A model based on material balance concepts and second-order reaction kinetics is presented for prediction of the performance of expanded-bed adsorption systems for treatment of complex mixtures of dissolved organic materials in aqueous solution. The model utilizes system parameters measured or calculated from bench-scale batch experiments, correlative techniques, and hydrodynamic considerations. The major focal point of these investigations is the description of the mixtures as composite solutes by using an overall concentration parameter (chemical oxygen demand, COD) and mathematic treatment of the mixtures as single-solute systems for prediction of continuous flow adsorber breakthrough profiles.