In the last decades, the research done in the field of membrane technology applied to wastewater has drastically increased. However, the applicability of this technology is limited due to the fouling of membranes, directly affecting its performance. In this study, several parameters thought to be in some extent responsible for membrane fouling are evaluated. Ultrafiltration was the selected membrane process and membranes with different molecular weight cut off (MWCO) have been employed. The feed of the experiments consisted of solutions containing humic and fulvic acids, natural organic matter (NOM), alginic acid and cellulose. The influence of different sets of operating parameters, such as applied pressure, concentration of polymer, content of calcium and pH of the feed solution in the performance of the process has been investigated.