Solar disinfection of natural waters with modified solar concentrators

Solar water disinfection is a proven method for household purification of drinking water. Compound parabolic collectors (CPCs) have been used to enhance the inactivation rate of microorganisms. In the present study, a modified CPC with a higher concentration ratio of 1.1 was employed to further speed up the process. A large number of tests were conducted with water samples collected from different naturally contaminated water sources of varying characteristics under natural sunlight. Results indicated substantial reduction in exposure time for complete inactivation of indicator organisms, total coliforms and Escherichia coli, in modified CPCs compared with that in PET bottles at different solar intensity conditions. Even with weak solar intensity conditions (average values <400 W/m(2)), complete inactivation of test organisms could be achieved in all the test waters including those with high initial concentrations (total coliforms -1.1 x 10(6) MPN/100 mL and E. coli - 1.25 x 10(5) CFU/mL) within 6 h of exposure when modified CPC was employed. No regrowth of microorganisms was observed in the modified CPC up to 48 h of storage following exposure. The study thus suggests that the use of modified solar concentrators can result in significant reduction in the exposure time required for complete inactivation of naturally occurring microorganisms.