<p>This study aims to identify the most effective pretreatment method for minimizing membrane fouling in the treatment of complex tannery wastewater. Three approaches were evaluated: coagulation with ferric chloride (FeCl₂), Fenton-coagulation using FeCl₃ and hydrogen peroxide, and electrocoagulation with iron electrodes. The study examines key contaminant removal metrics, including Chemical Oxygen Demand (COD), Chromium, and Total Kjeldahl Nitrogen (TKN), followed by advanced parameters such as SUVA, Zeta potential, UV₂₅₄, and Modified Fouling Index (MFI) to assess fouling potential. Results reveal that the electrocoagulation process significantly outperforms the other pretreatment methods in mitigating membrane fouling, with an MFI value, 1660 times lower than coagulation and 370 times lower than Fenton-coagulation. These findings demonstrate that the pretreatment processes improve effluent quality and significantly reduce the potential for membrane fouling. This study contributes to optimizing membrane-based treatment systems for industrial wastewater, offering scalable solutions for sustainable water reclamation in diverse applications.</p> Graphical abstract <p></p>