Performance and Kinetic Study on Bioremediation of Diazo Dye (Reactive Black 5) in Wastewater Using Spent GAC–Biofilm Sequencing Batch Reactor Soon-An Ong & Li-Ngee Ho & Yee-Shian Wong & Komalathevi Raman Received: 5 July 2011 /Accepted: 21 September 2011 /Published online: 5 October 2011 # Springer Science+Business Media B.V. 2011 Abstract Combinations of sequential anaerobic and aerobic process enhance the treatment of textile waste- water. The aim of this study was to investigate the treatment of diazo dye Reactive Black 5 (RB5)- containing wastewater using granular activated carbon (GAC)–biofilm sequencing batch reactor (SBR) as an integration of aerobic and anaerobic process in a single reactor. The GAC–biofilm SBR system demonstrated higher removal of COD, RB5 and aromatic amines. It was observed that the RB5 removal efficiency improved as the concentration of co-substrate in the influent increased. The alternative aeration introduced into the bioreactor enhanced mineralization of aromatic amines. Degradation of RB5 and co-substrate followed second-order kinetic and the constant (k 2 ) values for COD and RB5 decreased from 0.002 to 0.001 and 0.004 to 0.001 l/mg h, respectively, as the RB5 concentration increased from 100 to 200 mg/l in the GAC–biofilm SBR system. Keywords GAC–biofilm . Sequencing batch reactor . Color removal . RB5 . Kinetic study 1 Introduction Many dyes are difficult to decolorize due to their complex structure and synthetic origin. The discharge of this dyeing wastewater to the environment causes aesthetic problems and also damages the quality of the receiving water. Conventional physical and chemical techniques such as coagulation, adsorption on activated carbon, filtration and reverse osmosis can be used efficiently to remove dyes from textile wastewater. However, these processes are considered as non-destructive since they merely transfer the dye from liquid to solid wastes. Furthermore, these methods are quite expensive, have operational prob- lems, and generate huge quantities of sludge (Kapdan and Kargi 2002; Sandhaya et al. 2005; Eltaief et al. 2008). Biological treatment technologies (aerobic, anaerobic, aerobic/anaerobic, and anaerobic/aerobic) for textile wastewater treatment are economical alternative and have shown greater efficiency with remarkable results over physico-chemical methods (Lu et al. 2009; Kapdan and Alparslan 2005; Yang et al. 2009; Wijetunga et al. 2008). Decolorization of textile dye effluent generally does not occur when Water Air Soil Pollut (2012) 223:1615–1623 DOI 10.1007/s11270-011-0969-4 S.-A. Ong : Y.-S. Wong : K. Raman School of Environmental Engineering, University Malaysia Perlis, Arau, Perlis 02600, Malaysia L.-N. Ho School of Material Engineering, University Malaysia Perlis, Arau, Perlis 02600, Malaysia S.-A. Ong (*) School of Environmental Engineering, University Malaysia Perlis, Arau, Perlis 02600, Malaysia e-mail: ongsoonan@yahoo.com