A different approach for brackish-water desalination, comprising acidification of the feed-water and CO 2(aq) reuse for alkalinity, Ca 2+ and Mg 2+ supply in the post treatment stage

Shaul Oren, Liat Birnhack*, Orly Lehmann, Ori Lahav

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

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 H 2SO 4) is dosed to the feed water with the aim of converting HCO 3 - 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, Ca 2+ ions and also (indirectly) Mg 2+ ions, using the "calcite dissolution-ion exchange" 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.

Original languageEnglish
Pages (from-to)252-260
Number of pages9
JournalSeparation and Purification Technology
Volume89
DOIs
StatePublished - 22 Mar 2012
Externally publishedYes

Keywords

  • Brackish water desalination
  • CO rejection
  • Cost assessment
  • Mg supply
  • Post treatment

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