Locally Enhanced Electric Field Treatment (LEEFT) Promotes the Performance of Ozonation for Bacteria Inactivation by Disrupting the Cell Membrane.

The adoption of ozonation for water disinfection is hindered by its high ozone demand and the resulting high cost. Electric field treatment inactivates bacteria by physically disrupting the integrity of the cell membrane. Assisted by nanowire-modified electrodes, locally enhanced electric field treatment (LEEFT) reduces the required voltage to several volts to induce sufficient electric field strength for efficient bacteria inactivation. In this study, the LEEFT is applied as a pretreatment of ozonation for bacteria inactivation. Our results show that a low-voltage (<0.4 V) LEEFT has no obvious effect on the following ozonation, but a higher-voltage (0.6-1.2 V) LEEFT significantly enhances the ozone inactivation. After the LEEFT, a large number of viable cells with impaired cell membranes are observed, shown by both selective plate count and staining methods. The mechanism inducing the enhancement is explained by the initially reparable pores generated by LEEFT that cannot recover in the subsequent ozonation and the greater intracellular diffusion of ozone after the membrane disruption induced by LEEFT. The application of LEEFT as a pretreatment process is beneficial to reduce the ozone dosage and disinfection by-product formation with a broader inactivation spectrum, which facilitates the application of ozonation in primary water disinfection.