Intensified biodegradation of Congo red dye by mixed culture in a sequential bioreactor: Kinetics and phytotoxicity studies

Although textile industries lead the economic sector in several countries, the pollution that they cause, particularly to water bodies, is a serious environmental concern. Dyes and their metabolites are harmful to human and aquatic life due to their toxic, mutagenic, and carcinogenic potential. In this study, we have made an effort to treat the complex Congo red (CR) dye-containing wastewater in an anaerobic-aerobic sequential bioreactor. The impact of CR dye concentration (20-100 mg/L) on the performance of sequential bioreactor was examined. The CR dye removal efficiencies (REs) of 97, 88.1, 75.9, 68.7, and 42.56% were obtained at 20, 40, 60, 80 and 100 mg/L of CR dye, respectively. Similarly, the overall Chemical oxygen demand (COD) RE of 90% was also obtained. It was found that the CR dye and COD REs were high at low concentrations of CR dye. The obtained experimental data was fitted with growth and substrate inhibition models. A phytotoxic study indicated that the Chickpea (Cicer arietinum L.) grown in treated wastewater showed better germination (93%) than untreated wastewater (66%).