This innovative plant, using water in a virtually closed system, is of major importance not only for mountainous areas but also for arid regions all over the world.
Although there is no overall shortage of water in the Swiss Alps, it is a scarce resource in certain locations – for example, at the Hohtaelli cableway station operated by Zermatt Bergbahnen at 10,781 feet above sea level. Supplies cannot be drawn either from a natural spring or from a pressurized pipeline.
All the water required has to be brought up by cable car. As the operation of flush toilets would require around 2000 litres of water per day, this goal had initially appeared unattainable. It was then suggested that wastewater could be purified on site and recycled; local sewage treatment would also protect the sensitive Alpine environment from adverse impacts.
The “dry toilet” facilities in use until 2003 were associated with odour problems and high personnel costs and barely met the standards of comfort expected by visitors. In the autumn of 2003, a plant allowing toilet wastewater to be treated and reused was installed at the cableway station by terraLink, a Zurich-based company. The purification process involves a bioreactor containing a membrane filter with extremely fine micropores (diameter of 0.35 micrometres).
The plant experienced certain teething troubles, as the bioreactor was unable to cope fully with the volume of wastewater arising. Subsequently, the technology and processes were successfully optimized in a joint project carried out by terraLink, the Swiss Federal Institute of Aquatic Science and Technology (Eawag) and Zermatt Bergbahnen: the nutrient elimination rates are currently 100% for nitrogen and 85% for phosphorus. The yellow colour of the treated wastewater – which is unattractive, though unproblematic in terms of hygiene – is removed by controlled addition of powdered activated carbon. The project received financial support from the Federal Office for the Environment’s Technology Promotion programme.
The plant is particularly significant as it addresses a problem that is widespread in mountainous areas; in addition, reuse of treated wastewater is an issue of growing importance in arid regions worldwide. As well as demonstrating that wastewater can be efficiently and economically treated within a virtually closed system, the project provides an excellent example of successful cooperation between practitioners and researchers.
On 6 February, 2007, the inaugural Muelheim Water Award will be presented to terraLink and Eawag in Essen (Germany) in recognition of their innovative local wastewater treatment solution. The award, carrying a prize of EUR 20 000, is sponsored by the German energy company RWE. It is to be granted every two years to projects involving the practical implementation of innovative water supply and sewage disposal solutions.
Contact & Information:
Swiss Federal Institute of
Aquatic Science and Technology
Phone +41 (0)44 823 51 04
Fax +41 (0)44 823 53 75