Disinfection performance and mechanism of the carbon fiber-based flow-through electrode system (FES) towards Gram-negative and Gram-positive bacteria

The disinfection performance of a carbon fiber-based flow-through electrode system (FES) towards Gram-negative bacteria (Escherichia coli and fecal coliform) and Gram-positive bacteria (Enterococcus faecalis and Bacillus subtilis) in normal saline was systematically investigated over a wide range of applied voltages (1-5 V) and hydraulic retention times (HRTs) (1-10 s). It was revealed that the Gram-negative bacteria were more vulnerable to FES for their thinner cell walls, and over 6.5 log removal (no live bacteria detected) was achieved at the applied voltage of 2 V and HRT of 2 s; while Gram-positive bacteria were inactivated at slightly higher voltages (3 V, 2 s) or longer HRTs (2 V, 5 s). Bacterial inactivation was attributed to the change and rupture of cell membrane mainly by anode direct oxidation without bacterial regrowth/reactivation. In addition, negligible generation of the free chlorine at low voltages (<= 2 V) can avoid the formation of potential chlorinated disinfection byproducts (DBPs). Hence, FES can offer a potential alternative to conventional disinfection methods for bacterial inactivation in natural and contaminated water. (C) 2020 Elsevier Ltd. All rights reserved.