Application of Supercritical CO2 Bubbling to Inactivate E. coli and Coliform Bacteria in Drinking Water

Abstract

The e#ect of the continuous flow of supercritical CO, microbubbles (the SC-CO, method) on the inactivation of both Escherichia coli in model water and coliform bacteria in water prior to treatment at a municipal water filtering plant were studied as a way to produce safe drinkable tap water. The number of surviving cells in both samples drastically decreased above a certain concentration of dissolved CO, (gῌ,/). When treated for +-.-min, cells were not detected at concentrations over gῌ-*. The dependences of the number of surviving cells on the concentration of dissolved CO, were similar in both the treatments for 0.1 and +-.-min. Therefore, it was suggested that e#ective inactivation could be achieved by minimizing the treatment time. From these results, it was proposed that the SC-CO, method might be e#ective in inactivating E. coli and coliform bacteria for the production of public drinking water.

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

“…Electron micrographs of E. coli cells before and after SC-CO 2 treatment SEM photographs of E. coli cells before and after SC-CO 2 treatment are shown in Figure 4. In an earlier study we confirmed that surviving E. coli cells could not be detected after SC-CO 2 treatment (Kobayashi et al, 2007a). The damage in E. coli cells by SC-CO 2 treatment could not be observed by SEM.…”

“…As described in our previous paper (Kobayashi et al, 2007a), water was taken from a municipal water filtering plant (Miyoshi, Hiroshima, Japan) prior to being treated for use as tap water. The coliform bacteria and total bacterial counts in this untreated water were approximately 4.0×10 2 MPN/100ml and 9.0×10 2 ～1.2×10 3 CFU/ml, respectively.…”

“…In our previous papers, we reported that certain compounds that give tap water a musty odor could be removed by a continuous flow treatment with SC-CO 2 (Kobayashi et al, 2006) and suggested that inactivation of Escherichia coli in sterile distilled water and coliform bacteria in water prior to treatment at a municipal water filtering plant (untreated water) by the SC-CO 2 treatment depended on the dissolved CO 2 concentration (Kobayashi et al, 2007a). In this study, we aim to determine the effects of the CO 2 /sample flow rate and exposure time in the SC-CO 2 treatment on the inactivation of coliform and total bacteria in untreated water and to propose the SC-CO 2 treatment as a novel method for inactivating microorganisms in drinking water.…”

“…In this study, we aim to determine the effects of the CO 2 /sample flow rate and exposure time in the SC-CO 2 treatment on the inactivation of coliform and total bacteria in untreated water and to propose the SC-CO 2 treatment as a novel method for inactivating microorganisms in drinking water. In addition, we aim to investigate the effect of the SC-CO 2 treatment with regard to structural damage and enzyme inactivation in E. coli cells, which we previously demonstrated could be reduced to nondetectable levels by the SC-CO 2 treatment (Kobayashi et al, 2007a).…”

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

“…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.…”