Comparison of fouling propensity and physical cleaning effect in forward osmosis, reverse osmosis, and membrane distillation

Membrane-based desalination technologies including reverse osmosis (RO), forward osmosis (FO), and membrane distillation (MD) hold promise as efficient methods to produce fresh water from saline water sources. However, the fouling properties of these membranes are quite different due to the difference in the driving forces among them. Accordingly, the objective of this study is to compare fouling behavior and physical cleaning efficiency for these three membranes under similar operating conditions. Colloidal silica and alginate were used as model foulants and NaCl was added to feed solutions. Laboratory-scale experiments were carried out to compare fouling rates and recovery of flux by physical cleaning. Results showed that fouling propensity was the highest in FO membrane and the lowest in MD membrane, which may be attributed to the effect of cake-enhanced concentration polarization. On the other hand, physical cleaning was more efficient to recover flux in FO and RO than in MD, suggesting that the fouling in MD is less reversible than that in FO and RO.