7 - Forward Osmosis: A Novel Membrane Separation Technology of Relevance to Food and Related Industries

Abstract

Forward osmosis (FO) is an emerging membrane technology that enables the concentration of liquid streams through the removal of water across a semipermeable membrane driven by the osmotic pressure difference between the liquid feed stream and a draw solution across the membrane. Similar to other membrane-based concentration processes, including reverse osmosis (RO) and nanofiltration, FO is a nonthermal concentration process with minimal impact on the sensorial and nutritional quality of food products. However, FO has several advantages over pressure-driven membrane processes such as RO that make it commercially attractive. These include the following: (1) FO does not require external hydraulic pressure for operation and hence has potential for significant energy saving; (2) FO has lower membrane fouling propensity as the solids are not compressed against the membrane; and (3) unlike RO, FO can potentially be used to achieve the concentration factors typical of evaporation. This chapter discusses FO and its application in food concentration. The studies to date indicate that FO is an economically feasible alternative to evaporation for liquid food concentration. The development of membranes with improved mass transfer performance and economically recoverable draw solutes suitable for food application will further improve the prospect of widespread commercial application of FO in the concentration of food streams.