Factors affecting flux performance of forward osmosis systems
Lay, Winson Chee Loong
Tang, Chuyang Y.
Fane, Anthony Gordon
Date of Issue2012
School of Civil and Environmental Engineering
Singapore Membrane Technology Centre
The performance of a forward osmosis (FO) system may be characterised by the assessment parameters: FO–RO flux ratio (Jw/Jw(RO)), apparent FO water permeability (Jw/(πds − πml)), and the newly developed flux efficiency factor (Jw,ob/Jw,re). The former two parameters offer information on extent of internal concentration polarisation and driving force utilisation, respectively. The Jw,ob/Jw,re factor has practical relevance, and reveals the inevitable trade-off between flux and recovery (φ) for a FO system. The derived Jw,ob/Jw,re factors corresponded well to experimental observations. High water permeability, low salt-to-water permeability ratio, and large mass transfer coefficient improve the performance of a FO system, but these may also be influenced by operational and fouling effects, such as draw solute transmission, fouling resistance and cake-enhanced concentration polarisation. It was shown that membrane properties also play a significant role in fouling behaviour. Fouling amelioration factors include aeration and osmotic backwash. A thin-film composite membrane showed potential for FO application with favourable intrinsic transport parameters. It was demonstrated that a FO system could achieve stable water production with both relatively high flux efficiency (Jw,ob/Jw,re = 0.8) and high recovery (φ = 95.8%), which attested to the technology potential.
DRNTU::Engineering::Civil engineering::Water resources
Journal of membrane science