Biodegradation of Remazol Black B in sequential microaerophilic–aerobic operations by NAR-2 bacterial consortium

The ability of the NAR-2 bacterial consortium, consisting of A1, C1, and L17, to degrade the azo dye model, Remazol Black B (RBB), was studied in an upflow packed-bed reactor for continuous sequential microaerophilic–aerobic batch operations. Continuous decolourisation was performed in a borosilicate glass column (12 mm × 20 mm) packed with surfactant-modified clinoptilolite immobilised by the NAR-2 bacterial consortium. In column bioreactor studies, decolourisation was observed at 45 °C and was carried out by varying the flow rates and dye concentrations in a modified P5 medium with pH 7.0 under microaerophilic conditions. A decolourisation of 95.87 % of 0.1 g/L RBB was achieved at a flow rate of 0.2 mL/min under microaerophilic conditions by the immobilised NAR-2 bacterial consortium. An analysis of the decolourised and biodegradation products of the RBB using total aromatic amines showed that a reduction in the RBB resulted in the formation of aromatic amines. On further aerobic degradation for 15 days, the concentration of the amines dropped significantly, from an initial concentration of 34 to 11 mg/L, following the aerobic batch treatment experiment. The findings of this study showed that SMC can be a support material for bacterial cell immobilisation in a single upflow reactor with intermittent microaerophilic–aerobic operations, and it was found to be suitable and eco-friendly for the degradation of azo dyes.