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Solar disinfection as an appropriate Household Water Treatment and Storage (HWTS) intervention against childhood diarrhoeal disease in developing countries or emergency situations

Final Report Summary - SODISWATER (Solar disinfection as an appropriate household water treatment and storage ... against childhood diarrhoeal disease in developing countries or emergency situations)

Solar disinfection (SODIS) is a simple disinfection technique, during which microbially contaminated water is stored in transparent containers and exposed directly to sunlight for up to eight hours. The technology potentially reduces the incidence of diarrhoea in young children and its efficiency lies on both optical and thermal processes. SODIS can be used in developing countries or in urgent cases, such as after human disasters.

The SODISWATER project aimed to increase the number of communities in developing countries applying this technique through a variety of field and laboratory based studies. Its overall objective consisted of the following components:
1. to demonstrate that SODIS was an appropriate, acceptable and effective precaution against waterborne diseases;
2. to evaluate and test different diffusion and behavioural change strategies in areas with varying social and cultural conditions in order to achieve sustainable adoption of the proposal;
3. to disseminate research outcomes for the method to be widely adopted for use after the immediate aftermath of natural or man-made disasters;
4. to develop appropriate SODIS enhancement technological innovations, matching to varying socioeconomic conditions.

The project was divided in five well-connected work packages, which focussed on:
1. coordination, management and review;
2. health impact assessment;
3. pathogen inactivation acquired during the process;
4. SODIS enhancement technologies;
5. technology adoption and knowledge dissemination.

The necessity for SODISWATER project emerged after the 2004 tsunami, when the technology gaps impeding its large scale application became apparent. Health impact assessments became a priority, since clinical tests were insufficient. In addition, it was urgent to investigate SODIS effects on viral, protozoan and other eukaryotic pathogens. Alternatives which could enhance the overall performance of the process were also examined, such as provision of larger treated volumes, achievement of shorter inactivation times or indications that a sufficient solar dose had been reached. Finally, it was essential to ensure that the developed innovations could reach everyday use, particularly in developing communities.

The limited evidence on the effectiveness of SODIS was broadened via a health impact assessment carried out in the field. However, political unrest, financial problems and a cholera outbreak impacted significantly on data quantity and quality. In essence, given the variety of difficulties faced in the selected three countries and the associated lack of sufficient data, there was no obvious proof that SODIS was not effective in respect of diarrhoea. On the contrary, in the regions in which data quality was better, positive evidence was found for the technology efficiency.

As secondary objectives, the study intended to better understand the role of certain risk factors related to diarrhoea and the degree to which the SODIS method was accepted by the target communities, whose members were involved in the study as much as possible. Finally, toxicity studies resulted in the recommendation that bottles should be replaced every six months, while more sensitive studies on the health effects of photodegradation products were required.

Numerous waterborne microbes were investigated for their susceptibility to SODIS, which proved to be overall competent. Its application in a wider scale required though that the method was continuously assessed and improved to ensure that pathogenic organisms were killed while the process remained easy to use.

Moreover, technologies which could enhance the efficacy of the technique were investigated, both in terms of use and source treatment. Continuous flow systems were developed in order to treat larger volumes of water to address the requirements of small remote communities. It was also attempted to improve batch reactors either by the addition of a photocatalytic agent or with the incorporation of an inexpensive sensor to inform the user that water reached a sufficient dose of solar radiation.

After prototypes' testing an economic analysis was carried out, including monetary and non-monetary benefits, in order to determine the most suitable solutions for deployment in developing countries, while a business assessment was carried out. The alternatives scored poorly in terms of ensuring the sustainability of a venture. It turned out that it was essential to allocate funding and to identify project partners and developing distribution channels prior to large scale application of the innovations.

Dissemination and adoption of the developed technology was examined in a three year longitudinal study, in which interviews took turns with intervention strategies. Different methodologies were employed which could, either combined or alone, improve the penetration of the process in the daily routine of the target populations. Moreover, a conference was organised to allow for the research outcomes dissemination in an appropriate experts' audience.

SODISWATER proved beyond doubt the efficacy of solar radiation for water disinfection. Interesting parameters for further investigation were the combination of SODIS with other point of use household water treatments, the study of different target populations, the investigation of risks resulting from long-term consumption of SODIS treated water and the further refinement of the technology, related to probable risks that may be revealed by more detailed studies.