Water recovery from reverse osmosis concentrate by commercial nanofiltration membranes: A comparative study

In this work, the potential of three commercial nanofiltration membranes for the treatment of the RO concentrate of Fajr Petrochemical Complex, Iran, was examined. The effect of membrane type (TW30, NE70, and NE90), feed flow rate, and feed pressure on the permeation flux, flux decline, TDS removal, and ion rejections were inves-tigated. The experimental results showed that by increasing the feed pressure and feed flow rate, the rejection and permeation flux were enhanced. Among the studied membranes, the TW30 membrane resulted in the highest TDS removal of 93.4% and water permeability of 2.84 L.m(-2).h(-1).bar(-1) at 10 bar but showed more flux decline than NE90 and NE70. The rejection of calcium, magnesium, and chloride by TW30 membrane was 96.1%, 98.7%, and 90.3%, respectively, and the total hardness was reduced by 96.2%. The NE90 membrane showed also a good TDS removal (88.0%) but it had lower water permeability. The NE70 membrane exhibited the highest water permeability among the studied membranes but the permeate quality was not good and a TDS removal of 24.9% was observed which is not as good as the two other membranes.