Treatment of leather industry process wastewater by coagulation, UV/PS and nanofiltration method

The leather industry produces wastewater with a high level of pollution due to the production process steps. Proteins, oil, chromium compounds, lime, sodium sulphate and sodium hydroxide contained in it are among the most important pollution parameters. In this study, the wastewater from the washing, pickling and degreasing units in the three stages of the leather industry was studied. After precipitation with alum, pollution removal with persulfate (UV/PS) and nanofiltration as the last step of these wastewaters were analyzed. Optimum amounts were determined by comparing with the COD results. In order to recover the wastewater, first of all, precipitation with alum was performed to determine the optimum preferred alum concentration of 100 mg/L and pH 7. In UV/PS oxidation studies, 8000 mg/L S2O8 concentration and pH 8 for Washing unit wastewater and 16000 mg/L S2O8 concentration and pH 6 for Degreasing unit wastewater were selected as optimum. UV/PS oxidation inefficiency observed for the Pickling unit wastewater. A comparison of COD removal at different pHs was made using the nanofiltration system and the NP030 filter under 4 bar pressure. The best COD removal efficiency was obtained at pH 7 in the washing and degreasing units. As a result, it has been observed that the wastewater generated in the Washing and Degreasing units during leather production can be recovered by coagulation, UV/PS and nanofiltration system.