Tetertretert

Chemical Engineering Journal 178 (2011) 115–121

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Chemical Engineering Journal
journal homepage: www.elsevier.com/locate/cej

Tetracycline removal from waters by integrated technologies based on ozonation and biodegradation
˜ C.V. Gómez-Pacheco, M. Sánchez-Polo, J. Rivera-Utrilla ∗ , J. López-Penalver
Department of Inorganic Chemistry,Faculty of Science, University of Granada, 18071 Granada, Spain

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The main objective of this study was to analyze the effectiveness of ozone and of technologies based on the simultaneous use of ozone–hydrogen peroxide, ozone-activated carbon, and ozone-biological treatment in the removal of tetracyclines (TCs) from waters. The results obtained shown,regardless of the TC under study, TC degradation was complete after 10 min of ozonation. A slight decrease in total organic carbon (TOC) and medium toxicity was observed with longer TC ozonation treatment time. The presence of H2 O2 during TC ozonation considerably increases the TC removal rate. Moreover, the O3 /H2 O2 system had adequate oxidizing capacity to mineralize a high fraction of the totalorganic carbon. The presence of activated carbon during ozonation increases the TC removal rate and also produces a slight decrease in the concentration of TOC and a reduction in the medium toxicity; these effects are explained by: (i) the capacity of the carbon to adsorb TC degradation compounds, which have a smaller molecular size than the original TCs and, especially, (ii) its capacity totransform dissolved ozone into HO. The combined ozonebiological activated sludge system demonstrated a high effectiveness to degrade TCs and mineralize their degradation compounds. These are metabolized by the microorganisms in biological sludge, markedly reducing the TOC, chemical oxygen demand (COD), and biological oxygen demand (BOD); the longer the TC ozonation time before the biologicaltreatment, the greater are these reductions. © 2011 Elsevier B.V. All rights reserved.

Article history: Received 31 July 2011 Received in revised form 6 October 2011 Accepted 6 October 2011 Keywords: Tetracyclines Integrated technologies Ozonation Biodegradation

1. Introduction Over the past decade, the growing demand for drinking water has prompted the development of new treatment technologies tomeet increasingly strict regulations. For their practical application, account must be taken of the nature and physicochemical properties of the waters or effluents to be treated [1]. Waters contaminated by human activity are, in general, effectively processed by: biological treatment plants, adsorption with activated carbon or other adsorbents, or conventional chemical treatments (thermal oxidation,chlorination, ozonation, potassium permanganate, etc.). For some contaminants, however, these procedures are unable to achieve the degree of purity required by legislation and for the utilization of treated effluents. This is true for pharmacologically active products, which are inadequately removed by conventional treatments and have been detected in wastewaters and, in some cases, in surface andground waters [2–8]. Advanced oxidation processes (AOPs) are increasingly applied to address this problem, especially in industrialized countries [9–14]. Some of these technologies are based on the use of ozone (O3 ).

∗ Corresponding author. Tel.: +34 958248523; fax: +34 958248526. E-mail address: jrivera@ugr.es (J. Rivera-Utrilla). 1385-8947/$ – see front matter © 2011 Elsevier B.V. Allrights reserved. doi:10.1016/j.cej.2011.10.023

O3 dissolved in water can react with the contaminant by two different mechanisms, direct reaction and reaction by radicals [15]. The reaction rate and products formed depends on the predominant mechanism. Free hydroxyl radicals generated in O3 decomposition are highly reactive species, capable of successfully attacking most organic molecules, with...