Inactivation of microorganisms in untreated water by a continuous flow system with supercritical CO2 bubbling

Abstract

The effects of supercritical CO 2 bubbling (SC-CO 2 ) treatment on the inactivation of microorganisms in water prior to treatment at a municipal water filtering plant (untreated water) were investigated as a way to produce safe drinking water. The coliform bacterial count decreased concomitantly with increasing CO 2 /sample flow rate in the SC-CO 2 treatment. In particular, coliform bacteria could not be detected at a CO 2 /sample flow rate greater than 55%. Also, the total bacterial count dropped rapidly at first stage and slowly at second stage in the SC-CO 2 treatment. Upon observation of Escherichia coli before and after the SC-CO 2 treatment with scanning electron microscopy and transmission electron microscopy, it was observed that the cells treated with SC-CO 2 were shorter than untreated cells and that cytoplasm with low electronic density in the treated cells disappeared. In addition, four types of metabolic enzyme in E. coli cells were effectively inactivated by the SC-CO 2 treatment. These results suggested that SC-CO 2 treatment could effectively inactivate microorganisms in untreated water, and induce morphological changes and inactivate metabolic enzymes of E. coli cells.

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

“…Several studies recently investigated the application of high pressure CO 2 disinfection to water treatment. Supercritical pressure up to 10 MPa and high temperature (55°C) were reported to effectively inactivate E. coli and coliforms -498 - (Kobayashi et al, 2009). However, Cheng et al (2011) concluded that pH was not related to the inactivation mechanism of dissolved CO 2 , which differed from the results of previous studies (Ballestra et al, 1996;Dillow et al, 1999;Hong and Pyun, 1999;Garcia-Gonzalez et al, 2007).…”

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

“…Moreover, an increase of pressure, temperature, or treatment time of CO 2 under pressure enhanced the antimicrobial effect against E. coli (Kamihira et al, 1987;Dillow et al, 1999;Wu et al, 2007;Kobayashi et al, 2007Kobayashi et al, , 2009bGarcia-Gonzalez et al, 2010). Thus the use of pressurized CO 2 has been widely investigated (Wu et al, 2007;Kobayashi et al, 2007Kobayashi et al, , 2009aJung et al, 2009;Garcia-Gonzalez et al, 2010;Klangpetch et al, 2011;Cheng et al, 2011).…”

“…Far too little attention has been paid to water disinfection since the first study of Kobayashi et al (2007) have successfully carried out an attempt to transfer knowledge of HPCD from food disinfection to water disinfection. In recent years, there has been an increasing interest in applying HPCD to water treatment (Kobayashi et al, 2007(Kobayashi et al, , 2009a(Kobayashi et al, , 2009b(Kobayashi et al, , 2010Cheng et al, 2011) with the belief that pressurized CO 2 has all the advantages of conventional disinfection methods and overcomes their adverse effects to health. Questions have been raised as to why the major attention on HPCD has been paid to liquid media and water, as shown in Fig.…”

<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.…”

“…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].…”