Evaluating the performance of low-energy feed forward osmosis system for desalination using impaired and saline water sources

Abstract

Forward Osmosis (FO) is a natural process of treating water or wastewater due to the difference in osmotic pressures. FO is a membrane separation technology, applicable to food processing, industrial wastewater treatment and seawater or brackish water desalination. The phenomena of FO processes occur whereby water molecules are driven across a semipermeable membrane by an osmotic pressure gradient that is generated from a higher concentrate draw solution. FO processes can recover potable water resources from wastewater streams through the flow of pure water from a lower concentrated feed solution towards higher concentrated draw solutions leaving behind pollutants, impurities, and salts in the semi-permeable membrane. This paper assesses the design, build and testing of a laboratory scaled Feed Forward Osmosis (FFO) system for treating river water collected from the River Medway, Kent, England. The FO process was a highly effective form of river water treatment and able to treat the River Water with high rejection rates of solutes (>90%). Experimental results showed that the FFO system can achieve a better performance when the molarity of the draw solution is higher. The average solute rejection rate of the FO membrane for both inorganic and organic compounds was 94.83 %. Moreover, the operation of the forward osmosis membrane illustrated that it has a lower fouling propensity and higher solute rejection capabilities. The pilot scaled FFO system has the ability for greater salt rejection and lower electronic conductivity levels which resulted from the successful desalination of river water. A sodium chloride (NaCl) or saltwater draw solution performed positively in inducing higher osmotic pressures with a substantial effect of lower energy requirements for the system. Lower energy consumptions of the FFO system allow similar water treatment possibilities with energy savings potential. The FFO system showed to be an environmentally viable and economically feasible river water treatment technology.