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− +*Low cost+*DIY possible (to lower cost)+
+
+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.
[[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]]
−{{TOClimit|2}}
==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.
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==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
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|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
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|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
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==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
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|-
|-
|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
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|}
|}
−===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.
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*[[SWM ponds]]
*[[SWM ponds]]
*[[Dry ponds]]
*[[Dry ponds]]
+*[[Plants]]
==External links==
==External links==
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*[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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