Nitrate, contained in surface or groundwater, can be removed by sorption on protonated cross-linked chitosan gel beads. The sorption capacity is large enough to meet the standard of drinkable water. The isothermal equilibrium curves are straight lines which were established for a contaminated groundwater. The sorption kinetics is not limited by pore diffusion and is well modelled by a phenomenological equation. The experimental partition coefficient and overall mass transfer coefficient were used for simulating a plug flow fixed bed adsorber. The trend of the breakthrough curve was not affected by sinusoidal variations of the superficial velocity, which shows that the design can be carried out considering a conventional step injection. The breakthrough curve is more sensitive to the packing length than to the column diameter. (C) 2004 Elsevier B.V. All rights reserved.