Application of nanofiltration pretreatment to remove divalent ions for economical seawater reverse osmosis desalination

Minho Park, Jongkwan Park, Eunkyung Lee, Jeehyeong Khim, Jaeweon Cho

Research output: Contribution to journalArticlepeer-review

30 Citations (Scopus)


To minimize scale formation potential in the applications of reverse osmosis (RO) membranes as a pretreatment unit, relatively loose nanofiltration (NF) membrane systems coupled with ultrafiltration (UF) were used to remove divalent ions from seawater. However, the UF did not reject any ions because of pore size. The rejection of divalent ions by NF was in order of sulfate (>95%), magnesium (>60%), and calcium (>30%) in every rejection experiment based on water recovery rate (40, 50, 60, 70, and 80%). In the UF/NF/RO hybrid pilot system, most of the divalent (>99%) and the monovalent (>97%) ions were effectively rejected with slightly increased divalent ion rejection compared to the UF/RO system. Seawater temperature influenced rejection of ions with regards to either the diffusion- or convection-dominant transport of ions through the membrane pores. Electric power consumption was also compared between the UF/NF/RO process and the UF/RO process. For different salinity conditions (28,000 and 45,000 mg/L of total dissolved solids), the lowest energy consumption by NF/RO was 3.3 and 6 kWh/m3 with recovery of 80% for NF and 40% for RO, respectively.

Original languageEnglish
Pages (from-to)20661-20670
Number of pages10
JournalDesalination and Water Treatment
Issue number44
Publication statusPublished - 2016 Sept 19

Bibliographical note

Publisher Copyright:
© 2015 Balaban Desalination Publications. All rights reserved.


  • Desalination
  • Divalent ions
  • Energy consumption
  • Nanofiltration
  • SWRO
  • Scaling

ASJC Scopus subject areas

  • Water Science and Technology
  • Pollution
  • Ocean Engineering


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