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Input1=BlackwaterEffluent|Input2=Greywater Stormwater |Input3= | Input4= |Input5=|Output1= Effluent | Output2= Biomass | Output3= | Output4= | Output5=|english_link=Free-Water_Surface_Constructed_Wetland|french_link=Filtre_planté_à_écoulement_horizontal_superficiel
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[[Image:Icon_free-water_surface_constructed_wetland.png |right|95px80px]]'''A Freefree-Water Surface Constructed Wetland is a series of flooded channels that water surface constructed wetland aims to replicate the naturally occurring processes of a natural wetland,marsh or swamp. As water slowly flows through the wetland, particles settle, pathogens are destroyed, and organisms and plants utilize the nutrients. This type of constructed wetland is commonly used as an advanced treatment after secondary or tertiary treatment processes.'''
Unlike the [[Horizontal Subsurface Flow Constructed Wetland|Horizontal Subsurface Flow Constructed Wetland]](T.8), the Freefree-Water Surface Constructed Wetland water surface constructed wetland allows water to flow above ground, exposed to the atmosphere and to direct sunlight. The channel or basin is lined with an impermeable barrier (clay or geotextile) covered with rocks, gravel and soil and planted with native vegetation (e.g. cattails, reeds and/or rushes). The wetland is flooded with wastewater to a depth of 10 to 45cm above ground level. As the water slowly flows through the wetland, simultaneous physical, chemical and biological processes filter solids, degrade organics and remove nutrients from the wastewater. Raw blackwater should be pre-treated to prevent the excess accumulation of solids and garbage. Once in the pond, the heavier sediment particles settle out, and this also removes the nutrients attached to them. Plants, and the communities of microorganisms that they support (on the stems and roots), take up nutrients like nitrogen and phosphorus. Chemical reactions may cause other elements to precipitate out of the wastewater.
The efficiency of the free-water surface constructed wetland also depends on how well the water is distributed at the inlet. Wastewater can be fed into the wetland, using weirs or by drilling holes in a distribution pipe, to allow it to enter at evenly spaced intervals.
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{{procontable | pro=
- Aesthetically pleasing and provides animal habitat. <br> - High reduction in of BOD and solids; moderate pathogen removal. <br> - Can be built and repaired with locally available materials. <br> - Construction can provide short-term employment to local labourers. <br> - No electrical energy is required. <br> - No real problems with flies or odours if used designed and maintained correctly. <br>- Low operating costs| con=- May facilitate mosquito breeding. <br> - Requires a large land area <br>- Long start up startup time to work at full capacity. <br> - Requires large land area. <br> - Requires expert design and supervision. <br> - Moderate capital cost depending on land, liner, etc.; low operating costs.construction
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==Adequacy=Appropriateness=== Free-Water Surface Constructed Wetlands water surface constructed wetlands can achieve a high removals removal of suspended solids and moderate removal of pathogens, nutrients and other pollutants , such as heavy metals. Shade from plants This technology is able to tolerate variable water levels and protection from wind mixing nutrient loads. Plants limit the dissolved oxygen in the water, from their shade and their buffering of the wind; therefore, this technology type of wetland is only appropriate for low -strength wastewater. Usually this requires that Free-Water Surface Constructed Wetlands are This also makes it appropriate only appropriate when they follow it follows some type of primary treatment to lower the BOD. Because of the potential for human exposure to pathogens, this technology is rarely used as secondary treatment. Typically, it is used for polishing effluent that has been through secondary treatment, or for stormwater retention and treatment.
The free-water surface wetland is a good option where land is cheap and available. Depending on the volume of the water, and therefore the sizecorresponding area requirement of the wetland, wetlands it can be appropriate for small sections of urban areas or more appropriate , as well as for peri-urban and rural communities. This technology is a good treatment technology best suited for communities that have a primary treatment facility (e.g. [[Septic Tank|Septic Tank]]). Where land is cheap and availablewarm climates, it is a good option as long as the community is organized enough but can be designed to thoroughly plan tolerate some freezing and maintain the wetland for the duration periods of its lifelow biological activity.
==Health Aspects/Acceptance=Operation & Maintenance=== Regular maintenance should ensure that water is not short-circuiting, or backing up because of fallen branches, garbage, or beaver dams blocking the wetland outlet. Vegetation may have to be periodically cut back or thinned out.
* Crites, RU. and Tchobanoglous, GS. EPA (19982000). Small and Decentralized Wastewater Management Systems[https://cfpub. WCB and McGrawepa.gov/si/si_public_record_report.cfm?dirEntryId=64144&Lab=NRMRL Constructed Wetlands Treatment of Municipal Wastewaters]. EPA/625/R-Hill99/010. U.S. Environmental Protection Agency, New YorkWashington, USAD. pp 582–599C. (Comprehensive summary chapter including solved problems, US.)
* MaraVymazal, DDJ. (20032008). Domestic wastewater treatment in developing countries[http://fos. Earthscandarvodgeo.ru/CW_Vymazal_review_1.pdf Constructed Wetlands for Wastewater Treatment: A Review]. In: Proceedings of Taal 2007: The 12th World Lake Conference, London, UKM. Sengupta and R. Dalwani (Eds.). pp 85–187. 965-980.