Ultrasound, Hydrogen Peroxide, and Persulfate in Hybrid Advanced Oxidation Processes(AOPs): A Comparative Study for the Reuse of Sewage Treatment Effluent

Abstract

Objectives : As the variety and quantity of recalcitrant pollutants such as pharmaceuticals, pesticides, endocrine disruptors, and cosmetic products discharged into water bodies steadily increase, the need for AOPs following biological wastewater treatment processes is growing. In this study, we compared the Total Organic Carbon (TOC) removal capabilities of conventional AOPs, ultrasound, hydrogen peroxide, and persulfate-based multiple AOPs on the final effluent of S wastewater treatment plant. The study also evaluated the feasibility of wastewater reuse by examining the optimal operating conditions of the applied AOPs.Methods : The removal characteristics of TOC were investigated based on reaction time, US frequency, and oxidant dosage for the following conditions: ultrasound (US) alone, individual treatments with hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) and persulfate (PS) as oxidants, combined US/H<sub>2</sub>O<sub>2</sub> and US/PS dual AOPs, and a US/PS/H<sub>2</sub>O<sub>2</sub> multi-AOPs system.Results and Discussion : Only US oxidation treatment at 80 kHz for 60 minutes resulted in a 14.4% TOC removal efficiency. Individual treatment with H<sub>2</sub>O<sub>2</sub> at 174 mM showed 69.2% removal efficiency, while persulfate oxidation treatment at 43.5 mM showed 13.8%. The PS/H<sub>2</sub>O<sub>2</sub> oxidation treatment showed 68.5% removal efficiency at 174 mM H<sub>2</sub>O<sub>2</sub> and 0.52 mM PS, and an 85.3% removal efficiency at 2.08 mM PS and 350 mM H<sub>2</sub>O<sub>2</sub> conditions. Under the same 80 kHz ultrasound conditions, the combined US and other oxidant treatment resulted in an increased TOC removal efficiency: 87.8% for US/H<sub>2</sub>O<sub>2</sub> at 174 mM H<sub>2</sub>O<sub>2</sub>, and 81.9% for US/PS at 43.5 mM PS. Additionally, the multi-treatment with US, PS, and H<sub>2</sub>O<sub>2</sub> showed a removal efficiency of 87.0% at 2.08 mM PS and 350 mM H<sub>2</sub>O<sub>2</sub>, and 91.1% at 174 mM H<sub>2</sub>O<sub>2</sub> and 0.52 mM PS conditions.Conclusion : In this study, among the AOPs, the oxidation treatment with US/PS/H<sub>2</sub>O<sub>2</sub> exhibited the highest TOC removal efficiency at 91.1%. The integration of chemical oxidants with US demonstrated significant improvement in TOC removal capabilities, with PS showing superior performance at the same concentration conditions among the utilized chemical oxidants in the multi-AOPs. Although H<sub>2</sub>O<sub>2</sub> also displayed commendable TOC removal abilities, its oxidation efficiency was lower at low concentration injections, whereas higher concentrations of H<sub>2</sub>O<sub>2</sub> injections proved to be more effective in oxidation.