A critical flux to avoid biofouling of spiral wound nanofiltration and reverse osmosis membranes: Fact or fiction?

J. S. Vrouwenvelder*, J. A.M. van Paassen, J. M.C. van Agtmaal, M. C.M. van Loosdrecht, J. C. Kruithof

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

86 Scopus citations


The relation between biofouling and membrane flux in spiral wound nanofiltration and reverse osmosis membranes in drinking water stations with extensive pretreatment such as ultrafiltration has been studied. The flux - water volume flowing through the membrane per unit area and time - is not influencing the development of membrane biofouling. Irrespective whether a flux was applied or not, the feed spacer channel pressure drop and biofilm concentration increased in reverse osmosis and nanofiltration membranes in a monitor, test rigs, a pilot scale and a full-scale installation. Identical behavior with respect to biofouling and feed channel pressure drop development was observed in membrane elements in the same position in a nanofiltration installation operated with and without flux. Calculation of the ratio of diffusive and convective flux showed that the diffusive flux is considerably larger than the convective flux, supporting the observations that the convective flux due to permeate production is playing an insignificant role in biofouling. Since fouling occurred irrespective of the actual flux, the critical flux concept stating that "below a critical flux no fouling occurs" is not a suitable approach to control biofouling of spiral wound reverse osmosis and nanofiltration membranes.

Original languageEnglish (US)
Pages (from-to)36-44
Number of pages9
JournalJournal of Membrane Science
Issue number1
StatePublished - Jan 5 2009
Externally publishedYes


  • Biofilm
  • Biofouling
  • Critical flux
  • Drinking water
  • Feed spacer channel pressure drop
  • Flux
  • Nanofiltration
  • Reverse osmosis
  • Water treatment

ASJC Scopus subject areas

  • Biochemistry
  • General Materials Science
  • Physical and Theoretical Chemistry
  • Filtration and Separation


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