Clean water that costs nothing more than a discarded PET bottle and sunlight... that's the power, and promise of SODIS.

Harsh Kabra

In the aftermath of the tsunami recently, the biggest fear was the outbreak of epidemics. "Millions of people will be at grave risk of waterborne disease unless there is immediate action to provide clean water," the UNICEF had warned. Water-borne diseases such as cholera, typhoid, Hepatitis A, malaria and dengue lurked round the corner. Providing clean drinking water has always been a major challenge in a country strapped for resources. However, hope holds out in the form of cheap and practical ways to purify available water.

Solar Water Disinfection (SODIS) is one such method that is already in use across 20 countries and even received a special award at the Energy Globe Awards 2004. SODIS involves storing water in clear plastic bottles and keeping them in bright sunlight for at least six hours to get rid of most bacteria and viruses. According to Peter Kaufmann, head of the Swiss Agency for Development and Cooperation, "SODIS is particularly useful in villages where there are no proper water treatment systems."

Developed in 1991 after extensive research by the Swiss Federal Institute for Environmental Science and Technology (EAWAG) and its Department of Water and Sanitation in Developing Countries, SODIS is a simple, low-cost technology with great health potential not just for the over 5 million people hit by the tsunami, but also for a third of the population in developing countries that still has no access to safe drinking water and loses one child every 15 seconds to diarrhoeal dehydration.

SODIS harnesses the ultraviolet rays in sunlight to inactivate pathogens in drinking water. For water above 50 degrees Celsius, the process is three times faster. However, despite proven benefits, the main problem, according to experts, is convincing people about the effectiveness of such a simple method.

During a 1996 pilot project in Thailand, where rainwater harvesting is popular, selected water samples in Ban Phu Lek and Ban Nong Rue Kae reported not only improved taste, but also 86.6 per cent drop in sicknesses. A growing number of households are using the technique.

In another pilot project undertaken across five districts in Sri Lanka, as many as 81 per cent continued using the technique well after the project was over, thanks to the concerted efforts of community development workers. In parts of Kenya beset by diarrhoea and typhoid, rural women seemed aware of the goodness of sunlight, but needed training to tap it. To dispel scepticism about the SODIS technique, bacteriological tests of faecal coliform (FC) were undertaken. The near-zero FC content in SODIS water spoke for itself.

A beginning has been made in India as well by the League for Education and Development (LEAD), a Tiruchirapalli-based women's organisation. In Tamil Nadu, where a large section of the population does not have access to clean drinking water and even the available water sources are highly contaminated, LEAD has been using its network of Sangams (self-help groups of 12-20 women) to promote SODIS for over three years. It has also trained schoolteachers and students to help disseminate the message. A scheme to supply PET-bottles has been synchronised with the micro-credit system. SODIS-bottles are provided to Sangam members as credit that can be repaid in small instalments over several months.

In collaboration with other NGOs, LEAD has focused on the Tiruchi, Erode, Perambalur, Karur and Pudukkottai districts along the Cauvery basin. The field work involves project coordinators, who look after staff training and monitor progress; microbiologists, who monitor water quality; supervisors, who oversee field activities and make improvisations; and animators (all women), who promote the technique using flip-charts, posters, pamphlets and even theatre performances and cultural programmes. All activities are supported by local women volunteers. Apart from providing new PET-bottles, LEAD also collects recycled bottles from various sites such as hotels.

Over two years, 43,833 families and 99 schools were trained in SODIS and hygiene, and over 1.26 lakh PET bottles sold to users. Notably, 40 per cent of the target group has accepted the technique. "One of the difficulties is that people hardly believe in the presence of bacteria when they cannot see them," says N. Radha, Executive Director. Yet, thanks to unrelenting effort, SODIS has markedly brought down instances of cough-and-cold, diarrhoea, and stomach disorders. "Collaborating with government programmes, especially the public health and education systems, will be crucial for the dissemination of SODIS," says Radha.

In Assam's Cachar district, the Silchar-based Assam University (AU) collaborated with two partner organisations and village institutions to link SODIS promotion with community child improvement programmes. Nearly 48.6 per cent became regular users and instances of diarrhoea plummeted by 44-71.7 per cent. And this in an area where even the piped water supply often has faecal contaminants due to old, leaking pipelines.

People aren't convinced easily because SODIS is so simple, says Dr Abhik Gupta of AU's Department of Ecology and Environmental Science. "They tend to believe that efficient technology involves sophisticated machinery, filters or chemicals. In some areas, people thought that PET bottles were something special... It took a lot of effort to convince them to use soft drink or mineral water bottles."

He says that community participation and smaller NGOs were responsible for making SODIS a success in Assam's Barak Valley. "Coupled with rainwater harvesting, SODIS can help people reutilise surface water sources in arsenic and fluoride-prone areas of the State."

Delhi-based Earthcare Foundation studied the effectiveness of SODIS on the water flowing out of the Faridabad sewage treatment plant that had a dangerously high count of E.coli bacteria. "We found that the E.coli count had dipped to zero in nearly 80 per cent of the samples and was well under 15 in the rest," says Savita Gokhale, secretary. "In India, SODIS is quite feasible because there is no dearth of sunlight." She developed interest in the technique because she had seen her grandmother practise it during her childhood. "The method is backed by time-tested wisdom," she maintains.

The next big challenge, however, lies in helping the thirsting masses make the most of a simple, cost-effective technique like SODIS.

Get it right

*The container must be exposed to the sun for six hours if the sky is bright or up to 50 per cent cloudy, and for two consecutive days if the sky is 100 per cent cloudy.

*During continuous rainfall, SODIS does not perform satisfactorily and rainwater harvesting is recommended.

*Transparent plastic is a good transmitter of light in the UV and visible range of the solar spectrum. PET bottles are preferred because they contain less UV-stabilisers than PVC bottles.

*Glass bottles are less effective.

*Old plastic bottles with scratches can reduce UV transmittance. Heavily scratched or old bottles should be replaced.

*Containers with a larger exposed area would be more effective.

*Use water containing good amount of oxygen. Sunlight produces highly reactive forms of oxygen that kill microorganisms. Fill the bottle 3/4th with water, close and shake for about 20 seconds and then fill it completely. This increases the oxygen in the water. Avoid air pockets that can reflect solar radiation.

* The bottles must be placed horizontally on a surface that is fully exposed to the sun, and which reflects sunlight such as corrugated iron sheets.

*SODIS improves the water quality without changing the taste.

(This article was published in the Business Line print edition dated April 15, 2005)
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