About Project

Forward osmosis (FO) is an osmotic process that, like reverse osmosis (RO), uses a semi-permeable membrane to effect separation of water from dissolved solutes. The driving force for this separation is an osmotic pressure gradient, such that a “draw” solution of high concentration (relative to that of the feed solution), is used to induce a net flow of water through the membrane into the draw solution, thus effectively separating the feed water from its solutes. In contrast, the reverse osmosis process uses hydraulic pressure as the driving force for separation, which serves to counteract the osmotic pressure gradient that would otherwise favor water flux from the permeate to the feed. Hence significantly more energy is required for reverse osmosis compared to forward osmosis.

In the past decade, FO has attracted growing interest in wastew-ater treatment, seawater/brackish desalination, food processing and power generation. FO is an osmotically driven membrane process that takes advantage of the osmotic pressure gradient to drive water across the semiperme-able membrane from the feed solution (low osmotic pressure) side to the draw solution (high osmotic pressure) side. Due to the very low hydraulic pressure required, FO delivers many potential advan-tages such as less energy input, lower fouling tendency, easier fouling removal and higher water recovery over pressure-driven processes like reverse osmosis (RO), nanofiltration (NF) and ultrafiltration (UF).

Although osmotically driven membrane processes have been widely suggested and investigated in a variety of applications, FO is still facing some critical challenges. These challenges relate to the following aspets: concentration polarization, membrane fouling, reverse solute diffusion, and the need for memebrane development and the design of the draw solute. A recent study has indicated that both concentration polarization and reverse solute diffusion are the limiting factors in power genneration from salinity gradients by Presure Retarded Osmosis.