Exploring the microbial influence on seasonal nitrous oxide concentration in a full-scale wastewater treatment plant using metagenome assembled genomes

Laura Christina Valk, Miriam Peces, Caitlin Margaret Singleton, Mads Dyring Laursen, Mikkel Holmen Andersen, Artur Tomasz Mielczarek, Per Halkjær Nielsen*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

Nitrous oxide is a highly potent greenhouse gas and one of the main contributors to the greenhouse gas footprint of wastewater treatment plants (WWTP). Although nitrous oxide can be produced by abiotic reactions in these systems, biological N2O production resulting from the imbalance of nitrous oxide production and reduction by microbial populations is the dominant cause. The microbial populations responsible for the imbalance have not been clearly identified, yet they are likely responsible for strong seasonal nitrous oxide patterns. Here, we examined the seasonal nitrous oxide concentration pattern in Avedøre WWTP alongside abiotic parameters, the microbial community composition based on 16S rRNA gene sequencing and already available metagenome-assembled genomes (MAGs). We found that the WWTP parameters could not explain the observed pattern. While no distinct community changes between periods of high and low dissolved nitrous oxide concentrations were determined, we found 26 and 28 species with positive and negative correlations to the seasonal N2O concentrations, respectively. MAGs were identified for 124 species (approximately 31% mean relative abundance of the community), and analysis of their genomic nitrogen transformation potential could explain this correlation for four of the negatively correlated species. Other abundant species were also analysed for their nitrogen transformation potential. Interestingly, only one full-denitrifier (Candidatus Dechloromonas phosphorivorans) was identified. 59 species had a nosZ gene predicted, with the majority identified as a clade II nosZ gene, mainly from the phylum Bacteroidota. A correlation of MAG-derived functional guilds with the N2O concentration pattern showed that there was a small but significant negative correlation with nitrite oxidizing bacteria and species with a nosZ gene (N2O reducers (DEN)). More research is required, specifically long-term activity measurements in relation to the N2O concentration to increase the resolution of these findings.

Original languageEnglish
Article number118563
JournalWater Research
Volume219
ISSN0043-1354
DOIs
Publication statusPublished - Jul 2022

Bibliographical note

Funding Information:
The authors wish to thank the Avedøre WWTP for sharing the operational data, and all the student helpers and operators for taking the activated sludge samples. The authors additionally wish to thank Nick Green for help with the HQ MAG annotation. The project has been funded by the Villum Foundation (Dark Matter, grant 13351).

Funding Information:
The authors wish to thank the Avedøre WWTP for sharing the operational data, and all the student helpers and operators for taking the activated sludge samples. The authors additionally wish to thank Nick Green for help with the HQ MAG annotation. The project has been funded by the Villum Foundation (Dark Matter, grant 13351).

Publisher Copyright:
© 2022

Keywords

  • Full-scale WWTP
  • Genomes
  • Metagenomics
  • Nitrous oxide
  • Time-series
  • Greenhouse Gases/analysis
  • Nitrous Oxide/analysis
  • RNA, Ribosomal, 16S/genetics
  • Nitrogen/analysis
  • Water Purification
  • Denitrification
  • Seasons
  • Metagenome

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