In this study, anaerobic digestion of textile dye wastewater was carried in a batch reactor using mixed culture. Textile dye wastewater was collected and characterized. Response surface methodology (RSM) was employed to study the effect of process variables like pH, temperature, textile dye wastewater dilution ratio and MLVSS on dye decolourization and COD removal efficiency. The optimum condition was found for the maximum decolourization and COD removal efficiency. They are: pH – 7.1,

temperature – 31.5 °C, wastewater dilution ratio 1:2, and MLVSS – 6200 mg/L. The maximum decolourization and COD reduction was found to be 70.3% and 72.6% at the RSM optimized conditions.