The Valais mountain village of Zermatt consumes more than 6000 cubic metres of drinking water a day in the peak holiday period of Christmas and New Year – twice as much as in off-peak periods. Given that this huge demand for water overstretches the village’s existing sources, additional solutions, in the shape of the nearby Gand springs and nanotechnology, had to be found.

Membrane technology lowers calcium and sulphate levels

Water from the Gand Springs, which are near the Findel Glacier, 2280 metres above sea level, is perfectly hygienic, but it contains too much sulphate, giving it an unpleasant taste, and the high calcium content clogs up boilers, washing machines and dishwashers. Nevertheless, thanks to nanotechnology, these springs have been providing clean drinking water since 2006. The Wichje filtration plant uses the principle of reverse osmosis to ensure that the treated water meets current regulations on drinking water quality.
In the process of reverse osmosis, water is passed through a membrane which has pores that are less than 1 nanometre (nm) in diameter and can thus filter out the calcium and sulphate ions. This nanofiltration process also removes all chemical compounds, as well as viruses and bacteria present in the water.

Nanotechnology and the Swiss water industry

Nanotechnology has long been used by the water industry. The most modern, but by no means the only, ultrafiltration facility for water treatment in Switzerland is located in Männedorf (canton of Zurich). Since 2005 it has been supplying the 26,000 inhabitants of three lakeside towns with clean drinking water from the lake. The filter removes all particles and germs, even those as small as 2-60 nm in diameter. 

Membrane technology opportunities for Switzerland

One-fifth of the public drinking water used in Switzerland is extracted from lakes. Compared with conventional purification processes, membrane technology permits low-cost water treatment with fewer chemicals, less energy consumption and smaller space requirements. The water from karst sources, which is also not entirely free from micro-organisms, can be processed into drinking water with the aid of membrane technology.

Membrane technology opportunities for developing countries

The potential for the use of membrane technology is especially high in developing countries, where around 1.5 billion people do not have access to clean water today. In many places, polluted water flows into bodies of water that are used as a drinking water supply downstream. For such cases, Eawag, the Swiss Federal Institute of Technology’s aquatic research institute, is currently developing and testing low-cost membrane filtering processes that are simple to use. A household appliance called “LifeStraw Family” developed by a Swiss company is already available, and contains an integrated ultrafiltration membrane that eliminates all pathogenic germs.

Using nanotechnology to treat water – a broad spectrum of possibilities 

The options for treating water using nanotechnologies are as widely varied as the demands placed on them: everything that is undesirable in drinking water – dirt, bacteria, viruses, organic compounds, pesticides, heavy metals, radionuclides, nitrate, phosphate, calcium, sulphate, etc. – can be removed using certain processes.

Click on the link below to read the article “Nanopores for clean drinking water” in full, which originally appeared in the Federal Office for the Environment Umwelt magazine (March 2010).