Solar disinfection for household treatment of roof-harvested rainwater

Abstract

The effectiveness of solar disinfection in treating roof-harvested rainwater contaminates wih microorganism was evaluated with a view to its use as a household technology. Coliform and heterotrophic bacteria inactivation kinetics were studied using bottles with differen backing surfaces. The effects of various parameters such as turbidity, solar intensity, typr og organisms (naturally occuring versus laboratory grown) and bottle volume on bacterila inactivation were studied. Complete inactivation of total coliforms was observed in 6 h when solar radiation exceeded ~500W/m2. Under high contamination and overcast conditions, prolonged, expsure was needed. Moderate turbidity (38 NTU) did not reduce the inactivation efficiency, but slightly enhanced it. No regrowth of micoorganisms was observed after 24 h following solar disinfection. No significant difference in the inactivation kinetics was observed for bottle sizes in the range of 0.5 to 2.0L. Tests with naturally occuring and laboratory-grown organisms indicated that laboratory-grown oraganisms were inactivated faster than naturally occuring oragnisms. © IWA Publishing 2008.