LAUSR

Abstract Glauber salt (sodium sulfate decahydrate, Na2SO4·10H2O) is presented as a viable draw solute in forward osmosis (FO) process for dewatering of textile wastewater and brackish water. A widely available, commercial, low cost ultra low pressure reverse osmosis membrane is used in a bench scale FO unit. Water flux of 7 L m−2 h−1, 4.3 L m−2 h−1 and 5.3 L m−2 h−1 were obtained with DI water, synthetic wastewater and industrial wastewater feed solution using 1.5 M Na2SO4 draw solution. Desalination of brackish water (0.25 NaCl) and sea water (0.6 M NaCl) yielded water flux of 4.5 L m−2 h−1 and 2.6 L m−2 h−1 respectively. A minimal reverse salt flux of 0.42 g m−2 h−1 was attained with 1 M Na2SO4 draw solution against DI feed water. The diffusion coefficient for the FO process was determined to be 0.8 × 10-9 m2 s−1 and the membrane solute resistivity value was 1.25 × 107 s m−1. Reversible fouling caused by scattered and non-uniform loose deposition of particles at the membrane surface was observed which was easily cleaned and 90% water flux could be restored. Recovery of draw solute was attempted by low pressure nanofiltration process using less energy. Good quality permeate containing negligible salt (