Assessment of a Photoreactor with Immobilized Nanoparticle TiO2 Films for the Purification of Rainwater

Abstract

The heterogeneous photocatalysis consists of the generation of reactive oxygen species (•OH, •-O2) from a catalyst, UV light, and oxygen; these reactive species can degrade contaminants and eliminate microorganisms. The purpose of this research was to evaluate a heterogeneous photocatalysis system and an UV light disinfection system for the elimination of total coliforms and Escherichia coli bacteria present in rainwater stored in five cisterns in Mexico City. The elimination of total coliforms (MPN/100 mL) and Escherichia coli (CFU/100 mL) were evaluated both in the rainwater treated with TiO2/UV and UV (in time periods of 30 and 60 minutes), according to the treatments established in the statistical model 22. The results show that although complete elimination of initial total coliforms (9.3 x 104 MPN/100 mL) and E. coli bacterium (1.5 x 103 CFU/mL) was achieved in one of the samples of rainwater using only UV light at 254 nm for 30 minutes, the use of 8 films coated with Degussa P-25 titanium dioxide, UV light at 254 nm and 1.5 vvm air in a reactor, achieves a total pathogen removal in a shorter time of 15 minutes. Thus, we anticipate that the combined treatment could be an alternative disinfection process for rainwater stored in cisterns, reducing costs and making the treatment viable for a larger-scale application.