Safe drinking water from the Sun

October 26, 2006

Brussels, 25 October 2006

A simple, low cost technique to provide safe drinking water for people in developing countries is the subject of a new EU-funded project.

The SODISWATER project, which is funded with €1.9 million under the EU's Sixth Framework Programme, aims to demonstrate that the solar disinfection of drinking water is an effective method of preventing water-borne diseases.

According to the World Health Organisation, over 1 billion people around the world have no access to any kind of treated drinking water. Every year 1.6 million people, most of them young children, die of diarrhoeal diseases such as cholera which are attributable to a lack of access to safe drinking water and basic sanitation. Millions more are infected with water-borne parasites. The Millennium Development Goals call for the proportion of people without access to safe drinking water and basic sanitation to be halved by 2015.

Harnessing the power of the Sun to disinfect water is nothing new; the technique was used in India 4,000 years ago. In recent years solar disinfection (SODIS) has undergone something of a revival, as its ease of use and low costs make it ideal for use in poor, developing countries.

The only equipment required for SODIS is a water bottle and a steady supply of sunlight. The technique is simple. First the user removes any solids from the water by settling or filtration. Then the water is placed in a clear bottle and shaken vigorously to aerate the water. Finally the bottle is exposed to full sunlight for around six hours, or longer if there is only partial sunlight.

Under the heat of the Sun, the water soon reaches temperatures in excess of 50-60°C. This, combined with ultraviolet radiation from the Sun, inactivates many viruses, bacteria and parasites in the water within the space of a few hours. In this way, the technique has the potential to reduce the incidence of a range of water-borne diseases, including cholera, dysentery and polio.

SODIS has been approved by the WHO, and has also proved useful in emergency situations, such as the aftermath of the Asian tsunami of December 2004.

The SODISWATER partners hope to demonstrate that the solar disinfection of drinking water is an effective way of preventing water-borne diseases, particularly in developing countries where many people would not otherwise have access to safe drinking water.

They also plan to enhance the technique to make it easier to use, for example by developing indicators which show how much sunlight exposure the water has had. Another strand of work will look at photocatalysis; the use of catalysts (in this case nanoparticles) to speed up the killing of the microbes by the sun. This is important as the WHO has identified the length of time taken to kill the microbes as a potential user objection to the process.

'Our research has shown that the solar disinfection process can be greatly enhanced using photocatalytic materials, with no major additional cost,' explained Dr Tony Byrne of Ulster University, one of the SODISWATER project partners.

The partners will also look at the factors affecting a community's willingness to adopt SODIS and test a range of strategies to improve its uptake in areas with different social and cultural backgrounds.

Finally the consortium will run an education campaign in developing countries, and run workshops with aid agencies to inform them about the system and teach them how to use it.

According to Dr Byrne, what makes the project really exciting is the involvement of partners in Africa, who really know the situation on the ground; of the nine project partners, three are from Africa.

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