The effect of pH on N2O production in intermittently-fed nitritation reactors

Qingxian Su, Carlos Domingo-Felez, Zhen Zhang, Jan-Michael Blum, Marlene Mark Jensen*, Barth F. Smets

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The effect of pH on nitrous oxide (N2O) production rates was quantified in an intermittently-fed lab-scale sequencing batch reactor performing high-rate nitritation. N2O and other nitrogen (N) species (e.g. ammonium (NH4+), nitrite, hydroxylamine and nitric oxide) were monitored to identify in-cycle dynamics and determine N conversion rates at controlled pH set-points (6.5, 7, 7.5, 8 and 8.5). Operational conditions and microbial compositions remained similar during long-term reactor-scale pH campaigns. The specific ammonium removal rates and nitrite accumulation rates varied little with varying pH levels (p > 0.05). The specific net N2O production rates and net N2O yield of NH4+ removed (ΔN2O/ΔNH4+) increased up to seven-fold from pH 6.5 to 8, and decreased slightly with further pH increase to 8.5 (p < 0.05). Best-fit model simulations predicted nitrifier denitrification as the dominant N2O production pathway (≥87% of total net N2O production) at all examined pH. Our study highlights the effect of pH on biologically mediated N2O emissions in nitrogen removal systems and its importance in the design of N2O mitigation strategies.
Original languageEnglish
JournalWater Research
Volume156
Pages (from-to)223-231
ISSN0043-1354
DOIs
Publication statusPublished - 2019

Keywords

  • Ammonia oxidizing bacteria
  • Nitrifier denitrification
  • Nitritation
  • Nitrous oxide
  • pH effect

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