Low pressure membrane filtration processes are increasingly competing against conventional Surface water treatment plants. In comparison with conventional processes, UF technology has many advantages, but it is also important that a kind of membrane is Suitably selected and operated. In this paper, a pilot plant study on a polyvinylchloride ultrafiltration (MWCO of 80 kD) hollow fiber membrane process was performed for the treatment of surface water. The new membrane had an optimized pore size distribution over membrane thickness while membrane material and fiber dimensions remained the same, the modification resulted in a much higher pure water flux (160 l/(m(2) h bar) at 20 degrees C). The membrane system was operated in the dead-end filtration modes with different constant permeate fluxes. The results showed that the permeate quality was stable, regardless of different surface water for a long duration of filtration. The transmembrane pressure Should be operated in less than I bar to avoid irreversible fouling. Treating cold raw water below 5 degrees C in constant pressure operation mode was better than in constant permeate flux.