REJECTION OF EMERGING ORGANIC MICROPOLLUTANTS IN NANOFILTRATION/REVERSE OSMOSIS MEMBRANE APPLICATIONS

This study aimed to investigate factors affecting the rejection of emerging trace organics by a variety of commercial reverse osmosis (RO), nanofiltration (NF), and ultra-low pressure RO membranes during laboratory-scale experiments. Findings of this study indicated that rejection of negatively charged organics was driven by a combination of steric and electrostatic exclusion, which was independent of feed water recovery but affected by the presence of effluent organic matter (EfOM). Feed water recovery or EfOM did not affect the rejection of hydrophilic non-ionic solutes and removal was only driven by steric exclusion. Hydrophobic non-ionic compounds exhibited a high initial rejection due to hydrophobic/hydrophobic interactions and steric exclusion but rejection decreased significantly after 5 hours of operation due to partitioning of solutes through the membrane. Findings of this study imply that ULPRO and NF membranes, operated at lower feed pressure, perform similar to conventional RO membranes in removing trace organics of interest.