Health Stream Literature Summary - Issue 56 - December 2009

Factors supporting the sustained use of solar water disinfection - Experiences from a global promotion and dissemination programme.
Meierhofer, R. and Landolt, G. (2009) Desalination, 248(1-3); 144-151.

This paper reviews knowledge on factors relating to acceptance and sustained use of the SODIS disinfection system at the local level. The SODIS method involves microbiologically contaminated water being filled into transparent PET bottles of up to 3 L volume and exposed to full sunlight for 6 h. Two days of consecutive exposure are required under more than 50% cloudy skies. Preliminary treatment may be necessary if turbidity exceeds 30 NTU (sedimentation, flocculation, filtration) as suspended solids block UV radiation. There is a large body of microbiological research that has assessed and demonstrated the effectiveness of SODIS in destroying diarrhoea-causing bacteria, viruses as well as Giardia spp. and Cryptosporidium spp. Health impact studies of SODIS users have found a reduction in diarrhoea incidence ranging from 16-57%. Health impact assessments in Pakistan, Uzbekistan, Nepal, East Lombok and India have shown that diarrhoea rates in more than 970,000 SODIS users were reduced by about 50%. The mean costs of implementing SODIS in 13 countries, including the costs for bottles and educational material amounted to annually USD 0.75 per trained person. On average SODIS users pay USD 0.40 for the application of SODIS, i.e. to replace damaged bottles. In the SODIS project areas it is estimated that 2.4 million diarrhoea cases could be prevented annually. Assuming that the treatment of one diarrhoea case costs the health sector USD 10 then more than USD 24 million could be saved by the health sector. Also it is estimated that an improved economic labour force through improved health is worth USD 12 million. The cost-benefit ratio for the health sector with total project costs of USD 730,800 amounts to 1:49.

Since 2000, SODIS had been promoted in selected developing countries through information and awareness campaigns, training and advising of the public sector, networking activities and eduction of users at the grassroots level in SODIS application. SODIS is currently used in 33 countries. Project evaluation of SODIS implementation in 18 countries and two socio-scientific assessments has shown that a sustainable spread of the method is dependent on the promotion approach. One year after project implementation, 20-80% of the trained people used SODIS on a regular basis.

Factors influencing the sustained use of SODIS at grassroots level have been studied and based on half-year project evaluations in Nepal, India, Pakistan, Uzbekistan, Indonesia, Kenya, Uganda, Boliva, Nicaragua, Peru, Ecuador, Guatemala, Honduras and El Salvador and on two socio-scientific assessments, numerous factors were identified. One of the factors is the local availability of the required PET or glass bottles. In East Lombok a supply scheme is in place where empty bottles from the PET-bottle producer are bought and sold to users at the health posts.

Motivated promoters play a key role is sustained use and acceptance of SODIS. SODIS practice was highest in villages where locally respected people worked as highly motivated and convincing promoters. Interventions with just one information event were not sufficient to establish a sustainable SODIS practice, rather a long-tem intervention with promoters visiting trained users regularly over several months after initial training was required to raise awareness and establish a sustainable practice. SODIS acceptance was found to be more prominent in areas where SODIS is clearly visible in the community (many bottles on the roofs or in front of the houses) and used by a great number of people, including the community leaders. Education level was found to influence the willingness to change behaviour with initially those more highly educated being more difficult to convince that SODIS could efficiently treat drinking water. Scepticism about the microbiological efficiency of the method was reduced by bacteriological water quality tests with raw and treated water. Some field operations found that once doubts about SODIS efficiency were dispelled, people with a higher education and higher economic status were more likely to adopt SODIS, improve their hygiene behaviour and also sustain it over a longer period. A field study in Bolivia in 2007 revealed that integration of SODIS education into official institutions supported the continued dissemination and promotion of SODIS at grassroots level. When the SODIS messages were integrated into regular programs and local institutions (schools, health centres, local and superior governmental structures), a higher level of institutionalisation, continuation and extension of the SODIS promotion was achieved and a positive effect on the sustained use of SODIS at the household level was found.

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