The influence of natural organic matter (NOM) fouling on the rejection of micro pollutants in nanofiltration (NF) and the adsorption during granular activated carbon (GAC) filtration is investigated for a diverse group of pharmaceuticals. These pharmaceuticals were first spiked in feed waters filtered through a virgin NF-membrane and a corresponding NOM fouled membrane. The differences in rejection were never larger than 5%. The rejection of the negatively charged molecules on the fouled membrane slightly decreased and the rejection of the positively charged molecules slightly increased. These trends can be explained by a decrease of the repulsion of negative compounds and a decrease of the attraction of positive compounds by the fouled membrane. The sequential combination of NF and GAC was very effective in removing all types of pharmaceuticals. Compounds not well rejected by nanofiltration were more readily adsorbed by the GAC.

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