Effect of forward osmosis (Membrane) support layer fouling by organic matter in synthetic seawater solution

Recently, the forward osmosis (FO) process has received considerable attention because it has lower fouling characteristics compared to the generally high-pressure process, reverse osmosis. Most studies concerning the FO process focus on the active layer, the upper side of the FO membrane. However, a study reporting the support layer has a negative influence on active layer fouling was insignificant. Therefore, our study investigates the effects of organic matter, such as humic acid (HA) and sodium alginate (SA) in draw solution, in conjunction with synthetic seawater containing divalent ions, like Ca²⁺ and Mg²⁺ on the support layer. Furthermore, we investigate the effects of the supplemented synthetic seawater on support layer fouling when the spacer is present on the draw solution side, contacting the support layer membrane surface. This assemblage mitigates the internal concentration polarization increasing an effective osmotic pressure. Using 500 ppm of organic matter in the draw solution, such as HA and SA, results in an increased water flux reduction rate, 43–45%, respectively, and further increased water flux reduction rate by 49.5 and 48%, respectively, with the spacer. The water flux reduction rate using HA is increased without a spacer compared to SA; however, in the presence of the spacer, the results are the reverse. As a result, excessively high concentrations of organic matter (500 ppm) influence membrane fouling. Placing a spacer in contact with the support layer and organic matter accelerates membrane surface fouling.