Desalination, 2nd Edition

Chapter 5Forward Osmosis

Jeffrey McCutcheon, Lingling Xia and Nhu-Ngoc Bui

University of Connecticut, Department of Chemical & Biomolecular Engineering, Center for Environmental Sciences and Engineering

Abstract

Forward osmosis (FO) is an emerging desalination technology that has garnered an increasing amount of attention in recent years. In FO, water is driven across a semi-permeable membrane by an osmotic pressure gradient that is generated by a draw solution. The membrane rejects dissolved contaminants, much like they are in reverse osmosis. The draw solution is comprised of highly soluble solutes that are easily removed and reused in the process. When designed with an appropriate membrane and draw solution, FO promises to enable low cost desalination with improved recovery and fouling resistance. The road to commercialization still contains a number of technical hurdles. Membranes must be designed specifically for FO while retaining the high permselectivity of conventional reverse osmosis membranes. Draw solutes must be designed for high solubility, easy removal, and low toxicity. These challenges, while considerable, have not deterred a substantial worldwide research effort on forward osmosis. Commercialization of FO hinges on continued work in these area while eventual successful demonstration on the pilot scale will secure FO in its place among conventional desalination technologies.

Keywords: Forward osmosis, membrane, draw solution, low cost desalination

5.1 The Limitations ...