions: Answering the Call of Nature. Centre for Alternative Technology Publications.</ref><ref name="EPA">United States Environmental Protection Agency. 1995. A HANDBOOK OF CONSTRUCTED WETLANDS: A guide to creating wetlands for agricultural wastewater, domestic wastewater, coal mine drainage and stormwater.</ref>
|+ Types of Constructed Wetland<ref>Grant, N., M. Moodie, and C. Weedon. 2000. Sewage Treatment Solutions. p. 35–67. In Sewage Solutions: Answering the Call of Nature. Centre for Alternative Technology Publications.</ref><ref name="EPA">United States Environmental Protection Agency. 1995. A HANDBOOK OF CONSTRUCTED WETLANDS: A guide to creating wetlands for agricultural wastewater, domestic wastewater, coal mine drainage and stormwater.</ref><ref>Jacques Whitford Consultants, 2008. CONSTRUCTED & ENGINEERED WETLANDS p. 1-21</ref>
|-
|-
!Free-water surface flow
!Free-water surface flow
|style="text-align:left;"|'''Pros'''
|style="text-align:left;"|'''Pros'''
*Well established technology
*Well established technology
*May be natural looking, although often rectilinear in plan
*May be natural looking
*Need little to no gradient
*Need little to no gradient
*Provides buffer to discharge
*Provides buffer to discharge
*Good pathogen removal from die off and predation
*Good pathogen removal from die off and predation
*Minimal maintenance
*Minimal maintenance
*Wide range of plants suitable
*Wide range of [[Wetland: list|plants]] suitable
*Robust
*Robust
|style="text-align:left;"|'''Pros'''
|style="text-align:left;"|'''Pros'''
*High levels of treatment possible
*High levels of treatment possible
*May be run without power if significant gradient is available
*May be run without power if significant gradient is avaialble
*Can be attractively designed to generate interest in the technology, may be any shape.
*Can be attractively designed to generate interest in the technology.
*Maintenance is technically simple. Sludge easily removed
*Maintenance is technically simple
*Biologically complex and robust
*Biologically complex and robust
*Failure tends to be gradual
*Failure tends to be gradual
|style="text-align:left;"|'''Cons'''
|style="text-align:left;"|'''Cons'''
*Requires more land
*Requires more land
*Multiple substrate layers will promote stratification and channelization
|style="text-align:left;"|'''Cons'''
|style="text-align:left;"|'''Cons'''
*Requires fall of at least 1.5 m to provide sufficient treatment
*Requires fall of at least 1.5 m to provide sufficient treatment
==Design==
==Design==
===Sizing free-water===
{| class="wikitable"
{| class="wikitable"
|+Design parameters for free-water surface flow wetlands <ref>Toronto and Region Conservation Authority (TRCA), and CH2M Hill Canada. 2018. Inspection and Maintenance Guide for Stormwater Management Ponds and Constructed Wetlands (T van Seters, L Rocha, and K Delidjakovva, Eds.).</ref>
|+Design parameters for free-water surface flow wetlands <ref name="TRCA">Toronto and Region Conservation Authority (TRCA), and CH2M Hill Canada. 2018. Inspection and Maintenance Guide for Stormwater Management Ponds and Constructed Wetlands (T van Seters, L Rocha, and K Delidjakovva, Eds.).</ref>
!Element
!Element
!Design Objective
!Design Objective
|-
|-
|Treatment Volume
|Treatment Volume
|Provision of appropriate level of protection (Table 3.2)
|Provision of appropriate level of protection
|style="text-align: left|See Table 3.2
|style="text-align: left|See [[#.|below]]
|-
|-
|Active Storage
|Active Storage
|}
|}
===Modeling===
===.===
'''[http://www.unep.or.jp/Ietc/Publications/Water_Sanitation/SubWet2/index.asp SubWet 2.0]''' is a modeling tool for subsurface flow wetlands (both 100% constructed and naturalized/adapted). It can be used to simulate removal of nitrogen (including nitrogen in ammonia, nitrate and organic matter), phosphorus and BOD5 in mg/l and the corresponding removal efficiencies (in %). Although the model has been calibrated already with data from cold and warm climates, users can further calibrate and validate it using local data observations.
{| class="wikitable"
|+Water volume storage requirements based on catchment type and receiving waters<ref name ="TRCA"/>
!rowspan=2|Performance level
!colspan=4|Storage volume (m<sup>3</sup>/Ha) required according to catchment impervious cover
|-
!35%
!55%
!70%
!85%
|-
|80 % TSS removal||80||105||120||140
|-
|70 % TSS removal||60||70||80||90
|-
|60 % TSS removal||60||60||60||60
|}
===Modeling sub-surface===
'''[http://www.unep.or.jp/Ietc/Publications/Water_Sanitation/SubWet2/index.asp SubWet 2.0]''' is a modeling tool for <u>sub-surface flow wetlands</u> (both 100% constructed and naturalized/adapted). It can be used to simulate removal of nitrogen (including nitrogen in ammonia, nitrate and organic matter), phosphorus and BOD<sub>5</sub> in mg/l and the corresponding removal efficiencies (in %). Although the model has been calibrated already with data from cold and warm climates, users can further calibrate and validate it using local data observations.
==Materials==
===Planting===
See [[Wetlands: Plants]]
==Performance==
==Performance==
Relative to a wet pond, a constructed wetland may offer added pollutant removal benefits due to enhanced biological uptake and the filtration effects of the vegetation.
Relative to a wet pond, a constructed wetland may offer added pollutant removal benefits due to enhanced biological uptake and the filtration effects of the vegetation.
Early stage wetlands readily sorb phosphorus onto substrates and sediments. Phosphorus removal in wetland systems is usually carried out by incorporating alum sedimentation ponds or [[sand filters]] as cells of the system, and/or by polishing wetland effluent in an iron-dosed mechanical filter.<ref>Jacques Whitford Consultants, 2008. CONSTRUCTED & ENGINEERED WETLANDS p. 1-21</ref>
Freezing temperatures in winter and early spring can reduce treatment if the wetland either freezes solid or a cover of ice prevents the water from entering the wetland. If under-ice water becomes confined, water velocities may increase, thereby reducing contact times<ref name="EPA" />. Runoff in excess of maximum design flows should be [[Overflow#routing|diverted]] around the wetland to avoid excessive flows through the wetland.
Freezing temperatures in winter and early spring can reduce treatment if the wetland either freezes solid or a cover of ice prevents the water from entering the wetland. If under-ice water becomes confined, water velocities may increase, thereby reducing contact times<ref name="EPA" />. Runoff in excess of maximum design flows should be [[Overflow#routing|diverted]] around the wetland to avoid excessive flows through the wetland.
*[[SWM ponds]]
*[[SWM ponds]]
*[[Dry ponds]]
*[[Dry ponds]]
*[[Plants]]
==External links==
==External links==
*[https://cawt.ca/ Centre for Advancement of Water and Wastewater Technologies at Fleming College]
*[https://cawt.ca/ Centre for Advancement of Water and Wastewater Technologies at Fleming College]
===Articles for review===
#Kennedy, G., and T. Mayer. 2002. Natural and Constructed Wetlands in Canada: An Overview. Water Qual. Res. J. Canada 37(2): 295–325. doi: 10.2166/wqrj.2002.020.
#Bendoricchio, G., L. Dal Cin, and J. Persson. 2000. Guidelines for free water surface wetland design. EcoSys Bd 8: 51–91. http://www.pixelrauschen.de/wet/design.pdf (accessed 9 May 2018).
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