Rapid start-up and stable maintenance of the mainstream nitritation process based on the accumulation of free nitrous acid in a pilot-scale two-stage nitritation-anammox system

Alba Pedrouso, Nicolas Morales, Belen Rodelas, David Correa-Galeote, Angeles Val del Rio, Jose Luis Campos, Jose Vazquez-Padin, Anuska Mosquera-Corral

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5 Scopus citations

Abstract

Two-stage partial nitritation (PN) and anammox (AMX) systems showed promising results for applying autotrophic nitrogen removal under mainstream conditions. In this study, a pilot-scale (600 L per reactor) two-stage PN/AMX system was installed in a municipal wastewater treatment plant (WWTP) provided with a high-rate activated sludge (HRAS) system for organic carbon removal. The PN/AMX system was operated without temperature control (ranging from 11 to 28 °C) and was subjected to the same variations in wastewater characteristics as the WWTP (22 to 63 mg NH4+- N/L). The developed strategy is simple, does not require the addition of chemicals and is characterised by short start-up periods. The PN process was established by applying a high hydraulic load and maintained by in situ accumulated free nitrous acid (FNA) of 0.015–0.2 mg HNO2-N/L. Based on pH value, a controlled aeration strategy was applied to achieve the target nitrite to ammonium ratio in the effluent (1.1 g NO2-N/g NH4+-N) to feed the AMX reactor. Although NOB were not fully washed out from the system, nitrite accumulation remained (>99 %) stable with no evidence of NOB activity. In the AMX reactor, an overall nitrogen removal efficiency of 80 % was achieved. Regarding effluent quality, 12 ± 3 mg TN/L was obtained, but 5 mg NO3-N/L was already in the HRAS effluent. The relative abundance of NOB showed a strong negative correlation with the FNA concentration, providing a good strategy for establishing PN under mainstream conditions.

Original languageEnglish
Article number123851
JournalSeparation and Purification Technology
Volume317
DOIs
StatePublished - 15 Jul 2023
Externally publishedYes

Keywords

  • Ammonium oxidising bacteria (AOB)
  • Anammox
  • Municipal wastewater treatment
  • Nitrite oxidising bacteria (NOB) suppression
  • PN/AMX pilot plant

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