Coupling UV irradiation and electrocoagulation for reclamation of urban wastewater

• Iron electrodes allow removing turbidity and E. coli in urban wastewaters.
• Enmeshment into growing flocs and oxidation are the key disinfection processes.
• A synergistic effect of coupling UV and EC is found at low current densities.
• Efficiency of UV irradiation is lowered at high current density.

This work focuses on coupling electrocoagulation, with iron electrodes, and UV irradiation (photo-electrocoagulation) for the simultaneous removal of turbidity and E. coli from actual treated municipal wastewaters. Results show that single electrocoagulation behaves as a very efficient technology even using low current densities. E. coli is removed not only by the enmeshment of microorganisms into growing flocs, but also by the attack of electrochemically produced chlorine disinfectant species. Coupling UV irradiation to electrocoagulation with iron electrodes improves the process performance in terms of E. coli and turbidity removal. The effect of current density on process performance was evaluated, finding a synergistic interaction of both techniques at low current density (1.44 A m−2) but an antagonistic effect at higher values of current density (7.20 A m−2). This antagonistic effect is caused by the less efficient transmission of UV irradiation to the bulk solution due to the increase in the concentration of solids.

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