title: Synergistic effect of sequential or combined use of ozone and UV radiation for the disinfection of Bacillus subtilis spores.
abstract: This study was performed to evaluate the inactivation efficiency or synergy of combined ozone and UV processes (combined ozone/UV process) or sequential processes (ozone-UV, UV-ozone) compared with individual unit processes and to investigate the specific roles of ozone, UV and the hydroxyl radical, which is formed as an intermediate in the combined ozone/UV process. The Bacillus subtilis spore, which has often been used as a surrogate microorganism for Cryptosporidium parvum oocysts, was used as a target microorganism. Compared to individual unit processes with ozone or UV, the inactivation of B. subtilis spores by the combined ozone/UV process was enhanced under identical conditions. To investigate the specific roles of ozone and UV in the combined ozone/UV process, sequential ozone-UV and UV-ozone processes were tested for degrees of inactivation. Additionally, the experiment was performed in the presence and absence of tert-butyl alcohol, which acted as a hydroxyl radical scavenger to assess the role of inactivation by the hydroxyl radical in the combined ozone/UV process. Among the five candidate processes, the greatest synergistic effect was observed in the combined ozone/UV process. From the comparison of five candidate processes, the hydroxyl radical and ozone were each determined to significantly enhance the overall inactivation efficiency in the combined ozone/UV process.
authors.affiliation: Department of Environmental Engineering, Yonsei University, Wonju 220-710, Republic of Korea. chorong50@yonsei.ac.kr
authors.forename: Yeon Jung
authors.initials: YJ
authors.lastname: Jung
authors.forename: Byung Soo
authors.initials: BS
authors.lastname: Oh
authors.forename: Joon-Wun
authors.initials: JW
authors.lastname: Kang
mesh_terms: D001412:Bacillus subtilis / Q000502:physiology*; D004203:Disinfection; D007700:Kinetics; D010126:Ozone / Q000737:chemistry*; D013171:Spores, Bacterial; D014466:Ultraviolet Rays
chemical_list: D010126:Ozone