Enhancing permeate flux in a RO plant by controlling membrane fouling

Concentration polarization near the membrane surface increases local trans-membrane osmotic pressure and solute passage. It is governed by solute properties, membrane properties and hydrodynamics. Increasing the feed velocity confines the affected area to a thinner layer and usually results in reducing membrane fouling and scaling phenomena. Higher feed velocity reduces scaling and fouling. The results of fouling control by changing softening process from lime to caustic regime have been outlined in this work in the reverse osmosis (RO) units that treat brackish water for producing 400 m3/h industrial water. Performances of these RO units were not satisfactory for many months due to high tendency in membrane fouling even following the recommendations of membrane supplier. Therefore, a new softening method has been applied successfully for enhancing the RO plant performance. This improvement in performance of RO units clearly justifies the importance of softening regime as a key parameter in fouling control.