Singlet oxygen involved electrochemical disinfection by anodic oxidation of H2O2 in the presence of Cl−

Due to its potential applications in decentralized water treatment systems, electrochemical synthesis of H2O2 for water decontamination has been widely investigated in recent years. In this study, it is found that the anodic oxidation of the residual H2O2 in the presence of Cl− can be an efficient electrochemical disinfection technology to guarantee the microbiological safety of the treated water. H2O2 can be oxidized by HOCl generated at the anode to form singlet oxygen (1O2). 1O2 has been recognized as an important disinfectant in solar disinfection (SODIS) but it has not yet been reported in electrochemical disinfection. The generation of 1O2 was directly confirmed by the detection of 1O2 monomol emission using a near infrared imaging system. The concentration of 1O2 can reach up to 1.64 pM in the anodic oxidation of H2O2 with Cl−. 1O2 plays an important role in Escherichia coli (E. coli) inactivation, and HOCl only plays a subordinate role in the presence of 1 mM H2O2 due to its low concentration. For example, by adding up the inactivation of E. coli by sole H2O2 and micro-concentration HOCl together only attribute to about 2 log in 60 min but 1O2 itself can account for about 3 log. Besides, the formation of the chlorinated disinfection by-products (Cl-DBPs) was mitigated considerably benefited from the fast reduction of HOCl by H2O2. These findings have potential implications for H2O2-based decentralized water treatment systems and provide a novel strategy for electrochemical disinfection because electrochlorination is having the same problems that chlorination has.