Performance evaluation of a thermoresponsive polyelectrolyte draw solution in a pilot scale forward osmosis seawater desalination system

Abstract

The current study assesses the technical feasibility of using a thermoresponsive polyelectrolyte draw solution (DS) in a Forward Osmosis (FO) desalination pilot scale system of 10 m3/day capacity. The FO system utilized a commercial spiral wound hollow fiber FO membrane and ethylene oxide-propylene oxide copolymer as DS. This study evaluated the effect of DS flow rate and feed solution flow rates on the net water recovery and product water flow rates of the system. The osmotic pressure distribution of polyelectrolyte DS at different sections of the HF module was greatly influenced by DS flow rate. The study revealed that the DS had great potential to generate the high osmotic pressure (Δπ) difference in the various compartments of the HF module. The reliability of the FO pilot plant was proved over a long run without any severe FO membrane fouling with total dissolved solids of product water at 143 ppm and water recovery of 30%. The selected DS showed its potentiality towards the installation of commercial-scale FO desalination plant by witnessing its low viscosity and easy phase separation at a moderately lower temperature of 85 °C in the coalesce DS regeneration system.