Critical flux-based membrane fouling control of forward osmosis: Behavior, sustainability, and reversibility

Abstract

Membrane fouling is closely related to the concept of critical flux. Therefore, a fouling control stategy for forward osmosis (FO) membranes that is based on the critical flux is necessary. This study systematically investigated the critical flux behavior of FO membranes (CTA and PA-TFC) in the short-term using a stepping method (draw solution (DS) concentration stepping). In addition, to test the reliability of this method, long-term experiments were conducted to evaluate the influences of operational critical flux on the fouling behavior (sustainable operation and fouling reversibility/irreversibility), thereby determining the critical flux for reversibility. Our results showed that the DS concentration stepping could be applied for critical flux determination in FO. Both membranes exhibited higher critical flux values for alginate fouling compared to other single foulants such as colloidal silica or gypsum. The values were 15.9 LMH for a cellulose triacetate membrane (CTA) and 20.5 LMH for the polyamide thin-film composite (PA-TFC). Whilst these values should be adequate in FO applications they were determined for single foulants. The presence of multispecies of foulants caused a significant decline in the critical flux values. This study found 5.4 LMH for the CTA membrane and 8.3 LMH for the PA-TFC membrane for the combined foulants of alginate + gypsum. This indicates that the critical flux behavior in FO was dependent on the foulant type and membrane type. Importantly, 98-100% restoration of water flux was achieved with the PA-TFC membrane at an operation either close to or below critical flux (i.e., in case of negligible fouling), except for the combination of alginate-combined colloidal silica. The critical fluxes for reversibility obtained in this study will aid the efficient operation of practical FO processes.

Recent Progresses of Forward Osmosis Membranes Formulation and Design for Wastewater Treatment

“…To make the findings more relevant to their practical applications, fouling related studies should be performed using new FO membranes that can offer high flux and real wastewater with more complex foulant nature. Furthermore, as membrane fouling can be associated to the concept of critical flux, the fouling control strategy that is based on the critical flux behaviors in short-and long terms is necessary [145]. In accordance with the efforts to combat fouling in FO, in-situ real time fouling-monitoring techniques must also be established to gain a better understanding of the mechanism and fouling layer formation on the FO membrane.…”

An empirical determination of the whole-life cost of FO-based open-loop wastewater reclamation technologies

“…1). As with all membrane processes, the FO technology requires amelioration of membrane surface fouling (Nguyen et al, 2019;Siddiqui et al, 2018;Xie et al, 2017). For wastewater reclamation duties a widely accepted state-of-the-art RO pretreatment technology for fouling suppression is the membrane bioreactor (MBR), with a number of pilot and full-scale demonstration studies reported over the past 20 years (Blanco et al, 2016;Côté et al, 1997;De Jager et al, 2014;Dialynas and Diamadopoulos, 2009;Farias et al, 2014;Gündoğdu et al, 2018;Lawrence et al, 2003).…”

Characterization of seawater reverse osmosis fouled membranes from large scale commercial desalination plant

“…Generally, during the formation of fouling layers on the membrane surface can beg and generate the back diffusion of dissolved salt ions which generates an increase in the concentration of salt ions on the side of the membrane surface. Results revealed that the membrane performcae may change due to organic and inorganic matter in water during osmosis process, which needs to tackle by modifying the membrane with advanced material (Anis et al, 2019;Badruzzaman et al, 2019;Croll et al, 2019;Ghaemi and Khodakarami, 2019;Ghaseminezhad et al, 2019;Joseph and Damodaran, 2019;Liu et al, 2019;Nguyen et al, 2019;Rehman et al, 2019;Shakeri et al, 2019;Tang et al, 2019;Weinman et al, 2019;Zou et al, 2019).…”