Chemical Engineering Journal 161 (2010) 122–128 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej Sequencing batch reactor technology coupled with nanofiltration for textile wastewater reclamation E. Zuriaga-Agustí, M.I. Iborra-Clar, J.A. Mendoza-Roca ∗ , M. Tancredi, M.I. Alcaina-Miranda, A. Iborra-Clar Department of Chemical and Nuclear Engineering, Polytechnic University of Valencia, Camino de Vera s/n 46022 Valencia, Spain article info Article history: Received 29 October 2009 Received in revised form 19 April 2010 Accepted 23 April 2010 Keywords: Textile wastewater Azo dye SBR Colour removal abstract Textile wastewaters are characterized by high organic matter concentration and colour presence. Con- ventional treatments do not remove completely the colour since the aerobic bacteria cannot degrade the azo-bond of the reactive dyes. However, their elimination is a requirement for wastewater reuse. In this study, it is proposed the reuse of textile wastewater as process water by a hybrid process combining a sequencing batch reactor (SBR) process with nanofiltration (NF) membranes. The aim is to evaluate the colour removal yield in the SBR and to study the influence of the addition of NF retentate on the SBR feed. The laboratory SBR was operated in cycles of 20 h and was fed with a solution containing a mix- ture of three reactive dyes: Remazol Yellow RR, Remazol Blue RR and Remazol Red RR. Every day colour and COD removal efficiencies were determined. The NF retentate was stored in order to mix it with the synthetic wastewater for the SBR feed. Colour removal yield ranged from 85 to 90% for the red and blue dyes and from 70 to 75% for the yellow one when the SBR feed was only the textile synthetic wastewater. However, when the SBR feed was the mixture of 50% synthetic wastewater and 50% of NF rejection the colour removal efficiency was reduced between 10 and 15%. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Owing to water scarcity textile industries are upgrading their wastewater treatment plants (WWTPs) with the aim of achieving a final effluent that can be reused. When the first WWTPs for the textile mills were erected, con- ventional treatments, both physico-chemical and biological were implemented in order to meet the legal standards. The current tendency is the use of biological processes, since they achieve higher efficiencies, preparing the wastewater for further reclama- tion and reuse. In this way, although some authors have proposed treatments for the raw wastewater that do not include biolog- ical processes [1,2], in the last years most of the works have reported about systems based on biological processes that prepare the wastewater for further reclamation and reuse [3]. A typical raw wastewater from a dyeing, printing and finish- ing textile industry is characterized by high COD and conductivity values together with colour presence. Conventional biological wastewater treatment processes reduce significantly the wastewater COD. However, these processes do not eliminate the colour and conductivity is hardly modified by a bio- logical process. Minimizing the COD, eliminating the colour and reducing the conductivity value are of paramount importance in ∗ Corresponding author. Tel.: +34 963877630; fax: +34 963877639. E-mail address: jamendoz@iqn.upv.es (J.A. Mendoza-Roca). order to reuse the final effluent. Thus, the combination of different techniques is required. The use of biological and membrane processes can be appropri- ate for achieving the aforementioned aims. In this way, Sahinkaya et al. [4] studied the combination of a conventional activated sludge (CAS) process and nanofiltration (NF) for treating wastewater from a Denim textile mill. 75% of the colour was eliminated in the CAS process due mainly to its adsorption onto the sludge flocks and NF membranes retained around the 65% of the wastewater conductiv- ity. In the same way, in former works of our research group [5] NF was used as a treatment for the secondary effluent from a textile mill. Other authors also studied this processes combination [6,7]. However, membrane fouling may produce a fast decrease in the process performance [8,9]. A biological process degrading the reac- tive dyes could guarantee a less fouling tendency in a subsequent membrane stage. Reactive dyes are normally azo-based chromophores combined with different types of reactive groups, e.g., vinyl sulphone, chloro- triazine. They are characterized by binding to the cotton fibres through covalent bonds [10]. It is well known that biological mineralization of azo-dyes requires the integration of an anaerobic process that degrades the azo-bond to aromatic amine intermediates and an aerobic pro- cess for their total degradation. [11,12]. Melgoza et al. [13] studied the degradation of a synthetic wastewater containing the colorant DB79. These authors observed that the DB79 was biotransformed to amines in the anaerobic stage decolorizing the wastewater. The 1385-8947/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2010.04.044