Studies were performed to determine the effect of the presence of powdered activated carbon (PAC) on ultrafiltration (UF) process performance. The influence of PAC addition to the feed on permeate flux in terms of flux decline and the possibilities of membrane cleaning during backwashing were investigated. The effectiveness of the removal of organic contaminants from the Miedwie Lake water during UF and hybrid processes of adsorption on PAC-ultrafiltration (PAC/IJF) were determined. Fourier transform infrared (FTIR) spectroscopy was applied in order to examine the character of membrane foulants. Polyacrylonitrile (PAN) membranes formed by the phase inversion technique were used in the UF experiments. Commercial PAC CWZ 30 was applied as the adsorbent. PAC dosage was equal to 100 mg PAC 1(-1). The process was carried out in the cross-flow system. The experiments were performed at two different pH values (8.7 and 6.5) of the treated water. It was found that the combination of UF and adsorption on PAC was more effective in organics removal than UF alone. The treatment was more efficient at pH 8.7 than at pH 6.5. At both pH values, no significant effect of PAC addition to the feed on the permeate flux was observed. On the basis of the FTIR spectra, it was found that the foulants of the PAN membrane present in Miedwie Lake water were primarily silicates.