Bactericidal Effectiveness of O3, O3/H2O2 and O3/TiO2 on Clostridium perfringens

The purpose of this research is to evaluate the bactericidal capacity of different Advanced Oxidation Treatments (AOTs) based on ozone: ozone, ozone/hydrogen peroxide and ozone/titanium dioxide on a wild strain of Clostridium perfringens, a fecal bacterial indicator in drinking water. The dose of ozone consumed ranges from 0.6 mg L-1 min-1 to 5.13 mg L-1 min-1 depending on the process and on the sample. In the treatments combined with O3, H2O2 dose utilized is 0.04 mM and TiO2 dose, 1 g L-1. In order to evaluate the influence of natural organic matter and suspension solids over the disinfection rate, treatments are performed with two types of water - natural water from Ebro River (Zaragoza, Spain) and NaCl solution 0.9%. To achieve 4 log units of inactivation, 3.6 mg O3 L-1 is necessary in O3 treatment, 4.25 mg O3 L-1 in O3/TiO2 system and 2.7 mg O3 L-1 in O3/H2O2 after processing the natural water. In NaCl solution, to get the same inactivation, 0.42 mg O3 L-1 is necessary in O3 treatment, 1.15 mg O3 L-1 in O3/TiO2 system and 0.06 mg O3 L-1 in O3/H2O2 process. Even though the three treatments studied have a high bactericidal activity due to the number of surviving bacteria decreases to non-detectable levels, O3/H2O2 is the most effective system for eliminating C. perfringens cells in a lower contact time, followed by O3 and finally O3/TiO2 system.