Effect of pH, inoculum dose and initial dye concentration on the removal of azo dye mixture under aerobic conditions

Biodegradation of mixture of three dyes namely, reactive brilliant red X-3B (RBRX-3B), direct blue-6 (DB6) and direct black-19 (DB-19) in a batch shake flask was investigated in this study. Mixed microbial culture isolated from the sludge procured from a local common effluent treatment plant was used to degrade the dyes. Acclimatization of the bacterial culture was done prior to the experiment to obtain a culture with effective degradation ability. Batch kinetic studies were done and modelled using Monod and Michaelis-Menten models. The effects of process parameters, namely pH (5-9), inoculum dosage (5-15%) and initial dye concentration (20-100 mg l(-1)) on the biodegradation of dye mixture were studied systematically and optimized using response surface methodology (RSM). The maximum removal efficiencies obtained for RBRX-3B, DB-6 and DB-19 were 31.2%, 71.5% and 87.6% respectively. The model equations generated by RSM were found to be statistically significant and the optimized values of process parameters were experimentally validated. The error between experimental values and model prediction was found to be less than 10% for all the three dyes. (C) 2016 Elsevier Ltd. All rights reserved.