Integrated biological and ozone treatment of printing textile wastewater Adriana Maria Lotito a,⇑ , Umberto Fratino a , Giovanni Bergna b , Claudio Di Iaconi c,⇑ a Department of Water Engineering and Chemistry, Politecnico di Bari, via Orabona 4, 70125 Bari, Italy b CIDA s.p.a., via Laghetto 1, 22073 Fino Mornasco (CO), Italy c Water Research Institute, National Research Council, viale De Blasio 5, 70132 Bari, Italy highlights " Integrated ozone-SBBGR treatment was tested for printing wastewater treatment. " An effluent for direct discharge can be obtained with an ozone dose of 135 mg/l. " A synergetic biological and chemical oxidation activity is observed. " Sludge production is low (0.17 kg TSS /kg CODremoved ). article info Article history: Received 7 February 2012 Received in revised form 13 April 2012 Accepted 1 May 2012 Available online 11 May 2012 Keywords: Printing wastewater treatment Textile wastewater Sequencing batch biofilter granular reactor Ozone integration Synergetic oxidation abstract Textile effluents are among the most difficult industrial wastewaters to treat because of their composi- tional variability and of the presence of numerous different chemicals intentionally designed to resist degradation. Though biological technologies offer a cheaper and more environmental friendly alternative for the treatment of textile effluents, an additional step to remove recalcitrant compounds is still needed. Integrated biological and chemical treatment is a rather new approach that allows improving treatment performance and stability without increasing too much treatment costs. Ozone integration in a sequenc- ing batch biofilter granular reactor was tested at laboratory scale for treating a printing wastewater char- acterized by high concentrations of surfactants and nitrogen. The process was optimized in terms of applied organic load and ozone dose. The results have shown that the process assures the possibility to comply with the limits for direct discharge for all investigated parameters by operating at an organic load value lower than 1.5 kg COD /m 3 d and with an ozone dose of 135 mg/l. A synergetic biological and chemical oxidation activity was observed with a ratio between ozone dose and COD removed lower than 0.75. Finally, the process was characterized by a sludge production as low as 0.17 kg TSS /kg CODremoved due to the high biomass concentration in the biological system used. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction The textile industry is one of the longest and most complex manufacturing industrial chains, covering the entire production cycle from raw materials to semi-processed products (yarns, woven and knitted fabrics with their finishing process), to final products (carpets, home textiles, clothing and industrial use tex- tiles) [1,2]. The main environmental issue arising from textile production primarily regards water pollution. In fact, the textile industry uses water as the principal medium for removing impurities, applying dyes and finishing agents, and generating steam [1,3]. About 100– 200 l of water per kg of textile product are consumed and are then quite completely discharged as aqueous effluent, because both water losses to the product and water evaporated during drying are negligible [1,4]. Apart from the high volume of dis- charged water, the main concern regards the chemical load it car- ries, due to the high dosage of chemicals and auxiliaries (as high as 1 kg per kg of processed textiles) [1]. Among the products ap- plied during the process, the highest environmental load arises from salts, detergents and organic acids. Even if dyestuffs do not represent a significant load compared to other substances, they can convey difficult-to-eliminate organic compounds, adsorbable organic halogens (AOXs), metals and they are respon- sible for the colour of the effluent (which is mainly an aesthetic problem, but can also reduce light transmission to aquatic plants) [1,5]. 1385-8947/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.cej.2012.05.006 ⇑ Corresponding authors. Tel.: +39 3403005056; fax: +39 0805313365 (A.M. Lotito), tel.: +39 0805820525; fax: +39 0805313365 (C. Di Iaconi). E-mail addresses: adriana.lotito@libero.it (A.M. Lotito), claudio.diiaconi@ba. irsa.cnr.it (C. Di Iaconi). Chemical Engineering Journal 195–196 (2012) 261–269 Contents lists available at SciVerse ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej