Decolorization of Reactive Black 5 using Soil Bacterial Consortium under a Combined Dynamic and Static Condition

Abstract

Decolorization of Reactive Black 5 (RB-5) dye by isolated soil bacterial consortium had been conducted in this research. This study aims to determine the effect of operating conditions and kinetics of RB-5 decolorization by single strains and the consortium. Bacterial strains capable of RB-5 decolorization were isolated and identified as Micrococcus sp., Janibacter sp. and Rhodococcus sp. The RB-5 synthetic wastewater was used in the experiments with five days of incubation time. The studied conditions include combinations of shaking (dynamic) and static period of incubation, bacterial concentration, initial pH, temperature, and initial dye concentration. The results showed that the combined dynamic and static condition was important to RB-5 decolorization by the isolated bacteria. The decolorization with highest efficiency for all cultures was obtained at pH 7 with 2-day shaking period continued with 3-day static period for single strains and 1-day continued with 4-day for the consortium. The highest efficiency was given by Janibacter sp. (94.8% at 100 mg/L), which exhibited a good performance up to pH 11. All the decolorizations of RB-5 by single strains followed the first-order kinetics (4/-5 concentrations of 200 to 1,000 mg/L) but this was not observed with the consortium. Even though the decolorization efficiency of the consortium (88%) was not as high as the standalone Janibacter sp., the shaking period could be reduced from 2 days to 1 day without losing high ability to decolorize at pH 11. This suggests that working with consortium could give a benefit of reducing the aeration period compared to working with single strain, which will be useful for wastewater treatment application.