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Constructed wetlands

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One negative impact of CWs, especially FWS CWs, is the creation of a habitat for mosquitos. This problem can be mitigated with careful wetland design or incorporating anti-mosquito devices such as the mosquito fish. <ref>Knight, R. L., Walton, W. E., O’Meara, G. F., Reisen, W. K., & Wass, R. (2003). Strategies for effective mosquito control in constructed treatment wetlands. Ecological Engineering, 21(4), 211-232.</ref> Positive impacts include production of biomass from the harvesting of macrophytes, especially water hyacinths, <ref name = "Kivaisi"/> and less environmental impacts compared to other treatment methods, especially for the VF subsurface wetland. <ref>Fuchs, V. (2009). Nitrogen removal and sustainability of vertical flow constructed wetlands for small scale wastewater treatment. Houghton, MI: Michigan Technological University.</ref>
==Case Studies==
Houghton Lake, MI is a good example of a natural wetland altered for improving the quality of wastewater. In 1978 a wetland was added on to the wastewater treatment plant to better protect the large lake. The an average discharge is around 120 million gallons a year, with the wastewater being introduced into the wetland throughout the length of a 1,600 foot discharge pipe. The wetland is slightly sloped and water exits the wetland via nautual streams, with some minor backflow.
Impressively, the wetland has indicated consummption of over 90 % of the nitrogen and phosphorus from the treatment plant effluent.
Some changes have been noted in the wetland since the introduction of wastewaster, as sedimentation in the wetland has increased over 10 cm. Cattail and duckweed have taken over as dominant vegetation in the wetland, due to higher levels of nutrients in the effluent from the treatment facility.
Another example of a constructed wetland for wastewater treatment is the Lakeland wastewater treatment plant in Polk Co, FL. The treatment plant accepts 10.8 million gallons of wastewater daily. When effluent discharge into a nearby lake was determined to have a detrimental effect on the water quality, a wetland was created for the wastewaster treatment. Around 1,400 acres of wetlands were constructed for the treatment process.
The wetland significantly reduces the amount of nitrogen and phosphorus present in the wastewater, and provides habitat for an abundance of species.
Restoration processes have increased biodiversity within the wetland, which was predominatly covered in cattail and willow vegetation.
<ref name = "EPA">United States Environmental Protection Agency (1993). Constructed Wetlands for Wastewater Treatment and Wildlife Habitat
17 Case Studies. September 1993. EPA832-R-93-005.</ref>
Many groups are promoting constructed wetlands around the world. North America and Europe have been using CWs for decades, and now other areas are exploring them as well. CWs are researched at many universities and are used for many wastewater applications. The U.S. Environmental Protection Agency has created design manuals for the construction of treatment wetlands <ref>EPA. US Environmental Protection Agency, Office of Research and Development. (2000). Constructed wetlands treatment of municipal wastewaters (EPA/625/R-99/010). Retrieved from website: http://water.epa.gov/type/wetlands/restore/upload/constructed-wetlands-design-manual.pdf</ref> CW are not only being promoted by the government; individuals interested in green technology and sustainability can take classes where they learn to design and build their own home constructed wetland. <ref>YesterMorrow. (2012). Constructed wetlands for wastewater treatment. Retrieved from http://www.yestermorrow.org/workshops/detail/constructed-wetlands-for-wastewater-treatment</ref>


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