The performance of forward osmosis process in treating the surfactant wastewater: The rejection of surfactant, water flux and physical cleaning effectiveness

In this study, the rejection of surfactant (sodium dodecyl benzene sulfonate, SDBS) was investigated at different feed solution (FS) chemistries (ionic strengths and SDBS concentrations, with and without the presence of organic foulants BSA and Alg-Na), temperatures and flow velocities in the forward osmosis (FO) process. SDBS rejection increased with the increase of flow velocity and the decrease of temperature and SDBS concentration; while it had no obvious change with the increasing FS ionic strength. SDBS rejection of FO membrane was high (more than 99.77%), mainly due to the size exclusion. Moreover, the water flux and effectiveness of physical cleaning were also measured. SDBS impacted water flux by two ways: one was the positive role that SDBS micelles enhanced the hydrophilia of membrane; the other one was the negative role that SDBS formed a gel cake layer and increase the resistance. The membrane fouling caused by Alg-Na increased solute rejection and water flux in the FO mode, which was beneficial to the total membrane process. Though BSA fouling increased solute rejection in the PRO mode, it declined water flux, and caused a severe pore blocking which was hard to remove just by the simple rinse.