A multifunctional application of membrane filtration offers good possibilities to produce high quality drinking water. To implement and design membrane filtration installations for this multifunctional approach, intensive bench and pilot scale studies are necessary. A simplified model is developed to translate the data from these bench and pilot scale studies to full scale. Moreover, modeling of the operation of the membrane filtration gives more insight into the operation of an installation and can be used for optimizing and predicting the plant performance. In this paper a simplified model is developed and verified with chloride and DNOC rejections of two pilot plants. In both situations a good prediction of the permeate concentrations was found. One of the purposes of the membrane filtration in the multifunctional approach is the removal of organic micropollutants. Because of the large number of different compounds which can be present in the raw water, the determination of their individual rejection is impossible. Therefore it is necessary to develop a model to predict the rejection of the organic micropollutants. The data presented in this paper, as well as data from literature, indicate a major influence of the physicochemical properties of the membrane materials and the solutes, and that modeling of the rejections is possible.