Use of Solar Radiation in Disinfection of Drinking Water for Non-Urban Areas

Introduction. The solar disinfection of water (SODIS) is a simple technique used to destroy pathogenic microorganisms and so to improve microbiological quality of drinking water. SODTS is ideal for treating small quantities of water. In this way, transparent plastic bottles are filled with contaminated water and then are exposed to sunlight for at least one hour.If bottles are made from transparent material, sunlight disinfects water to meet drinking standards through two mechanisms: polychromatic radiation and increased water temperature. If water temperature rises above 50°C, the process is 3 times faster. Material and Methods. Two types of locally available plastic bottles with UV transmittance values of 0.1 and 0.8 percent were selected as possible containers, and used in disinfection process of a surface polluted water according to WHO guidelines about SODIS. Examination of microbiological quality of all water samples has been performed by determination of fecal coliform group (5-tube fermentation technique) according to the procedure outlined in Standard Methods. Results. Results indicate that SODIS is also possible if available plastic bottles with less transparency are used instead of standard bottles. According to our results about 99.9% disinfection of water (up to 3 log reduction in fecal coliforms) is possible in 39.6°C, if about 6 hours solar radiation of water in such bottles would be accomplished. It should be noted that these available bottles are relatively transparent to other portions of the UV light spectrum. Discussion. SODIS which is recommended for use in non-urban areas is often subject to difficulties because PET bottles with high light transparency characteristics are not always available. On the basis of this study, it becomes quite sure that even by using other bottles with less transparency to UV light, SODIS objectives are also attainable, provided that the temperature of water rises to about 40°C. Accordingly, use of these local containers may have enough justification for SODIS process in many non-urban areas of our country in warm seasons.