Scaling prevention of thin film composite polyamide Reverse Osmosis membranes by Zn ions.

On the West Coast of South Africa, there is an abundance of brackish groundwater. Reverse Osmosis membrane systems are used to make the borehole water fresh. Unfortunately, the salts that are removed from the water, precipitates on the membrane surface, thus, decreasing the overall process efficiency. In this study, the use of Zn2+ ions as an anti-scalant was investigated in terms of feasibility in the treatment of brackish water influent. Experimental tests were conducted on a bench scale unit, followed with a pilot plant thereafter. Three commercial membranes were exposed to natural groundwater scaling. The first, commercial anti-scalant treatment, second, anti-scalant treatment with Zn2+ ions and the third, untreated. The results, after a period of close to 5 months, showed that the flux of the membranes treated with commercial (32.78 L·m−2·h−1) and zinc (30.80 L·m−2·h−1) ions anti-scalant was higher than the untreated membrane flux (25.56 L·m−2·h−1), which decreased continuously. Unlabelled Image • Maximum concentration of Zn ions generated in the electrolytic was obtained at a potential difference of 2 volts. • The use of Zn2+ improved anti-scaling capacity of the membrane when treating brackish water • Scaling of the membrane in the pilot plant was minimized with the use of commercial anti-scalant as well as Zn ions. • SEM and OM analyses showed that deposits on the membrane surface were minimized with the use of both anti-scalants tested [ABSTRACT FROM AUTHOR]