Flat sheet submerged membranes coupled with it membrane bioreactor (MBR) have been run for 200 days to evaluate membrane performance during wastewater treatment. The chlorinated poly(vinylchloride) (CPVC) membranes prepared in this study have different characteristics such as the degree of hydrophobicity or hydrophilicity and different pore sizes. Poly(vinylpyrrolidinone) (PVP) was used as the pore-forming agent and to increase the wettability of the surface. A relatively hydrophilic membrane (CCP-2) showed the characteristics of high flux, low transmembrane pressure (TMP), and low membrane filtration index (MFI) in comparison with a hydrophobic membrane (CP-2). The hydrophilic membrane (CCP-2) showed a better recovery efficiency in a pure-water flux than that of the others owing to the hydrophilized surface characteristics as well as large pore sizes. These results suggest that useful reduction in membrane fouling can be achieved by the control of pore size using PVP as well as induction of hydrophilicity on the membrane surface by chemical cross-linking. Consequently, it was considered from the results of water flux and removal efficiency that the introduction of hydrophilic polymer to membrane effectively improved final membrane performance. CCP-2 membrane (1.15 mum, crosslinked by PVP) showed the best performance possible for use in actual MBR application.