Exploring bioremediation strategies to enhance the mineralization of textile industrial wastewater through sequential anaerobic-microaerophilic process

• The textile wastewater treated sequentially by anaerobic-microaerophilic process.
• The combine treatment reduced COD and BOD upto 97% and color by 99% with 60 h HRT.
• Toxicity of wastewater gradually decreased upon anaerobic-microaerophilic process.

The study exemplifies sequential anaerobic-microaerophilic bioremediation process for treatment of textile industrial wastewater having 10,000 mg l−1 of COD and 3330 mg l−1 of the BOD. The experimental results showed that, in an anaerobic phase, with cattle dung slurry as an initial feed, nearly 60% of COD and BOD was removed from textile wastewater at an optimum HRT of 2d and OLR of 5.0 kg COD m−3d−1. Further, COD and BOD removal efficiency of bacterial consortium BDN was enhanced upto 97% under microaerophilic phase, at HRT of 12 h. Moreover, optimum color removal (80%) was observed in anaerobic reactor. The combine treatment process removed 99% of color at combine HRT of 60 h. The activity of lignin peroxidase was higher as compared to other enzymes studied. The UV–vis, FTIR, 1H NMR and GC–MS analyses of treated textile industrial wastewater revealed the degradation of dye compounds and formation of lower molecular weight intermediates. The toxicity of textile industrial wastewater decreased subsequently from anaerobic to microaerophilic treatment process.