energies Article Denitrification Process Enhancement and Diversity of the Denitrifying Community in the Full Scale Activated Sludge System after Adaptation to Fusel Oil Przemysław Kowal 1 , Sławomir Ciesielski 2,* , Jeremiah Otieno 1, Joanna Barbara Majtacz 1, Krzysztof Czerwionka 1 and Jacek M ˛akinia 1 1 Faculty of Civil and Environmental Engineering, Gdansk University of Technology, Narutowicza 11/12, 80-233 Gdansk, Poland;
[email protected] (P.K.);
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[email protected] (J.B.M.);
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[email protected] (J.M.) 2 Department of Environmental Biotechnology, Faculty of Geoengineering, University of Warmia and Mazury in Olsztyn, ul. Słoneczna 45G, 10-709 Olsztyn, Poland * Correspondence:
[email protected] Abstract: Implementation of anaerobic digestion of primary sludge in modern wastewater treat- ment plants (WWTPs) limits the availability of organic carbon for denitrification in conventional nitrification-denitrification (N/DN) systems. In order to ensure efficient denitrification, dosage of the external carbon source is commonly undertaken. However, application of commercial products, such us ethanol or acetate, greatly increases operational costs. As such, inexpensive and efficient alternative carbon sources are strongly desirable. In this study, the use of the fusel oil, a by-product from the distillery industry, was validated in terms of the denitrification process enhancement and Citation: Kowal, P.; Ciesielski, S.; impact on the activated sludge bacterial community structure. The experiment was conducted at a Otieno, J.; Majtacz, J.B.; Czerwionka, full scale biological nutrient removal facility (210,000 PE), in the set of the two technological lines: the K.; M ˛akinia,J.