Toxicity of azoles towards the anaerobic ammonium oxidation (anammox) process

Nivrutti Lakhey, Guangbin Li, Reyes Sierra-Alvarez, Jim A. Field

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


BACKGROUND: Azoles are an important class of compounds that are widely used as corrosion inhibitors in aircraft de-icing agents, cooling towers, semiconductor manufacturing and household dishwashing detergents. They also are important moieties in pharmaceutical drugs and fungicides. Azoles are widespread emerging contaminants occurring frequently in water bodies. Azole compounds can potentially cause inhibition towards key biological processes in natural ecosystems and wastewater treatment processes. Of particular concern is the inhibition of azoles to the nitrification process (aerobic oxidation of ammonium). This study investigated the acute toxicity of azole compounds towards the anaerobic ammonia oxidation (anammox) process, which is an important environmental biotechnology gaining traction for nutrient-nitrogen removal during wastewater treatment. In this study, using batch bioassay techniques, the anammox toxicity of eight commonly occurring azole compounds was evaluated. RESULTS: The results show that 1H-benzotriazole and 5-methyl-1H-benzotriazole had the highest inhibitory effect on the anammox process, causing 50% decrease in anammox activity (IC50) at concentrations of 19.6 and 17.8 mg L−1, respectively. 1H-imidazole caused less severe toxicity with an IC50 of 79.4 mg L−1. The other azole compounds were either nontoxic (1H-pyrazole, 1H-1,2,4-triazole and 1-methyl-pyrazole) or at best mildly toxic (1H-benzotriazole-5-carboxylic acid and 3,5-dimethyl-1H-pyrazole) towards the anammox bacteria at the concentrations tested. CONCLUSIONS: This study showed that most azole compounds tested displayed mild to low or no toxicity towards the anammox bacteria. The anammox bacteria were found to be far less sensitive to azoles compared to nitrifying bacteria.

Original languageEnglish (US)
Pages (from-to)1057-1063
Number of pages7
JournalJournal of Chemical Technology and Biotechnology
Issue number4
StatePublished - Apr 1 2020


  • anaerobic
  • bacteria
  • environmental biotechnology
  • toxicity
  • wastewater

ASJC Scopus subject areas

  • Biotechnology
  • General Chemical Engineering
  • Renewable Energy, Sustainability and the Environment
  • Fuel Technology
  • Waste Management and Disposal
  • Pollution
  • Organic Chemistry
  • Inorganic Chemistry


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