Presentation on theme: "Constructed Wetlands (CWs)"— Presentation transcript:
1 Constructed Wetlands (CWs) Beat Stauffer, international seecon gmbh
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3 ContentsConceptHow can Constructed Wetlands optimise SSWMDesign PrinciplesTreatment EfficiencyOperation and MaintenanceApplicabilityPros and ConsReferences
4 1. Concept Introduction Treatment step of DEWATS systems Secondary treatment facilities for household (blackwater or greywater, brownwater) and/or municipal or biodegredable industrial wastewater. (HOFFMANN et al. 2010)Tertiary treatment system for polishing (e.g. activated sludge, trickling filter plants) before safety disposal or reuse.Outflow of CW: groundwater recharge, fertigation, aquacultureTypes of constructed wetlands. They are classified according to the water flow regime as:Horizontal flow constructed wetlandsVertical flow constructed wetlandsFree surface constructed wetlandsCombined flow regimes are so called hybrid constructed wetlands and exploit the specific advantages of the different systems.
5 Example 1: Onsite or Semi-centralised Treatment System 2. How can Constructed Wetlands Optimise SSWMExample 1: Onsite or Semi-centralised Treatment SystemLow-flush toilet, shower, kitchen sink, etc.Groundwater rechargeCompost filter (above), septic tank, imhoff tank, anaerobic baffled reactor (below), etc.Horizontal (picture), vertical, free surface or a combined hybrid filterWater for irrigation or aquaculture, etc.Source: UN-HABITAT (2008); STAUFFER (2012); MOREL & DIENER (2006); RUUESCH (2011); IPTRID (2008)
6 Example 2: Hybrid CW for a Community 2. How can Constructed Wetlands Optimise SSWMExample 2: Hybrid CW for a CommunityCW’s can also act as a treatment system for a community up to 3400 people (e.g. Bayawan City):Protecting coastal waters from pollutionProtect the health of local residentsReuse of treated waste water for irrigationWastewater is collected in septic tanks and transferred through a small bore sewer system to the hybrid constructed wetland. The treated water can be reused (irrigation), one part is recirculated or it could be disposed (optional).Source: LIPKOW and MUENCH (2010)
7 Example 3: Greywater Treatment in Urban Areas (Norway) 2. How can Constructed Wetlands Optimise SSWMExample 3: Greywater Treatment in Urban Areas (Norway)CW’s can be embedded nicely in urban areas that greywater can be reused for irrigation or recharge groundwater.The latest generation of constructed wetlands for cold climate with integrated aerobic biofilter in Norway.Source: JENSSEN (n.y)
8 Example 3: Greywater Treatment in Urban Areas (Norway) 2. How can Constructed Wetlands Optimise SSWMExample 3: Greywater Treatment in Urban Areas (Norway)Upper right: the wetland in the foreground the biofilter is underneath the playground behind the stonewall. UpperLeft: flowforms.Lower left: the effluent is exposed in a shallow pond and can be discharged in a local stream (lower right).Source: JENSSEN (n.y)
9 2. How can Constructed Wetlands Optimise SSWM Example 4: Stormwater Wetlands (also called Wet Ponds or Retention Ponds)Adapted design for stormwater managementMicrobiological breakdown of pollutantsPlant uptake (nutrients)Retention, settling and adsorptionFlood controlAesthetic design for rural areas (e.g. city parks)Source: METROCOUNCIL (n.y.); COASTAL WATER WATCH (2010)
10 3. Design Principals Horizontal Flow (HF) Large gravel and sand-filled channel, planted with aquatic vegetationWastewater flows horizontally through the channelMainly anaerobic conditionsThe filter material filters out particles and microorganisms degrade organic matterSource: MOREL and DIENER (2006)
11 3. Design Principals Vertical Flow (VF) Gravel and sand filter, aquatic vegetationIntermittent appliance (pump or syphon) of wastewater over the whole filter surface higher O2 injectionWastewater drains vertically through the filter layers towards a drainage system at the bottomSource: MOREL and DIENER (2006)Source: HOFFMANN et al. (2010)
12 Free Water Surface Flow (FWS) 3. Design PrincipalsFree Water Surface Flow (FWS)Flooded and planted channelsImitate the naturally occurring processes of a natural wetland, marsh or swampWater slowly flows through the wetland (on the surface), particles settle, pathogens are destroyed, and organisms and plants utilise the nutrients (TILLEY et al. 2008)Source: TILLEY et al (2008)
13 3. Design Principals Hybrid Flow Combined CWs, sequentially arranged (usually VF and HF)HF provide denitrification, VF nitrificationObviously the advantages of both systems can be combinedPrototype of an integrated blackwater system (hybrid CW): UASB, followed by a vertical and then a horizontal flow wetland).Source: UPC (n.y.)
14 4. Treatment Efficiency Pollution Removal Horizontal CW High reduction in BOD, suspended solids and pathogens. Provides mainly denitrification. (TILLEY et al. 2008)Vertical CWHigh reduction in BOD, suspended solids and pathogens. Provides mainly nitrification.Free-Surface CWHigh removals of suspended solidsModerate removal of pathogens, nutrients and other pollutants such as heavy metals (TILLEY et al. 2008)Hybrid CWIncreased performance due to a combination of different methods (e.g. VF HF)
15 4. Treatment Efficiency Health Aspect A CW system provides an adequate handling of wastewater and minimises health risks caused by pathogens and avoids contamination of the environment by untreated wastewater.High risk of infection if contact with the liquid filter influent or the settled sludge in the pre-treatment facilityLow risk of mosquito breeding (could be a problem of free-surface CW due to open water surface)Settled sludge must be disposed safe and correctlyCorrect handling of treated water if used for irrigation
16 5. Operation and Maintenance CWs constantly require basic maintenance throughout the duration of its life but its relatively simple (no high-tech appliances or chemical additives). (GAUSS 2008)It is important to ensure that primary treatment effectively lowers organics and solids concentrations. (TILLEY et al. 2008)The pre-treatment facility (e.g. septic tank) should be emptied periodically and sludge discharged in a safe way properly (see photo – ABR in Pune, India).Filter material has to be replaced every 8 to 15 years. (TILLEY et al. 2008)Source: SPUHLER (2010)
17 6. ApplicabilitySecondary or tertiary treatment process for black, brown and greywaterAdequate strategy if land is no limiting factor (space and costs)Constructed wetlands are natural systems and do not require electrical energy (unless for pumps) or chemicalsBest suited for warm climates, but can be designed to tolerate freezing periodsCW’s can be combined with many other techniques such as aquaculture, irrigation and several pre-treatment options.
18 7. Pros’ and Cons’ Advantages: Simple O&M due to high process stabilityNo chemicals requiredCan be built and repaired with locally available materialsUtilisation of natural processesEfficient removal of suspended and dissolved organic matter, nutrients and pathogensDisadvantages:Permanent land requiredRequires expert design and supervisionModerate capital cost depending on land, liner, fill, etc.; low operating costsPre-treatment is required to prevent cloggingLow tolerance to durable cold climatesElectricity may be required
19 8. ReferencesCOASTAL WATER WATCH (Editor) (2010): Rain Garden and Ponds. URL: [Accessed: ]GAUSS, M.; WSP (Editor) (2008): Constructed Wetlands: A Promising Wastewater Treatment system for Small Localities. Experiences from Latin America. Washington D.C.: The World Bank. URL: [Accessed: ]HOFFMANN, H.; PLATZER, C.; WINKER, M.; MUENCH, E., v.; GTZ (Editor) (2011): Technology Review of Constructed Wetlands. Subsurface Flow Constructed Wetlands for Greywater and Domestic Wastewater Treatment. Eschborn: Deutsche Gesellschaft für Technische Zusammenarbeit GmbH (GTZ) Sustainable sanitation - ecosan program. URL: [Accessed: ]IPTRID (Editor) (2008): Grid – IPTRID Network Magazine. February Rome: International Programme for Technology and Research in Irrigation and Drainage (IPTRID). URL: [Accessed: ]JENSSEN, P. (n.y.): Decentralized Urban Greywater Treatment at Klosterenga Oslo. In: Ecological Engineering-Bridging between Ecology and Civil Engineering, URL: [Accessed: ].LIPKOW, U.; MUENCH, E. von (2010): Constructed Wetland for a Peri-urban Housing Area Bayawan City, Philippines. Eschborn: Sustainable Sanitation Alliance (SuSanA). URL: [Accessed: ]METROCOUNCIL (n.y.): Constructed Wetlands: Stormwater Wetlands. Saint Paul: Metropolitan Council. URL: [Accessed: ]MOREL, A.; DIENER, S. (2006): Greywater Management in Low and Middle-Income Countries, Review of different treatment systems for households or neighbourhoods. Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). URL: [Accessed: ]TILLEY, E.; LUETHY, C.; MOREL, A.; ZURBRUEGG, C.; SCHERTENLEIB, R. (2008): Compendium of Sanitation Systems and Technologies. Duebendorf and Geneva: Swiss Federal Institute of Aquatic Science and Technology (EAWAG). URL: [Accessed: ]UN-HABITAT (Editor) (2008): Constructed Wetlands Manual. Kathmandu: UN-HABITAT, Water for Asian Cities Program. URL: [Accessed: ]UPC (n.y.): Prototype of an Integrated Blackwater System. Barcelona: Universitat Politecnica de Catalunya.VYMAZAL, J. (2005): Horizontal Sub-Surface Flow and Hybrid Constructed Wetlands Systems for Wastewater Treatment. Durham: Duke University Wetland Center. URL: [Accessed: ]
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