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Ammonia-oxidizing microbial communities in reactors with efficient nitrification at low-dissolved oxygen.

Colin M Fitzgerald1, Pamela Camejo1, J Zachary Oshlag1

  • 1Department of Civil and Environmental Engineering, University of Wisconsin - Madison, 1415 Engineering Drive, Madison, WI 53706, USA.

Water Research
|December 16, 2014
PubMed
Summary

Low dissolved oxygen (DO) conditions challenge nitrification. This study identified ammonia-oxidizing bacteria (AOB) in one reactor, but unexpected microbes in another, suggesting novel low-DO ammonia oxidation pathways.

Keywords:
Activated sludgeAmmonia oxidizing archaeaAmmonia oxidizing bacteriaLow dissolved oxygenNitrification

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Area of Science:

  • Environmental microbiology
  • Wastewater treatment
  • Biogeochemical cycles

Background:

  • Nitrification is crucial for wastewater treatment, converting ammonia to nitrate.
  • Low dissolved oxygen (DO) conditions (<0.3 mg/L) present challenges for conventional nitrification processes.
  • Understanding microbial communities under low DO is vital for optimizing treatment efficiency.

Purpose of the Study:

  • To investigate ammonia-oxidizing microbial communities under low DO conditions.
  • To identify key microorganisms responsible for nitrification in low DO environments.
  • To explore potential novel pathways for ammonia oxidation in wastewater treatment.

Main Methods:

  • Utilized chemostat reactors to simulate low DO conditions.
  • Employed quantitative PCR (qPCR) for microbial abundance.
  • Applied rDNA tag pyrosequencing and fluorescence in situ hybridization (FISH) for community analysis.

Main Results:

  • Ammonia-oxidizing bacteria (AOB) of the Nitrosomonas genus dominated low DO nitrification in one reactor.
  • The second reactor showed nitrification not linked to known ammonia oxidizers.
  • Neither reactor harbored significant ammonia-oxidizing archaea (AOA) or anammox bacteria.
  • Isolated organisms utilized ammonia but did not produce nitrite/nitrate stoichiometrically.

Conclusions:

  • Nitrosomonas AOB are key players in some low DO nitrification systems.
  • Novel microbial groups, potentially including Pseudomonas, Xanthomonadaceae, Rhodococcus, and Sphingomonas, may be involved in low DO ammonia oxidation.
  • Further research is needed to elucidate the mechanisms of this non-conventional nitrification.