Fouling Study of Cellulose Triacetate and New Generation Thin-Film Composite Forward Osmosis Membranes

A leader in forward osmosis (FO) technology, Hydration Technology Innovations, LLC (HTI) has recently developed a new generation high-performance thin-film composite (TFC) FO membrane. The TFC FO membrane has high flux (>20 lmh), low reverse salt transfer (<200 mg/l), and can be used for extreme pH conditions (2-12). As a next step, a systematic study of fouling and cleaning behavior of FO membranes is of paramount importance to take FO technology to the next stage of real-world water purification and water desalination applications. This study investigates the fouling and cleaning behavior of HTI’s cellulose triacetate (CTA) and new generation high flux and antifouling TFC FO membranes. Results of several model foulants will be presented including, oil-water emulsion, bovine serum albumin, alginate with calcium ions, humic acid with calcium ions, and bentonite clay. The study was also extended to see if the coexistence of all the model foulants has a more profound effect on flux decline as opposed to the presence of individual foulants. Effect of membrane orientation (FO/PRO mode) and initial permeate flux (hydrodynamic conditions) on characteristic fouling behavior of membranes was also analyzed critically. Osmotic backwashing was used to clean the membranes after fouling and the flux recovery for each of the model foulants is also presented in this study. Atomic force microscopy was used to characterize surface morphology and estimate surface roughness of CTA and TFC FO membranes in order to elucidate foulant-membrane interactions. Overall findings of this investigation showed that HTI’s new generation TFC membrane has slightly better fouling resistance performance compared to CTA which has already been recognized by independent research laboratories and industry for its good antifouling properties.