Enhanced Bactericidal Effect of O3/H2O2 Followed by Cl2

Abstract

With the appearance of chlorine resistant microorganisms such as Cryptosporidium parvum and Giardia lamblia in drinking water, significant attention has been drawn to the sequential application of multiple disinfectants including ozone, chlorine dioxide, and UV as a primary disinfectant. However, few studies have reported about the inactivation behavior of ozone-based AOP (advanced oxidation process) or its sequential application combined with other disinfectants. This is especially important since ozone itself experiences difficulty in the inactivation of these pathogens, especially at low temperatures: This study investigates the enhanced inactivation of Bacillus subtilis spores by the presence of an OH radical in the O3/H2O2 system and the synergistically enhanced inactivation in the application of the O3/H2O2 system followed by Cl2. The results suggest that the O3/H2O2 process can be considered as one of the viable alternatives when O3 alone does not satisfy the disinfection requirement.