Optimization of persulfate activation system using ferrous sulfate for TOC removal from real domestic wastewater

The reuse of treated wastewater is increasingly recognized as a sustainable solution to address global water shortage. This study investigates the effectiveness of a persulfate-based advanced oxidation process (AOP) using sodium persulfate (Na2S2O8) activated by ferrous sulfate (FeSO4) as a tertiary treatment for secondary effluents. Real municipal wastewater was collected from Agouzain Wastewater Treatment Plant (WWTP) in Kafr El-Sheikh, Egypt. A Box Benkhen design (BBD) was employed to optimize three key variables: FeSO4 dose (0.5–2.0 g/L), Na2S2O8 dose (0.5–2.0 g/L), and pH (3.0–9.0), with total organic carbon (TOC) removal as the main response. Under optimized conditions (0.50 g/L FeSO4, 2.00 g/L Na2S2O8, pH 9.0), a maximum TOC removal efficiency of 87.29% was attained within 60 min. The treated effluent revealed significant reductions in COD, BOD5, TOC, and microbial indicators, confirming compliance with general standards for non-potable reuse. Overall, the Na2S2O8/FeSO4 system demonstrated high efficiency and reliability, offering a practical and cost-effective approach for tertiary wastewater treatment and safe reuse applications.