title: Synergistic effect of pressurized carbon dioxide and sodium hypochlorite on the inactivation of Enterococcus sp. in seawater.
abstract: This study investigated the effect of combined treatments using pressurized carbon dioxide (PCD) and sodium hypochlorite (NaOCl) on the inactivation of Enterococcus sp. in artificial seawater. Bacterial inactivation was conducted in a liquid-film-forming apparatus with various pressure conditions, CO2supply rates, and chlorine dosages. Combined PCD/chlorine treatments resulted in greater disinfection efficiency than those for the two individual treatments. Synergy values were correlated with pressure and CO2concentrations (p < 0.001). Combination of 0.9 MPa PCD (various CO2supply rates: 25% CO2+ 75% N2, 50% CO2+ 50% N2, and 100% CO2) and chlorine (0.20 mg L-1) yielded average synergy values of 4.9, 5.2, and 4.4 log, respectively, within 3 min. Combined treatment with PCD (100% CO2, 0.3 MPa, and 20 °C) and chlorine (0.20-0.22 mg L-1) achieved an average synergy value of 4.6 log and complete inactivation (5.2-5.5 log reductions) of Enterococcus sp. within 4 min. In contrast, when the two individual treatments (PCD and chlorine) were used, only 3.7 and 1.8-2.3 log reductions, respectively, were achieved after 25 min. These findings suggest that the combined PCD/chlorine treatment has synergistic benefits and provides a promising method for the disinfection of ballast water.
authors.affiliation: Graduate School of Science and Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi, 755-8611, Japan; Department of Environmental Science, College of Sciences, Hue University, Hue, 470000, Viet Nam.
authors.forename: Thanh-Loc Thi
authors.initials: TT
authors.lastname: Dang
authors.affiliation: Graduate School of Sciences and Technology for Innovation, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi, 755-8611, Japan. Electronic address: imai@yamaguchi-u.ac.jp.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Imai
authors.affiliation: Department of Environmental Science, College of Sciences, Hue University, Hue, 470000, Viet Nam.
authors.forename: Tuan Van
authors.initials: TV
authors.lastname: Le
authors.affiliation: Graduate School of Science and Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi, 755-8611, Japan.
authors.forename: Diem-Mai Kim
authors.initials: DK
authors.lastname: Nguyen
authors.affiliation: Graduate School of Sciences and Technology for Innovation, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi, 755-8611, Japan.
authors.forename: Takaya
authors.initials: T
authors.lastname: Higuchi
authors.affiliation: Graduate School of Sciences and Technology for Innovation, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi, 755-8611, Japan.
authors.forename: Ariyo
authors.initials: A
authors.lastname: Kanno
authors.affiliation: Graduate School of Sciences and Technology for Innovation, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi, 755-8611, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Yamamoto
authors.affiliation: Graduate School of Sciences and Technology for Innovation, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi, 755-8611, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Sekine
mesh_terms: D002245:Carbon Dioxide; D004202:Disinfectants; D004203:Disinfection; D016983:Enterococcus; D012623:Seawater / Q000382:microbiology; D012973:Sodium Hypochlorite
chemical_list: D004202:Disinfectants; D002245:Carbon Dioxide; D012973:Sodium Hypochlorite
keywords: Bactericidal inactivation; Ballast water disinfection; Enterococcus sp.; Pressurized carbon dioxide; Sodium hypochlorite; Synergy