EcoEng Newsletter No. 10, December 2004


Waterharmonica - a new and widely applicable concept for integrated water management

  A report of the Waterharmonica session during the 7th INTECOL Wetlands Conference on July 29th 2004

By Theo Claassen and Ruud Kampf

General questions:
Theo Claassen:
Ruud Kampf:




Some words about Intecol and the Waterharmonica idea
 Fig. 1: The Waterharmonica concepts tries to mitigate the discharge of treated water to surface waters by adding a constructed wetland in between
The Dutch "Waterharmonica" project (2003-2004) was featured as a parallel session at the International Wetlands Conference of INTECOL (the International Association of Ecology,, which took place in Utrecht, the Netherlands, July 25-29, 2004. These INTECOL meetings take place every four years, and are mainly focused on presentations of and discussions about recent knowledge and information on the science and management of wetlands. This 7th conference was organized by Utrecht University

About 900 people (among them scientists, policy makers and field managers) took part, representing around 30 countries worldwide. Main emphasis was put on topics like flood management and nature restoration, biological invasions, river basin management, greenhouse gas emissions, trophic interactions, water level fluctuations in lakes and wetlands, and wetland conservation and management ( ).For a scientific wetland conference, mainly aimed at natural wetlands, the Waterharmonica seems a bit out of the mainstream.

The Waterharmonica aims for integrated water management, bringing the engineering world of the "Water Chain" and the ecological world of the "Water System" together. The Water Chain encompasses the chain of techniques needed to produce drinking water, bring it to people's homes, and discharge it as sewage, together with stormwater management. The Water System is the all-in-one name for lakes, rivers, ditches: indicating that surface water is a manageable system. Though these different parts of the water cycle are not dealt with as a combined system, the Waterharmonica proves that a system approach can be attractive. Above that, cases in the project made clear that constructed wetlands, which in many cases have considerable natural values, play a role in the Waterharmonica. The Waterharmonica project is a Dutch project, originating from a prize-winning idea at the 25th anniversary of the Dutch Foundation of Applied Water Research (STOWA) in 1996.

The special session at the Intecol conference gave us the opportunity to invite several scientists and practitioners to learn more about the Waterharmonica, and especially to receive comments, reactions, and help on how to continue with the Waterharmonica on a national and international level.

The program contained four Dutch presentations and five from abroad. A handout with the summaries of the presentations was available beforehand, see the project site . PDF files of the presentations can also be found on the web site. The speakers from various backgrounds gave an interesting view on the principles and (possible) applications of the Waterharmonica-concept.

Ruud Kampf of the water board Hoogheemraadschap Hollands Noorderkwartier chaired this session, while the opening address was given by Lydia Snuif-Verwey, member of the governing board of the Hoogheemraadschap, who put emphasis on the meaning of the 'accordion' (the Dutch word for harmonica), connecting the two worlds of the Water Chain and the Water System in the practice for Dutch water boards. Each of the presentations is summarized below (more information).

  Introduction to the Waterharmonica,
by Theo Claassen (Wetterskip Fryslân)
  The concept of the Waterharmonica has been developed by the water boards Hoogheemraadschap Hollands Noorderkwartier (Ruud Kampf) and Wetterskip Fryslân (Theo Claassen). The Waterharmonica is a natural, soft, eco-technologically based linkage between emissions (point as well as diffuse sources) and receiving surface waters, or between the Water Chain and the Water System.

The theoretical concept was developed by Theo Claassen (1996), while Ruud Kampf worked out practical applications. The ongoing STOWA project is focused on and limited to effluents of sewage treatment plants (STPs) and the connected surface waters. Even treated wastewater is biologically dead water. Polishing that effluent in a constructed wetland, or even a "constructed surface water", rejuvenates the effluent, makes it a "living" reanimated water, useful for various purposes. Wetland treatment makes it both possible and attractive to use the effluent in agriculture, wildlife conservation, and city parks.

For example, the 'kwekelbaarsjes' project on the Dutch island of Texel does research on the use of the water itself and its nutrients and organic particles in a food chain. Daphnia are grown as food for fish, mainly stickleback, and the fish serves as food for birds ( Sticklebacks are the main food for the spoonbill, one of the rarest bird species in Europe, which has about 95% of the western European breeding population in the Netherlands (more information).

  Description of the STOWA-project "Waterharmonica",
by Ton Schomaker (Royal Haskoning)
Fig. 2: The constructed wetland at Everstekoog, Texel, Netherlands - an example for the Waterharmonica concept
In the Netherlands, several examples of the Waterharmonica have been realized, mainly based on the experiences obtained with the constructed wetland on Everstekoog on the island of Texel.

Six constructed wetlands are operative, and a similar number are in planning. Depending on the effluent sources and the purposes of effluent reuse, different options for lay out, dimensions, and loads are possible.

Basic design options are horizontal flow beds, vertical (infiltration) systems, and/or combined food chain ponds. Removal efficiencies are variable.

The results show a limited reduction of nutrients, depending on the hydraulic retention time. However, good results are found for dissolved oxygen, BOD, and bacteria. The treated effluent shows a diurnal rhythm in oxygen concentrations and becomes alive. Biodiversity increases with algae, zooplankton, macrophytes and even fishes in the constructed wetlands.

  Results from Dutch practice (learning process, policy making, errors),
by Peter de Jong on behalf of Rob van den Boomen (Witteveen + Bos, Deventer)
  The basic principles of Everstekoog at Texel (retention basin, reed zone system, and discharge ditch) are used elsewhere in The Netherlands, as by Land van Cuijk. While general principles of design have not yet been developed, the obtained results do give a good insight into the possibilities for these systems. The main effect is regeneration of the dynamics of dissolved oxygen and subsequent processes. P and N removal is limited (10 to 60 %). In addition to polishing of effluents of STPs, treatment of smaller wastewater flows is possible, like discharges of mushroom farms and poultry farms. Constructed wetland use a large amount of land, so attractive combinations with other types of land use seems to be necessary for further introductions.
  Multiple benefits of the environmental reuse project at the Aiguamolls de l'Empordà Nature Reserve (Costa Brava, Girona, Spain),
by Lluis Sala
 Fig. 3: Depuradora Empuriabrava, Spain - cleaning up effluent from a wastewater treatment plant for discharge into a lagoon
In Spain, the main objectives for a constructed wetland near Empuriabrava are:
  1. To provide sufficient water of high quality to the Cortalet lagoon to avoid its desiccation in summer and/or to flood the wet meadows in the surrounding area
  2. To restore the healthy ecological condition of the area's flora and fauna to achieve biodiversity similar to that of natural ecosystems

Ammonia is an important steering parameter: if the NH4-N content of the effluent of the STP is below 5 mg/l, it's allowed in the constructed wetland. Next, all N is oxidized. Once oxidation has "turned the corner," other processes happen spontaneously, improving the effluent and upgrading the nature reserve.

For more information go to the respective newsgroup.

  Effluent polishing in constructed wetlands in the United States,
by Ruud Kampf on behalf of Bob Gearhart (Environmental Resources Engineering, Engineering Department, Humboldt State University, Arcata, United States)
  In the United States, treated effluent is mainly used for infiltration to recharge groundwater and prevent salt water intrusion. Direct use of the effluent after treatment in constructed wetlands is also possible, as these natural systems make reuse of wastewater more acceptable to the public. After a constructed wetland it is not a waste anymore, but a valuable resource.

One of the famous examples is the Arcata constructed wetland in northern California. A large reconstruction project of the old industrial harbor front created the village and exposed the sea shore. A visitor center gives a lovely view of the wetland, which is at the same time a wildlife sanctuary and a well accepted recreational area.

The long term research projects of the Humbolt State University on processes in the constructed wetland system, including stocking of native fish populations and other fish cultivation (aquaculture) techniques, has proven the values and possibilities of "Waterharmonica systems." (more information on the Arcata wetland)

  Some innovative reuse processes (Greenhouse, Baobabs),
by Andreas Graber (University of Applied Sciences Waedenswil, Switzerland)
  Many different economically sound applications of effluent reuse are possible, like fish stocking and aquaculture of plants. Using solar energy and working fish cascade systems (see e.g., makes these systems even more beneficial. The project in Waedenswil demonstrates that it is possible to combine horticulture and aquaculture in closed nutrient loops. The water from the fishponds is used as fertilizer in tropical fruit and flower growing, while the water is purified enough to be reused in the aquaculture.

Another nice example is the Baobab farm in Mombasa, Kenya [see also EcoEng-Newsletter No. 8, 2003]. A former limestone quarry, devoid of live, is reshaped into a rich and high productive system. Tree needles are converted to humus, and other products are crocodile leather, fish, timber, as well as a well developed food-chain. Flexibility, local management, and economically based applications are important for sustainable successes, but many more applications are needed for demonstration purposes and economic assessments.

  Waterharmonica in the "developing world",
by Adriaan Mels (Lettinga Associates Foundation, Wageningen, The Netherlands)
Fig. 4: Adriaan Mels
Because of less sophisticated STPs in developing countries, the Western applications of constructed wetlands seem not to be useful in most developing countries. Nevertheless, there is a high potential for reuse of wastewater. The Waterharmonica should be an instrument for integrated planning and design of sanitation and reuse (e.g. for irrigation purposes). So, developing countries need an adapted and specific application of eco-engineered wastewater treatment (more information).

Examples in Nicaragua (Matagalpa) and Nepal show, among other things, good results with reed bed systems. The Waterharmonica could be a good alternative for separate sewer systems (as proposed by Ecosan concepts), in situations where a sewerage system is already available, making reuse of nutrients in constructed wetlands possible. This applies especially in densely populated areas where direct use of blackwater wastes is not possible or feasible and where stormwater sewers are needed to discharge rain water to prevent flooding.

  Could the Waterharmonica play a role in the developing world? A review of practical experiences, successful and less successful experiences,
by B. B. Jana (Department of Zoology & International Centre of Ecological Engineering, University of Kalyani, Kalyani)
Fig. 5: B.B. Jana
In India wastewater is often used for fish production: wastewater-fed aquaculture. In these systems, fish production is more important than a good effluent quality. Nutrients in the wastewater represent economic values. The Kalyani Farm produces 7,000-8,000 tonnes of fish per month, which equals a value of €5.6 million. Only fish tolerant to low oxygen levels are appropriate. And in tropical countries like India only ornamental fish or fish for consumption are produced by wastewater; there is no support yet for systems like the 'kwekelbaarsjes'-project at Texel, focused on wildlife conservation. Jana reported no fear of endangering food safety by raising fish for human consumption in effluent.

[for more information on the activities at Kalyani University see also EcoEng-Newsletter Nr. 7, 2003]

  Summary, synthesis, discussion
by Karin Tonderski-Sundblad (University of Linköping, Sweden)
 Fig. 6: Ruud Kampf and Karin Sundblad-Tonderski at Everstekoog
The Waterharmonica means:
  • polishing and reuse of wastewater;
  • integrating Water Chain and Water System;
  • using ecological engineering concepts

There is already worldwide a lot of knowledge about polishing and reuse of wastewater and of effluents of STPs. It's important to use that knowledge. Karin put emphasis on the water polishing wetland as a part or lake restoration in Hässleholm in Sweden as a good example of an integrated approach.

The knowledge is widely available but fragmented and often misunderstood. Therefore the Waterharmonica is about communication:

  • Communicating the need for integrated water management. Wastewater managers should consider the effect of their activities on adjacent ecosystems–including humans;
  • Communicating "integrated knowledge in a useable form".

In the Waterharmonica approach, wetland creation and restoration are possible using wastewater. To promote the Waterharmonica, economic, recreational, and environmental benefits of the Waterharmonica should be spread beyond the wastewater managers, the city managers, the water boards, and the immediate landowners.

In the European Union, as in other developed countries, wastewater has to be managed using a watershed and ecosystem approach. The Waterharmonica is a good tool to obtain wise management of wastewater to promote hygienically safe surface water (for use and reuse) and to promote biodiversity and create recreational values. Another important issue to be worked out is the use of the Waterharmonica within the European Water Frame Work Directive; it seems that the Waterharmonica is also very useful in fulfilling the ecological standards which are to be implemented in the new regulations.

In tropical and developing countries, wise use of water and nutrient resources in wastewater to alleviate poverty and achieve sustainable development is the key factor, while maintaining vital ecosystem functions is also important. As in the western world, wastewater in developing countries has to be managed using a watershed and ecosystem approach, with some major advantages:

  • Low external energy requirement;
  • Easy operation;
  • Low maintenance requirements while maintaining acceptable effluent quality;
  • Safe biomass production (building material, energy source, food production or stocking wild populations);
  • Feasibility (using different systems) for urban, peri-urban, and rural areas.

Karin Sundblad concluded that the main task for the Waterharmonica is to disseminate knowledge about how to use a watershed and ecosystem approach when managing wastewater:

  • Make examples of successful, and less successful cases of such management accessible.
  • Provide technical and practical knowledge about design and management of e.g. constructed wetlands and aquaculture systems.
  • Use the internet site, but also imbed the concept in other forums like the Ecological Engineering Society (, the user groups of IWA, etc. This should lead to a contact network of scientists and practioners to promote the Waterharmonica approach.
  Overall conclusion
  This session fit well at the INTECOL conference. The presentations give a good and complete review of the state of the art of the Waterharmonica project, which has its main focus on linking the Water Chain and the Water System based on ecological-engineering, sustainable principles. This Dutch project has become an anchor for international efforts. The discussions during and after the workshop were fruitful and triggered the progress of this project. We thank the presenters, the participants, and the organizers of the Intecol conference.

© 2004, International Ecological Engineering Society, Wolhusen, Switzerland