The current research was aimed to investigate the performance of combined persulfate oxidation process and tannin via coagulation-flocculation processes as a post treatment of anaerobically treated palm oil mill effluent (AnT-POME). Different dosages of sodium persulfate (Na2S2O8, 238 g/mol) 0.1 (w/v) and modified tannin were combined as a simultaneous reaction to treat AnT-POME. Different dosages of tannin ranged between 0.02g and 0.12g with pH variation ranged between 3 and 11 retention and retention time of (30, 90, 120 and 180) were evaluated. The performance of the treatment processes was evaluated based on the removal of three different parameters namely; chemical oxygen demand (COD), ammoniacal nitrogen (NH3-N) and color under the following operational conditions: persulfate dosage, tannin dosage, pH and retention time (min). Using persulfate alone, the maximum removal efficiency of COD, color, and NH3-N were 50%, 60% and 22%, respectively by using 4 mL of 0.1 (w/v) persulfate dosage at pH 7 and 60 min retention time. While, the performance of simultaneous reaction improve the removal efficiencies of COD, color, and NH3-N to 90%, 96% and 44%, respectively using 4 mL of 0.1 (w/v) persulfate and 0.06 g of tannin during 120 min retention time at pH 7. However, the maximum removal of NH3-N (59%) was achieved at pH 11. The study revealed that the simultaneous persulfate/tannin reaction is a promising treatment method for industrial wastewater treatment.