Enhancement of chlorine-resistant bacteria inactivation via coupling Magnéli phase Ti4O7-based electrochemical oxidation and chlorination

Abstract

The widespread use of chlorination prompts the selection of chlorine-resistant bacteria in drinking water, posing a great threat to public health. Herein, according to sequential electrochemical oxidation/reduction (Ox/Red) processes with a flow-through mode, electrochemical devices (ED) with sequential Ox-Red, Red-Ox and Ox-Red-Ox processes were coupled with chlorination (AC) to evaluate their synergistic effects and mechanisms for inactivation of chlorine-resistant bacteria in drinking water. ED/AC enabled ∼ 3.0 log of synergistic effect and ∼ 2.5 times lower energy consumption for inactivation of various chlorine-sensitive/-resistant bacteria and gram-positive/-negative bacteria in DI and tap waters. Especially, ED/AC with Ox-Red-Ox device exhibited the best disinfection performance with achieving over 6.7 log inactivation of Bacillus cereus at 4.0 V and 0.5 mg/L-Cl2 as compared with ED alone (∼1.25 log) and AC (∼2.67 log) disinfection. The electrochemical oxidation on Ti4O7-based anode promoted the generation of free chlorine radicals and H+ ions, which was accompanied with the formation of neutral HClO molecules. Characterizations of SEM and flow cytometer suggested that oxidative species of neutral HClO molecules and free chlorine radicals enhanced the bacterial inactivation via severe damages of cell structures. This work provided a promising strategy via coupling electrochemical oxidation and chlorination for eliminating chlorine-resistant bacteria in drinking water.