BACKGROUND AND OBJECTIVES: The increasing need for efficient wastewater treatment solutions has driven research toward the development of integrated processes capable of addressing complex contaminant compositions. Standard single-stage treatment approaches frequently do not effectively remove a variety of pollutants, including organic compounds, heavy metals, and pathogenic microorganisms. Furthermore, information on the integration of coagulation-flocculation, biofiltration, and advanced oxidation processes within a cohesive treatment system. This study aimed to develop and evaluate a multi-stage wastewater treatment system that combines coagulation-flocculation, biofiltration, and advanced oxidation processes to enhance pollutant removal efficiency and improve effluent quality.METHODS: The experimental setup consisted of three sequential treatment units. In the first stage,
coagulation-flocculation was employed to aggregate and remove suspended solids and colloidal matter. Coagulant dosages of ۲۰, ۴۰, ۶۰, and ۱۰۰ milligrams per liter were tested to determine the optimal chemical requirement. The second phase employed biofiltration to enhance the biological breakdown of dissolved organic substances, with the hydraulic retention time fine-tuned for optimal microbial activity. The final stage applied ultraviolet light and hydrogen peroxide oxidation to degrade residual organic pollutants and ensure microbial disinfection. FINDINGS: As the dosage of coagulant was raised, the
coagulation-flocculation performance showed improvement. At ۲۰ milligrams per liter, total suspended solids removal was ۵۲.۳ percent and chemical oxygen demand reduction was ۱۵.۷ percent. At ۴۰ milligrams per liter, these values increased to ۷۲.۸ percent and ۲۸.۴ percent, respectively. The optimal dosage of ۶۰ milligrams per liter achieved ۸۸.۵ percent removal of total suspended solids and ۳۹.۶ percent reduction in chemical oxygen demand, while at ۱۰۰ milligrams per liter, the efficiency reached ۹۲.۵ percent and ۴۳.۳ percent, respectively. The integrated multi-stage system achieved average overall removal efficiencies of ۹۲ percent for chemical oxygen demand, ۸۵ percent for heavy metals, and more than ۹۹ percent for microbial inactivation. CONCLUSION: The findings indicate that the combined treatment system significantly improves pollutant removal by leveraging the synergistic interaction between physicochemical, biological, and oxidation processes. The study confirms the potential of the system for pilot-scale and full-scale adaptation, suggesting its viability as an integrated solution for effective wastewater management and the protection of public health.
