In groundwater treatment plant (GWTP) adsorption is often the last treatment step to remove recalcitrant compounds from contaminated water in order to reach the groundwater threshold values. Granular Activated Carbon (GAC) is the most common adsorbent material since it combines high efficiency with low cost. Generally, the design of adsorption stage is based on the isotherm of each compound. However, sometimes, a complex mix of contaminants is present in the water to treat. In these cases, a competitive effect can arise from the multicompound interaction with the GAC: they compete with each other to occupy the GAC available sites. As results of this phenomenon, the operating life of the filter can be reduced compare to the designed one.