A composite nanofiltration (NF) membrane was prepared by coating a thin layer of sodium alginate (NaAlg)-polyvinyl alcohol (PVA) blend on the polysulfone support, then cross linked in two steps with calcium chloride and glutaraldehyde respectively. Structural and morphological characteristics of the NF composite membranes were determined by FT-IR and SEM. The performance of the membrane was evaluated in nanofiltration studies, and the effect on performance of experimental parameters including the NaAlg/PVA blend ratio, cross linking reaction time, membrane thickness and operating, time was investigated. The permeance properties of the membrane were determined using 2000 ppm solutions of NaCl and MgSO4. A water flux of 80 L/m(2).h with 46% salt rejection was observed for the monovalent salt solution. However, a decrease in flux to 68 L/m(2) h with an increase in salt rejection to 80% was noticed for the divalent ions. The chlorine tolerance of the composite membrane was tested by exposing it to the NaOCl solution for a different time span. A slight change in water flux and salt rejection was observed, revealing a good stability of the membrane in the chlorine retaining environment. Hence, the prepared binary cross-linked NaAlg/PVA composite membrane can successfully be utilized for the purpose of nanofiltration and/or desalination. (C) 2014 Elsevier B.V. All rights reserved.