An important trend in the development of ultrafiltration (UF) of wastewater effluent is the integration of pretreatment to improve the performance of membranes. In this paper the results of a study on the effect of three prefiltration techniques (multimedia filtration, granulated activated carbon filtration and biological activated carbon filtration) on foulants and performance of UF are presented. The objectives of the study are: ( 1) to establish the different effect of three prefiltration configurations on performance of UF and foulants of wastewater effluent and (2), to determine in which particle size range the most particles or colloidals are removed after the three prefiltration configurations. From all of the filters, the biological granulated activated carbon filter (BGAC) presented the highest increase of filterability. During this study. the specific ultrafiltration resistance (SUR) value of the filtrate is always below 5. 10(12)m(-2) independent on the incoming SUR value. From all the foulants especially the proteins and humic substances are removed by granulated activated carbon filter (GAC) and BGAC. BGAC is the only prefiltration technique that shows significant removal of the fraction between 0.1 mu m and 0.2 mu m. (C) 2009 Elsevier B.V. Ail rights reserved.