Changes

Jump to navigation Jump to search
no edit summary
Line 1: Line 1: −
[[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.  
Line 12: Line 12:  
==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
Line 30: Line 30:  
|style="text-align:left;"|'''Pros'''
 
|style="text-align:left;"|'''Pros'''
 
*Well established technology
 
*Well established technology
*Low cost
+
*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
*DIY possible (to lower cost)
+
*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
Line 54: Line 52:  
|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
Line 61: Line 60:     
==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  
Line 72: Line 73:  
|-
 
|-
 
|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
Line 132: Line 133:  
|}
 
|}
   −
===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.
Line 150: Line 174:  
*[[SWM ponds]]
 
*[[SWM ponds]]
 
*[[Dry ponds]]
 
*[[Dry ponds]]
 +
*[[Plants]]
    
==External links==
 
==External links==
Line 155: Line 180:  
*[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).
 
----
 
----
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.
 

Navigation menu