Pressure Retarded Osmosis (PRO) process is one of membrane processes for renewable energy production. When water transports from low saline feed solution (i.e. river water) to high saline draw solution (i.e. seawater), osmotic pressure occurs to equalize salinity between two solutions. In PRO process, hydraulic pressure is applied to high saline draw solution and the water goes to hydo-turbine for clean energy production. Membrane fouling, accumulation of contaminants on membrane surface, is inevitable for all membrane processes. Membrane fouling is serious problem because it causes severe water permeation decrease and plant decay. Therefore, prevent and control membrane fouling is important in membrane processes. In spite of the importance of membrane fouling study, membrane fouling issue in PRO process has not fully investigated. Although membrane fouling issues have studied in various membrane processes, fouling mechanisms and control methods in PRO process could be different; therefore, it is required to investigate fouling behavior and its efficient control methods.
In this study, fouling effect in PRO process were investigated and several cleaning methods were applied to control the fouling. As a model membrane, commercial FO membrane (cellulose triacetate material, HTI) was used and sodium alginate was used as a model foulant. To compare fouling effect, various operating conditions were applied such as different hydraulic pressure, different draw solution concentration, different calcium ion concentration, and foulant in draw solution. As cleaning methods, two physical cleaning methods, increasing cross-flow velocity and backwash, and one chemical cleaning by using sodium hydropxide was applied. As a result, in all operating condition, severe water flux declines were shown as the effect of sodium alginate fouling in PRO process. In this study, water flux and calcium ions affected to the fouling effect, while applied hydraulic pressure and foulants in draw solution didn’t show correlations between fouling effect. For controlling sodium alginate fouling by cleaning process, all methods showed great cleaning efficiency for organic fouling in PRO process; however, effective cleaning methods by considering real PRO process should be investigated.