Wastewater reduction of Salmonella Typhimurium and H₂S by using TiO₂ films deposited by spin coating or magnetron sputtering

Salmonellosis is one of the most common infectious diseases transmitted by contaminated food or water. The emergence of antibiotic-resistant strains of Salmonella Typhimurium is associated with an increase in the incidence of invasive salmonellosis, acquired through contaminated products or water. Therefore, wastewater treatment is crucial for reducing the risk of infection, especially when this water is to be used or reused in agro-industrial sectors without proper treatment. This research studied TiO₂ film photocatalysis deposited by spin coating and magnetron sputtering for the simultaneous reduction of Salmonella Typhimurium and H₂S in wastewater. The TiO₂ films produced by spin coating and annealed at 550 °C exhibit aggregate-dominated growth, generating heterogeneous and clustered surfaces, with the anatase phase (bandwidth 3.14 eV) as the predominant crystalline structure; while the films deposited by magnetron sputtering showed a dense and uniform morphology, associated with the columnar growth typical of this technique, with good adhesion to the porous biochar substrate. At 200 °C, a mixture of anatase–rutile phases with a bandwidth of 3.21 eV occurred. Results showed that both types of TiO₂ films reduced more than 79 ± 2 % of bacteria and generated qualitative changes in H₂S production by the colonies and reducing more than 78 ± 2 % of the H₂S responsible for unpleasant odours. These results suggest that the photocatalysis process with both kinds of TiO₂ films could serve as a complementary treatment to conventional wastewater treatment technologies, favouring the production of water free of Salmonella Typhimurium and reusable in activities that do not involve direct human consumption.