In the present study, the characteristics of combined ultraviolet (UV) and ozone disinfection process were investigated from the kinetic and mechanistic viewpoints employing Escherichia coli (E. coli) as an indicator microorganism. Compared to individual unit processes, the combined UV/O3 tests produced excess hydroxyl radicals (HO•) and yield synergistic inactivation of E. coli in the initial phase of reaction. The presence of O3 during UV exposure caused the destruction of cell structure, and then repressed the bacteria regrowth after treatment. Moreover, the formation of malondialdehyde (MDA) showed that the improved generation of intermediate HO• via ozone photolysis accelerated the decomposition of bacterial cell surface, which was further confirmed by the leakage of intracellular potassium ion (K+). The results suggested that the synergistic bactericidal effect of combined UV/O3 was mainly owing to the enhanced destruction of bacterial cell structure.
- Escherichia coli
- hydroxyl radicals
- inactivation mechanism
- UV/O3 process
- First received 29 December 2014.
- Accepted in revised form 29 July 2015.
- © IWA Publishing 2015