Toxicity of fluoride to microorganisms in biological wastewater treatment systems

Valeria Ochoa-Herrera, Qais Banihani, Glendy León, Chandra Khatri, James A. Field, Reyes Sierra-Alvarez

Research output: Contribution to journalArticlepeer-review

92 Scopus citations


Fluoride is a common contaminant in a variety of industrial wastewaters. Available information on the potential toxicity of fluoride to microorganisms implicated in biological wastewater treatment is very limited. The objective of this study was to evaluate the inhibitory effect of fluoride towards the main microbial populations responsible for the removal of organic constituents and nutrients in wastewater treatment processes. The results of short-term batch bioassays indicated that the toxicity of sodium fluoride varied widely depending on the microbial population. Anaerobic microorganisms involved in various metabolic steps of anaerobic digestion processes were found to be very sensitive to the presence of fluoride. The concentrations of fluoride causing 50% metabolic inhibition (IC50) of propionate- and butyrate-degrading microorganisms as well as mesophilic and thermophilic acetate-utilizing methanogens ranged from 18 to 43 mg/L. Fluoride was also inhibitory to nitrification, albeit at relatively high levels (IC50 = 149 mg/L). Nitrifying bacteria appeared to adapt rapidly to fluoride, and a near complete recovery of their metabolic activity was observed after only 4 d of exposure to high fluoride levels (up to 500 mg/L). All other microbial populations evaluated in this study, i.e., glucose fermenters, aerobic glucose-degrading heterotrophs, denitrifying bacteria, and H2-utilizing methanogens, tolerated fluoride at very high concentrations (>500 mg/L).

Original languageEnglish (US)
Pages (from-to)3177-3186
Number of pages10
JournalWater research
Issue number13
StatePublished - Jul 2009


  • Fluoride
  • Microbial inhibition
  • Wastewater treatment

ASJC Scopus subject areas

  • Water Science and Technology
  • Ecological Modeling
  • Pollution
  • Waste Management and Disposal
  • Environmental Engineering
  • Civil and Structural Engineering


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