The aim of this work is to Study the catalytic removal of nitrates in natural water (not the water prepared in the laboratory by adding a nitrate salt to distilled water) from polluted aquifers, using a continuous stirred tank reactor. The catalysts studied are (Cu or Sn)/Pd supported on alumina. The activity and selectivity of these catalysts in different types of polluted waters are analyzed, optimizing the Pd-metal ratio and the reaction conditions. The deactivation of the catalysts, when using different types of water, is studied and discussed. (C) 2009 Elsevier B.V. All rights reserved.