Analysis of microbial communities involved in organic matter and nitrogen removal in a full-scale moving bed biofilm reactor located near the Polar Arctic Circle

Abstract The communities of Bacteria, Archaea and Fungi in a full-scale moving bed biofilm reactor in Rukatunturi (Ruka, Finland, in the Polar Arctic Circle) were analyzed in order to observe their ecological role in the operation of this system at low temperature. The bioreactor achieved efficient removal performances organic matter (>96%) and for ammonium (>95%), however a modest removal for total nitrogen (>63–75%). Bacteria dominant phylotypes changed in relation to the different functions: Trichococcus and Polaromonas for denitrification, Trichococcus and Simplicispira for organic matter removal, and Devosia and Thermomonas for nitrification. Bacteria predicted metagenome related to nitrification confirmed ammonium oxidation in nitrification chamber, and reduction of nitrate and nitrite in the denitrification and organic matter removal chambers. Dynamics of Fungi, dominated by Trichosporonaceae and Ascomycota clones, were linked to aeration conditions but not to substrate concentrations. Archaea communities, dominated by Methanobrevibacter genus and Thermoplasmatales-related clones, were not affected by aeration or substrate concentrations. The results obtained offer a valuable insight into the ecological role of microbial communities in full-scale moving bed biofilm reactor operating under extremely low temperatures.