A review of the various development steps of a catalytic reduction process of nitrate ions in drinking water is presented. The approach followed to define and improve the catalyst at the lab scale, including kinetic study and molecular modelling, is described. The chemical engineering aspects, including diffusion and mass transfer, as well as reactor design are discussed in the light of a first pilot plant experiment in the field. The practical difficulties encountered due to the growth of micro-organisms in the reactor are also discussed in the light of process engineering rules. The results of a new field trial are presented, and some hints for future work are also given. Finally, the interest of reductive catalytic step in drinking and wastewater treatment is briefly discussed.