Enhancing disinfection performance of the carbon fiber-based flow-through electrode system (FES) by alternating pulse current (APC) with low-frequency square wave

Abstract

This study was aimed to investigate the influence of low-frequency alternative pulse current (APC) with square wave on the disinfection performance of carbon fiber-based flow-through electrode system (FES) towards a model bacterium (Escherichia coli). The FES disinfection under direct current (DC) supply was limited by the weak disinfection efficiency of cathode. Compared with DC supply (less than 1 log removal), FES under APC supply achieved superior disinfection performance (over 6 log removal) at the voltage of 3 V and flow rate of 125 mL/min. The optimum condition was acquired when pulse cycle time (T) equaled to hydraulic retention time (HRT), i.e. HRT/T = 1, corresponding to the low frequency (less than 1 Hz), under which the disinfection performance was improved by alternating of anode and cathode. In-situ sampling experiments revealed that redox reactions were carried out alternatively in each electrode, and both electrodes made great contributions to disinfection under APC supply, which was significantly different from DC supply. In addition, FES disinfection under APC supply also caused irreversible damage to bacterial cells, resulting in no bacterial regrowth/reactivation during storage, and guaranteed low energy consumption (11.4 ~ 12.1 Wh/m3) with high flow rate (100 ~ 125 mL/min). Therefore, the development of a novel FES under APC supply provided exciting possibilities for future application of electrochemical disinfection to achieve superior disinfection performance with no bacterial regrowth and low energy consumption.