Electrochemical advanced oxidation processes for Staphylococcus aureus disinfection in municipal WWTP effluents

This paper presents the Staphylococcus aureus inactivation in a simulated wastewater treatment plant effluent by different electrochemical techniques, including the photo-electro-Fenton process. S. aureus, dissolved organic carbon (DOC), total oxidants and H₂O₂ concentrations, as well as pH, were monitored during the assays. An electrolytic cell, including a UVA lamp, a gas diffusion electrode (GDE) as cathode and an IrO₂ anode, was used to conduct the experiments under galvanostatic conditions (20 mA). Low inactivation (-0.4) and low DOC removal were achieved within 120 min when applying the GDE-IrO₂ system, in which bacteria disinfection was caused by the generated H₂O₂. When light was combined with GDE-IrO₂, the process efficiency noticeably increased (-3.7 log inactivation) due to the synergistic effect between UVA and H₂O₂. Introducing iron (5 mg L^-1 Fe²⁺) into the system also produced higher disinfection and DOC mineralization. The electro-Fenton process (GDE-IrO₂+Fe²⁺) led to a bacterial reduction of -0.9 log units and DOC reduction of 14%, while with the photo-electro-Fenton process (GDE-IrO₂+UVA + Fe²⁺) -5.2 units of bacteria and 26% of DOC were removed. Increasing the current intensity (20 mA, 30 mA and 40 mA) in the photo-electro-Fenton system increased H₂O₂ production and, consequently, augmented the bacterial inactivation (-5.2 log, -6.2 log and -6.5 log, respectively). However, mineralization extent slightly increased or remained practically the same. When comparing the influence of Fe²⁺ and Fe³⁺ on photo-electro-Fenton, similar S. aureus inactivation was observed, while DOC removal was higher with Fe²⁺ (31%) than with Fe³⁺ (19%). Finally, by testing the system with a Ti anode, the direct anodic oxidation contribution of the IrO₂ anode was identified as negligible.