In this study, the effect of metal oxide particle distribution pattern on the performance and physical characteristics of 0.03, 0.05 and 0.1 Al 2 O 3 /PES and ZrO 2 /PES composite membranes was investigated. Membrane morphology was characterized by field-emission scanning electron microscopy (FESEM) and the metal oxides particles distribution patterns were determined using Image J software (U.S. National Institutes of Health, Bethesda, MD, USA). The prepared metal oxides/PES membranes were skin-type membranes and showed a structural change from finger-to sponge-type structure. The finger structure was associated with high metal oxides percentage of the total metal oxide particles entrapped in the membrane (60-95% and 52-100% for Al 2 O 3 /PES and ZrO 2 /PES, respectively) in the membrane matrix. No statistical correlations have been observed between either the particles densities at the 0-10 or 10-20 m depths and membrane physical characteristics or performance parameters. However, strong inverse correlations were observed between the metal oxides particles densities at the membranes depths of 30-40 and 40-50 m, respectively, and membrane fouling resistances (R f ). According to the constant pressure models, the experimental results for sludge filtration using all tested membranes were in good agreement with the standard blocking model (SBM).