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Constructed Wetlands Ashley Buffington

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1 Constructed Wetlands Ashley Buffington

2 Constructed Wetlands Created to treat variety of wastewaters
First experiments carried out by Käthe Siedel in Germany in 1952 Classified into four categories: Free-water surface flow (FWS) Sub-surface flow (SSF) Hybrid systems Zero discharge systems Domestic, industrial, and agricultural wastewaters, stormwater, mine drainage, landfill leachate, and runoff First experiments using wetland vegetation for wastewater treatment were carried out by Kathe Siedel at the Max Planck Institute in Plon, Germany in 1952

3 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

4 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

5 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 VF + HF: vertical subsurface system leads to horizontal subsurface system> aims toward more efficient de-nitrification HF + VF: horizontal subsurface, then vertical subsurface; H SSF removes most organic and suspended solids; V SSF > high oxidation and efficient nitrification HF +VF +HF +FWS: achieves de-nitrification through last HF, FWS removes nitrogen components and accomplishes microbial load

6 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 Use for individual households Evapotranspiration: Soil and plant surfaces 1/3 willows harvested yearly to keep stock young and healthy. encourages high transpiration rates, and removes some nutrients and heavy metals

7 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

8 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 (2-3) growing seasons

9 Constructed Wetlands: Costs
C A = $196,336 A −0.511 Where C A is the capital cost of wetland construction per unit area ($ ha −1 ) and A 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)

10 Constructed Wetlands: Operation and Maintenance
Life expectancy between 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 If rehabilitated every 10 years

11 Case Study: Apache Powder Superfund Site Cochise 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 Including nitroglycerin, nitric acid, ammonium nitrates, blasting agents, and liquid and solid-based fertilizers; Primary production was nitroglycerin Through a drain into unlined ditches Soil: Some Contaminants of concern included: barium, beryllium, chromium, lead, manganese and nitrate Groundwater. Perched water table as well as shallow groundwater aquifer contaminated: COC included: arsenic, fluoride, nitrate (perched) and nitrate and perchlorate in aquifer Residents used shallow groundwater aquifer as source of drinking water. Sampling detected 470mg/l nitrate in one drinking well on the site.

12 Case Study: Apache Powder Superfund Site Cochise 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 Case Study: Apache Powder Superfund Site Cochise County, Arizona Consists of 5 cells: first 3 are planted with emergent plants, fourth cell is planted with submerged, and the fifth is a polishing cell Nitrate levels consistently reduced to less than 10ppm

13 References Federico, R., and J. Kandasamy. "Operation and Maintenance of Wetlands." Constructed Wetlands. Ed. Jaya Kandasamy and Saravanamuthu Vigneswaran. New York: Nova Science, Print. Ghanem, P. and B. Simpson. "Design and Construction of Constructed Wetlands." Constructed Wetlands. Ed. Jaya Kandasamy and Saravanamuthu Vigneswaran. New York: Nova Science, Print. Lorion, Renee. "Constructed Wetlands: Passive Systems for Wastewater Treatment." U.S. Environmental Protection Agency, Aug Web. 20 Mar <>. Mitsch, William J., and James G. Gosselink. Wetlands. 4th ed. Hoboken, NJ: Wiley, Print. Moat, G., B. Simpson, P. Ghanem, J. Kandasamy, and S. Vigneswaran. "Constructed Wetlands: Classification, Functions, and Treatment." Constructed Wetlands. Ed. Jaya Kandasamy and Saravanamuthu Vigneswaran. New York: Nova Science, Print. "Region 9: Superfund." Environmental Protection Agency, 14 July Web. 19 Apr <> Vymazal, Jan, and Lenka Kröpfelová. Wastewater Treatment in Constructed Wetlands with Horizontal Sub-surface Flow. Berlin: Springer Netherland, Print. Vymazal, Jan, Margaret Greenway, Karin Tonderski, Hans Brix, and Ulo Mander. "Constructed Wetlands for Wastewater Treatment." Wetlands and Natural Resource Management. Ed. J. T. A. Verhoeven, B. Beltman, R. Bobblink, and D. F. Whigman. Vol Berlin: Springer, Print. Ecological Studies.

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