The Effect of Osmotic Dehydration on Reverse Osmosis Membrane Performance

Akin type (asymmetric) reverse osmosis membranes undergo an irreversible osmotic dehydration upon coming into contact (skin side) with salt solutions. The extent of consequent changes (in appearance; decrease in linear dimension, water flux and salt rejection) are dependent on the salt concentration. These observations are correlated with the expected morphological changes taking place during dehydration (drying). It is thus speculated that such phenomena may inadvertently happen during the start-up phase of new RO units treating high salinity waters. To avert such event, it is recommended the start-up phase to be programmed in such a way that feed concentration is gradually elevated to its ultimate level.