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Student term project 2006:
Assessing the Waterharmonica at Everstekoog, Texel, NL

By Reto Stippler, Markus Schwager, Anne Klauser* and Barbara Krummenacher

Students of Environmental Engineering
University of Applied Science Zurich
Dep. Life Sciences und Facility Management

*Contact:

1. The site

Waterharmonica is a constructed wetland system to improve the effluents of a wastewater treatment plant (WWTP) and to enhance the natural values on the Island of Texel, The Netherlands. The crucial requirements for building up such a wetland system are briefly explained in the following. One problem was the effluents of the WWTP, which still contained fine activated sludge particles with a variety of odour-causing bacteria. Another problem was the declining population of the three-spined stickleback (Gastrosteus acculeatus), a small fish that spawns in inland waters. Consequently the number of spoonbills (Platalea leucordia), tall white water birds that feed mainly on sticklebacks, decreased too. The Waterharmonica wetland system tries to mitigate these problems.

The system consists of different partially planted ditches to mimic a nutrient chain, as shown in figure 1. In the presetting basin the sludge particles are used to culture zooplankton, mainly daphnia. Next, the water flows through the shallow ditch, where the reed cleans it, making it suitable for fish. In the deeper zones, submerged aquatic plants are cultivated and sticklebacks are bred and fed with harvested daphnia from the presetting basin. Finally, the discharge ditch is used as a control and can be constructed as foraging area for spoonbills. As a consequence of this constructed wetland treatment, the water can be re-circulated to the natural surface water system.

The Waterharmonica was selected for this case study, as it is a multifunctional system on an island with its peculiar water system and for its remarkable design.

2. Criteria

The criteria proposed by Heeb (1994), as cited in [1] were closely reviewed and then applied to the evaluation of the Waterharmonica. Heeb's criteria are more detailed and more substantial than the criteria devised by other authors, which were also checked by us but were considered to be less adequate.

3. Evaluation

a) Begin-of-pipe thinking (means to tackle a problem at its source)

The Waterharmonica system treats the sewage, but makes no visible effort to reduce the wastewater. Therefore the criterion was regarded as "not fulfilled".

b) Sustainability and multifunctionality

Fulfilled: The resource water is used in a cycle. The wastewater is cleaned and re-used. As a result, the diversity of animals and plants in the wetlands increases. For example, we have seen an increase in the population of spoonbills since the construction of the Waterharmonica.

[Note by the editor: this may be a misunderstanding of the authors. Even though the number of spoonbills has drastically increased in the Netherlands between 1980 and 2002 [2] and 220 pairs are breeding on Texel alone [2], I could find no information on the direct influence of the Waterharmonica on the spoonbill population in the cited references].

c) Ecosystem

Fulfilled. The constructed wetland is a natural ecosystem in itself. There is a natural food chain: sludge flocks eaten by the daphnia (mostly Daphnia magna), which in turn are eaten by the three-spined and nine-spined sticklebacks (Gasterosteus acculeatus and Pungitius pungitius), which serve as the food source for spoonbills (Platalea leucorodia). [2]

d) Aim at self-stability and self integration

Fulfilled. The cleaned wastewater is re-integrated into the water cycle of the island. Because it is built in a natural way out in nature, animals and plants have the possibility to use the constructed wetland as a suitable habitat. The system is actually self-regulated by natural processes at work. Due to the fact that the cleaning mechanisms depend on living organisms, they are highly adaptable to changes in situation.

e) Recycling of energy

Fulfilled. The energy consumption and the resource consumption are kept low as characterized in the description. The system uses solar-based energy resources.

f) Nature orientated

Partially fulfilled. The materials are natural, but the construction is somewhat too linear, and has a distinct man-made appearance. The design of the arrangement at Everstekoog is function- rather than nature-orientated. A good example for more natural design is the constructed wetland of Sint Maartensdijk [2].

g) Low impact on environment

Fulfilled. As it is built in a mainly agricultural landscape, the effects are not too negative for the environment. Although it uses a lot of space, the construction of a wetland increases the diversity of animals and plants in the region.

h) Combination of different knowledge

Fulfilled. A large number of people from different sectors were involved in the construction of this project, e.g., limnologist, ornithologists, wastewater engineer and chemists, to illustrate the diversity of expertise needed.

i) Decentralised structures

Partially fulfilled. As detailed before, a large number of people are engaged in this project. This pioneering project made the tour of the world and found appliance on some other spots on earth. The system is very adaptable, and can be readily modified to fit in any desired location and landscape, but it is bounded to a sewage work.

4. Conclusion

The Waterharmonica seems to be a good ecological engineering project, as most of the used criteria are fulfilled. The two criteria that could be further improved are the nature-orientated style of the constructed wetland and the beginning-of-pipe thinking. One recommendation is to develop a parallel concept to the Waterharmonica that can also achieve a reduction in the production of wastewater of the island. It would be interesting and important to know more details about the energy use, however we did not have enough time to obtain the required information.

5. References

[1] Bohemen van, H.D (2005): Ecological Engineering - bringing between ecology and civil engineering, Aeneas Technical Publishers, Delft, 2005

[2] Kampf, R., Graansma, J., Van Dokkum, H., Foekema, E., Claassen, T. (2003): Increasing the natural values of treated wastewater, the Waterharmonica: the missing link to transfer treated wastewater into a usable surface water. http://www.ecological-engineering.nl/artikelen/Waterharmonica_introduction_Kampf_et_al_04.pdf (9-14-2007)

[3] Utrecht University: Everstekoog demonstration project. http://www.compris.nl/eco/texel.html (9-14-2007)