Membrane technology as a key water treatment process
Dübendorf, 17.11.2009 - Membrane technology is playing an increasingly important role in drinking water treatment. The latest developments in this area were discussed by experts from Switzerland and abroad at a conference held in Zurich on 16 November 2009, jointly organized by the Swiss Gas and Water Industry Association (SVGW) and the Swiss Federal Institute of Aquatic Science and Technology (Eawag).
In Switzerland, more than a third of all raw water is of such good quality that it can be supplied as drinking water without treatment of any kind. However, where water fails to meet the stringent requirements of food legislation, it first has to be treated. This applies in particular to around 40 lake water facilities across Switzerland – unlike groundwater, which is purified as it percolates, water sourced from lakes does not undergo any natural cleansing process. For this reason, a wide variety of treatment processes are currently used, such as sand filtration, activated carbon filtration or ozonation.
Eliminating viruses
At the international SVGW-Eawag conference in Dübendorf, experts noted that membrane technology has become established as a new process over the past ten years. Attention has been focused on ultrafiltration in particular: in this process, raw water is forced under pressure through a membrane with a pore size of around 0.01 micrometres (µm; 1 µm = a thousandth of a millimetre). For comparison, the average diameter of a human hair is approx. 70 µm.Thanks to ultrafiltration, minute particles such as suspended matter, bacteria, parasites and even viruses are effectively eliminated. This means that, with this technology, water is not only mechanically purified but also disinfected. The use of chemical additives such as chlorine or ozone can thus be reduced or dispensed with entirely.
Advantages in karstic regions
In the Swiss pre-Alps, in the Jura and in the mountainous cantons of Graubünden and Valais, many utilities obtain raw water from karstic springs. Here, water infiltrates very rapidly and – especially after heavy precipitation – is inadequately filtered as it passes through the ground. Water suppliers are therefore often confronted with the problem of highly variable raw water quality.Ultrafiltration is ideally suited for use in karstic regions: unlike other treatment methods, this process remains fully functional in all weathers, thereby significantly enhancing the provision of safe drinking water supplies.New risks associated with climate change
Water supplies in Switzerland are also likely to be affected by climate change – e.g. as a result of more extreme fluctuations in water levels. For this reason, connections between water utilities have been expanded in recent years, so as to ensure the security of supplies even during prolonged dry periods. But the climate also has an impact on water quality: as flooding becomes more frequent, groundwater wells near rivers are increasingly infiltrated by river water. At karstic springs, more intense precipitation leads to extremely high discharges. In addition, as the temperature of raw water rises, the risk of microbial contamination is increased.Scientists and water facilities have recognized and responded to these emerging risks. In joint projects, the application of membrane technology is being optimized, e.g. with regard to operational safety or energy consumption. This process – especially combined with conventional treatment steps – can ensure effective, safe and low-cost treatment of raw water, so that adequate supplies of clean drinking water are available for the public, commerce and industry despite the effects of climate change. Membrane technology will thus play a key role in this sector.Professor Markus Boller
The SVGW-Eawag conference was also a farewell event for Professor Markus Boller, who is retiring. Originally a rural engineer, Markus Boller trained as a sanitary engineer and joined Eawag in 1973. As well as pursuing his research at this institution for several decades, he taught at the ETH Zurich from 1990 onwards. With a particular interest in contact filtration, he became the leading European expert in this area. In recent years, his research focused on urban rainwater runoff and drinking water supplies. At an early stage, he recognized the opportunities presented by membrane technology both for drinking water treatment and for wastewater management. However, he always emphasized the importance of “at source” measures for preventing releases of pollutants into water resources. To this end, he promoted cooperation among scientists, manufacturers, professional associations and authorities. The research groups led by Markus Boller have certainly made a significant contribution to the success and the reputation of Switzerland’s urban water management sector.
Address for enquiries
Contact SVGW:
Urs Kamm, Vice Director, Head of Water Division, Tel. +41 (0)44 288 33 33
Contact Eawag:
Dr Wouter Pronk, Process Engineering Department, Tel. +41 (0)44 823 53 81
Publisher
Eawag: Swiss Federal Institute of Aquatic Science and Technology
http://www.eawag.ch
