Patent ID: 9034179
Filing Date: 2015-05-19
Classification: B01D

Abstract:
1. Method for the cleaning of spiral wound nano-filtration or hyper-filtration membrane modules arranged in series, inside in at least one pressure tube, in which an aqueous fluid to be purified is separated into permeate along with simultaneous and continuous emission of concentrate, wherein suspended substances that are present in the aqueous fluid, including solid particles, bacteria, viruses, and dissolved substances, including salts, dissolved organic substances, and pesticides, are removed as said concentrate flows, and in which the membranes are periodically rinsed with water and a gas for cleaning purposes, wherein said cleaning method comprises the following steps: (i) dosing of gas in said water, (ii) dissolving said gas of step (i) in said water, (iii) longitudinal rinsing of the membrane with said water, in which according to step (ii) a readily soluble gas or mixture of soluble gasses has been dissolved in advance, wherein in the discharge tube of the membranes a counter-pressure is maintained, at which this counter-pressure is alternately decreased and increased, and wherein simultaneously the pressure in the feed to the first membrane with the same values, but opposite, is increased and decreased, and (iv) transferring said dissolved gas from the liquid phase to the gas phase for removing the fouling and particulates that were set free from the membranes, wherein step (iv) is carried out by hydraulic headloss or relaxation of pressure.