Comparative evaluation of osmotically-driven cleaning methods for organic-inorganic fouling in pressure retarded osmosis (PRO)

Pressure retarded osmosis (PRO) is a promising technique of desalination techniques. However, one of the major problems is permeate flux decline by fouling. This study investigates the mitigation of organic and inorganic fouling in PRO by osmotically driven cleaning methods. This study comparatively evaluates the effective cleaning methods: (i) Osmotic Backwashing (OB), (ii) Reverse Osmosis Flushing (ROF), and (iii) Pressure Assisted Osmotic Backwashing (PAOB). The results showed that PAOB was a more effective method than the others in terms of cleaning efficiency and permeability. CaCO3 solution of 1000 mg/L and humic acid 100 mg/L were used as a representative inorganic and organic foulant, respectively. After cleaning, cleaning efficiency and flux decline rate were compared. The PAOB method showed the higher performance compared to other cleaning methods, had 92% recovery rate and lower flux decline after cleaning. Also, by using instrumental analysis-scanning electron microscope (SEM), it was proven to find out the proper cleaning method in PRO.