Direct observation (DO) technique allowed the visualisation of fouling deposition and rem oval in rea I time and in a non-invasive manner. The DO setup was relatively simple and featured a crossflow hollow fibre membrane module, a microscope and a video camera, Transmembrane pressure (TMP) and fouling height were observed to characterise in detail the mechanisms of fouling deposition. At the end of the bentonite filtration at crossflow velocity (CFV) of 4 mm/s, the fouling thickness was measured as 85 mu m. Specific cake resistance was calculated by taking into account the cake height measurements with this technique. The DO technique also allowed unique insights into the mechanisms related to the fouling removal. The effect of bentonite concentrations were assessed to provide credibility of the technique.