Quantitative estimation of internal concentration polarization in a spiral wound forward osmosis membrane module compared to a flat sheet membrane module

Abstract

Internal concentration polarization (ICP) within the forward osmosis (FO) membrane affects the reduction of driving force. The magnitude of ICP in the FO membrane was investigated experimentally by measuring water flux in both spiral wound (SW) and flat-sheet (FS) modules with different draw solutions (sodium chloride, sodium sulfate, and disodium phosphate). The FO SW module always shows inferior water flux performance to the FO FS module. The water flux in the FO SW module can be easily estimated by just changing structure parameter. The estimated structure parameter in the FO SW module is 9.1325x10(-4) m, which is quite higher than 4.2x10(-4) m in the FO FS module. The increase of the structure parameter is attributed to the bending of the FO membrane in the SW module. It can be concluded that a module design such like SW type is not suitable for the FO process.