Inactivation of intracellular bacteriophages in host bacterial cells by integrating Ti4O7-based electrochemical oxidation with chlorination

Electrochemical oxidation and chlorination were integrated for i-phage inactivation. • The integrated ED/Cl 2 exhibited obvious synergistic effects for phage inactivation. • ED/Cl 2 lowered the required chlorine dosage and DBPs formation for phage inactivation. • Ti 4 O 7 -anode dominated phage inactivation via producing free radicals and neutral HClO. • ED/Cl 2 enhanced i-phage leakage and subsequent inactivation via damaging host cells. The presence of intracellular bacteriophages (i-phages) trapped inside host bacteria presents a formidable obstacle to drinking water disinfection, primarily because they exhibit markedly higher resistance than cell-free extracellular phages (e-phages). This work studied the inactivation of i-phages with an integrated electrochemical oxidation and chlorination (ED/Cl 2 ) system employing Magnéli phase Ti 4 O 7 -based anodes in a flow-through configuration that implemented a sequential oxidation-reduction-oxidation process. The results demonstrated that ED/Cl 2 system significantly promoted the inactivation of both e-phages and i-phages with obvious synergistic effects, especially achieving 3.8-log i-T4 inactivation and 2.7-log of synergistic effect at 5.0 V and 1.5 mg/L-Cl 2 as compared with the insignificant inactivation by the individual ED (0.3-log) and Cl 2 (0.8-log). Furthermore, this integrated approach reduced energy consumption by approximately 8.4–16.5 times compared to electrochemical treatment alone, and significantly lowered the chlorine dosage required to achieve phage inactivation levels comparable to chlorination alone, thereby reducing formation of disinfection by-products. The disinfection mechanisms were involved the generation of reactive chlorine radicals and neutral hypochlorous acid at the anode, which facilitated the oxidative injury to bacterial cellular structures for releasing i-phage and subsequent inactivation, as evidenced by flow cytometry, SEM and TEM analyses. The application potentials of the integrated ED/Cl 2 system were further validated in contaminated tap water, confirming it as a promising, energy-efficient strategy for controlling i-phages in drinking water treatment systems. Download: Download high-res image (116KB) Download: Download full-size image