Concurrent removal of reactive blue HERD dye and Cr(VI) by aerobic bacterial granules

Removal of toxic and recalcitrant co-contaminant dyes and Cr(VI) has become a challenge in the textile industry. The present study attempts to resolve this uncharted problem of pollution by biotransformation and detoxification of Reactive blue HERD dye and Cr(VI) using aerobic bacterial granules (ABGs). The ABGs effectively decolorized 99.2% dye at static condition within broad pH (5.0-11.0) and temperature (20-60 degrees C) ranges. A noteworthy reduction and tolerance towards dye (6000 mg l- 1) and chromate (800 mg l- 1) was observed for ABGs. Besides this ABGs also remarkably decolorized the dye (500-2000 mg l- 1) and reduced chromate (25-100 mg l- 1) simultaneously with their variable concentrations. Despite at continuous supply of dye the ABGs maintained their decolorization capacity up to the 16th cycle, making them a viable option for commercial application in textile effluent treatment. The chromatographic and spectroscopic characterization endorsed the biotransformation of dye while toxicological testing revealed a non-hazardous impact of dye metabolites on plant, and animal cells and also at their genetic scale. Metagenomics profiling of ABGs demonstrated predominant role of Firmicutes, Proteobacteria, Acidobacteria and Bacteroidetes whereas, imputed metagenomics exhibited higher expression of metabolic and xenobiotic biotransformation pathways during dye degradation. Hence, present study strongly suggests that ABGs would be a sustainable technology for the remediation of dye effluent containing organic and inorganic materials.

Automated summary

This study investigated the pollution problem of dye and Cr(VI) and found that aerobic bacterial granules (ABGs) can effectively degrade dye and reduce chromate within a wide range of pH and temperature. The ABGs also demonstrated the potential to maintain their degradation capacity under continuous supply of dye.