Anti-influenza drugs constitute a key component of pandemic preparedness plans against influenza. However, the occurrence of such drugs in water environments, the potential of resistance development in the natural hosts, and the risk for transmission of antiviral resistance to humans call for measures to increase removal in wastewater treatment plants (WWTPs). In this study, removal of three anti-influenza drugs; amantadine (AM), oseltamivir carboxylate (OC) and zanamivir (ZA), and formation/removal of their transformation products during ozonation of wastewater effluents from two Swedish WWTPs in Uppsala and Stockholm were studied. The removal profile of target antivirals and formation/removal of their transformation products were studied by liquid chromatography/high resolution mass spectrometry. 3.5 h of ozone exposure (total dose of ozone 5.95 g) led to complete removal of the three anti-influenza drugs with a degradation in the following order ZA > OC > AM. Two, five and one transformation products were identified and semi-quantified for AM, OC and ZA, respectively. Increasing and later decreasing transformation products concentration followed the decrease in concentration of target compounds. All transformation products detected, except one of AM in wastewater from Stockholm WWTP, were removed at the end of the experiment. The removal efficiency was higher for all studied compounds in wastewater from Uppsala WWTP, which had lower TOC and COD values, less phosphorus, and also higher pH in the water. Ozonation thus offers multiple benefits through its potential to degrade influenza antivirals, hence decrease the risk of environmental resistance development, in addition to degrading other pharmaceuticals and resistant microorganisms.

Department of Chemistry Umeå University SE 90187 Umeå Sweden

Department of Chemistry Umeå University SE 90187 Umeå Sweden; University of South Bohemia in Ceske Budejovice Faculty of Fisheries and Protection of Waters South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses Zatisi 728 2 389 25 Vodnany Czech Republic

Ozone Tech Systems OTS AB SE 126 30 Hägersten Sweden

Section for Infectious Diseases Department of Medical Sciences Uppsala University SE 75185 Uppsala Sweden; Zoonosis Science Center Department of Medical Biochemistry and Microbiology Uppsala University SE 75123 Uppsala Sweden

University of South Bohemia in Ceske Budejovice Faculty of Fisheries and Protection of Waters South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses Zatisi 728 2 389 25 Vodnany Czech Republic

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