Bactericidal effect of an electrodialysis system on E. coli cells

Abstract

Using a new electrodialysis system with both cation- and anion-exchange membranes, the bactericidal effect on Escherichia coli has been investigated in detail from the standpoint of electrochemistry. Various electrolyte solutions containing E. coli (10 5 cells/cm 3) were passed through a desalting chamber at a flow rate of 3 cm 3/min under varying current densities, and the viability of the cell (%) and the pH changes in the effluents were measured. When a 0.1 M NaCl aqueous suspension was used, a disinfection effect emerged in the vicinity of the limiting current density (LCD 0.81 A/dm 2) and increased with an increase in the current density. The pH value of the suspensions decreased owing to the dissociation of water to H + and OH − ions by the well-known “neutrality disturbance phenomenon” in the region beyond the LCD. These tendencies were also observed when other electrolyte suspensions were used. Concerning the effect of the various species on the disinfection of E. coli cells, ionic systems in which a LCD was easily attained were found to have a strong effect. The germicidal effect may be due to a synergistic effect of acidic H + and basic OH − ions which are produced on the anion-exchange membrane and cation-exchange membrane, respectively, of the desalting chamber.