Fouling behaviour in forward osmosis and preliminary comparison with reverse osmosis

The aim of this thesis project is to investigate the fouling behavior for the emerging forward osmosis membrane technology and for the well-established reverse osmosis process. Fouling is caused by the attachment of compounds onto the membrane. A better understanding of the mechanism of fouling is important because this phenomenon represents a severe hurdle in membrane filtration. A set of experimental tests were run with two lab scale set up filtration plants, using the same conditions in RO and in FO. The effect of the feed water composition and of initial flux was significant on the flux decline due to fouling of organic molecules. Also, nature and behavior of the draw solution is important; a draw solution with low reverse solute diffusion should be chosen, because its effect can be significant on the FO performance. Overall, the results imply that further improvements of this novel technology are needed to reach a full-scale implementation of FO and that, as it stands today, FO is not necessarily characterized by worse fouling behavior than RO.