Treatment of Real Tannery Industrial Wastewater via Sequential Biological and US/UV/activated Persulfate-Hydrogen Peroxide Processes

The purpose of this study is to assess the efficacy of an integrated system for treating tannery effluents from Fez City. The system includes aeration as a pretreatment, followed by a binary oxidation process using hydrogen peroxide (H₂O₂) and persulfate (K₂S₂O₈) (PS) as oxidants, with UV-A irradiation, and ultrasound (US) as activators (US-UV-PS-H₂O₂). Aeration effectiveness as a preliminary treatment was evaluated, resulting in a 71% and 78% reduction in chemical organic demand (COD) and color, respectively. The US-UV-PS-H₂O₂ process effectiveness was further evaluated in terms of COD and color removal. A factorial design with two levels was used to optimize the operating parameters (pH, H₂O₂ concentration, and K₂S₂O₈ dose). The findings showed that, under optimal conditions (pH = 3; [H₂O₂] = 225 mg/L and [K₂S₂O₈] = 3670 mg/L), the highest COD and color reduction rates in the tannery effluent were 85% and 93%, respectively. Additionally, phytotoxicity assessments, based on seed germination and root elongation tests, revealed promising results in toxicity reduction, with a germination rate of 75% for both M. sativa and wheat seeds. Overall, the sequential treatment involving aeration followed by US-UV-PS-H₂O₂ process proves to be an effective and practical strategy for the sustainable management of tannery wastewater, with a total treatment cost of $8.07/m³.