Inhibition of biomass activity in the via nitrite nitrogen removal processes by veterinary pharmaceuticals Teresa Alvarino a,⇑ , Evina Katsou b , Simos Malamis b , Sonia Suarez a , Francisco Omil a , Francesco Fatone b a Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, E-15782 Santiago de Compostela, Spain b Department of Biotechnology, University of Verona, Strada Le Grazie 15, I-37134 Verona, Italy highlights  Inhibitory effect of veterinary products on via nitrite bioprocesses was studied.  Anammox & nitrifiers are the most sensitive bacteria to the tested pharmaceuticals.  Heterotrophic denitrifiers were the most stable bacteria.  Activity tests showed that doxycycline is more toxic than acetaminophen. graphical abstract article info Article history: Received 19 August 2013 Received in revised form 25 October 2013 Accepted 29 October 2013 Available online 12 November 2013 Keywords: Veterinary pharmaceuticals Activity inhibition Short-cut nutrients removal Anammox FISH abstract The inhibitory effect of two veterinary pharmaceuticals was studied for different types of biomass involved in via nitrite nitrogen removal processes. Batch tests were conducted to determine the inhibi- tion level of acetaminophen (PAR) and doxycycline (DOX) on the activity of short-cut nitrifying, denitri- fying and anoxic ammonium oxidation (anammox) biomass and phosphorus accumulating organisms (PAOs). All biomass types were affected by PAR and DOX, with anammox being the most sensitive bac- teria. DOX inhibited more the biomass treating high strength nitrogenous effluents (HSNE) than low strength nitrogenous effluents (LSNE). The phosphorus uptake inhibition under anoxic conditions was lower than 25% in the presence of PAR up to 400 mg L 1 . The same DOX concentration inhibited anoxic phosphorus uptake more than 65% for biomass treating LSNE and HSNE. Heterotrophic denitrifying bacteria seem to be more robust at high DOX and PAR concentrations than anammox. Both veterinary products inactivated ammonium oxidizing, Accumulibacter phosphatis and denitrifying bacteria. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction During the anaerobic treatment of nitrogenous effluents (i.e. pig slurry), proteins are degraded to ammonium; when such effluents are disposed to water recipients they cause significant environ- mental problems, such as oxygen depletion, fish toxicity, and eutrophication. In the conventional biological nitrogen removal process the ammonium and organic nitrogen are removed via the nitrate pathway. Nowadays, alternative biological processes have been developed and tested to reduce the cost of nutrients removal. The short-cut via nitrite processes can be accomplished through the autotrophic/heterotrophic process of nitritation/denitritation or through the completely autotrophic nitrogen removal process involving nitritation and anoxic ammonium oxidation (anammox). In the nitritation process ammonium is oxidized to nitrite, while nitrite oxidation to nitrate is avoided, by promoting the ammo- nium oxidizing bacteria (AOB) and at the same time inhibiting the nitrite oxidizing bacteria (NOB). In the denitritation process, nitrite is reduced to nitrogen gas by heterotrophic bacteria under 0960-8524/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biortech.2013.10.107 ⇑ Corresponding author. Tel.: +34 881 816784; fax: +34 881 816702. E-mail addresses: teresa.alvarino@usc.es (T. Alvarino), evangelia.katsou@univr.it (E. Katsou), malamis.simos@gmail.com (S. Malamis), sonia.suarez@usc.es (S. Suarez), francisco.omil@usc.es (F. Omil), franceso.fatone@univr.it (F. Fatone). Bioresource Technology 152 (2014) 477–483 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech