Slide 1Constructed Wetlands
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Contents
Concept
Design Principles
Treatment Efficiency
Introduction
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, aquaculture
Types of constructed wetlands. They are classified according to the water flow regime as:
Horizontal flow constructed wetlands
Vertical flow constructed wetlands
Free surface constructed wetlands
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Source: UN-HABITAT (2008); STAUFFER (2012); MOREL & DIENER (2006); RUUESCH (2011); IPTRID (2008)
Low-flush toilet, shower, kitchen sink, etc.
Horizontal (picture), vertical, free surface or a combined hybrid filter
Water for irrigation or aquaculture, etc.
Groundwater recharge
Compost filter (above), septic tank, imhoff tank, anaerobic baffled reactor (below), etc.
Constructed Wetlands
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Example 2: Hybrid CW for a Community
CW’s can also act as a treatment system for a community up to 3400 people (e.g. Bayawan City):
Protecting coastal waters from pollution
Protect the health of local residents
Reuse of treated waste water for irrigation
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Source: LIPKOW and MUENCH (2010) 
Wastewater 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).
Constructed Wetlands
Example 3: Greywater Treatment in Urban Areas (Norway)
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Source: JENSSEN (n.y)  
The latest generation of constructed wetlands for cold climate with integrated aerobic biofilter in Norway.
Constructed Wetlands
Example 3: Greywater Treatment in Urban Areas (Norway)
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Source: JENSSEN (n.y)  
Upper right: the wetland in the foreground the biofilter is underneath the playground behind the stonewall. Upper
Left: flowforms.
Lower left: the effluent is exposed in a shallow pond and can be discharged in a local stream (lower right).
Constructed Wetlands
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Example 4: Stormwater Wetlands (also called Wet Ponds or Retention Ponds)
Adapted design for stormwater management
Microbiological breakdown of pollutants
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Constructed Wetlands
Horizontal Flow (HF)
Wastewater flows horizontally through the channel
Mainly anaerobic conditions
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Constructed Wetlands
Vertical Flow (VF)
Gravel and sand filter, aquatic vegetation
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Constructed Wetlands
Free Water Surface Flow (FWS)
Flooded and planted channels
Imitate the naturally occurring processes of a natural wetland, marsh or swamp
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Constructed Wetlands
Hybrid Flow
HF provide denitrification, VF nitrification
Obviously the advantages of both systems can be combined
Source: UPC (n.y.)
Prototype of an integrated blackwater system (hybrid CW): UASB, followed by a vertical and then a horizontal flow wetland).
Constructed Wetlands
Pollution Removal
High reduction in BOD, suspended solids and pathogens. Provides mainly denitrification. (TILLEY et al. 2008)
Vertical CW
High reduction in BOD, suspended solids and pathogens. Provides mainly nitrification.
Free-Surface CW
High removals of suspended solids Moderate removal of pathogens, nutrients and other pollutants such as heavy metals (TILLEY et al. 2008)
Hybrid CW
Increased performance due to a combination of different methods (e.g. VF HF)
Constructed Wetlands
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 facility
Low risk of mosquito breeding (could be a problem of free-surface CW due to open water surface)
Settled sludge must be disposed safe and correctly
Correct handling of treated water if used for irrigation
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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).
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Secondary or tertiary treatment process for black, brown and greywater
Adequate 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 chemicals
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No chemicals required
Utilisation of natural processes
Efficient removal of suspended and dissolved organic matter, nutrients and pathogens
Disadvantages:
Requires expert design and supervision
Moderate capital cost depending on land, liner, fill, etc.; low operating costs
Pre-treatment is required to prevent clogging
Low tolerance to durable cold climates
Electricity may be required
7. Pros’ and Cons’
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COASTAL WATER WATCH (Editor) (2010): Rain Garden and Ponds. URL: http://www.coastalwaterwatch.com/product2121.htm [Accessed: 21.02.2012]
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: http://www.wsp.org/wsp/sites/wsp.org/files/publications/ConstructedWetlands.pdf [Accessed: 12.12.2011]
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: http://www.gtz.de/en/dokumente/giz2011-en-technology-review-constructed-wetlands.pdf [Accessed: 14.11.2011]
IPTRID (Editor) (2008): Grid – IPTRID Network Magazine. February 2008. Rome: International Programme for Technology and Research in Irrigation and Drainage (IPTRID). URL: http://www.fao.org/landandwater/iptrid/docs/GRID28eng.pdf [Accessed: 27.06.2011]
JENSSEN, P. (n.y.): Decentralized Urban Greywater Treatment at Klosterenga Oslo. In: Ecological Engineering-Bridging between Ecology and Civil Engineering, 84-86. URL: http://www.umb.no/statisk/ecosan/publications/Klosterenga.pdf [Accessed: 21.02.2012].
LIPKOW, U.; MUENCH, E. von (2010): Constructed Wetland for a Peri-urban Housing Area Bayawan City, Philippines. Eschborn: Sustainable Sanitation Alliance (SuSanA). URL: http://www.susana.org/docs_ccbk/susana_download/2-51-en-susana-cs-philippines-bayawan-constr-wetlands-2009.pdf [Accessed: 10.01.2011]
METROCOUNCIL (n.y.): Constructed Wetlands: Stormwater Wetlands. Saint Paul: Metropolitan Council. URL: http://www.metrocouncil.org/environment/water/bmp/CH3_STConstWLSwWetland.pdf [Accessed: 21.02.2012]
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: http://www.eawag.ch/forschung/sandec/publikationen/index [Accessed: 15.02.2010]
UN-HABITAT (Editor) (2008): Constructed Wetlands Manual. Kathmandu: UN-HABITAT, Water for Asian Cities Program. URL: http://www.un.org.np/sites/default/files/CWManual.pdf [Accessed: 15.02.2012]
UPC (n.y.): Prototype of an Integrated Blackwater System. Barcelona: Universitat Politecnica de Catalunya.
Constructed Wetlands
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