The main objective of this work is to reduce the chemical oxygen demand (COD) and color of the effluent containing reactive textile dye by microbial method. Anaerobic digestion has the potential to break down complex refractory organic compounds so that they may be further degraded aerobically or to completely mineralize them. An anaerobic digestion technique was applied to synthetic reactive red 2 dye cotton textile effluent aiming at the dye degradation. Halophilic and halotolerant bacterial culture Halomonas variabilis and Halomonas glaciei were used for degradation in batch-mode static condition. The temperature was kept constant at 30 degrees C using CO(2) incubator. Maximum degradation was achieved within 144 h of experimental run. Degradation studies were made by determining COD and biochemical oxygen demand (BUD). Statistical analysis showed that the BOD and COD reduction rate were optimal in the concentration of 1297 mg L(-1) for the time duration of nearly 100 h. (C) 2011 Elsevier Ltd. All rights reserved.