Worku Legesse, Associate Researcher of the Tree Foundation, co-published the following article. The final version of the article has been published in the Journal of Environmental Health Science and Engineering.

The electronic version of this article can be found on the Journal of Environmental Health Science and Engineering website with the following citation:  Journal of Environmental Health Science and Engineering 2014, 12:25 doi:10.1186/2052-336X-12-25


Disinfection of contaminated water using solar radiation (SODIS) is known to inactivate bacteria. Its inactivation efficiency depends on local conditions where the disinfection is made. This study was aiming to test the efficiency of solar disinfection using different water parameters as low-cost household water treatment technology. Inactivation of microbes was tested using fecal coliform as test organism. The SODIS experiment was carried out at turbidity 2NTU, pH 7, and various water temperature (38.1°C, 41.8°C, 45.6°Cand 51.1°C) and solar intensities, using clear and black plastic bottles filled to different depths. The results show that the rate of microbial inactivation in relation to depth of water, turbidity, container type, intensity of light and color of container was statistically significant (p < 0.05). However, bottle placement, exposure and water pH were unrelated to microbial inactivation. Bacterial re-growth was not observed after solar disinfection. By adjusting the parameters, complete and irreversible fecal coliform inactivation was achieved within an exposure time of less than four hours in the areas where the solar irradiance is about 3.99 kW/m2 and above. Our results indicate that application of SODIS could play a significant role in the provision of safe water in rural communities of developing countries where there is ample sunshine, specifically in sub-Saharan African countries.


Safe water supply; Water disinfection; Household water treatment; Solar radiation


Ethiopia and some other developing countries have large fresh water resources. However, those countries cannot cover the expense of constructing water and wastewater treatment plants, distribution systems and the cost of the treatment processes for all residents. Globally, over 1.1 billion people are at risk of becoming infected with water-related pathogens due to lack of access to safe drinking water [1], a problem that is also widespread in Ethiopia [2].

Conventional water treatment plants in Ethiopia are scarce and the existing plants are vulnerable to frequent interruption and technical malfunction. Expanding treatment plants in rural areas is difficult due to logistics and scarcity of chemicals, energy, and lack of know-how [3]. Commercially produced filters are relatively costly, and filters made of locally available material are generally of limited treatment efficiency in improving microbiological water quality [4].

Several studies indicated that solar disinfection may be an alternative, low- cost, effective and simple method of water purification for use at the household level [5-7]. However, additional studies under different local environmental conditions (solar intensity, temperatures, precipitation), are necessary because the disinfection potential of SODIS varies from place to place. Adequate databases of environmental conditions in a given area of SODIS application may permit the development of models that could be used to test optimum disinfection potential [5]. No database exists on environmental parameters in Ethiopia to carry out SODIS experiments using coliform or other water-related pathogens.

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