Process for removing the nitrite and/or nitrate content in water

A continuously performable process for decreasing the nitrite or nitrate content of nitrite-polluted or nitrate-polluted water with the selective formation of nitrogen, comprising the steps of introducing hydrogen gas into the nitrite or nitrate-polluted water, and contacting the resulting hydrogen-loaded water with a metal catalyst formed of a porous inorganic carrier impregnated with a metal component selected from the group consisting of palladium, rhodium, mixtures of palladium and rhodium, and mixtures of palladium and a metal of the copper group, wherein said inorganic carrier has at least one of the following characteristics (a), (b) and (c):

• (a) a bimodal pore radius distribution with a proportion of at least 20%, relative to the overall pore volume, of macropores having a minimum radius of 2,000 .ANG.;
• (b) a non-homogenous distribution of the metal with a concentration in the surface area or
• (c) is a powder, and
• wherein for treating water polluted only with nitrite, a catalyst is used in which the metal component is selected from the group consisting of palladium, rhodium and mixtures thereof, and wherein for treating water also polluted with nitrate, a catalyst is used in which the metal component is selected from the group consisting of mixtures of palladium and a metal of the copper group, rhodium, and mixtures of rhodium and palladium, or wherein a mixture is used of a catalyst in which the metal component comprises palladium and a metal of the copper group, and of a catalyst in which the metal component consists solely of palladium, and wherein the pH value of the water is maintained not higher than pH 8.