Assessing the stability of one-stage PN/A process through experimental and modelling investigations

Jia Meng, Tao Liu, Jing Zhao, Xin Lu, Jianzheng Li, Min Zheng

Research output: Journal article publicationJournal articleAcademic researchpeer-review

18 Citations (Scopus)


The mainstream partial nitritation/anammox (PN/A) process has been intensively studied but its stability remains a key challenge. It is shown here that biofilm thickness can exhibit a critical role in controlling the process stability of mainstream PN/A against dissolved oxygen (DO) variation. In a laboratory moving bed biofilm reactor (MBBR), PN/A performance was initially established in 200 days by controlling a low DO of 0.13 ± 0.07 mg O2/L in the bulk liquid, which deteriorated with an increase of DO (0.35 ± 0.13 mg O2/L) for over two months, and then rapidly recovered in a month with the initial low DO level re-applied. Biofilm thickness of PN/A carriers was measured during the experiment, which became significantly thinner (367 ± 146 μm) at mainstream conditions. The thin thickness primarily decreased the in-situ consumption rate of nitrite, rather than ammonium, when DO increased from 0.1 to 0.4 mg O2/L, due to that the thin thickness can only restrict anammox capacity. These results illustrated the role of biofilm thickness in regulating PN/A performance and microbial activities. Further investigation using an established model revealed the joint contribution of biofilm thickness and DO concentration to PN/A process, while particularly, the biofilm thickness can determine the optimal DO level for maximizing the nitrogen removal efficiency and system robustness against DO variation. These results highlight the need of considering biofilm thickness in PN/A process optimization and stability improvement in low-strength wastewater treatment.

Original languageEnglish
Article number149740
JournalScience of the Total Environment
Publication statusPublished - 20 Dec 2021
Externally publishedYes


  • Biofilm thickness
  • DO control
  • NOB suppression
  • PN/A process stability

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution


Dive into the research topics of 'Assessing the stability of one-stage PN/A process through experimental and modelling investigations'. Together they form a unique fingerprint.

Cite this