Removal of CaCO3 scaling salt from RO concentrates by air-blow and inorganic inducers

Qing Feng Yang*, Yangqiao Liu, David Hasson, Raphael Semiat

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


The reuse of reverse osmosis (RO) concentrates generally involves the removal of scaling salts such as CaSO4/CaCO3, and then the recycle part of the treated concentrate to the feed. By this method, the water recovery can be remarkably increased. However, the time necessary for precipitating the scaling components may extentennd to a few days, esppcially in the presence of antiscalants. In the present study, CaCO3 scaling salt removal was carried out from RO concentrates in the presence of three antiscalants by accelcrating precipitation approaches. Three methods were adopted, including the air-blow method, inorganic inducer addition, and the combinative method of air-blow and inorganic inducer addition. Calcium ion concentration, pH and antiscalant concentration of the test solutions were monitored. Morphologies of the precipitated CaCO3 were observed by scanning electron microscopy (SEM). These methods were found to be effective, reaching a calcium removal ratio as high as 50-80%. The removal of scaling salt was always accompanied by the adsorption precipitation of antiscalants. In the presence of antiscalants, saw-toothed growth edges and holes on the precipitated CaCO3 surfaces were found. Moreover, fragmented small particles were also observed. The economic analysis shows that the methods are feasible.

Original languageEnglish
Pages (from-to)13-20
Number of pages8
JournalJournal of Chemical Engineering of Japan
Issue number1
StatePublished - 2008
Externally publishedYes


  • Air-blow
  • Calcium carbonate
  • Inorganic inducers
  • RO concentrate

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