The Role of Free Radicals in Electrochemical Disinfection

Electrochemical disinfection has been widely investigated for its potential application in water industry. Compared with conventional chlorination disinfection, electrochemical method has shown good environmental compatibility and versatility to kill all kinds of bacteria. In general, the disinfectants have been mainly ascribed to electrogenerated active chlorines. However, the function of free radicals remains unclear. This work explored the role of free radicals generated in the electrochemical disinfection. To eliminate the confusion caused by chlorine, a chloride-free model wastewater was used and E. coli was chosen as an indicator of microorganism. Electron spin resonance detection was carried out to determine which free radical played the critical role in bacteria inactivation. The results gave out clear evidence that hydroxy! radicals were the major germicidal species in the chloride-free wastewater. When chloride was added to the wastewater, the germicidal efficiency could be improved and the treating time would be remarkably reduced. The experiments further demonstrated that electrochemical disinfection with the generation of chlorine could provide residual disinfection in addition to primary disinfection.