The effect of transmembrane pressure (TMP) on flux decline and protein retention due to concentration polarization and fouling resistances have been investigated.UF experiments were carried out using a pilot plant unit equipped with spiral wound module and polysulfonamide UF membrane.A three-stage experimental strategy based on an resistance-in-series model (boundary layer-adsorption) was used to seperately determine the hydraulic membrane resistance,concentration polarization and fouling resistances. The results showed that increasing TMP had no effect on initial flux reduction (Jrt), but flux decline in each TMP was greatly due to concentration polarization, and fouling had small role in flux decline. Dynamic response of flux proved that increasing Jrt during operation is due to fouling. The influence of TMP on resistances showed that total hydraulic resistance and reversible fouling resistance were increased with increasing TMP, but Intrinsic membrane resistance and irreversible fouling resistance did not change. Increasing the total hydraulic resistance with time was resulted to increasing both reversible and irreversible fouling resistances. Increasing TMP or operation time had no signifieant effect on protein retention and it only led to an increase about 1-4 percent.

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