Nanofiltration of textile industry wastewater using a physicochemical process as a pre-treatment

The main environmental problem of textile industries is the high water consumption for their processes. Thus it is very important to reuse wastewater, especially in areas with a water scarcity such as Comunidad Valenciana (Spain). The goal of this work is wastewater reuse combining chemical neutralization, physicochemical treatment and membranes. Neutralization studies were conducted in order to select the most appropriate neutralizing agent in terms of conductivity of the neutralized wastewater. For the physicochemical treatment four coagulants from the Cibaâ Company (Mangasol 5389, Mangasol 6348, Zetag 7103 and Alcyl 955) were compared by carrying out jar tests using different concentrations and pH values. The experimental tests were made according to the statistics program Statgraphics. After that, nanofiltration experiments of the physicochemically treated wastewater were performed in a laboratory plant equipped with a pressure vessel containing one spiral-wound membrane element (A = 2.51 m2). The operating conditions were: transmembrane pressure of 20 bar, cross-flow velocity of 1.66 m/s and a temperature of 25°C. The membrane tested was the Desal DK2540 from Osmonics. Physicochemical experiments showed that the Zetag 7130 coagulant achieved higher reductions in COD and turbidity. In addition, the sludge volume was lower than 100 mL/L. NF experiments showed that permeates, COD and conductivity were around 100 mg/L and 1000 μS/cm, respectively, with a volume concentration factor of 2.5. As a result, the combination of physicochemical treatment and nanofiltration provided treated water with good enough quality to be reused in the industry.