Dry composite biomass of cyanobacterial consortium collected from thermal springs was used as biosorbent in immobilized form for decolorization of Crystal violet (CV) dye under thermal conditions that generally prevail in textile effluent. Response surface methodology (RSM) was employed to investigate the effect of process variables on the biological treatment of dye containing water. The variables investigated were pH, initial dye concentration and temperature using Box-Behnkhen Design (BBD) model. Predicted values were found to be in good agreement with experimental values (R2=0.9501), which indicated suitability of the model. Maximum decolorization occurred at pH-6, 150mg/l dye concentration and 45oC indicating suitability of biosorbent for removal of Crystal violet dye.