Beaches along natural open waters provide a healthy bathing pleasure in a natural environment. Imagine having a miniature lake in your own garden? Natural swimming pools or swim ponds in short are becoming increasingly popular both in the public and the private sector. The water of the swimming pools is treated in a filtration device just like in conventional swimming pools. This treatment is done without adding chemicals (chlorine or ozone) but in a completely natural way. Different types of systems are available on the market, all of them assuring a bathing pleasure in clean water without any risk for health hazards
Starting 1980 in Austria, swim ponds became "en vogue" in the last two decades. At present, more than 30'000 private sim ponds are in use in Austria. In Germany as much as 70 communities provide public swim ponds, some of them ready to accept several thousand visitors a day. The situation in Switzerland is lagging behind this trend, with about 80 swim ponds per year constructed for private owners. At present, only few are open to the public: in 1999 the community of Biberstein was the first to convert its conventional bath to the public swim pond Biberstein near Aarau. In July 2005, Migros, the largest Swiss food company opened a Naturpool in the Milandia Greifensee near Zurich. Will this trend continue?
Do you like to read more about natural swim ponds? The Swiss Association for Swim Ponds and constructed Wetlands (SVBP) provides a large list of adresses from companies which gladly answer your questions in an personal meeting: www.svbp.org. In September 2005, the 3rd international congress on swim ponds will be held in Interlaken, Switzerland: www.schwimmteich-kongress.ch (in german and french).
The Institute for Ecological Engineering at the Department for Natural Resource Sciences has ten years of experience in developing systems to reuse nutrients contained in industrial and agricultural waste waters for fish and crop plant production. Swim ponds are very similar systems in respect to nutrient cycles, decomposition processes, water recirculation, water analysis and system design. Since 2004 there is a close collaboration between the Institute and the SVBP to improve the systems by developing new components for the pond equipment. These innovations will allow the design of more attractive pond systems.
In a current R&D-Project together with the SVBP, eleven Swiss swim pond construction companies and financed by the Swiss government, our institute is developing a biological method to remove posphorous from the pond water and thus prevent the growth of filamentous algae in the swimming zone. Thereby the requirements of water quality can be fulfilled even better. This innovation should allow to increase the percentage of the swimming area by at least 10 per cent, reduce construction costs by 20 per cent and running costs by 40 to 50 per cent. A second goal of the project is to strengthen the market position of swim pond constructers in Switzerland.
Object of research is an algal turf scrubber, a system invented and patented in the USA for nutrient removal from wastewaters. The filter removes phosphorous from natural swimming ponds and thus reduces or eliminates algae growth in the swimming zone. Additionally, the filter takes advantage of sunlight to remove bacterial contamination and improves microbial quality of the target water. By selecting water circulation during daytime, night time or permanently, the water temperature of the target water can be increased or decreased as desired.
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left: First pilot plant in practice: five algal turf scrubbers situated on a garage roof eliminate phosphorous from the swimming pond.
middle: Algal turf scrubber after cleaning.
right: Algal turf scrubber 5 weeks after cleaning.
right border: algae harvest from 5x 1 m2 algal turf scrubbers after 2 weeks.
Contrary to conventional fixed bed filters the algal turf scrubber enables a biological water treatment without damaging the zooplancton community in the pond. The system is intended to be used as a supplementary phosphorous elimination device in cases where ponds are too heavily charged with nutrient input or with an unsatisfying microbial situation.
The project goals are set at a high level: by using algal turf scrubbers, the area of the swimming zone should be increased regarding the area of the whole system, thus construction and running costs could be reduced. A device for online-monitoring of the water quality has been set up and tested successfully. In a second step, water pumps shall be improved and tested in order not to damage zooplancton.
There is also the possibilty for students to tackle specific topics in their term or diploma thesis and in case studies. The topics include water plants, filter substrates (purification efficiency, nutrient elimination capacity, design) as well as participation in the research project.
Together with the SVBP the University of Applied Sciences Waedenswil provides an education program for swim pond constructors. The course is scheduled to start in January 2006 and comprises 35 days of teaching, practice and field trips, spread over two winter semesters. The target audience are professionels working in swim pond construction. More Information and application or contact the course administration.
The Competence Center for natural Swim Ponds offers water analysis, calculation of nutrient balances and expertises for private ponds:
For more Informationen please visit the Project website KTI Swim Ponds (in German only).
Andreas Graber
Hochschule Waedenswil
Gruental 40
CH-8820 Waedenswil
Tel. +41 44 789 99 28
Fax +41 44 789 99 40
a.graber@hsw.ch
www.cascadesystems.ch