Solar photocatalytic disinfection of well water using immobilized TiO$_2$: A comparative field study with SODIS in Antananarivo

Abstract

Access to safe drinking water remains a major challenge in rural areas of developing countries. This study investigates the feasibility of a simple, low-cost solar photocatalytic reactor coated with commercial titanium dioxide (TiO$_2$) for the disinfection of well water contaminated with fecal coliforms. A TiO$_2$ film was deposited on a glass plate using a straightforward acetone slurry method and exposed to natural sunlight in Antananarivo, Madagascar. The efficiency was compared to the conventional SODIS method (solar disinfection without catalyst). Water samples from ten different wells were characterized for physicochemical parameters and bacteriological quality. After only 10 minutes of solar exposure, the photocatalytic reactor achieved complete inactivation (0 CFU/100 mL) of fecal coliforms for all ten samples tested, whereas the SODIS control only reduced the initial count by approximately $51\%$ in a representative sample. While disinfection kinetics varied slightly with water turbidity and pH, complete inactivation was consistently achieved. The results demonstrate that even a non-uniform, low-purity TiO$_2$ coating significantly accelerates bacterial disinfection under solar radiation, offering a promising and affordable household-scale treatment technology for low-resource settings.