Conventional wastewater treatment plants are mainly based on biological treatment technologies that do not suit for the removal of some organic pollutants in cold climate regions. Therefore, the research on complementary or post-treatment technologies such as advanced oxidation processes (AOPs) is important. AOPs are mainly based on the generation of hydroxyl and sulfate radicals for further oxidation of the pollutants. In this work, the sources of the sulfate radicals such as potassium persulfate (K2S2O8), sodium persulfate (Na2S2O8), and ammonium persulfate ((NH4)2S2O8) were compared in term of the total organic carbon (TOC) removal from the synthetic wastewater at low temperature. For this purpose, a three-level Box-Behnken design (BBD) in conjunction with the response surface methodology has been used. UV irradiation at 254 nm, the reaction time of 120 min, and Fe2+ dosage at 10 mg/L were used as hold values. According to the analysis of variance (ANOVA), the BBD-RSM models for TOC removal showed significant regression coefficients (R2 = 0.9753, adjusted-R2 = 0.9309, and predicted-R2 = 0.6221). Pareto chart indicated that the concentration of the ammonium persulfate was the most significant factor at 12 °C.