Novel, environmentally friendly dynamic system based on titanium dioxide photocatalysts, for the elimination of Escherichia coli bacteria from water

EU regulations establish a limit for both chemical and microbiological contamination in water, which are very stringent for drinking water, and impose a precise threshold even for bathing and recreational waters. In the case of the last two, great attention is paid on bacteria, especially those with pathogenic potential, such as Escherichia coli (E. coli), universally recognized as an indicator of faecal contamination. A classic approach to prevent the growth of E. coli in water, is the addition of chlorine to water sources, which acts as a disinfectant able to kill bacteria. But chlorine can be harmful to the aquatic ecosystems and cause respiratory, ocular and skin damages to animal and humans. Photocatalysis is one of the most promising, green and low-cost technology to allow access to purified water. It is based on the photo-induced properties of some oxides, such as TiO2, SrTiO3, ZnO and SnO2, which can oxidize, especially in the nanometric form, various contaminants in water, once illuminated by UV radiation. In this study, we want to couple the photocatalytic properties of TiO2 with the multiple properties of polymer by realizing a hybrid organic-inorganic photo-catalytically active material that will be applied for the purification of contaminated water. With this purpose, an innovative automatic system has been designed, composed of a reactor with external optical heads, and internal transparent polymer plates where nanostructured titanium dioxide has been suitably deposited. The system is completed by a peristaltic pump and a microfluidic apparatus. The characteristic of the system is that it is highly versatile, low cost and portable: indeed, it can be housed inside a box of small dimensions, and powered by batteries. Another technical advantage is that it can be fully adjustable, from the intensity of the light, to the speed of the flow. The applications could be recreational waters in rural environments.