A different approach for brackish-water desalination, comprising acidification of the feed-water and CO_2(aq) reuse for alkalinity, Ca²⁺ and Mg²⁺ supply in the post treatment stage

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• 作者：Shaul Oren ; Liat Birnhack ; ^{birbirit@tx.technion.ac.il} ; Orly Lehmann ; Ori Lahav
• 关键词：Brackish water desalination ; CO2 rejection ; Post treatment ; Mg2+ supply ; Cost assessment
• 刊名：Separation and Purification Technology
• 出版年：2012
• 期刊代码：78_13835866
• 类别：ce
• 出版时间：22 March, 2012
• 卷：89
• 期：Complete
• 页码：252-260
• 文件大小：557 K

摘要

An alternative approach is presented for the operation of the pre- and post-treatment stages of desalination plants fed by brackish waters characterized by a high carbonate concentration. A strong acid (either HCl or H₂SO₄) is dosed to the feed water with the aim of converting HCO₃^{鈭?/sup> to CO_2(aq) thereby eliminating potential precipitation of solids and scale inhibitor requirement. CO_2(aq) is a small, uncharged molecule, which readily passes RO membranes. Consequently, since the CO_2(aq) concentration in the feed/brine water closely equals the CO_2(aq) concentration that develops in the permeate water, the corresponding negative calcium carbonate precipitation potential values in the permeate is further utilized in the post treatment stage for enhancing CaCO_3(s) dissolution, resulting in supply of carbonate alkalinity, Ca2+ ions and also (indirectly) Mg2+ ions, using the 鈥渃alcite dissolution-ion exchange鈥?process introduced in previous works. Thereby, the dosage of the strong acid to the feed water accomplishes two goals, making the approach cost effective. The paper addresses experimental (at both laboratory and full scale) and theoretical aspects of the proposed process, as well as assessment of engineering and economic feasibility.}