Decolourization of synthetic wastewater containing azo dyes by immobilized Phanerochaete chrysosporium in a continuously operated RBC reactor.

laboratory-scale rotating biological contactor (RBC) reactor with immobilized fungal biomass of Phanerochaete chrysosporium was investigated for its performance in decolourizing synthetic wastewater containing single or mixture of azo dyes, Direct Red-80 (DR-80) and Mordant Blue-9 (MB-9). Decolourization efficiency in the continuously operated bioreactor was studied by varying dye inlet concentration and disc rotation speed at two different wastewater hydraulic retention times (HRTs), i.e. 24and 48 h. Results from the single dye-containing experiments showed that the system could completely decolourize the wastewater for a maximum inlet dye concentration within the range 25-200 mg L and 48 h HRT in the reactor; for an inlet dye concentration above 200 mg L, the decolourization efficiency slightly reduced up to 85% for the same HRT. However, wastewater containing DR-80 was found to be decolourized more efficiently compared to that containing MB-9. Further, the effect of increase in the disc rotation speed from 2 to 6 rpm in the study revealed no large differences in the decolourization efficiencies of the wastewaters. Similar results were obtained with wastewater containing the dyes together at various concentration combinations as per the two-level factorial design of experiments. Enzyme activities of lignin peroxidase and manganese peroxidase by the fungus were also analysed in the study, and the results indicated that while DR-80 showed a large negative effect on both the enzymes, MB-9 affected mainly the MnP activity by the fungus. [ABSTRACT FROM AUTHOR]