The aim of this study was to evaluate the potential use of ozone integrated with a microtiltration (MF) process, focusing on the role of ozone in reducing the membrane fouling caused by dissolved organic matter. In this study, several pharmaceuticals, including Ibuprofen (IB), Bezafibrate (BZ), Amoxicillin (AM) and Sulfamethoxazole (SMX), were tested as model foulants. The mechanism of fouling of these compounds in the tested MF was found to be adequately predicted by the adsorptive fouling model rather than any other of the classical fouling models. In the ozone-MF hybrid experiments, the pre-ozonation was able to reduce the membrane fouling due to: (1) the preventive effect of the ozone destruction of the pharmaceuticals in the aqueous phase prior to foulant accumulation on MF, and (2) the treatability of a fouled membrane with ozone. The ozone-MF hybrid mode of operation effectively suppressed increases in the transmembrane pressure (TMP), yielding a two-fold lower TMP value after 20 h of filtration with an ozone dose of 4.8 mg/L, compared to the increase in the TMP observed in the MF process alone. It was also found that the adsorptive fouling onto the membrane could be totally attributed to the test pharmaceutical, IB, and not to the by-products formed during its ozonation. In this study, the performance of the MF-postozone hybrid scheme was also investigated from two perspectives; measuring of the changes in both the O-3-Ct and (OH)-O-.-Ct values after the MF process. Higher O-3-Ct values were observed, which are favorable conditions from a disinfection perspective. However, lower (OH)-O-.-Ct values, which are negative from an oxidative standpoint, were observed in the MF-postozone hybrid. (c) 2006 Elsevier B.V. All rights reserved.