Solar photocatalytic treatment of trimethoprim in four environmental matrices at a pilot scale: Transformation products and ecotoxicity evaluation I. Michael a, b , E. Hapeshi a, b , V. Osorio c , S. Perez c , M. Petrovic e, f , A. Zapata d , S. Malato d , D. Barceló c, e , D. Fatta-Kassinos a, b, ⁎ a Department of Civil and Environmental Engineering, University of Cyprus, 75 Kallipoleos St., 1678, Nicosia, Cyprus b Nireas, International Water Research Center, University of Cyprus c Department of Environmental Chemistry, IDAEA-CSIC, c/JordiGirona 18-26, 08034 Barcelona, Spain d Plataforma Solar de Almería (CIEMAT), Carretera Senéskm 4, 04200 Tabernas (Almería), Spain e Catalan Institute of Water Research, c/Emili Grahit, 101, Edifici H2O, Parc Científic I Tecnològic de la Universitat de Girona, Girona 17003, Spain f Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, Spain abstract article info Article history: Received 27 March 2012 Received in revised form 1 May 2012 Accepted 1 May 2012 Available online 28 May 2012 Keywords: Antibiotics QToF–MS Solar Fenton Transformation products Trimethoprim The pilot-scale solar degradation of trimethoprim (TMP) in different water matrices (demineralized water: DW, simulated natural freshwater: SW; simulated wastewater: SWW; and real effluent: RE) was investigated in this study. DOC removal was lower in the case of SW compared to DW, which can be attributed to the presence of inorganic anions which may act as scavengers of the HO•. Furthermore, the presence of organic carbon and higher salt content in SWW and RE led to lower mineralization per dose of hydrogen peroxide compared to DW and SW. Toxicity assays in SWW and RE were also performed indicating that toxicity is attributed to the compounds present in RE and their by-products formed during solar Fenton treatment and not to the interme- diates formed by the oxidation of TMP. A large number of compounds generated by the photocatalytic transfor- mation of TMP were identified by UPLC-QToF/MS. The degradation pathway revealed differences among the four matrices; however hydroxylation, demethylation and cleavage reactions were observed in all matrices. To the best of our knowledge this is the first time that TMP degradation products have been identified by adopting a solar Fenton process at a pilot-scale set-up, using four different aqueous matrices. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Antibiotics are a group of chemotherapeutic agents with varying chemical structures that have the ability to inhibit or abolish the growth of microorganisms. They are used in human and veterinary medicine for the purpose of preventing or treating microbial infec- tions (Blom, 2009; Kümmerer, 2009). However, the extensive use of these compounds has led to the development of antibacterial resis- tance in human pathogenic microorganisms since a great number of these compounds escape the conventional biological treatment and as a result enter receiving environmental media either in their parent form or as transformation products (Costanzo et al., 2005). Although antibiotics are found in the environment at sub-inhibitory levels (ng L -1 –μgL -1 ), relatively low concentrations of these compounds can still promote bacterial resistance (Castiglioni et al., 2008). Advanced oxidation processes (AOPs) through the generation of hy- droxyl radicals (HO•) have proved to be extremely promising alternative techniques to conventional treatments of wastewaters due to their high efficiency in destroying complex organic molecules (Klavarioti et al., 2009). Among the various AOPs, photo-Fenton has gained increasing attention due to its environmentally friendly application and the prospect of operating under solar irradiation hence, lowering the operation cost considerably (Malato et al., 2009; Méndez-Arriaga et al., 2010). In the Fenton reaction proposed by Haber and Weiss (1934), HO• are generated through the interaction of H 2 O 2 with Fe 2+ in the absence of light. The pro- cess efficiency can increase remarkably in the presence of an irradiation source (photo-Fenton) by photoreducing the Fe 3+ to Fe 2+ and the gen- eration of additional HO•. A variety of photodegradation by-products are formed during the photo-Fenton process; however, it has been repeatedly shown that not much attention is being given to the possible formation of these by-products that, would allow the degradation process to be better un- derstood and evaluated (Rizzo, 2011). The identification of transforma- tion products and the elucidation of photocatalysis-reaction pathways are important in optimizing the overall process efficiency, as they are frequently related to toxicity and biodegradability evolution (Amat et al., 2009). The overall aims of this work were to (i) investigate the pilot-scale solar degradation of trimethoprim (TMP); (ii) elucidate the major Science of the Total Environment 430 (2012) 167–173 ⁎ Corresponding author at: Department of Civil and Environmental Engineering, University of Cyprus, 75 Kallipoleos St., 1678, Nicosia, Cyprus. Tel.: + 357 22892275; fax: + 357 22892295. E-mail address: dfatta@ucy.ac.cy (D. Fatta-Kassinos). 0048-9697/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2012.05.003 Contents lists available at SciVerse ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv