Porous and fractal analysis on the permeability of nanofiltration membranes was investigated for the removal of metal ions. The permeability of a porous membranes used in wastewater treatment is strongly depended on its local geometry and connectivity, the size distribution of the pores available for flow. Fouling studies with two different membranes at three different pHs were carried out with manganese and magnesium. It was shown that the tighter membrane was less rougher and less fouled compared with the rougher membrane. NF90-2450 showed the highest degree of fouling. The X-ray diffraction showed that NF90-2540 consist of a pronounced diamond at the angle of 45 A degrees C which was responsible for porosity. The threshold images were obtained from the scanning electron microscopy images with the use of Image J software confirmed that NF90-2540 has higher percentage porosity when compared with the percentage porosity of NF1540-3. An evaluation of the relationships between porosity and permeability for the fractal analysis by a box counting was done. The evaluation also confirmed that the lower fractal dimension corresponds to a lower value of porosity. The higher the pH, the lower the fractal dimension of the used membranes due to the blockage of pores. A higher value of fractal dimension of the used membrane at a lower pH corresponds to a lower rejection of the metal ions.