Treatment of dye-producing chemical industry wastewater by persulfate advanced oxidation

Abstract

A dye-producing chemical industry wastewater in Çorlu (Tekirdağ) is treated by the coagulation-flocculation process of the wastewater. However, the wastewater discharged after coagulation-flocculation still has a very high COD (4402 mg L-1) with very high proportion of dissolved COD (4316 mg L-1). Therefore, the aim of this study is to achieve higher COD and color removal in wastewater using Fe2+/S2O8 or UV/S2O8 oxidation process after coagulation-flocculation. The processes in the oxidation of this industrial wastewater using Fe2+/S2O8 and UV/S2O8 were examined and the effect of COD/Fe2+/S2O8 ratio (in Fe2+/S2O8) or COD/S2O8 ratio (in UV/S2O8), pH and oxidation time were evaluated in the study. While high organic matter and color removal was observed in acidic conditions for both processes, optimum pH were 3 and 6 in Fe2+/S2O8 and UV/S2O8 oxidation processes, respectively. In Fe2+/S2O8 oxidation, 61.1% of COD removal and above 97% of color (UV436, UV525 and UV620) removal was obtained at 1/8/8 of COD/Fe2+/S2O8 ratio and pH 3 after 1 h oxidation. In UV/S2O8 oxidation (COD/S2O8 ratio 1/8, pH 6), 54.4% of COD and 98% of color (UV436, UV525 and UV620) removals were achieved after 4 h oxidation. As a result, both Fe2+/S2O8 and UV/S2O8 oxidation processes were applied to ensure discharge standards for color removal from this chemical industry wastewater are effective methods as they provide over 97% color removal. Moreover, COD removal efficiency was approximately 55-60% in both methods.