title: Escherichia coli inactivation by pressurized CO2 treatment methods at room temperature: Critical issues.
abstract: This study aims to increase the inactivation efficiency of CO2 against Escherichia coli under mild conditions to facilitate the application of pressurized CO2 technology in water disinfection. Based on an aerating-cycling apparatus, three different treatment methods (continuous aeration, continuous reflux, and simultaneous aeration and reflux) were compared for the same temperature, pressure (0.3-0.7MPa), initial concentration, and exposure time (25min). The simultaneous aeration and reflux treatment (combined method) was shown to be the best method under optimum conditions, which were determined to be 0.7MPa, room temperature, and an exposure time of 10min. This treatment achieved 5.1-log reduction after 25min of treatment at the pressure of 0.3MPa and 5.73-log reduction after 10min at 0.7MPa. Log reductions of 4.4 and 5.0 occurred at the end of continuous aeration and continuous reflux treatments at 0.7MPa, respectively. Scanning electron microscopy (SEM) images suggested that cells were ruptured after the simultaneous aeration and reflux treatment and the continuous reflux treatment. The increase of the solubilization rate of CO2 due to intense hydraulic conditions led to a rapid inactivation effect. It was found that the reduction of intracellular pH caused by CO2 led to a more lethal bactericidal effect.
authors.affiliation: Key Laboratory of Yangtze River Water Environment, Ministry of Education, Tongji University, Shanghai 200092, China. Electronic address: yongjizhang@126.com.
authors.forename: Yongji
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Yangtze River Water Environment, Ministry of Education, Tongji University, Shanghai 200092, China.
authors.forename: Doudou
authors.initials: D
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science & Engineering, Tongji University, Shanghai 200092, China. Electronic address: angelina-zhou@163.com.
authors.forename: Lingling
authors.initials: L
authors.lastname: Zhou
mesh_terms: D000900:Anti-Bacterial Agents / Q000633:toxicity*; D002245:Carbon Dioxide / Q000633:toxicity*; D004203:Disinfection / Q000379:methods; D004926:Escherichia coli; D011312:Pressure; D013696:Temperature; D014871:Water Microbiology; D018508:Water Purification / Q000379:methods*
chemical_list: D000900:Anti-Bacterial Agents; D002245:Carbon Dioxide
keywords: Aeration; Intracellular pH; Pressurized carbon dioxide; Reflux; Solubilization rate; Water disinfection