A1 Journal article (refereed)
Nitrate removal microbiology in woodchip bioreactors : a case-study with full-scale bioreactors treating aquaculture effluents (2020)

Aalto, S. L., Suurnäkki, S., von Ahnen, M., Siljanen, H. M. P., Pedersen, P. B., & Tiirola, M. (2020). Nitrate removal microbiology in woodchip bioreactors : a case-study with full-scale bioreactors treating aquaculture effluents. Science of the Total Environment, 723, Article 138093. https://doi.org/10.1016/j.scitotenv.2020.138093

JYU authors or editors

Publication details

All authors or editors: Aalto, Sanni L.; Suurnäkki, Suvi; von Ahnen, Mathis; Siljanen, Henri M. P.; Pedersen, Per Bovbjerg; Tiirola, Marja

Journal or series: Science of the Total Environment

ISSN: 0048-9697

eISSN: 1879-1026

Publication year: 2020

Volume: 723

Article number: 138093

Publisher: Elsevier

Publication country: Netherlands

Publication language: English

DOI: https://doi.org/10.1016/j.scitotenv.2020.138093

Publication open access: Not open

Publication channel open access:

Publication is parallel published (JYX): https://jyx.jyu.fi/handle/123456789/68374


Woodchip bioreactors are viable low-cost nitrate (NO3−) removal applications for treating agricultural and aquaculture discharges. The active microbial biofilms growing on woodchips are conducting nitrogen (N) removal, reducing NO3− while oxidizing the carbon (C) from woodchips. However, bioreactor age, and changes in the operating conditions or in the microbial community might affect the NO3− removal as well as potentially promote nitrous oxide (N2O) production through either incomplete denitrification or dissimilatory NO3− reduction to ammonium (DNRA). Here, we combined stable isotope approach, amplicon sequencing, and captured metagenomics for studying the potential NO3− removal rates, and the abundance and community composition of microbes involved in N transformation processes in the three different full-scale woodchip bioreactors treating recirculating aquaculture system (RAS) effluents. We confirmed denitrification producing di‑nitrogen gas (N2) to be the primary NO3− removal pathway, but found that 6% of NO3− could be released as N2O under high NO3− concentrations and low amounts of bioavailable C, whereas DNRA rates tend to increase with the C amount. The abundance of denitrifiers was equally high between the studied bioreactors, yet the potential NO3− removal rates were linked to the denitrifying community diversity. The same core proteobacterial groups were driving the denitrification, while Bacteroidetes dominated the DNRA carrying microbes in all the three bioreactors studied. Altogether, our results suggest that woodchip bioreactors have a high genetic potential for NO3− removal through a highly abundant and diverse denitrifying community, but that the rates and dynamics between the NO3− removal pathways depend on the other factors (e.g., bioreactor design, operating conditions, and the amount of bioavailable C in relation to the incoming NO3− concentrations).

Keywords: denitrification; nitrous oxide; nitrogen; bioreactors; aquaculture

Free keywords: denitrification; DNRA; nitrogen removal; nitrous oxide; recirculation aquaculture systems

Contributing organizations

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Ministry reporting: Yes

Reporting Year: 2020

JUFO rating: 2

Last updated on 2021-09-08 at 14:35