Impact of elevated Ca2+/Mg2+ concentrations of reverse osmosis membrane desalinated seawater on the stability of water pipe materials

• Published in: Journal of water and health Vol. 12; no. 1; pp. 24 - 33
• Main Authors: JUAN LIANG, ANQI DENG, RONGJING XIE, GOMEZ, Mylene, JIANGYONG HU, JUFANG ZHANG, CHOON NAM ONG, ADIN, Avner
• Format: Journal Article
• Language: English
• Published: London IWA Publishing 01.03.2014
• Subjects: Alkalinity; Applied sciences; Calcium; Calcium carbonate; Cast iron; Chemical analysis; Corrosion; Corrosion effects; Corrosion mechanisms; Corrosion products; Corrosion rate; Corrosion resistance; Desalination; Drinking water and swimming-pool water. Desalination; Exact sciences and technology; Iron; Magnesium; Marine; Nodular iron; Pipes; Pollution; Reverse osmosis; Scale (corrosion); Scale formation; Scaling; Seawater; Stability; Tropical climate; Water analysis; Water distribution; Water engineering; Water hardness; Water treatment and pollution; X-ray diffraction; Water treatment; post-treatment; Drinking water pipe; Chemical stability; remineralisation; Water distribution; Membrane separation; desalinated water; Calcium ion; Corrosion; Desalination; water distribution pipeline; Magnesium ion; Reverse osmosis; Mg; Distribution network; Ca; Seawater; Remineralization
• ISSN: 1477-8920; 1996-7829
• DOI: 10.2166/wh.2013.060

Hardness and alkalinity are known factors influencing the chemical stability of desalinated water. This study was carried out to investigate the effect of Ca2+ and Mg2+ on corrosion and/or scale formation on the surface of different water distribution pipe materials under tropical conditions. The corrosion rates of ductile iron, cast iron and cement-lined ductile iron coupons were examined in reverse osmosis (RO) membrane desalinated seawater which was remineralised using different concentrations of Ca2+ and Mg2+. The changes in water characteristics and the coupon corrosion rates were studied before and after the post-treatment. The corrosion mechanisms and corrosion products were examined using scanning electron microscope and X-ray diffraction, respectively. We found that the combination of Ca2+ and Mg2+ (60/40 mg/L as CaCO3) resulted in lower corrosion rates than all other treatments for the three types of pipe materials, suggesting that Ca2+/Mg2+ combination improves the chemical stability of desalinated seawater rather than Ca2+ only.