In RED method, numbers of alternately stacked cation exchange membranes (CEM) and anion exchange membranes (AEM) are used. This technique was first proposed by Pattle in 1954. But, it is gaining interest in the first decade of the twenty first century when search for sustainable energy resource takes place at *Corresponding author: E-mail: bagarijit@gmail.com the top of the global research interests . In PRO method, semipermeable membranes are used to allow the transport of water from a low-concentration solution (such as river or waste water) into the high-concentration solution (such as sea water) .