High linear correlation (R2= 0.964 for GR60PP and R2= 0.989for OT050) between the tap water flux and the TMP (Fig. 2)was found. The slope of the line corresponds to the hydraulic permeability to pure water (Lp), which characterizes the membrane in the filtration process. It was 132.30 L/m2h bar for the OT050, whereas of only 33.52 L/m2h bar for the GR60PP. This can be attributed to the larger porosity of the OT050 membrane, which is 27% higher than that of GR60PP