Decolorization and toxicity evaluation of simulated textile effluent via natural microbial consortia in attached growth reactors

Textile wastewater is heterogeneous in nature with multiple types of dyes and other chemicals. Considering this point, attached growth bioreactors were constructed, using sludge (SD), alkalophilic (AK), and thermophilic (TH) bacterial consortia to develop an effective dye biodegradation system. Simulated dye wastewater, containing a 50 ppm mixture of three reactive azo dyes, viz. Reactive Blue (RB 221), Reactive Yellow (RY 145), and Reactive Red (RR 195) were treated under batch mode operation for up to 192 h. Overall, the color removal efficiency of the reactors varied from 85 to 94 % in 192 h. The thermophilic consortium achieved maximum decolorization (93.5 %), operated at 50 degrees C, while the alkalophilic consortium attained maximum COD reduction (93.0 %). Nitrites and nitrates were reduced to (14.7 - 79.3) - (84 - 239.4) mg/L, while sulfates ranged from 624.7 - 1003 mg/L. In addition, scanning electron microscopy (SEM) analysis revealed the biofilm community structure, indicating diverse bacterial interactions among each consortium. The biodegradation of dyes was further confirmed through Fourier-transform infrared spectroscopy (FTIR). Phytotoxicity and cytotoxicity analyses revealed that the dye mixture became non-toxic after treatment. This study outlines that natural microbial consortia are efficient dye decolorizers and confers the possibility of using microbial consortia for upscale biological treatment of dyeing effluents. (C) 2022 The Author(s). Published by Elsevier B.V.

Automated summary

Textile wastewater, containing multiple types of dyes and chemicals, was treated using attached growth bioreactors constructed with sludge, alkalophilic, and thermophilic bacterial consortia. The study showed high color removal efficiency and COD reduction by the bacterial consortia, with the thermophilic consortium achieving maximum decolorization and the alkalophilic consortium attaining maximum COD reduction. The treated dye mixture was confirmed to be non-toxic, indicating the potential of using microbial consortia for biological treatment of dyeing effluents on a larger scale.