This paper presents the results of research on the possibility of photodecolourization of trace amounts of copper complexes of chlorophyllins (E141(ii) commercial dye) in water (sewage). Experiments were carried out in model UV-VIS/E141 (ii)/TiO₂/H₂O and UV-VIS/E141(ii)/H₂O systems. The degree of decolourization of the dye was determined spectrophotometrically. The loss of dye in a UV-VIS/E141(ii)/TiO₂/H₂O system was directly proportional to the initial substance concentration and ranged from 55% to 82%, depending on the initial concentration of the dye in the solution. Kinetic studies confirmed that over a range of examined concentrations of dye E141(ii), the photocatalytic decolourization process occurs in accordance with the commonly acknowledged Langmuir-Hinshelwood model. The course of changes in pH upon exposure indicates the formation of acidic derivatives of chlorophyllins. We found that the amount of photodegradable dye strongly depends on the initial pH of the solution. The increase of the pH of the solution inhibited the process of photocatalytic decolourization of E141(ii), whose yield reached a minimum value at pH 8. Results of this study confirm that the photocatalytic processes can be an alternative to traditional methods of food industry sewage treatment.