Reducing the specific energy consumption of 1st-pass SWRO by application of high-flux membranes fed with high-pH, decarbonated seawater

Liron Ophek, Liat Birnhack, Oded Nir, Eitan Binshtein, Ori Lahav*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

A new operational approach is presented, which has the potential to substantially cut down on the energy and cost demand associated with seawater reverse osmosis (SWRO) desalination, without changing the currently-installed infrastructure. The approach comprises acidification/decarbonation of the feed seawater followed by high-pH single RO pass using high-flux membranes. Since the limitation imposed by CaCO3(s) precipitation is overcome, the recovery ratio can be significantly increased. This work presents a new operational concept aimed at maximizing the benefits that can be obtained from new low-energy RO membranes available on the market. Results obtained from operating a pilot RO system revealed that following an acidification and decarbonation step, recovery ratio of 56% could be practically attained, along with effluent TDS and boron concentrations of 375 and 0.3 mg/l, respectively (feed water pH was adjusted to pH9.53 following the decarbonation step). The specific energy consumption (SEC) of this operation was calculated to be 5%-10% lower than the SEC typically associated with "conventional" SWRO operation. Two further scenarios were theoretically considered, under which the limiting operational parameter became Mg(OH)2(s) and BaSO4(s) precipitation. It was concluded that despite the fact that higher recovery ratios could be obtained, the high pressure required in these scenarios made them less appealing from both the SEC and cost standpoints. The normalized cost of the suggested approach was found to be ~$0.07 ± 0.02/m3 cheaper than the currently-practiced SWRO approach for obtaining product water characterized by TDS < 500 and B < 0.5 mg/l.

Original languageEnglish
Pages (from-to)185-192
Number of pages8
JournalWater Research
Volume85
DOIs
StatePublished - 15 Nov 2015
Externally publishedYes

Keywords

  • Boron
  • High-flux membranes
  • SEC
  • Single pass
  • SWRO

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