Prevention and Management of Silica Scaling in Membrane Distillation Using pH Adjustment

Craig Turchi, John Bush, Johan Vanneste, Emily Gustafson, Christopher Waechter, David Jassby, Tzahi Cath

Research output: Contribution to journalArticlepeer-review

71 Scopus Citations

Abstract

Membrane scaling by silica is a major challenge in desalination, particularly for inland desalination of brackish groundwater or geothermal water, which often contain high concentrations of silica and dissolved solids. Adjustment of feed pH may reduce silica scaling risk, which is important for inland facilities that operate at high water recoveries to reduce brine disposal costs. However, water recovery of reverse osmosis is also limited due to increased osmotic pressure with feed water concentration. Membrane distillation (MD) is a thermally driven membrane desalination technique that is not limited by increased osmotic pressure of the feed. In this investigation, pH adjustment was tested as a strategy to reduce silica scaling risk in the MD process. With feed water pH less than 5 or higher than 10, scaling impacts were negligible at silica concentrations up to 600 mg/L. Scaling rates were highest at neutral pH between 6 and 8. Cleaning strategies were also explored to remove silica scale from membranes. Cleaning using NaOH solutions at pH higher than 11 to induce dissolution of silica scale was effective at temporarily restoring performance; however, some silica remained on membrane surfaces and scaling upon re-exposure to supersaturated silica concentrations occurred faster than with new membranes.

Original languageAmerican English
Pages (from-to)366-377
Number of pages12
JournalJournal of Membrane Science
Volume554
DOIs
StatePublished - 15 May 2018

Bibliographical note

Publisher Copyright:
© 2018 Elsevier B.V.

NREL Publication Number

  • NREL/JA-5500-71164

Keywords

  • Membrane cleaning
  • Membrane distillation
  • Membrane fouling
  • Membrane scaling
  • Silica

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