Inactivation of Clostridium perfringens spores and vegetative cells by photolysis and TiO2 photocatalysis with H2O2

Due to public health concerns related to the generation of dangerous by-products from conventional systems of water disinfection, innovative technologies based on the generation of oxidant radicals are being developed. The aim of this work is to evaluate the bactericidal activity of different treatments with light (λ: 320–800 nm), TiO2 (1 g L−1) and H2O2 (0.04 mM) on the viability of vegetative cells and spores of Clostridium perfringens. After spiking a natural water sample (from the Ebro River, Zaragoza (Spain)), the population of vegetative cells was of 108 CFU·100 mL−1 and of spores about 103 CFU·100 mL−1. Treatments without radiation source (TiO2, H2O2, TiO2/H2O2) show a poor level of inactivation (<0.5 log) on both bacterial forms. The light treatment achieves a vegetative cell inactivation of 1.2 log after 5 min of treatment and <0.5 log on spores after 30 min. The combined light/TiO2 system increases the level of disinfection with a vegetative cell removal in the order of 6 log after 5 min and 0.6 log of spores after 5 min. Light/H2O2 and light/TiO2/H2O2 treatments also significantly increase the disinfection of vegetative cells of C. perfringens (>6 log). Regarding spores, light/H2O2 and light/TiO2/H2O2 treatments achieve constant inactivation of 1 log after 5 min of treatment. The application of a light/TiO2/H2O2 treatment does not increase the level of inactivation with regard to the level reached by the light/TiO2 and light/H2O2 systems. This fact shows there is no a significant interaction between TiO2 and H2O2 under the conditions studied.