Decolorization of azo Direct Blue 71 dye in aqueous solutions using sequential upflow anaerobic sludge blanket reactor and UV/H2O2 process

Abstract

In this research, decolorization of synthetic textile wastewater was investigated by upflow anaerobic sludge blanket (UASB) reactor and advanced oxidation UV/H2O2. In the acclimation phase, an 18 L UASB reactor with a discharge of 18 cm3/min was fed with a colorless synthetic wastewater for 40 days. Then the reactor was fed with wastewater containing Direct Blue 71 as the coloring agent at 6 consecutive steps with concentrations of 10, 50, 100, 200, 300 and 400 mg/L. In the first step, the removal efficiency was the least due to the low inflow dye concentration. However, by further increment of dye concentration in the influent to greater than 200 mg/L, the removal efficiency gradually increased and reached above 80 %. Since the treated effluent from steps 4–6 did not meet regulations, it was discharged into a UV/H2O2 reactor for further treatment. The results showed that with increasing H2O2 concentration, the removal efficiency increased, although excessive increase in H2O2 concentration reduced the removal efficiency. The pseudo-first order kinetic model was in good agreement with the degradation data with the optimal reaction rate constant at a concentration of 2225 mg/L of H2O2.