16 April 2019

Vertical Flow Constructed Wetland (VFCW)

Author/Compiled by
Fabio Masi (IRIDRA S.R.L.)
Riccardo Bresciani (IRIDRA S.R.L.)

Executive Summary

VFCWs are secondary and/or tertiary treatment facilities for household, municipal and industrial wastewater. Pre-treated wastewater is intermittently distributed over the whole surface and flows vertically through the filtering media. The plants’ role is less important than in Horizontal Flow Constructed Wetlands (HFCWs), but it still improves the performances especially in the long term. Organic matter, ammonium and suspended solids are removed by filtration and microbial degradation in mainly aerobic conditions.

Efficient removal of organic matter, nutrients and pathogens.
Low O&M costs and process stability.
No high-tech components or chemical additives.
Utilisation of natural processes and energy.
Permanent space required – high footprint.
Requires expert design and supervision.
Pre-treatment required to prevent clogging (except FRB).
Low denitrification and disinfection performances.

The contents of this factsheet are results of the Indo-European Project NaWaTech- “Natural Water Systems and Treatment Technologies to cope with Water Shortages in Urbanised Areas in India”, co-financed by the EC and the DST – India.

Design and construction principles

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Vertical Flow Constructed Wetlands

The water in CWs is treated by a combination of biological and physical processes such as adsorption, precipitation, filtration, etc. (HOFFMANN et al. 2011). VFCWs are particularly efficient in suspended solids and carbon removal, as well as for nitrification, while denitrification is limited. Pre-treated wastewater is distributed above the entire surface of the bed by a system of pipes, fed by a pump or energy-free siphon devices, with an intermittent short-term loading intervals (4 to 12 doses/day), and long resting periods (2-6 h); the wastewater flows through the porous medium in a vertical path until it reaches the drainage system on the bottom connected to an outlet manhole.

Normally the filling media consists of a sand layer of at least 50 cm, with an additional 15-20 cm of drainage layer with coarse gravel on the bottom, a transitional layer between sand and coarse gravel of 10-15 cm, and 10-20 cm of fine gravel on the top of the bed for ensuring a proper even distribution over the sand layer. The total height is generally around 0.8-1.2 m.To avoid clogging of the wetland, pre-treatment is necessary, except in “French System” vertical flow beds (FRB) that are used for treating raw wastewater without any primary treatment and any production of primary sludge. French systems are composed by two stages for a total of 2-2.5 m²/PE (MOLLE et al. 2005). Here the sludge is accumulated on the top of the 1st stage and the filling material has a different layers and granulometries distribution.

In VFCWs as well as FRB the basins are waterproofed by a plastic liner and planted with suitable plants. In Austria a two-stage VF system that reduces the footprint to 2 m²/PE is developed (LANGERGRABER et al. 2010). The hydraulic loading rate in cold climates should not exceed 100-120 mm/d (DWA 2006). The reduction of BOD5 is about 90-99 %, for TSS is from 90 to 99 %, for TN about 30 % (RIDDERSTOLPE 2004) and for FC is about 1-2 logs (MOREL & DIENER 2006).

Operation and maintenance

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O&M requirements for VFCWs are relatively simple and can be conducted by unskilled labour (there are not high-tech components or chemicals to be added). The maintenance includes a periodical sludge and scum control and emptying in the primary treatment unit (not for FRBs), plant harvesting (usable as biomass for energy production, or as building material for thermal and acoustic insulation), ensuring clogging does not occur in the bed (a VF bed can recover well after a resting period of two-three weeks in sunny and dry season) and sampling of the discharged water. For FRBs, the organic layer which is developing and increasing in thickness on the surface of the first stage has to be removed with a frequency of about 10 years (this organic matter is not similar to a primary sludge, but instead to a composted and dehydrated sludge that can be used as soil conditioner if not polluted by heavy metals or persistent organics).

Cost considerations

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VFCWs realisation costs are in the range of 50-110 €/m2 depending by the design, the country, the availability of suitable material (i.e. filling media and waterproofing liner) in the region and the labour cost. The price of pre-treatment units and pipe connections has to be added to the above mentioned costs. Filling media constitutes 30-50% of the total investment cost. WSP (2008) reports cost of 2,100 Rs/m2 (50 USD/m2) for vertical flow beds.In developed countries the maintenance cost is in the range of 10-15 €/PE, in developing countries this cost is in the range of 2-8 €/PE. The average O&M cost in Nepal is about 0.5-2 USD/m2 (UN-HABITAT 2008).

Experiences in Europe and other cities of the world

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VFCWs are less affected by the low temperatures compared to the other CWs and also require less land, so they are mostly used in the northern European countries (Austria, Denmark, France, Germany, and UK) (KADLEC & WALLACE 2009). Moreover, the vertical flow systems are better suited to manage fluctuations in the hydraulic and the organic load. In Orhei, Moldova, the largest CW in the world for secondary treatment is under realisation: construction began in early 2012, founded by World Bank. The urban wastewater will be pre-treated, and then treated by a “French CW system” formed by four parallel lines, each one composed by two stages in series, the first being a RBF and the second a normal VF bed;at the end the water will have the option of an emergency disinfection treatment, and then it will be discharged to the Raut river.

The plant has been designed for an average flow of 4,600 m3/d estimated for 2020 (in 2010 the measured flow was 2,100 m3/d) and occupies an area of 4 ha (1.8 ha for VFB and 1.7 ha for VF bed). The French System has been used since over 20 years, and approximately 1,000 CWs of this type are in operation in France (MOLLE et al. 2005). Several thousand of conventional VF plants are nowadays in use in Germany (more than 100,000 units, mainly for households), Portugal, Spain (HOFFMANN et al. 2011) and more than 3,000 in Austria (LANGERGRABER & HABERL 2012).

Experiences in India

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Despite CWs have a strong potential for application in developing countries, particularly by small rural communities, due to their low cost and easy maintenance, these systems have not found widespread use in India, due to lack of awareness, and local expertise in developing the technology on a local basis.

BORKAR & MAHATME (2011) studied a VF CW with raw wastewater collected from Amba Nala. The experiment was conducted with a constructed wetland pilot model made of plastic, and consisting in a cylinder with diameter 23 cm and height 45 cm filled from the top with 15 cm of soil media (black cotton soil and sandy soil), 5 cm of sand layer, a geotextile layer and two layers of gravel, 10 cm deep (16 mm Ø) and 15 cm deep (31.5 mm Ø). The experiment compared a system without plants and a system with Typha orientalis: the planted system with a black cotton soil showed the better results in terms of BOD and COD reduction (respectively 59 % and 53 % for unplanted CW and 86% and 63% for the planted one).

A pilot scale CW unit was realised in the at Anna University, Chennai, to study the capacity of a VF bed to remove heavy metal (nickel); the cells were filled with gravel and sand and planted with Arundo donax, showing removal of 70-75% of nickel from an initial concentration of 7-8 mg/l (SIVARAMAN et al. 2011).

In Nepal, thanks to the efforts of various NGOs and UN cooperation services, several CWs were realised for various type of wastewater (as reported in UN-HABITAT 2008). Examples of VF CWs reported are:

  • Combined laboratory and domestic wastewater treatment (ENPHO), a little VF bed of 15 m2 for 7 PE running since 2002;
  • Grey water treatment (Private residence), a little 6 m2 VF bed for 8 PE planted with Phragmites Karka and Canna latifolia that permits the reuse for gardening.

For more information please visit: Vertical Flow CW


The research leading to these results has received funding from the European Union Seventh Framework Programme ([FP7/2007-2013]) under Grant Agreement N° [308336] and the Department of Science and Technology of the Government of India  DS.O DST/IMRCD/NaWaTech/ 2012/(G).

Library References

Wastewater Treatment with Vertical Flow Constructed Wetland

Water is one of the most important elements involved in the creation and development of healthy life. Haphazard disposal of untreated wastewater from households as well as institutions and industry is causing severe deterioration of water bodies in many urban areas in the developing world. There are several methods to treat the municipal wastewater for intended use. One of the methods of the treatment is constructed wetland. Constructed wetland system for wastewater treatment has been proven to be effective and sustainable alternative for conventional wastewater treatment technologies. In the present study performance of the fabricated model on which the local Amba Nala effluent characteristics like pH, DO, TS, BOD, COD with and without plant species were studied.

BORKAR, R.P. ; MAHATME, P.S. (2011): Wastewater Treatment with Vertical Flow Constructed Wetland. In: International Journal of Environmental Sciences: Volume 2 , 590-603. URL [Accessed: 04.05.2013]

Arbeitsblatt DWA-A 262: Grundsaetze fuer Bemessung, Bau und Betrieb in Pflanzenklaeranlagen mit bepflanzten Bodenfiltern zur biologischen Reinigung kommunalen Abwassers

Im Jahr 1998 hat die ATV-DVWK erstmalig Bemessungsvorgaben für bepflanzte Bodenfilter in Form eines Arbeitsblattes veröffentlicht. Die seither gesammelten Praxiserfahrungen haben gezeigt, dass der Vorbehandlung ein größerer Stellenwert einzuräumen ist und die Flächenbemessung nach den bisherigen Vorgaben unzureichend war. In der vorliegenden Neufassung des Arbeitsblattes DWA-A 262 finden die aktuellen Erkenntnisse Berücksichtigung.

DWA (2006): Arbeitsblatt DWA-A 262: Grundsaetze fuer Bemessung, Bau und Betrieb in Pflanzenklaeranlagen mit bepflanzten Bodenfiltern zur biologischen Reinigung kommunalen Abwassers. Hennef: Deutsche Vereinigung fuer Wasserwirtschaft, Abwasser und Abfall e.V. (DWA)

Language: German

Technology Review of Constructed Wetlands

This publication intends to help spread awareness and knowledge about the technology of subsurface flow constructed wetlands in developing countries. Constructed wetlands (CWs) can be used as part of decentralised wastewater treatment systems, due to their “robust”, “low-tech” nature with none or few moving parts (pumps) and relatively low operational requirements. CWs can be used for the treatment of domestic and municipal wastewater or greywater, and play an important role in many ecological sanitation (ecosan) concepts.

HOFFMANN, H. PLATZER, C. WINKER, M. MUENCH, E. von GIZ (2011): Technology Review of Constructed Wetlands. Subsurface Flow Constructed Wetlands for Greywater and Domestic Wastewater Treatment. Eschborn: Deutsche Gesellschaft fuer Internationale Zusammenarbeit (GIZ) GmbH URL [Accessed: 01.06.2019]

Constructed Wetland Technology in Austria

This paper tries to give an historical overview on the development of the use of CWs in Austria, describes the current practices and new developments are discussed.

LANGERGRABER, G. ; HABERL, R. (2012): Constructed Wetland Technology in Austria. History, Current Practices and New Developments. In: Sciences Eaux & Territoires: Volume 9 , 32-34. URL [Accessed: 26.03.2015]

Comparison of Single-Stage and a Two-Stage Vertical Flow Constructed Wetland Systems for Different Load Scenarios

Constructed wetlands (CWs) are known to be robust wastewater treatment systems and are therefore very suitable for small villages and single households. When nitrification is required, vertical flow (VF) CWs are widely used. This contribution compares the behaviour and treatment efficiencies of a single-stage VF CW and a two-stage VF CW system under varying operating and loading conditions according to standardized testing procedures for small wastewater treatment plants as described in the European standard EN 12566-3.

LANGERGRABER, G. ; PRESSL, A. ; LEROCH, K. ; ROHRHOFER, R. ; HABERL, R. (2010): Comparison of Single-Stage and a Two-Stage Vertical Flow Constructed Wetland Systems for Different Load Scenarios. In: Water Science and Technology: Volume 61 , 1341-1348. URL [Accessed: 26.03.2015]

How to Treat Raw Sewage with Constructed Wetlands: An Overview of the French Systems

The development of vertical flow constructed wetlands treating raw wastewater in France has proved to be very successful over the last 20 years. In view of this a survey was carried out on more than 80 plants in order to study their performance and correct the design if necessary. This study shows that such systems perform well in terms of respecting the goals of both low level outlet COD and SS and nitrification.

MOLLE, P. ; LIENHARD, A. ; BOUTIN, C. ; MERLIN, G. ; IWEMA, A. (2005): How to Treat Raw Sewage with Constructed Wetlands: An Overview of the French Systems. In: Water Science and Technology: Volume 51 , 11-21. URL [Accessed: 26.03.2015]

Greywater Management in Low and Middle-Income Countries, Review of Different Treatment Systems for Households or Neighbourhoods

This report compiles international experience in greywater management on household and neighbourhood level in low and middle-income countries. The documented systems, which vary significantly in terms of complexity, performance and costs, range from simple systems for single-house applications (e.g. local infiltration or garden irrigation) to rather complex treatment trains for neighbourhoods (e.g. series of vertical and horizontal-flow planted soil filters).

MOREL, A. DIENER, S. (2006): Greywater Management in Low and Middle-Income Countries, Review of Different Treatment Systems for Households or Neighbourhoods. (= SANDEC Report No. 14/06 ). Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC) URL [Accessed: 27.05.2019]

Introduction to Greywater Management

The report gives a comprehensive description of the main components in successful greywater management. Examples as well as recommendations are given for designing and dimensioning treatment systems.

RIDDERSTOLPE, P. (2004): Introduction to Greywater Management. (= EcoSanRes Publication Series, Report 2004-4 ). Stockholm: Stockholm Environment Institute, EcoSanRes Programme URL [Accessed: 19.05.2010]

Feasibility Studies for Reuse of Constructed Wetlands Treating Simulated Nickel Containing Groundwater

Constructed wetlands are considered as low cost treatment option for domestic and industrial wastewater in the recent decades. The presence of toxic heavy metals in wastewater is a problematic issue, since these heavy metals have potential to accumulate in the treatment systems. Thus heavy metals greatly influence the efficiency of constructed wetlands. Therefore a feasibility study was proposed for long term usage of constructed wetlands as treatment systems.

SIVARAMAN, C. ; ARULAZHAGAN, P. ; WALTHER, D. ; VASUDEVAN, N. (2011): Feasibility Studies for Reuse of Constructed Wetlands Treating Simulated Nickel Containing Groundwater. In: Universal Journal of Environmental Research and Technology: Volume 1 , 293-300. URL [Accessed: 04.05.2013]

Constructed Wetlands Manual

This manual has been prepared as a general guide to the design, construction, operation and maintenance of constructed wetlands for the treatment of domestic wastewater as well as introduction to the design of constructed wetland for sludge drying.

UN-HABITAT (2008): Constructed Wetlands Manual. Kathmandu: UN-HABITAT, Water for Asian Cities Program URL [Accessed: 15.02.2012]

Technology Options for Urban Sanitation in India. A Guide to Decision-Making

These guidance notes are designed to provide state governments and urban local bodies with additional information on available technologies on sanitation. The notes also aid in making an informed choice and explain the suitability of approaches.

WSP (2008): Technology Options for Urban Sanitation in India. A Guide to Decision-Making. pdf presentation. New Delhi: Water and Sanitation Program (WSP) URL [Accessed: 03.06.2019]
Further Readings

Constructed Wetlands: A Promising Wastewater Treatment system for Small Localities. Experiences from Latin America

This report provides an overview of how constructed wetlands serve as natural wastewater treatment systems. It focuses especially on the subsurface horizontal flow type—a technology that has high potential for small and medium-size communities because of its simplicity, performance reliability, and low operation and maintenance requirements. The ability of this wetland to reduce pathogens renders the effluent suitable for irrigation of certain crop species if additional health and environmental protection measures are taken. This report describes several experiences with constructed wetland schemes in Central and South America: a full-scale pilot plant in Nicaragua, a community-managed constructed wetland scheme in El Salvador, and other systems in Colombia, Brazil, and Peru.

GAUSS, M. WSP (2008): Constructed Wetlands: A Promising Wastewater Treatment system for Small Localities. Experiences from Latin America. Washington D.C.: The World Bank URL [Accessed: 12.12.2011]

Compendium of Natural Water Systems and Treatment Technologies to cope with Water Shortages in Urbanised Areas in India

The Compendium of NaWaTech Technologies presents appropriate water and wastewater technologies that could enable the sustainable water management in Indian cities. It is intended as a reference for water professionals in charge of planning, designing and implementing sustainable water systems in the Indian urban scenario, based on a decentralised approach.

BARRETO DILLON, L. ; DOYLE, L. ; LANGERGRABER, G. ; SATISH, S. ; POPHALI, G. (2013): Compendium of Natural Water Systems and Treatment Technologies to cope with Water Shortages in Urbanised Areas in India. Berlin: EPUBLI GMBH URL [Accessed: 11.12.2015]

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