Nitrate contamination of drinking water supplies is of acute public health concern worldwide. Donnan dialysis is a potentially advantageous physiochemical process for nitrate removal from contaminated waters. Investigation of nitrate ion removal by Donnan dialysis using a stripping solution with three different anion exchange membranes (Selemion AMV, Neosepta AMX, Fumasep FAB) revealed that in all cases part of the nitrate was adsorbed by the ion exchange membrane. Experimental data covered a range of Reynolds numbers, using stripping solutions of NaCI and Na2SO4. The level of adsorption is related to the concentration of the stripping solution, the counter ion species and the membrane type. A model is presented which incorporates the adsorption phenomenon in the kinetics of Donnan dialysis and is well supported by the experimental data.