Cleaning strategy of fouled reverse osmosis membrane: Direct osmosis at high salinities (DO-HS) as on-line technique without interruption of RO operation

This paper summarize the critical examination of the cleaning performance of the polyamide RO membrane with DO-HS method as novel backwash approach for on-line membrane cleaning in RO operation. In this work, the effect of pulse injection of salt demonstrate on RO membrane cleaning. A short injection of feed water with increased salt concentrations (8 and 10% NaCl solution) with an associated osmotic pressure of 35 and 43 bar overcomes feed pump gauge pressure and reverse osmosis shifts to direct osmosis, leading to a permeate backwash stream through the reverse osmosis membrane. The results illustrate that there is more increasing in water permeate flux and permeability coefficient of RO membrane by pulse injection of 10% NaCl than the other one(8% NaCl solution). Results observed a rise of the permeability coefficient of membrane, indicating the foulant removal from the membrane. Permeability coefficient of membrane reached to approximately 90 percent after pulse injection in 10% of NaCl. As result salt concentration of 10% of NaCl s that injected to RO system was chosen as the optimal concentration.