The experiments were performed in a laboratory-scale cross-flow membrane system (Fig. 1) using synthetic waste-water as a model for tanning effluent. The operation time was 250 min. The feed solution (5 L) was pumped to the UF cell by a piston pump (Interpump Fe-5102 Model) and the operating pressure was controlled by regulating valve. Assays were carried out at two different transmembrane pressures (TMP):2.5 bar and 5 bar. The UF cell used was rectangular and flat,made of stainless steel, with membrane effective surface of 0.004 m2. The retentate stream was recycled to the feed tank,while the permeate stream was collected separately and not recirculated to the storage vessel. The UF was carried out until the retentate volume was minimum and the volume of accumulated permeate was close to 200 mL (the volume reduction factor was closed to one). The sampling was conducted in the feed tank and permeate flux stream.