Treatment of a denim producing textile industry wastewater using pilot-scale membrane bioreactor N.O. Yigit a , N. Uzal b , H. Koseoglu a , I. Harman a , H. Yukseler b , U. Yetis b , G. Civelekoglu a , M. Kitis a * a Department of Environmental Engineering, Suleyman Demirel University, Isparta, 32260 Turkey Tel. +90 246 211 1855; Fax +90 246 237 0859; email: mkitis@mmf.sdu.edu.tr b Department of Environmental Engineering, Middle East Technical University, Ankara, 06531 Turkey Received 31 July 2007; revised 29 October 2007; accepted 5 November 2007 Abstract The objective of this study was to investigate the performance of a pilot-scale membrane bioreactor (MBR) system for the treatment of a highly concentrated mixed wastewater from wet processes (dyeing, finishing, and sizing) of a denim producing textile industry. The MBR system, containing a submerged hollow fiber membrane module in the aeration tank, was operated aerobically for about 3 months on-site at a continuous flow mode. The system was operated at two different operation stages: (1) no sludge wastage with a typical permeate flux of 20 L/m 2 h and (2) a solids retention time of 25 days with the same flux. During the whole operation period, despite the high dissolved solids content in the influent, very high treatment efficiencies were achieved. The performance of the MBR system was not adversely affected by the variations in the influent characteristics, food/ microorganism ratio, organic loading rate, and specific substrate utilization rate. The average values of some effluent quality parameters found in the entire operation period were color, 53 Pt Co; turbidity, 0.31 NTU; TSS, 0.6 mg/L; BOD 5 , 15 mg/L; COD, 37 mg/L; NH 3 Á N, 1.0 mg/L; NO 3 Á N, 9.6 mg/L; and TN, 10.5 mg/L. Reduction in permeate flux due to membrane fouling was observed only once during all operation and such fouling was removed by applying chemical backwashing and chemical cleaning procedures. The results indicated that complex and highly polluted denim textile wastewaters could be treated very effectively by MBR systems. Color values from as high as 8100 Pt Co levels were significantly reduced to about 50 Pt Co levels, indicating that MBR effluent could be reused in the production processes. Keywords: Color; Dyeing; Membrane bioreactor; Textile wastewater; Treatment Presented at the Third Membrane Science and Technology Conference of Visegrad Countries (PERMEA), Siofok, Hungary, 2–6 September 2007. *Corresponding author. Desalination 240 (2009) 143 Á 150 0011-9164/09/$– See front matter # 2009 Published by Elsevier B.V. doi:10.1016/j.desal.2007.11.071