Rejection of Trace Organic Pollutants With High Pressure Membranes (NF/RO) A.R.D. Verliefde, a * S.G.J. Heijman, a,b E.R. Cornelissen, b G.L. Amy, c B. Van der Bruggen, d and J.C. van Dijk a a Department of Sanitary Engineering, Delft University of Technology, Faculty of Civil Engineering and Geosciences, The Netherlands; a.r.d.verliefde@tudelft.nl (for correspondence) b Kiwa Water Research, Nieuwegein, The Netherlands c UNESCO-IHE, The Netherlands d Department of Chemical Engineering, Laboratory for Applied Physical Chemistry and Environmental Technology, University of Leuven, Belgium Published online 12 May 2008 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ep.10272 This article presents a modeling approach for the rejection of trace organic pollutants in high-pressure membranes. The rejection values of uncharged or- ganic solutes with a wide range of solute size and hydrophobicity are determined. Sigmoidal rejection curves are constructed and modeled for solutes of dif- ferent hydrophobicity. The model is based on a log- normal pore size distribution model. A model is also presented to model the rejection of charged organic solutes, based on the rejection of uncharged solutes and the concept of a ‘‘charge concentration polariza- tion.’’ Moreover, scale-up issues arising when trans- lating results from bench-scale units to full-scale plants are addressed, by assessing the viability of a full-scale rejection model. The full-scale model is based on a convection-diffusion model for the trans- port of organic solutes through the high-pressure membranes and the use of mass balances in the system. Ó 2008 American Institute of Chemical Engineers Environ Prog, 27: 180–188, 2008 Keywords: rejection, reverse osmosis, nanofiltra- tion, organic micropollutants INTRODUCTION The issue of trace organic pollutants in the envi- ronment has drawn attention of an increasing number of research organizations and water utilities all over the world. The ever increasing demand and con- sumption of industrial chemicals, pesticides, but also of pharmaceuticals, combined with an incomplete use, or incomplete metabolism in the human body, have led to increasing concentrations of these pollu- tants in wastewater effluents and associated receiving surface waters [1]. Since health effects, related to the consumption of drinking water polluted with traces of organic pollutants are yet to be clarified [2], cau- tion is urged and the water utilities prefer removal of these pollutants in the treatment. In contrast to classi- cal treatment techniques, more innovative techniques such as membrane filtration, may offer very good opportunities for the removal of trace organic solutes [3], especially since the average molecular weight of the bulk of trace organic solutes coincides with the molecular weight cut-off of nanofiltration (NF) and reverse osmosis (RO) membranes (e.g., around 200– 300 g/mol). Removal of trace organic solutes with high pres- sure membranes has received special attention in recent literature. Most studies focus on the interac- tions of solutes and membranes which lead to the eventual removal of the solute. However, all ap- proaches up until now have been quite empiric in nature, and there is still a need for good models that are able to describe the phenomena related to organ- ics rejection and can predict rejection on full-scale installations. Ó 2008 American Institute of Chemical Engineers 180 July 2008 Environmental Progress (Vol.27, No.2) DOI 10.1002/ep