Comparison of dye wastewater treatment by normal and anoxic + anaerobic/aerobic SBR activated sludge processes.

In this research, the effects of different color intensities, anoxic + anaerobic times and types of substrate on color removal effectiveness were studied using 16-litre bench scale sequencing batch reactor (SBR) anoxic + anaerobic/aerobic models. The systems were fed with a synthetic wastewater containing 500 mg/l of COD, 50 mg/l of N, 15 mg/l of P along with 10, 40 and 80 mg/l of reactive diazo Remazol Black B dye. The anoxic + anaerobic/aerobic periods were 0/11 (normal aerobic SBR), 2/9, 4/7 and 8/3 hours, respectively. The color removal occurred mainly under the anaerobic environment, while a slight attenuation was noticed under the aerobic condition. A better decolorization could be achieved with a longer anoxic + anaerobic period. The sodium acetate was a slightly better co-substrate for the color removal than glucose. The decolorization efficiency dwindled as the fed dye concentration increased, but the overall color removal leaned in the opposite direction. The phosphorus removal of the anoxic + anaerobic/aerobic systems was outstanding, whereas only 50% removal was achieved for the aerobic process. A dye concentration of up to 80 mg/l did not have any significant impact on the performance of the polyphosphate accumulating organisms (PAOs). The removal of organic carbon and TKN was comparable among all experiments regardless of system configurations, color intensities and types of substrate.