N2-fixation can sustain wastewater treatment performance of photogranules under nitrogen-limiting conditions

Lukas M. Trebuch*, Kobe Schoofs, Stijn M.F. Vaessen, Thomas R. Neu, Marcel Janssen, René H. Wijffels, Louise E.M. Vet, Tânia V. Fernandes

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

3 Citations (Scopus)

Abstract

Wastewater characteristics can vary significantly, and in some municipal wastewaters the N:P ratio is as low as 5 resulting in nitrogen-limiting conditions. In this study, the microbial community, function, and morphology of photogranules under nitrogen-replete (N+) and limiting (N−) conditions was assessed in sequencing batch reactors. Photogranules under N− condition were nitrogen deprived 2/3 of a batch cycle duration. Surprisingly, this nitrogen limitation had no adverse effect on biomass productivity. Moreover, phosphorus and chemical oxygen demand removal were similar to their removal under N+ conditions. Although performance was similar, the difference in granule morphology was obvious. While N+ photogranules were dense and structurally confined, N− photogranules showed loose structures with occasional voids. Microbial community analysis revealed high abundance of cyanobacteria capable of N2-fixation. These were higher at N− (38%) than N+ (29%) treatments, showing that photogranules could adjust and maintain treatment performance and high biomass productivity by means of N2-fixation.

Original languageEnglish
Pages (from-to)1303-1315
JournalBiotechnology and Bioengineering
Volume120
Issue number5
DOIs
Publication statusPublished - May 2023

Keywords

  • confocal laser scanning microscopy
  • FAPROTAX
  • functional annotation
  • microalgal-bacterial granules
  • nitrogen fixation
  • nitrogen limitation

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