Towards sustainable wastewater treatment: Cost and efficiency trade-offs in the photo-fenton process

• Optimized photo-Fenton process targets COD removal and cost efficiency. • COD removal reached up to 76.58% with costs from 147.02–2,087.66 USD/m³. • Fuzzy optimization achieved 71.12% satisfaction balancing cost and removal. • Optimal conditions: 83.68 W/m³ UVA, 0.4730 mM Fe²⁺, 9.00 mM H₂O₂. • Achieved 2.48× better cost-efficiency vs. conventional at 57.22% removal. . This study examines the efficiency of COD removal in the photo-Fenton process, considering UVA irradiation, Fe 2+ concentration, and H 2 O 2 dosage as key operating variables. The primary objective is to simultaneously maximize COD removal and minimize operating costs using fuzzy optimization within a multi-objective framework. Pareto-optimal solutions established COD removal efficiencies ranging from 10.54±1.81% to 76.58±0.14%, corresponding to costs of 147.02 to 2,087.66 USD·m −3 . Fuzzy optimization achieved a 71.12% overall satisfaction level, balancing trade-offs between performance and cost. Optimal conditions were determined as 83.68 W·m −3 UVA irradiation, 0.4730 mM Fe 2+ , and 9.00 mM H 2 O 2 , yielding a 57.22±0.91% COD removal at a total cost of 707.40 USD·m −3 . This demonstrates a 2.48 times greater cost-efficiency than conventional methods, despite an 18.58% lower removal efficiency. To improve the photo-Fenton process for industrial applications, future work can consider dynamic optimization for variable wastewater compositions, low-cost catalysts to reduce reagent expenses, hybrid systems to enhance scalability, and real-time monitoring to automate adjustments in irradiation and dosing. .