A SURVEY ON THE APPLICATION OF SOLAR DISINFECTION (SODIS) TECHNOLOGY ON WATER MICROBIAL REDUCTION

Nowadays, application of low cost available methods for minimum treatment of surface waters for drinking in emergency conditions, and in conditions of non-available healthy water was approved by international healthcare organizations. SODIS technology, i.e., the use of solar radiation for disinfection of water, is one of the most important technologies. In this research, the effect of UV-A radiation of solar in disinfection of surface water in Urmia geological conditions was studied. In a cross- sectional study, in June and July of 2013, sampling was done from surface water for 9 days. Then the samples were transferred to laboratory, and the parameters of initial microbial load, turbidity, pH, and water temperature was performed on them. The samples have been exposed to sunlight for 6 hours from 9 to 15 in two types of transparent PET and glass containers. The process was repeated in two 3-hour sessions. The intensity of UV radiation in the UV-A range was measured by UV meter hourly and the average intensity was obtained. By using an statistical analysis, the relationship between reduce of microbial load and contact time, water temperature, turbidity, initial microbial load and pH have been investigated. The results of this study showed a reduction in microbial load of samples after 3 and 6 hours of exposure time which was 1.32 log10 and 0.32 log 10, respectively, when water turbidity is less than 20 NTU. Also by increasing intensity of UV-A radiation, disinfection efficiency was increased and the initial microbial load of water samples didn’t have significant effect on water disinfection. Also results showed that there was a direct relationship between water and environmental temperature with microbial load reduction. SODIS technology can be considered as a method of water disinfection in emergency conditions.