Decolorization of mixture of UV/ TiO2 pre-treated azo dyes by using developed bacterial consortium – An excellent outcome

Abstract

The degradation of the mixture of azo dyes by the developed bacterial consortium, photocatalytic process (TiO2/UV) and their combined effects were investigated in this study. The bacteria consortium was developed from waste disposal drains in the local textile dyeing industry. The consortium consists of two different bacteria which were identified as Stenotrophomonas pavanii and Bacillus licheniformis through 16S rDNA sequence alignment. The decolorization efficiency was estimated by spectrophotometry and it was observed that biological and photochemical methods alone could not effectively remove the dyes as the decolorization efficiency was low and the absorption peak in the UV region was not completely removed. After 5 days of incubation at 37°C, pH 7 and a dye concentration of 150 mg/L, the microbial dye degradation reached a decolorization efficiency of more than 55%. Additionally, the UV treatment alone was also able to decolorize the dye less than 20% at 45°C, pH 9 at 150 mg/L of dye. A two-step treatment process, namely, photocatalytic treatment followed by biological degradation, was assessed. Ultraviolet-Visible (UVVis) spectral analysis showed that the combined effects were most efficient in the dye degradation (97-98%) which involved a complex interaction of enzyme activity, biosorption and photocatalytic action. Here we also report the optimization of various operational parameters.