Constructed Wetlands (CWs)
Beat Stauffer, international seecon gmbh
Constructed Wetlands
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Depending on the initial situations and respective local circumstances, there is no guarantee that single measures described in the toolbox
will make the local water and sanitation system more sustainable. The main aim of the SSWM Toolbox is to be a reference tool to provide
ideas for improving the local water and sanitation situation in a sustainable manner. Results depend largely on the respective situation
and the implementation and combination of the measures described. An in-depth analysis of respective advantages and disadvantages and
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Constructed Wetlands
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Contents
1. Concept
2. How can Constructed Wetlands optimise SSWM
3. Design Principles
4. Treatment Efficiency
5. Operation and Maintenance
6. Applicability
7. Pros and Cons
8. References
Constructed Wetlands
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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, 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
• Combined flow regimes are so called hybrid constructed wetlands
and exploit the specific advantages of the different systems.
Constructed Wetlands
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2. How can Constructed Wetlands Optimise SSWM
Example 1: Onsite or Semi-centralised Treatment System
Low-flush
toilet,
shower,
kitchen sink,
etc.
Groundwater
recharge
Compost filter (above), septic tank, imhoff tank,
anaerobic baffled reactor (below), etc.
Horizontal (picture), vertical,
free surface or a combined
hybrid filter
Water for irrigation or
aquaculture, etc.
Source: UN-HABITAT (2008); STAUFFER (2012); MOREL & DIENER (2006); RUUESCH (2011); IPTRID (2008)
Constructed Wetlands
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2. How can Constructed Wetlands Optimise SSWM
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
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).
Source: LIPKOW and MUENCH (2010)
Constructed Wetlands
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2. How can Constructed Wetlands Optimise SSWM
Example 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)
Constructed Wetlands
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2. How can Constructed Wetlands Optimise SSWM
Example 3: Greywater Treatment in Urban Areas (Norway)
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).
Source: JENSSEN (n.y)
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2. How can Constructed Wetlands Optimise SSWM
Example 4: Stormwater Wetlands (also called Wet Ponds or
Retention Ponds)
• Adapted design for
stormwater management
• Microbiological
breakdown of pollutants
• Plant uptake (nutrients)
• Retention, settling and
adsorption
• Flood control
• Aesthetic design for rural
areas (e.g. city parks)
Source: METROCOUNCIL (n.y.); COASTAL WATER WATCH (2010)
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3. Design Principals
Horizontal Flow (HF)
• Large gravel and sand-filled channel, planted with aquatic
vegetation
• Wastewater flows horizontally through the channel
• Mainly anaerobic conditions
• The filter material filters out particles and microorganisms degrade
organic matter
Constructed Wetlands
Source: MOREL and DIENER (2006)
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3. Design Principals
Vertical Flow (VF)
• Gravel and sand filter, aquatic vegetation
• Intermittent appliance (pump or syphon) of wastewater over the
whole filter surface  higher O2 injection
• Wastewater drains vertically through the filter layers towards a
drainage system at the bottom
Source: HOFFMANN et al. (2010)
Source: MOREL and DIENER (2006)
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3. Design Principals
Free Water Surface Flow (FWS)
• Flooded and planted channels
• Imitate the naturally occurring processes of a natural wetland,
marsh or swamp
• Water 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)
Constructed Wetlands
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3. Design Principals
Hybrid Flow
• Combined CWs, sequentially arranged (usually VF and HF)
• HF provide denitrification, VF nitrification
• Obviously the advantages of both systems can be combined
Prototype of an integrated blackwater system (hybrid CW): UASB, followed by a vertical and then a
horizontal flow wetland).
Source: UPC (n.y.)
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4. Treatment Efficiency
Pollution Removal
Horizontal CW
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
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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 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
Constructed Wetlands
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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)
Constructed Wetlands
Source: SPUHLER (2010)
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6. Applicability
• 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
• Best suited for warm climates, but can be designed to tolerate
freezing periods
• CW’s can be combined with many other techniques such as
aquaculture, irrigation and several pre-treatment options.
Constructed Wetlands
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7. Pros’ and Cons’
Advantages:
• Simple O&M due to high
process stability
• No chemicals required
• Can be built and repaired with
locally available materials
• Utilisation of natural
processes
• Efficient removal of
suspended and dissolved
organic matter, nutrients and
pathogens
Constructed Wetlands
Disadvantages:
• Permanent land required
• 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
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8. References
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]
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: http://www.eawag.ch/forschung/sandec/publikationen/ewm/dl/Morel_Diener_Greywater_2006.pdf [Accessed: 19.05.2010]
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.
VYMAZAL, J. (2005): Horizontal Sub-Surface Flow and Hybrid Constructed Wetlands Systems for Wastewater Treatment. Durham: Duke University
Wetland Center. URL:
http://www.uvm.edu/~atuttle/john%20todd%20copy/zanzibar/HSF%20and%20hybrid%20CW%20for%20WW%20treatment%20Vymazal.pdf [Accessed:
22.08.2011]
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Constructed Wetlands - Sustainable Sanitation and Water