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Waterborne diseases are still common in developing countries as drinking water sources are contaminated and feasible means to reliably treat these water sources are not available. Many of these developing countries are in the tropical regions of the world where sunlight is plentiful. The objective of this study was to optimize solar disinfection system for household water treatment. An experimental study was carried out from April1 to June7, 2011 at the laboratory of Jimma University. Inactivation of microbes was tested at different variables (turbidity, pH, water depth, dissolved oxygen concentration, water temperature, container type, color of container, solar intensity) using fecal coliform as a test organism. Optimization of solar disinfection (SODIS) system was done by testing the efficiency of SODIS at optimized conditions (at turbidity of 2NTU, pH 7, dissolved oxygen concentration of 6.52mg/L, half-surfaced black colored PET bottle, and water depth of 10 cm ). Fecal coliform enumeration was performed by pour plate method. The results showed that complete fecal coliform inactivation was found on clear water samples having 2 nephlometric turbidity units (NTU) with six hour exposure time. On the contrary, complete inactivation was not found for a water sample having turbidity of 13NTU. Depth of water, container type, intensity of light and color of container have shown statistically significant difference on the rate of microbial inactivation (p<0.05). Whereas, place of bottle exposure and pH of raw water have not shown statistically significant difference on the rate of microbial inactivation (p>0.05). The study demonstrated that complete fecal coliform inactivation can be achieved within an exposure time of less than four hour in the areas which are receiving solar irradiance of 3.99kWh/m2 and above. Transferring this low cost technology could solve safe water problems in Ethiopia
Keywords: Bacteriologically contaminated water, water disinfection, household water treatment, solar radiation
Learning Objectives: 1.To determine the efficiency of solar disinfection under different water depth, exposure time, pH, water temperature, turbidity level, color and type of container and radiation intensity 2. To determine the efficiency of solar disinfection at optimized conditions for water disinfection 3. To evaluate the possibility of bacterial re-growth after solar disinfection