Optimization of solar water disinfection technology for efficient pathogen removal :

Abstract

SODIS technology has been used for many years as a Household Water Treatment System (HWTS). However, due to the high density of houses in slums, a slight movement of the sun results in to the houses casting a shadow on to the bottles. This implies that the contact time required for disinfection of the pathogens in the water while using the SODIS technology may not be attained in slums. This study sought to optimize the Solar water technology by reducing the contact time for pathogen disinfection by black wrapping PET bottles using polythene bags of gauge 30 microns. Black wrapping increases thermal inactivation of the pathogens in the water thereby reducing the contact time required for deactivation. This study investigated the effect of black wrapping on the solar disinfection rate of pathogens in drinking water from springs in slums. Results of raw water samples from the study area have showed the need for treatment of water before it is used for drinking as 80% of the springs had their water contaminated with faecal matter. The rate of disinfection in the first run for black wrapped was obtained as 1.833 per hour and 1.363 per hour for the unwrapped bottles and the rate of disinfection in the second run for black wrapped was obtained as 2.657 per hour and 1.689 per hour for the unwrapped bottles 100% disinfection of pathogens was attained by the fifth and fourth hour of exposure for the black wrapped bottles and by the eight and sixth hour for the unwrapped bottles for the first and second run respectively. This shows that the black wrapping makes the disinfection faster and thus this solves the problem of envisaged inadequate contact time for disinfection encountered in slums due to the casting of the shadows from the closely spaced houses.