Assessment of pilot scale forward osmosis system for Arabian Gulf seawater desalination using polyelectrolyte draw solution

The main objective of this study is to assess and validate the feasibility of polyelectrolyte driven forward osmosis (FO) process in actual seawater desalination at pilot scale capacity of 10 m³ d^–1. The pilot scale FO system constructed by Trevi Systems Inc., (USA) was tested at Desalination Research Plant in Kuwait for desalinating beach well seawater. The pilot plant consisted of a commercial scale hollow fiber (HF) FO membrane (bore diameter of 230 μm), ethylene oxide-propylene oxide copolymer with molecular weight of ~2,000 Da as a thermo responsive draw solution (DS), a coalesce tank for the regeneration of DS on thermal separation principle, and nanofiltration membrane processes as a post treatment process. The study revealed that the polyelectrolyte DS had great potential to generate the high osmotic pressure difference at various compartments of the HF module leading to an average water recovery of 30%. Simulation studies revealed that the osmotic pressure difference distribution of polyelectrolyte DS at different sections of the HF module was greatly influenced by DS flow rate. In conclusion, the FO system operation using low grade heat allows the FO system to operate with a lower cost of energy than a reverse osmosis plant.