Effect of antiscalants on precipitation of an RO concentrate: metals precipitated and particle characteristics for several water compositions

Lauren F. Greenlee, Fabrice Testa, Desmond F. Lawler, Benny D. Freeman, Philippe Moulin

Research output: Contribution to journalArticleResearchpeer-review

43 Citations (Scopus)


Inland brackish water reverse osmosis (RO) is economically and technically limited by the large volume of salty waste (concentrate) produced. The use of a controlled precipitation step, followed by solid/liquid separation (filtration), has emerged as a promising side-stream treatment process to treat reverse osmosis concentrate and increase overall system recovery. The addition of antiscalants to the RO feed prevents precipitation within the membrane system but might have a deleterious effect on a concentrate treatment process that uses precipitation to remove problematic precipitates. The effects of antiscalant type and concentration on salt precipitation and precipitate particle morphology were evaluated for several water compositions. The primary precipitate for the synthetic brackish waters tested was calcium carbonate; the presence of magnesium, sulfate, minor ions, and antiscalant compounds affected the amount of calcium precipitated, as well as the phases of calcium carbonate formed during precipitation. Addition of antiscalant decreased calcium precipitation but increased incorporation of magnesium and sulfate into precipitating calcium carbonate. Antiscalants prevented the growth of nucleated precipitates, resulting in the formation of small (100-200. nm diameter) particles, as well as larger (6-10μm) particles. Elemental analysis revealed changes in composition and calcium carbonate polymorph with antiscalant addition and antiscalant type. Results indicate that the presence of antiscalants does reduce the extent of calcium precipitation and can worsen subsequent filtration performance.

Original languageEnglish
Pages (from-to)2672-2684
Number of pages13
JournalWater Research
Issue number8
Publication statusPublished - Apr 2010
Externally publishedYes


  • Antiscalants
  • Brackish water
  • Concentrate treatment
  • Desalination
  • Precipitation
  • Reverse osmosis

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