Biological treatment of wastewater containing an azo dye using mixed culture in alternating anaerobic/aerobic sequencing batch reactors

The performance of one stage anaerobic/aerobic processes for the biological treatment of synthetic wastewaters containing Acid Red 18 was studied. In addition, a method for evaluating dye mineralization using lumped parameters was investigated. The selected initial dye concentrations were 0, 35, 70, 140, and 280 mg/L, in reactors R1 ～ R5, respectively. This study showed that average COD removal was not lower than 85% while the remaining COD originated from Acid Red 18 and its degradation products. The majority of the dye removal occurred in the anaerobic phases and the aerobic phase contributions were insignificant. The kinetics data of dye removal showed that the increase in initial dye concentration (35 ～ 280 mg/L) caused a decrease in first-order kinetic rate constants (0.0593 ～ 0.0384/h). The overall mineralization of AR 18 dye was at least 44, 35, 13, and 0% in R2 ～ R5, respectively. Increase in initial dye concentrations had no significant effect on sludge characteristics.