The gradual increase of salt concentration (0 to 35 g-NaCl/L) on the performance of membrane bioreactor (MBR) was studied. The uptake rate of dissolved organic carbon and ammonia decreased from around 17.0 mg-DOC/g-MLVSS.d to 1.8 mg-DOC/g-MLVSS.d and from 82 mg-NH4-N/g-MLVSS.d to 0 mg-NH4-N/g-MLVSS.d respectively when salt concentration reached to 35 g-NaCl/L Similarly the specific oxygen uptake rate (SOUR) reduced from 8 to 9 to around 0.3 mg-O-2/g-MLVSS.h. The removal of bio-polymers, humic acids, building blocks and low molecular weight neutral decreased with increase in salt concentration. The concentration of dissolved organic nitrogen (DON) in bio-polymer increased from 0.05 to 3.31 mg/L when the salt concentration reached to 35 g-NaCl/L This study provides good information for understanding the effect of continuous increase of salt concentration in treating saline wastewater in a MBR process. (c) 2013 Elsevier B.V. All rights reserved.