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

Abstract

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.

Keywords:

• Clostridium perfringens
• Ozone
• Hydrogen Peroxide
• Titanium Dioxide
• Drinking Water
• Disinfection
• Advanced Oxidation

ACKNOWLEDGMENTS

This research is partially financed by the “Secretaría de Estado de Universidades e Investigación” of the Ministry of Education and Science (Spain) with the Project CTM2005–04585/TECNO called “Drinking Water Production By Advanced Oxidation Technologies In River Ebro Basin”. The authors also thank “Gobierno de Aragón” for the PhD grant to Munia Lanao.

Notes

EPA Guidance Manual. Alternative Disinfectants and Oxidants Office of Water. US Environmental Protection Agency 815-R-99-OP4 (1999).

ISO 6461-2:1986: “Water quality—Detection and Enumeration of the Spores of Sulfite- Reducing Anaerobes (clostridia)—Part 2: Method by Membrane Filtration”.