Microbially mediated cleavage of Reactive Black 5 in attached growth bioreactors with immobilized Shewanella indica strain on different carriers

Abstract

Decolorization and removal of contaminants in textile wastewater are essential for pollution control. This study investigated the potential application of a halophilic and halotolerant Shewanella indica (S. indica) strain as immobilized biofilm in two attached growth bioreactors with moving bed bioreactor carrier and polyurethane porous gel carrier, respectively. Under optimized operation conditions, both bioreactors had high tolerance for Reactive Black 5 (RB5) concentration fluctuation and could decolorize RB5 effectively and stably (97% on average) for over 6 months. The decolorization of RB5 in bioreactors was mainly due to microbially mediated cleavage of the azo dye, though adsorption by biofilm and carrier (contribution of different carriers varied) also contributed to the process. However, the azo dye was barely mineralized, and the toxicity remained after decolorization. Overall, this study demonstrated the viability and sustainability of the bioreactors incubated with S. indica in decolorizing RB5. Nevertheless, further technologies need to be explored to detoxify the degradation metabolites.