2 Constructed Wetlands Created to treat variety of wastewaters First experiments carried out by Käthe Siedel in Germany in 1952Classified into four categories:Free-water surface flow (FWS)Sub-surface flow (SSF)Hybrid systemsZero discharge systemsDomestic, industrial, and agricultural wastewaters, stormwater, mine drainage, landfill leachate, and runoffFirst 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 vegetationFirst FWS CW created in Ijssel Lake Polder Authority in Flevoland in the Netherlands in 1967FWS CW systems with:Free-floating macrophytesFloating-leaved macrophytesSubmerged macrophytesEmergent macrophytes
4 Constructed Wetlands: Sub-Surface Flow Contain underground flow of wastewater through substrateCan be beneficial in areas where wildlife is discouragedTypes of SSF CWs:Horizontal Flow (HF)Vertical Flow (VF)Down flowUp flow
5 Constructed Wetlands: Hybrid Systems Result from combining different types of CWsAdvantages and disadvantages of CWs combined to complement each otherHigher treatment effect accomplishedVF + HF: vertical subsurface system leads to horizontal subsurface system> aims toward more efficient de-nitrificationHF + VF: horizontal subsurface, then vertical subsurface; H SSF removes most organic and suspended solids; V SSF > high oxidation and efficient nitrificationHF +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 areasConsists of basins lined with HDPE, filled with soil and planted with willowsRemoval of water via evapotranspirationHarvested regularlyUse for individual householdsEvapotranspiration: Soil and plant surfaces1/3 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 systemsRequire little external energy inputRely on solar energy to operateMore sustainable compared to conventional treatment plantsImprove air quality and help fight global warmingProvide green space, habitat for wildlife, recreational and educational opportunities
8 Constructed Wetlands: Limitations Require large areas of landRequire long periods for vegetation to establish for optimal treatment efficienciesPotentially susceptible to influences such as storms, wind, and floodsSteep topography and high water table limit these systemsExpensive to implement(2-3) growing seasons
9 Constructed Wetlands: Costs C A = $196,336 A −0.511Where C A is the capital cost of wetland construction per unit area ($ ha −1 ) and A is the wetland area (ha)1-ha wetland ≈ $200,00010-ha wetland ≈ $60,000 per ha100-ha wetland≈ $19,000 per haSSF CWs are more expensive than FWS CWsInitial cost ≈ $388,000 (SSF); ≈ $58,000 (FWS)
10 Constructed Wetlands: Operation and Maintenance Life expectancy between yearsGeneral maintenance tasks:Removing debris/litterMonitoring depth of sedimentsChecking for channelizationIdentifying any damage from vandalismInspecting inlet and outletOperation and maintenance cost ≈ $85,000 annuallyEstimated for a 175 ha wetlandIncludes approx. $50,000 for personnelCosts range from $5,000-$50,000 for smaller wetlandsIf 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 1922Produced liquid and solid wastes disposed on ANP propertyInvestigated in 1987Soils showed high levels of heavy metals and arsenicGroundwater showed high levels of contamination as wellIncluding nitroglycerin, nitric acid, ammonium nitrates, blasting agents, and liquid and solid-based fertilizers; Primary production was nitroglycerinThrough a drain into unlined ditchesSoil: Some Contaminants of concern included: barium, beryllium, chromium, lead, manganese and nitrateGroundwater. Perched water table as well as shallow groundwater aquifer contaminated: COC included: arsenic, fluoride, nitrate (perched) and nitrate and perchlorate in aquiferResidents 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 usedGroundwater pumped from shallow aquifer to first cellNitrate levels in groundwater entering first cell were approx. 250 ppmNitrate levels leaving fifth cell were approx. 10 ppmCan treat 200 gallons water per minuteWater stays about 5 days in systemCosts savings estimated to be $15 millionCase Study: Apache Powder Superfund Site Cochise County, ArizonaConsists of 5 cells: first 3 are planted with emergent plants, fourth cell is planted with submerged, and the fifth is a polishing cellNitrate levels consistently reduced to less than 10ppm
13 ReferencesFederico, 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 <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, 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 <http://yosemite.epa.gov/r9/sfund/r9sfdocw.nsf/vwsoalphabetic/Apache+Powder+Company?OpenDocument>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.