Growing problems associated with the increased production of wastewater have encouraged studies on the development of photocatalytic materials for wastewater treatment to decrease its impact on the environment and on human health. In particular, one important issue is related to the presence of pollutants, such as bacteria and dissolved organic constituents, in wastewater. There have been various approaches for wastewater treatment using semiconductors as photocatalytic materials. Among them, the most widely used is based on titanium dioxide (TiO2) thin films; however, the applications of TiO2 have been limited by its low quantum yield and relatively large band gap. Therefore, research has been focused on the improvement of the photocatalytic properties of TiO2 by doping it with metals such as Fe, Co, Ni, Au, Ag, Pt and oxides such as WO3. The main aim of this work is to report the preparation of TiO2 thin films modified with different nickel content (Ni-x:TiO2) using the sol-gel technique and their application as catalysts in the degradation of a dye solution unpolluted and polluted with some easier organic material, such as sucrose and Escherichia Coli (E. coli) microorganisms, which were used as a first approximation of wastewaters pollutants to assess whether the dye is degraded in presence of pollutants. From EDS and XPS analysis, was determined atomic nickel content of about 1, 5, 10 and 20 at.%. The results of the catalytic performance showed that Ni-1:TiO2 was able to obtain the same percent of degradation of malachite green (MG) when both polluted and unpolluted dye solutions were employed. The Ni-10:TiO2 and Ni-20:TiO2 catalysts showed a decrease in their catalytic performance when pollutants were present in the MG solution. (C) 2012 Elsevier Ltd. All rights reserved.