Acid azo dye remediation in anoxic–aerobic–anoxic microenvironment under periodic discontinuous batch operation: Bio-electro kinetics and microbial inventory

▸ C.I. Acid black 10B degradation was studied in periodic discontinuous batch operation. ▸ Anoxic–aerobic–anoxic microenvironment showed good removal of azo dye. ▸ Azo-reductase and dehydrogenase activity were monitored during dye degradation. ▸ Tafel analysis and bioprocess parameters correlated well with dye removal. ▸ Presence of specific organism capable of dye degradation was observed. Functional behavior of anoxic–aerobic–anoxic microenvironment on azo dye (C.I. Acid black 10B) degradation was evaluated in a periodic discontinuous batch mode operation for 26 cycles. Dye removal efficiency and azo-reductase activity (30.50±1U) increased with each feeding event until 13th cycle and further stabilized. Dehydrogenase activity also increased gradually and stabilized (2.0±0.2μg/ml) indicating the stable proton shuttling between metabolic intermediates providing higher number of reducing equivalents towards dye degradation. Voltammetric profiles showed drop in redox catalytic currents during stabilized phase also supports the consumption of reducing equivalents towards dye removal. Change in Tafel slopes, polarization resistance and other bioprocess parameters correlated well with the observed dye removal and biocatalyst behavior. Microbial community analysis documented the involvement of specific organism pertaining to aerobic and facultative functions with heterotrophic and autotrophic metabolism. Integrating anoxic microenvironment with aerobic operation might have facilitated effective dye mineralization due to the possibility of combining redox functions.