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Constructed Wetlands. Ashley Buffington. http://www.gocolumbiamo.com/PublicWorks/Sewer/wwtppg_4.php. Constructed Wetlands. Created to treat variety of wastewaters First experiments carried out by Käthe Siedel in Germany in 1952 Classified into four categories :
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Constructed Wetlands Ashley Buffington http://www.gocolumbiamo.com/PublicWorks/Sewer/wwtppg_4.php
Constructed Wetlands • Created to treat variety of wastewaters • First experiments carried out by KätheSiedel in Germany in 1952 • Classified into four categories: • Free-water surface flow (FWS) • Sub-surface flow (SSF) • Hybrid systems • Zero discharge systems
Constructed Wetlands:Free-Water Surface Flow • Basins with shallow waters and substrate to support rooted vegetation • First FWS CW created in Ijssel Lake Polder Authority in Flevoland in the Netherlands in 1967 • FWS CW systems with: • Free-floating macrophytes • Floating-leaved macrophytes • Submerged macrophytes • Emergent macrophytes http://sudied.blogspot.com/2010/04/water-and-city.html
Constructed Wetlands:Sub-Surface Flow • Contain underground flow of wastewater through substrate • Can be beneficial in areas where wildlife is discouraged • Types of SSF CWs: • Horizontal Flow (HF) • Vertical Flow (VF) • Down flow • Up flow http://sudied.blogspot.com/2010/04/water-and-city.html http://sudied.blogspot.com/2010/04/water-and-city.html
Constructed Wetlands:Hybrid Systems • Result from combining different types of CWs • Advantages and disadvantages of CWs combined to complement each other • Higher treatment effect accomplished http://www.iridra.com/eng/cw_ibr.htm
Constructed Wetlands:Zero-discharge Systems • Developed in Denmark for sewage disposal in rural areas • Consists of basins lined with HDPE, filled with soil and planted with willows • Removal of water via evapotranspiration • Harvested regularly http://www.pilerensning.dk/english/index.php?option=com_content&view=article&id=53&Itemid=56&lang=da
Constructed Wetlands:Advantages • Cost 50-90% less than conventional wastewater treatment systems • Require little external energy input • Rely on solar energy to operate • More sustainable compared to conventional treatment plants • Improve air quality and help fight global warming • Provide green space, habitat for wildlife, recreational and educational opportunities
Constructed Wetlands:Limitations • Require large areas of land • Require long periods for vegetation to establish for optimal treatment efficiencies • Potentially susceptible to influences such as storms, wind, and floods • Steep topography and high water table limit these systems • Expensive to implement
Constructed Wetlands:Costs • Where is the capital cost of wetland construction per unit area ($ and is the wetland area (ha) • 1-ha wetland ≈ $200,000 • 10-ha wetland ≈ $60,000 per ha • 100-ha wetland≈ $19,000 per ha • SSF CWs are more expensive than FWS CWs • Initial cost ≈ $388,000 (SSF); ≈ $58,000 (FWS)
Constructed Wetlands:Operation and Maintenance • Life expectancy between 30-50 years • General maintenance tasks: • Removing debris/litter • Monitoring depth of sediments • Checking for channelization • Identifying any damage from vandalism • Inspecting inlet and outlet • Operation and maintenance cost ≈ $85,000 annually • Estimated for a 175 ha wetland • Includes approx. $50,000 for personnel • Costs range from $5,000-$50,000 for smaller wetlands
Case Study:Apache Powder Superfund SiteCochise County, Arizona • Approx. 9 mi² and 1,100 acres owned by Apache Nitrogen Products (ANP) • Began manufacturing industrial chemicals and explosives in 1922 • Produced liquid and solid wastes disposed on ANP property • Investigated in 1987 • Soils showed high levels of heavy metals and arsenic • Groundwater showed high levels of contamination as well
Case Study:Apache Powder Superfund SiteCochise County, Arizona • Multi-celled wetland system used • Groundwater pumped from shallow aquifer to first cell • Nitrate levels in groundwater entering first cell were approx. 250 ppm • Nitrate levels leaving fifth cell were approx. 10 ppm • Can treat 200 gallons water per minute • Water stays about 5 days in system • Costs savings estimated to be $15 million
References • Federico, R., and J. Kandasamy. "Operation and Maintenance of Wetlands." Constructed Wetlands. Ed. Jaya Kandasamy and SaravanamuthuVigneswaran. New York: Nova Science, 2008. 57-73. Print. • Ghanem, P. and B. Simpson. "Design and Construction of Constructed Wetlands." Constructed Wetlands. Ed. Jaya Kandasamy and SaravanamuthuVigneswaran. New York: Nova Science, 2008. 27-56. Print. • Lorion, Renee. "Constructed Wetlands: Passive Systems for Wastewater Treatment." U.S. Environmental Protection Agency, Aug. 2001. Web. 20 Mar. 2011. <http://permanent.access.gpo.gov/websites/epagov/www.epa.gov/swertio1/download/remed/constructed_wetlands.pdf>. • Mitsch, William J., and James G. Gosselink. Wetlands. 4th ed. Hoboken, NJ: Wiley, 2007. Print. • Moat, G., B. Simpson, P. Ghanem, J. Kandasamy, and S. Vigneswaran. "Constructed Wetlands: Classification, Functions, and Treatment." Constructed Wetlands. Ed. Jaya Kandasamy and SaravanamuthuVigneswaran. New York: Nova Science, 2008. 1-26. Print. • "Region 9: Superfund." Environmental Protection Agency, 14 July 2010. Web. 19 Apr. 2011. <http://yosemite.epa.gov/r9/sfund/r9sfdocw.nsf/vwsoalphabetic/Apache+Powder+Company?OpenDocument> • Vymazal, Jan, and LenkaKröpfelová. Wastewater Treatment in Constructed Wetlands with Horizontal Sub-surface Flow. Berlin: Springer Netherland, 2008. Print. • Vymazal, Jan, Margaret Greenway, Karin Tonderski, Hans Brix, and UloMander. "Constructed Wetlands for Wastewater Treatment." Wetlands and Natural Resource Management. Ed. J. T. A. Verhoeven, B. Beltman, R. Bobblink, and D. F. Whigman. Vol. 190. Berlin: Springer, 2006. 69-96. Print. Ecological Studies.
