Comparison of disinfection effect of pressurized gases of CO2, N2O, and N2 on Escherichia coli

Abstract Based on the production of gas bubbles with the support of a liquid film-forming apparatus, a device inducing contact between gas and water was used to inactivate pathogens for water disinfection. In this study, the inactivation effect of CO 2 against Escherichia coli was investigated and compared with the effects of N 2 O and N 2 under the same pressure (0.3–0.9 MPa), initial concentration, and temperature. The optimum conditions were found to be 0.7 MPa and an exposure time of 25 min. Under identical treatment conditions, a greater than 5.0-log reduction in E. coli was achieved by CO 2 , while 3.3 log and 2.4 log reductions were observed when N 2 O and N 2 were used, respectively. Observation under scanning electron microscopy and measurement of bacterial cell substances by UV-absorbance revealed greater cell rupture of E. coli following treatment with CO 2 than when treatment was conducted using N 2 O, N 2 and untreated water. The physical effects of the pump, acidified characteristics and the release of intracellular substances caused by CO 2 were bactericidal mechanism of this process. Overall, the results of this study indicate that CO 2 has the disinfection potential without undesired by-product forming.