ORIGINAL PAPER On-site treatment of textile yarn dyeing effluents using an integrated biological–chemical oxidation process A. M. Lotito • M. De Sanctis • S. Rossetti • A. Lopez • C. Di Iaconi Received: 3 September 2012 / Revised: 11 February 2013 / Accepted: 16 March 2013 / Published online: 17 April 2013 Ó Islamic Azad University (IAU) 2013 Abstract This paper reports the results of the treatment of a yarn dyeing effluent using an integrated biological– chemical oxidation process. In particular, the biological unit was based on a sequencing batch biofilter granular sludge reactor (SBBGR), while the chemical treatment consisted of an ozonation step. Biological treatment alone was first performed as a reference for comparison. While biological treatment did not produce an effluent for direct discharge, the integrated process assured good treatment results, with satisfactory removal of chemical oxygen demand (up to 89.8 %), total nitrogen (up to 88.2 %), surfactants (up to 90.7 %) and colour (up to 99 %), with an ozone dose of 110 mg of ozone per litre of wastewater. Biomass characterization by fluorescence in situ hybrid- ization has revealed that filamentous bacteria represented about 20 % of biomass (coherently with high sludge vol- ume index values); thanks to its special design, SBBGR guaranteed, however, stable treatment performances and low effluent suspended solids concentrations, while con- ventional activated sludge systems suffer from sludge bulking and even treatment failure in such a condition. Furthermore, biomass characterization has evidenced the presence of a shortcut nitrification–denitrification process. Keywords Yarn dyeing wastewater  Biological treatment  Ozonation  Integrated treatment  Biomass characterization Introduction Textiles and wearing apparel represent an important eco- nomic sector in Europe, accounting for about 3.6 % of the EU-27 manufacturing in terms of value added and 6.3 % in terms of employment in 2008 (European Commission 2011). Even if textile industry activities are distributed across Europe, they are mainly concentrated in few coun- tries, among which Italy is the leading producer, with a turnover of about 60 billion € (25 billion € for textile manufacturing) against about 170 billion € from all EU-27 in 2008 (Eurostat data). The textile industry is a water-intensive sector (con- suming about 100–200 L of high-quality water per kg of textile product) and is rated as the most polluting among all industrial activities (considering both discharged volume and effluent composition) (Andleeb et al. 2010; Bechtold et al. 2004; Chen et al. 2011; Grekova-Vasileva and Topalova 2009; Tehrani-Bagha et al. 2010; Vandevivere et al. 1998). Water is used for cleaning the raw material and for many flushing steps during the whole production; furthermore, water is used as solvent in many dyeing baths. Textile processing involves many steps, which differ as a function of the processed fibres (European Commission 2003). Basically, for making a fabric, a source of fibre from which a yarn can be made is required. The yarn is then processed by knitting or weaving, which turns the yarn into fabric. The yarn can be coloured before or after the con- version in fabric. According to this step, the textile pro- cessing may be classified into four categories, namely A. M. Lotito Department of Water Engineering and Chemistry, Politecnico di Bari, via Orabona 4, 70125 Bari, Italy M. De Sanctis  A. Lopez  C. Di Iaconi (&) Water Research Institute, National Research Council, viale De Blasio 5, 70132 Bari, Italy e-mail: claudio.diiaconi@ba.irsa.cnr.it S. Rossetti Water Research Institute, National Research Council, via Salaria km 29.300, C. P. 10, 00015 Monterotondo St. (RM), Italy 123 Int. J. Environ. Sci. Technol. (2014) 11:623–632 DOI 10.1007/s13762-013-0271-7