Evaluation of colour removal in synthetic saline wastewater containing azo dyes using an immobilized halotolerant cell system

Studies were carried out to evaluate the colour removal capacity of a moderately halotolerant bacterium, Bacillus firmus, in synthetic saline wastewater medium (SSWM) under static condition. The bacterial strain effectively decolourized Polar red B (an azo dye) in a wide range of sodium chloride (1–6%, w/v), dye (5–100 mg/L) and SDS (0.1–5.0 mg/L) concentrations and at pH range of 6–10 after 24 h of incubation. Cell immobilization studies indicated that colour removal was significantly higher (p < 0.05) in immobilized halotolerant cell systems than with free cells of B. firmus especially at salt concentrations higher than 4%. Results suggest the potential of using the immobilized halotolerant cell system for effective treatment of dye-contaminated saline wastewaters.