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sys1=[[Single Pit System |1]]|
sys2=[[Blackwater Treatment System with Infiltration|56]]|sys3=[[Blackwater Treatment System with SewerageEffluent Transport|67]]|sys4=[[Blackwater Transport to (Semi-) Centralized Treatment System |78]]|sys5=[[Sewerage System with Urine Diversion|89]]|
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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
[[Image:Icon_free-water_surface_constructed_wetland.png |right|80px]]
'''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]](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.
Raw blackwater should be pretreated to prevent the excess accumulation of solids and garbage. Once in the pond, the heavier sediment particles settle out, also removing nutrients that are attached to particles. 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. Pathogens are removed from the water by natural decay, predation from higher organisms, sedimentation and UV irradiation. Although the soil layer below the water is anaerobic, the plant roots exude (release) oxygen into the area immediately surrounding the root hairs, thus, creating an environment for complex biological and chemical activity.
Although the soil layer below the water ===Design Considerations=== The channel or basin is anaerobiclined with an impermeable barrier (clay or geo-textile) covered with rocks, the plant roots exude gravel and soil and planted with native vegetation (releasee.g., cattails, reeds and/or rushes) oxygen . The wetland is flooded with wastewater to a depth of 10 to 45 cm above ground level. The wetland is compartmentalized into at least two independent flow paths. The number of compartments in series depends on the area immediately surrounding the root hairs, thus creating an environment for complex biological and chemical activitytreatment target.
The efficiency of the Freefree-Water Surface Constructed Wetland water surface constructed wetland also depends on how well the water is distributed at the inlet. Wastewater can be input to fed into the wetland , using weirs or by drilling holes in a distribution pipe , to allow it to enter in even 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
}}
===AdequacyAppropriateness===Free-water surface constructed wetlands can achieve a high removal of suspended solids and moderate removal of pathogens, nutrients and other pollutants, such as heavy metals. This technology is able to tolerate variable water levels and nutrient loads. Plants limit the dissolved oxygen in the water from their shade and their buffering of the wind; therefore, this type of wetland is only appropriate for low-strengthwastewater. This also makes it appropriate only when 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.
FreeThe free-Water Surface Constructed Wetlands can achieve high removals of suspended solids water surface wetland is a good option where land is cheap and moderate removal available. Depending on the volume of pathogens, nutrients the water and other pollutants such as heavy metals. Shade from plants and protection from wind mixing limit the dissolved oxygen in corresponding area requirement of the waterwetland, thereforeit can be appropriate for small sections of urban areas, this as well as for peri-urban and rural communities. This technology is only appropriate best suited for low strength wastewater. Usually this requires that Free-Water Surface Constructed Wetlands are only appropriate when they follow warm climates, but can be designed to tolerate some type freezing and periods of primary treatment to lower the BODlow biological activity.
Depending on the volume of water, and therefore the size, wetlands ===Health Aspects/Acceptance=== The open surface can be appropriate act as a potential breeding ground for small sections of urban areas or more appropriate for peri-urban and rural communitiesmosquitoes. This is a However, good treatment technology for communities that have a primary treatment facility (edesign and maintenance can prevent this.gFree-water surface constructed wetlands are generally aesthetically pleasing, especially when they are integrated into pre-existing natural areas. [[Septic Tank|Septic Tank]]). Where land is cheap and available, it is a good option as long as Care should be taken to prevent people from coming in contact with the community is organized enough to thoroughly plan and maintain effluent because of the wetland potential for disease transmission and the duration risk of its lifedrowning in deep water.
This technology is best suited to warm climates but can be designed to tolerate some freezing and periods of low biological activity. ===Health Aspects/Acceptance=== The open surface can act as a potential breeding ground for mosquitoes. However, good design and maintenance can prevent this. The Free-Water Surface Constructed Wetlands are generally aesthetically pleasing, especially when they are integrated into pre-existing natural areas. Care should be taken to prevent people from coming in contact with the effluent because of the potential for disease transmission and the risk of drowning in deeper waters. ===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 periodically.
===References===
* Crites, R. and Tchobanoglous, G. (1998). Small and Decentralized Wastewater Management Systems. WCB/McGraw- Hill, New York, US. pp. 582-599. (Comprehensive summary chapter including solved problems)
* CritesKadlec, R. H., Knight, R. L., Vymazal, J., Brix, H., Cooper, P. and TchobanoglousHaberl, GR. (19982000). Small Constructed Wetlands for Pollution Control. Processes, Performance, Design and Decentralized Wastewater Management SystemsOperation. WCB Scientific and McGraw-HillTechnical Report No. 8. IWA Publishing, New YorkLondon, USAUK.:Available at: [http://www. pp 582–599iwawaterwiki. (Comprehensive summary chapter including solved problemsorg iwawaterwiki.)org]
* MaraKadlec, DDR. H. and Wallace, S. D. (20032009). Domestic wastewater treatment in developing countriesTreatment Wetlands, 2nd Ed. EarthscanCRC Press, LondonTaylor & Francis Group, UK. pp 85–187Boca Raton, US.
* Poh-EngMerz, S. L. and Polprasert, C. (19982000). Guidelines for Using Free Water Surface Constructed Wetlands for Wastewater Treatment and Resource Recoveryto Treat Municipal Sewage. Environmental Sanitation Information Center, AITQueensland Department of Natural Resources, BangkokBrisbane, ThailandAU.
* Poh-Eng, L. and Polprasert, C., et al. (20011998). Constructed Wetlands for Wastewater Treatment IIand Resource Recovery. Environmental Sanitation Information Center, Natural Systems for Wastewater Management. IHE DelftAIT, Bangkok, The Netherlands. Chapter 6TH.
* QLD DNR (2000)Polprasert, C. Guidelines for using free water surface constructed wetlands to treat municipal sewage. Queensland Government, Department of Natural ResourcesVeenstra, BrisbaneS. and van der Steen, AustraliaP. Available: http://www(2001).epaWastewater Treatment II.qldNatural Systems for Wastewater Management, Chapter 6.govUNESCO-IHE, Delft, NL.au
* General information about Planted soil filter U.S. EPA (2000). Constructed Wetlands Treatment of Municipal Wastewaters. EPA/625/R-99/010. U.S.Environmental Protection Agency, Washington, D.C., US.:Available at: [http://www.bodenfilter.de/engdef.htm www.bodenfilterepa.de/engdefgov epa.htm gov]
* General information Vymazal, J. (2008). Constructed Wetlands for Wastewater Treatment: A Review. In: Proceedings of Taal 2007: The 12th World Lake Conference, M. Sengupta and R. Dalwani (Eds.). pp. 965-980.:Available at: [http://www.constructedwetlandsmoef.nic.org wwwin moef.constructedwetlandsnic.org in]
===Acknowledgements===
{{:Acknowledgements Sanitation}}