In a typical wastewater treatment flow sheet used by several industrial units in India, various stages of treatment include the primary treatment-oil/grease removal and neutralization, followed by the secondary treatment-chemical/biological oxidation and clarification, and the tertiary treatment-adsorption onto activated carbon. The neutralization of the wastewater with acid/milk of lime increases the concentration of total dissolved solids, which adversely affects the activity of microorganisms during biological oxidation process. To overcome this limitation, adsorption is proposed in the first stage of treatment and other stages could follow depending on the quality of the wastewater. Experiments were carried out on wastewater samples from different plants manufacturing dyes using adsorbents-activated carbon, fly ash, bentonite and lignite. The effectiveness of adsorbents in reducing chemical oxygen demand (COD) and colour was evaluated. The results of COD reduction are fitted into different models available in the literature. A model for predicting COD equilibrium values is proposed. Sorption kinetics and rate of reduction of COD over time are also discussed.