Simultaneous decolorization/degradation of AB-113 and chromium(VI) removal by a salt-tolerant Klebsiella sp. AB-PR and detoxification of biotransformed-metabolites

Abstract

Textile wastewater contains dyes, heavy metals, and salts. In this study, a salt-tolerant decolorizing strain was isolated from vermicompost and identified as Klebsiella sp. strain AB-PR by 16S ribosomal RNA gene analysis. Klebsiella sp. strain AB-PR was presented to simultaneously remove high concentrations of diazo dye and hexavalent chromium under saline conditions for the first time. Maximum decolorization of 95.50% was observed for 800 mg/L of Acid Blue-113 at pH 7 and temperature 35 °C with 5% inoculum size under static conditions. Also, decolorization efficiencies for 13 and 8 g/L of glucose and yeast extract as optimum carbon and nitrogen sources were 94.52 and 94.70%, respectively. Klebsiella sp. strain AB-PR could tolerate 50 g/L of NaCl and decolorize 94.18% of Acid Blue-113. The maximum decolorization and removal efficiencies for 800 mg/L of Acid Blue-113 and 30 mg/L of hexavalent chromium with 50 g/L of NaCl were 90.98 and 89.42%, respectively. Gas chromatography–mass spectrometry and Fourier transform-infrared spectroscopy studies showed that Acid Blue-113 was cleaved to the aromatic amines metabolites with lower molecular weight. The phyto-toxicity study exhibited that Acid Blue-113 was not toxic for Triticum aestivum and Maize. But after biological treatment, the toxicity was increased, and the seeds could not germinate. Therefore, ultraviolet-C/H2O2 was applied for the detoxification of biotransformed metabolites. After application of ultraviolet-C/H2O2, toxic aromatic metabolites were converted to nontoxic and linear organic products, and the seeds were germinated completely. Thus, the combined application of biological–chemical treatment is effective in the detoxification of textile wastewater.