Polyacrylonitrile (PAN)-based hollow fiber membranes incorporated with graft copolymers beating hydrophilic polyvinyl alcohol (PVA) and PAN segments were developed for the treatment of heavily polluted natural rubber (NR) effluent via direct ultrafiltration (UF) process. The effects of the copolymer addition on the membrane properties were studied systematically. Their separation and anti-fouling performances were firstly tested using the solutions of various proteins such as bovine serum albumin, albumin from chicken egg and trypsin as model foulants. The membranes were further tested for the UF treatment of real NR effluent collected from a local latex concentrate industry. The experimental results indicate that the membrane properties, in particular pore size and pore size distribution are the dominant factors influencing the UF performance and fouling resistance during protein and NR filtrations. The best anti-fouling membrane achieved the highest flux recovery of 84% (after first NR filtration cycle) and 76% (after second NR filtration cycle) by simple hydraulic cleansing. With respect to organic and inorganic pollutant reduction, all the membranes showed remarkable performance in reducing turbidity (>99%) and color (>97%). Reduction percentages of 68-70% (total proteins), 29-38% (COD), 14-32% (TOC), 8-11% (TDS) and 7-8% (conductivity) could be achieved, depending on the membrane properties. (C) 2014 Elsevier B.V. All rights reserved.