Disinfection Using Pressurized Carbon Dioxide Microbubbles to Inactivate Escherichia coli, Bacteriophage MS2 and T4

Abstract

This study investigated the potential application of pressurized CO 2 for water disinfection. Under supporting high pressure, a high volume of CO 2 microbubbles were produced in a liquid environment. Specifically, the inactivation effects of CO 2 against Escherichia coli, bacteriophage MS2 and T4 were examined at equal pressures (0.3 -0.9 MPa) and temperatures. 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, while over 3.0 log and nearly 4.0 log reductions were observed for phage MS2 and phage T4, respectively. Comparison of the inactivation effect of CO 2 , N 2 O, a common acid and buffer solution against phage MS2, revealed that the change in pH caused by CO 2 plays an important role in its virucidal effects. Moreover, the pumping cycle and depressurization rate contributed to the inhibition of microorganisms. Overall, the results of this study indicate that CO 2 has the potential for use as a disinfectant without the formation of by-products.

Potential application of high pressure carbon dioxide in treated wastewater and water disinfection: Recent overview and further trends

“…Moreover, at high temperature, proteins more easily denatured and the components of external membranes are disintegrated and broken down, so that CO 2 molecules more easily penetrate into the lipid phase and cytoplasm. Most of the recent studies found that increasing temperature led to more effective microorganism inactivation (Kamihira et al, 1987;Dillow et al, 1999;Zhang et al, 2006;Wu et al, 2007;Kobayashi et al, 2009b;Garcia-Gonzalez et al, 2010;Ferrentino et al, 2010;Vo et al, 2013bVo et al, , 2014. However, because rising temperature also decreases the CO 2 solubility in water, a temperature may be reached where no further improvement is gained.…”

“…Increasing pressure accelerates the CO 2 diffusivity into cell membranes and its solubility in cell cytoplasm. For the same reduction ratio of microorganisms, increasing the working pressure enables a shorter exposure time to treatment process (Kumugai et al, 1997;Erkmen, 2000a,b,c;Garcia-Gonzalez et al, 2010;Vo et al, 2013bVo et al, , 2014. However, excessive pressure does not strongly increase bacterial deaths due to saturation limitations of CO 2 in the suspension phase (Spilimbergo and Bertucco, 2003).…”

<i>Escherichia coli</i> Inactivation Using Pressurized Carbon Dioxide as an Innovative Method for Water Disinfection

“…In recent years, pressurized CO 2 has shown great potential as a sustainable disinfection technology in water and wastewater treatment applications [16][17][18][19][20][21][22] largely because this method does not generate DBPs [9,22]. Kobayashi et al [16,17] employed CO 2 microbubbles in the treatment of drinking water and succeeded in inhibiting Escherichia coli within 13.3 min.…”

“…However, the pressure (10 MPa) and temperature (35-55°C) requirements for effective inactivation [16,17] are still high from a practical standpoint. Our research group has developed a novel method that uses low-pressure CO 2 treatments (0.2-1.0 MPa) based on technology that produces high amounts of dissolved gas in water to inactive bacteria and bacteriophages in freshwater [19][20][21] and seawater [23,24]. Cheng et al [19] suggested that the sudden discharge and resulting reduction of pressure could cause cells to rupture via a mechanical mechanism, and further, that this would be lethal to cells at high levels of dissolved CO 2 at 0.3-0.6 MPa and room temperature.…”

“…Cheng et al [19] suggested that the sudden discharge and resulting reduction of pressure could cause cells to rupture via a mechanical mechanism, and further, that this would be lethal to cells at high levels of dissolved CO 2 at 0.3-0.6 MPa and room temperature. Vo et al [20,21] demonstrated that acidified water and cellular lipid extraction caused by pressurized CO 2 at 0.7 MPa and room temperature were major factors for efficient disinfection within a treatment time of 25 min.…”