Starved anammox cells are less resistant to NO2- inhibition

José M. Carvajal-Arroyo, Daniel Puyol, Guangbin Li, Andrew Swartwout, Reyes Sierra-Álvarez, Jim A. Field

Research output: Contribution to journalArticle

28 Scopus citations

Abstract

Anaerobic ammonium oxidizing (anammox) bacteria are be inhibited by their terminal electron acceptor, nitrite. Serious nitrite inhibition of the anammox bacteria occurs if the exposure coincides with the absence of the electron donating substrate, ammonium and pH<7.2. Starvation of biomass occurs during underloading of bioreactors or biomass storage. This work investigated the effect of starvation on the sensitivity of anammox bacteria to nitrite exposure. Batch activity tests were carried out evaluating the response of anammox biomass subjected to different levels of starvation upon exposure to nitrite in the presence and absence of ammonium (active- and resting-cells, respectively). The response of the bacteria was evaluated by measuring the specific anammox activity and the evolution of the ATP content in the biomass over time. The 50% inhibitory concentrations of nitrite in starved- and fresh-resting-cells was 7mgNL-1 and 52mgNL-1, respectively. By contrast, only moderate nitrite inhibition occurred to starved anammox biomass when exposed to nitrite and ammonium simultaneously. Maximum ATP levels were observed in fresh cells. The ATP content in starved resting cells peaked 2-3h after addition of NO2--. The response was hindered in cells starved for long periods. These findings agreed with a bioreactor study in which underloading of anammox biomass (0.10gNL-1d-1) decreased its tolerance to a nitrite (only) exposure (101mg NO2--NL-1) and completely disrupted the N removal capacity of the biomass. A similar accumulation of 108mg NO2--NL-1 after operation at 0.95gNL-1d-1 did not cause observable inhibition of the bacteria. The results taken as a whole demonstrate that starved anammox biomass is highly sensitive to nitrite toxicity. An explanation is proposed based on energy requirements to translocate nitrite in the cell.

Original languageEnglish (US)
Pages (from-to)170-176
Number of pages7
JournalWater research
Volume65
DOIs
StatePublished - Nov 15 2014

Keywords

  • ATP
  • Anaerobic ammonium oxidation
  • Autotrophic nitrogen removal
  • Granular sludge
  • Inhibition
  • Underloading

ASJC Scopus subject areas

  • Ecological Modeling
  • Water Science and Technology
  • Waste Management and Disposal
  • Pollution

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