A study on osmotically-driven separation process: preferable membrane configuration

Abstract

Osmotically-driven separation processes, i.e. forward osmosis (FO) and pressure-retarded osmosis (PRO), are potentially applied for wastewater treatment, desalination and energy production. Osmotic pressure difference between two sides of a permeable membrane governs water transport through the membrane. However, the theoretical osmotic pressure is severely suppressed by effect of concentration polarization (CP). This study focused on CP effect on various membrane types in osmotically-driven separation processes. The experimental and modelling results showed that common belief on membrane configuration for FO and PRO (dense active layer facing feed solution (AL-FS) and draw solution (AL-DS), respectively) was limited by FS concentration. At certainly high concentration of FS, AL-DS yielded lower water flux, higher fouling propensity and more difficult cleaning than AL-FS. This study suggests AL-FS as preferable configuration for both FO and PRO in application to real natural water.