Low-Temperature Adapted Nitrifying Microbial Communities of Finnish Wastewater Treatment Systems

Antonina Kruglova*, Jenni Kesulahti, Minh Le, Alejandro Gonzalez Martinez, Anna Mikola, Riku Vahala

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

13 Citations (Scopus)
66 Downloads (Pure)


In this study, the microbial community of nitrifying activated sludge adapted to Finnish climate conditions was studied to clarify the microbial populations involved in low-temperature nitrification. Microbial community analysis of five full-scale wastewater treatment plants (WWTPs) showed several differences compared to WWTPs from other countries with a similar climate. In particular, very low abundance of ammonium oxidizing bacteria (AOBs) (altogether < 0.25% of total community) as well as typical NOBs (<0.35%) and a high abundance of orders Cytophagales and Micrococcales was observed in all Finnish WWTPs. To shed light on the importance of autotrophic and heterotrophic nitrifying processes, laboratory studies of activated sludge were carried out with a presence of and a lack of organic carbon in wastewater at 10 ± 1 °C. Two different sludge retention times (SRTs) were compared to determine the effect of this operational parameter on low-temperature nitrogen removal. The important role of previously reported Candidatus Nitrotogaarctica for nitrite oxidizing in cold climate conditions was confirmed in both full-scale and laboratory scale results. Additionally, potential participation of Dokdonella sp. and Flexibacter sp. in nitrogen removal at low-temperatures is proposed. Operation at SRT of 100 days demonstrated more stable and efficient nitrogen removal after a sharp temperature decrease compared to 14 days SRT.

Original languageEnglish
Article number2450
Number of pages16
Issue number9
Publication statusPublished - Sept 2020
MoE publication typeA1 Journal article-refereed


  • nitrogen removal
  • activated sludge
  • nitrogen oxidizing bacteria
  • low temperature
  • ammonium oxidizing bacteria;


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