Integrated membrane techniques nanofiltration/pervaporation for desalination of textile wastewater

The textile industry is a sector that causes significant environmental pollution through the production of polluted wastewater. In this work, desalination tests of wastewater were carried out using a hybrid nanofiltration/pervaporation (NF/PV) system. A model textile wastewater after the dyeing process was prepared and tested at four different NaCl water solution concentrations. The properties of the obtained filtrates and concentrates (pH, conductivity, color and chemical oxygen demand (COD)) for both membrane processes were analyzed. The possibility of textile wastewater treatment using nanofiltration and pervaporation integrated processes using commercial polymer membranes was validated. For comparison, experiments with commercial ultrafiltration membrane in the pre-treatment stage were performed. The performance (permeate flux and resistance) and conductivity reduction were calculated. The hydrophilicity of the membrane surfaces was measured using a method based on contact angle measurements. In the integrated NF/PV processes, each of them was considered separately. The higher the initial salt concentration in the wastewater after NF process, the lower the permeate flux passing through the membrane (62.98 to 300.8 kg/(m(2)center dot h)), degree of conductivity reduction (16% to 48%), color (34% to 99%), and COD (81% to 97%). Fouling and concentration polarization phenomena were observed. The purified NF filtrate was then fed to the PV process for desalting. In PV, the initial various salt concentration in the wastewater did not significantly affect the permeate flux (1.18 to 1.46 kg/(m(2)center dot h)) or the conductivity reduction, which was almost 100% in all cases. The results indicate the potential of integrated NF/PV techniques for desalination of textile wastewater from the dyeing process.