Patent ID: 7658852
Filing Date: 2010-02-09
Classification: B01D,C02F,Y02A

Abstract:
1. Direct-osmosis (DO) method for cleaning a semi-permeable membrane in a reverse osmosis (RO) separation module, said membrane having a feed side with foulant located thereon and an opposite permeate side, a normal RO separation process in the same module including: feeding by a feed pump, under gauge pressure (PGr), raw saline solution comprising solvent and dissolved salts and having osmotic pressure (POr) to said membrane feed side; collecting permeate having osmotic pressure (POp) from said permeate side, under gauge pressure (PGp); and removing residual brine from said membrane feed side, the RO separation being driven by a positive net driving pressure defined by the balance of the pressures PGr, POr, POp and PGp, wherein said direct osmosis method of membrane cleaning comprises feeding to said feed side of the membrane, for a predetermined injection time, without releasing the gauge pressure PGr of the RO process, super saline solution (SSS) having an osmotic pressure POs>POr chosen such that the net driving pressure becomes negative, whereby there is provided a backward flow of permeate towards the feed side so as to lift said foulant from said feed side, wherein at the same time instance, both an RO separation process and a DO separation process take place simultaneously within the module.