Experimental study of a cellulose triacetate spiral wound forward osmosis membrane for desalination process integration

This paper aimed at assessing the feasibility of the forward osmosis (FO) membrane process step of the FO desalination process, on a laboratory bench-scale test unit using batch mode, for extracting freshwater from feed and simultaneously diluting draw solution (DS). A commercially available spiral wound FO membrane made of cellulose triacetate (CTA) was experimentally tested at different operating conditions. Several affecting parameters, namely, feed concentration, draw solute concentrations, flow rate, and temperature, on water flux and permeate water recovery ratio were investigated. Deionized (DI) water, sodium chloride (NaCl) solutions, Gulf seawater and reverse osmosis (RO) brine were used as feed solutions (FS). Different concentrations of NaCl solutions ranging from 3.5 to 26 wt% were used and tested as DS. The results showed that the water flux increased with increasing DS osmotic pressure. The experimental results indicated that the water flux is dependent on the temperatures of FS and DS. It was observed that the water flux is directly proportional to the temperature of the FS and DS. The experimental results were highly encouraging, and proved that the FO membrane stage could be an efficient desalination system component for either desalting seawater or concentrating highly saline waters including RO brine.