HFCWs are secondary treatment facilities for household, municipal and industrial wastewater, and they can also be used as a tertiary treatment system for polishing. Pre-treated wastewater flows horizontally through a planted filter bed. Plants provide suitable environments for microbiological attachment, aerobic biofilm growth and transfer of oxygen to the root zone. Organic matter and suspended solids are mainly removed by filtration and degradation.
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
Horizontal Flow Constructed Wetland
The water in constructed wetlands is treated by a combination of biological and physical processes such as adsorption, precipitation, filtration, nitrification, denitrification, decomposition, etc. (HOFFMANN et al. 2011). HFCWs, being water saturated filtering beds, are particularly efficient in suspended solids, carbon and pathogens removal, as well as for denitrification, whereas nitrification is limited (VYMAZAL & KROEPFELOVA 2008).
In horizontal flow systems the wastewater is fed at the inlet zone, usually by gravity, and flows horizontally through the porous filter medium (that is normally small, round, evenly sized gravel of 5−20 mm in Ø, while sand is more prone to clogging and should be avoided), remaining under the surface of the bed and without any contact with the atmosphere, until it reaches the outlet zone. To avoid clogging of the wetland, pre-treatment is necessary to separate solid materials, grease or oils from the liquid.
The basins are waterproofed by a plastic liner to avoid soil contamination and planted with aquatic plants (Phragmites is the most common). The depth of filter beds is normally 60-80 cm. The bottom slope should be 0.5-1% from inlet to outlet to achieve good drainage (MOREL & DIENER 2006) and the filter length no longer than 25-30 m. The hydraulic retention time and the specific surface area depend on the results to achieve, normally 2-5 days and about 2-5 m²/PEare enough for discharge in fresh water (the lowest values are applied in warm climates). The hydraulic loading should be 60-80 mm/d for greywater (RIDDERSTOLPE 2004; MOREL & DIENER 2006), 30-40 mm/d for mixed wastewater. The reduction of BOD is about 80-90 %, TSS is from 80 to 95 %, TN until 60 % and for Faecal Coliform is about 2 to 4 log.
Operation and maintenance
O&M requirements for HFCWs are relatively simple and conducted by unskilled labour (no high-tech appliances or chemical additives), which may allow a community organisation or a private to manage the system. The maintenance includes a periodical sludge and scum control and emptying in primary treatment, plant harvesting, ensuring clogging does not occur in the bed (with time the gravel will become clogged, and may have to be replaced or regenerated every 10-20 or more years), sampling of the discharged water.
HFCWs construction costs are in the range of 40-100 €/m2 depending by the design, the extension, the country, the availability of suitable material in the region and the labour cost. To this cost, the price of pre-treatment installation and pipe connection has to be added. Filling media constitutes the 30-50% of the total investment cost. WSP (2008) reports cost of 1,300 Rs/m2 (30 USD/m2) for horizontal flow beds.In developed country 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
This type of a constructed wetland was developed in the 1950s in Germany by Kaethe Seidel, who designed the HFCWs making use of coarse materials as rooting medium. In the ‘60s, Reinhold Kickuth experimented soil media with high clay content and called the system the “Root Zone Method”. In the early ‘80s, the HFCWs technology was introduced to Denmark and by 1987 nearly 100 soil-based systems were put in operation. During the late ‘80s, the HFCWs were also introduced to other countries, such as Austria and UK and then in the 1990s, this system spread into most European countries and also to North America, Australia, Asia and Africa. In this period, soil or sand was replaced by coarser material (VYMAZAL 2010).
Nowadays several thousands of HFCW systems are in operation, mainly applied to domestic/municipal wastewater as also for industrial effluents with high organic loads (wineries, dairy farms, landfill leachates, oil firms, etc.) and urban or agricultural runoffs. HFCWs are considered in most cases the most appropriate constructed wetland technology for greywater treatment (MASI et al. 2010). When compared to VFCWs, the main advantage appears to be the chance of feeding the system by gravity, with no needs of alternate dosing of the wastewater.
Experiences in India
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. India's first constructed wetland (HF of 2,700 m2) was installed at Sainik School, Bhubaneshwar in the State of Orissa; planted with two types of macrophytes, viz. Typha latifolia and Phragmites karka. At present 180-200 m3 wastewater are being treated by the wetland. BOD and nitrogen removal were 67-90% and 58-63% respectively (JUWARKAR et al. 1995).
An HF demonstration unit was constructed by EPCO at Ekant Park in Bhopal to treat 70 m3/day: a septic tank of 35 m3 was installed before the HF system of 700 m2 filled with gravel and planted with Phragmites karka. The monitoring results (April 2002-Sept 2003) show good removal for COD (77%), TSS (79%), Coliform bacteria (99%) (VIPAT et al. 2008). Another field scale HF case study was realised at the Ujjain Charitable Trust Hospital and Research Centre (Madhya Pradesh): the system, filled with gravel 10-25 mm and planted with Typha latifolia, treats 8 m3/day with a surface of 80 m2 and showed during the monitoring good removal for BOD (75%), TSS (78%), NH4 (68%) (DIWAN et al. 2008), with a hydraulic retention time less than 2 days. In similar climatic conditions, at the Ravindra Nagar Township Ujjain (Madhya Pradesh), another HF system, filled with zeolite 3-9 mm, was monitored from 2006 to 2008 (BILLORE et al. 2008), showing ammonia removal of about 70%.
Few studies on pilot scale were carried on during the last 10-15 year: i.e. in Mahendragiri (Tamil Nadu) for domestic wastewater; and at Mother Dairy, Delhi, for dairy wastewater by CPCB and GTZ. Another interesting pilot study was carried on for a small community of residential areas in Ujjain, Central India, where the functioning of a horizontal flow system of 42 m2 and planted with Phragmites karka was investigated: average treatment performance after five months from this HF system recorded removal efficiencies of 78% for NH4-N, TSS; 58-65% for P, BOD and TKN (BILLORE et al. 1999).
In 2000 in Ujjain, on the abandoned playground of the Education College, an HF system that receives the outfall of sewage from the Ravindra Nagar residential colony was built. The wastewater is pre-treated in sedimentation tank, and then it goes to the HF system, consisting on a rectangular bed with an effective surface area of 300 m2 and hydraulic loading of 40 m3/d. The surface area of gravel bed was planted with Phragmites karka. The removal efficiency of organic nitrogen and of ammonium nitrogen were 86% and 40%, respectively (BILLORE et al. 2006).
The CDD Society is a non-governmental and non-profit organisation located in India, that promotes the use of DEWATS, and has so far implemented more than 350 projects in South Asia, including India (CDD 2013). The adopted treatment is a modular system with a simple design, non-dependent on energy, consisting in 4 treatment phases: a septic tank or UASB, an anaerobic filter or baffled reactor, a planted gravel filter (HF) and in some cases a polishing ponds (free water system). About thirty DEWATS system have been realised in India, most of these near Bangalore and in Karnataka regions, but also in Maharashtra, Kerala and Tamil Nadu. The volume of wastewater treated in these plants ranges from 1.5 to 615 m3/d and the size of the HF CWs range from 1.4 to 14.6 m2/m3 of wastewater, with an average of 5.7 m2/m3. The system allows in most cases a reduction of BOD and COD of 97/99%.
For further information please visit: Horizontal Subsurface 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°  and the Department of Science and Technology of the Government of India DS.O DST/IMRCD/NaWaTech/ 2012/(G).|
Treatment performance of a field-scale horizontal subsurface (SF) constructed wetland (CW) was evaluated for removal efficiency of BOD, TSS, NH4−N, NO3−N, TKN and P from municipal wastewater emanating from a small community of residential areas in Ujjain, Central India. The SF wetland had a rectangular size and covered an effective surface area of 41.82 m2 with a water retention capacity of 18 m3.BILLORE, S.K. ; SINGH, N. ; SHARMA, J.K. ; DASS, P. ; NELSON, R.M. (1999): Horizontal Subsurface Flow Gravel Bed Constructed Wetland with Phragmites Karka in Central India. In: Water Science and Technology : Volume 40 , 163-171. URL [Accessed: 26.03.2015]
Evaluation of Optimization Processes for Management of Nitrogen Removal from Domestic Wastewater in a Horizontal Subsurface Flow Constructed Wetland at Central India
Removal of Ammonium-N from Domestic Wastewater by Using Zeolite Bed Through Constructed Wetland, India
CDD Society aims to address the challenges posed by increasing quantities of wastewater produced in urban and peri-urban areas in South Asia through the provision of Decentralised Basic Needs Services (DBNS).CDD (2013): Consortium for DEWATS Dissemination Society. Bangalore: CDD (Consortium for DEWATS Dissemination) Society URL [Accessed: 14.04.2013]
Horizontal Subsurface Flow Constructed Wetland in a Tropical Climate a Performance from Ujjain, India
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]
The paper highlights the use of constructed wetlands for the removal of BOD, nitrogen, phosphorus and pathogens from primary treated wastewater.JUWARKAR, A.S. ; OKE, B. ; JUWARKAR, A. ; PATNAIK, S.M. (1995): Domestic Wastewater Treatment through Constructed Wetland in India. In: Water Science and Technology: Volume 32 , 291-294. URL [Accessed: 26.03.2015]
Segregated Black/Grey Domestic Wastewater Treatment by Constructed Wetlands in the Mediterranean Basin: The zer0-m Experience
Concerns about water shortage and pollution have received increased attention over the past few years, especially in developing countries with warm climate. In order to help local water management in these countries, the Euro-Mediterranean Regional Programme (MEDA) has financed the Zer0-m project. As a part of this project, several constructed wetland (CW) pilot systems with different pre-treatments have been implemented in four Technological Demonstration Centres in Egypt, Morocco, Tunisia and Turkey. The aim of this research was to establish appropriate designs for treatment of segregated domestic black (BW) and grey water (GW). We tested several different multistage CW configurations, consisting of horizontal and vertical subsurface flow CW for secondary treatment and free water systems as tertiary stage.MASI, F. ; EL HAMOURI, B. ; ABDEL SHAFI, H. ; BABAN, A. ; GHRABI, A. ; REGELSBERGER, M. (2010): Segregated Black/Grey Domestic Wastewater Treatment by Constructed Wetlands in the Mediterranean Basin: The zer0-m Experience. In: Water Science and Technology: Volume 61 , 97-105. 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]
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]
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]
Efficacy of Rootzone Technology for Treatment of Domestic Wastewater: Field Scale Study of a Pilot Project in Bhopal (MP), India
The urban water bodies in tropical developing countries are the worst victim of domestic wastewater / sewage, basically because of the widening gap between the increasing waste water generation and unavailability of commensurating economical resources to address the issue through conventional technologies. Hence, biological machines may prove to be a novel tool for sustainable management of water bodies. Rootzone technology being natural biological systems operating solely on solar energy is low cost and almost negligible operation and maintenance. The paper under reference therefore is an attempt to evaluate the performance efficiency of a field scale Horizontal Subsurface Flow constructed Wetland/Rootzone demonstration unit was constructed by Environmental Planning & Coordination Organisation (EPCO) at Ekant Park, Bhopal as an economically and ecologically viable pilot project.VIPAT, V. SINGH, U. BILLORE, S.K. (2008): Efficacy of Rootzone Technology for Treatment of Domestic Wastewater: Field Scale Study of a Pilot Project in Bhopal (MP), India. In: SENGUPTA, M. ; DALWANI, R. (2007): Proceedings of Taal 2007: 12th World Lake Conference October 28 to November 2 2007, Jaipur, India. Jaipur: 995-1003. URL [Accessed: 26.03.2015]
Constructed wetlands with horizontal sub-surface flow (HF CWs) have been used for wastewater treatment for more than four decades. HF CWs are used around the world for many types of wastewater, including municipal sewage, agricultural and industrial wastewaters, runoff waters, wastewaters containing endocrine-disrupting chemicals, and landfill leachate. This book fills a gap in the literature by providing an extensive, worldwide overview of this treatment technology. Special attention is paid to assessing the use of this treatment technology in individual countries and treatment performance of various HF CWs with respect to major pollutants in different types of wastewater.VYMAZAL, J. KROEPFELOVA, L. ALLOWAY, B.J. ; TREVORS, J.T. (2008): Wastewater Treatment in Constructed Wetlands with Horizontal Sub-Surface Flow. (= Environmental Pollution , 14 ). Dordrecht: Springer Science + Business Media B.V. URL [Accessed: 26.03.2015]
This document explains how constructed wetlands work and there is a collection of different wetlands all over the world.VYMAZAL, J. (2010): Constructed Wetlands for Wastewater Treatment. Prague: Department of Landscape Ecology URL [Accessed: 17.08.2011]
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]
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]