Abstract A hybrid process, consisting of ozonation and membrane filtration, was studied for the treatment of surface water or low-contaminated process wastewater. The main focus of this study centres on tests to determine the effect of ozone on membrane fouling during microfiltration and ultrafiltration. In this work, ceramic membranes with pore sizes in the range of 0.2 μm to a cut-off of 1 kD underwent lab-scale tests using model bentonite and humic acid solutions. Results showed that, by adding ozone during microfiltration and ultrafiltration of the humic acid solutions, membrane fouling for all membranes could be greatly reduced, thus obviating the need to backflush or clean the membranes. As for the bentonite solutions however, membrane fouling, which was caused by deposits of suspended inorganic substances, was not affected to any great extent by the addition of ozone. Microporous membranes with a pore size in the range of 10–50 nm proved to be the best possible option for this hybrid process.