The following pages report the evaluation of Nanofiltration (NF) and Ultrafiltration (UF) membrane filters experiment at Gaddvik drinking water plant, Luleå (Sweden).Recently, concepts of direct use of membrane technology, a minimized process for the treatment of surface waters to portable water: have aroused more and more interest. In Gaddvik drinking water plant experiments with this technology were carried out, UF membrane filter and NF membrane filter were used. In the pilot plant experiments were also investigated the effect of filtration on the membrane fouling and the removal efficiency of natural dissolved organic matter in which the turbidity values of the well water before and after the filter membranes were 0.5 NTU and 0.05 NTU respectively. It is observed that filtration prior to membrane filtration process decreased the membrane fouling problems and increased the removal efficiency of natural dissolved organic matter.