SOLAR WATER DISINFECTION AND POSSIBLE APPLICATION FOR HOUSEHOLD PURPOSES

Abstract

Sunlight possesses a potential germicidal activity, which varies throughout the day and the year, as well as with geographical locations and climatological status. In order to explore this phenomenon an attempt was made to investigate the possibility of using sunlight for water disinfection in the hope to apply this technique in areas where conventional water disinfection processes are not available. Autoclave sterilized raw river water containing a known concentration of E.coli cells was exposed to sunlight, for varying time intervals, in 50, 100, 500 and 1000ml glass bottles. Cells mounted on membrane filters were also exposed to sunlight in the same manner in order to study the direct effect of sunlight on bacterial cells. Results showed that about 4 hours of continuous sunlight exposure were required to reduce survivors to about 0.01% (4 log cycles) in bottles. The volume of exposed samples did not have significant influence on the efficiency of inactivation. However, about one hour was needed to achieve the same level of survivors with cells mounted on filters. Generally, solar inactivation capacity increased with the progression of the day giving a peak efficiency at 12:00-16:00 in winter, 11:00-17:00 in spring and autumn, and 10:00-18:00 in summer.