Pilot scale study of chlorination-induced transport property changes of a seawater reverse osmosis membrane

• Published in: Desalination Vol. 311; pp. 24 - 30
• Main Authors: Ettori, Axel, Gaudichet-Maurin, Emmanuelle, Aimar, Pierre, Causserand, Christel
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.02.2013; Elsevier
• Subjects: Applied sciences; Chemical and Process Engineering; Chemical engineering; Chemical Sciences; Chlorination; Chlorine; Desalination; Drinking water and swimming-pool water. Desalination; Elemental analysis; Engineering Sciences; Exact sciences and technology; Filtration; ions; Liquid-liquid and fluid-solid mechanical separations; Marine; Membrane separation (reverse osmosis, dialysis...); Membranes; Natural water pollution; Pollution; Polyamide; Rejection; Reverse osmosis; RO module; Sea water; seawater; Seawater desalination; Seawaters, estuaries; sodium; Water treatment and pollution; Polyamide; RO module; Chlorine; Seawater desalination; Elemental analysis; Elementary analysis; Chlorination; Filtration; Transport properties; Desalination plant; Retention; Spiral; Long term; Composite material; Rejection; Membrane separation; Surveillance; Desalination; pH; Permeance; Reverse osmosis; Seawater
• ISSN: 0011-9164; 1873-4464
• DOI: 10.1016/j.desal.2012.11.004

A pilot-scale study was performed to assess variations of reverse osmosis (RO) membrane water permeance (A) and salt retention (Robs) induced by chlorination and to compare them with those observed at the lab-scale. A chlorination protocol was adapted to expose only the surface active layer (an aromatic polyamide) of a composite RO membrane to consecutive free chlorine doses ranging from 40 to 4000ppm h, at pH 6.9. Along the long-term filtration of seawater, performed with a 4" spiral wound RO module, we monitored the variations of A, the decrease of Robs and the rate of increase of A with time, and found them quantitatively similar to those reported in previous studies performed at the lab-scale under accelerated exposure conditions. The elemental analysis of the feed and permeate streams revealed that the rejection of divalent ions remained constant (ca. 100%), irrespective of the free chlorine dose reached, whereas the rejection of monovalent ions of the seawater (mainly sodium, chloride and bromide ions) decreased as the exposure dose increased. Overall, transposing the characterization procedure to the pilot-scale further supports that chlorination of PA, under pH conditions usually found in desalination plants (6.9 to 8.0), is controlled by the concentration of HOCl, as observed from elemental analysis of the surface by XPS. ► A 4" spiral wound reverse osmosis module is exposed to hypochlorite on a long term basis. ► Changes in water and salts permeances are similar to those found in lab scale studies. ► Hypochlorous acid was confirmed to be the most important factor in membrane modification over time.