Solar Water Disinfection Studies With Supported $TiO2$ and Polymer-Supported Ru(II) Sensitizer in a Compound Parabolic Collector

Solar water disinfection was performed using $TiO2$ and a Ru(II) complex as fixed catalysts located in a compound parabolic collector photoreactor. Studies were performed in the laboratory as well as at a greenfield site. Under laboratory conditions, natural water contaminated with cultured bacteria was photocatalytically treated and the influence of the photolysis as well as of both catalysts was studied. Experiments were performed with contaminated water flowing at 12 l/min; under these conditions, photocatalytic experiments performed with a supported heterogeneous photocatalyst (Ahlstrom paper impregnated with $TiO2$⁠) showed it to be effective in degrading bacteria in water. The Ru complex catalyst, however, showed no clear evidence for disinfecting water, and its efficiency was comparable to the simple photolysis. Under on-site experiments, bacteria contaminated water from the Yaurisque river at Cusco, Peru was treated. As a general trend, after photocatalytic treatment a reduction in the E-coli population present in water was observed. Whenever disinfection was achieved in the experiments, no regrowth of bacteria was observed after 24 h. However, a reduction in the prototype efficiency was observed both in laboratory and on-site experiments. This was ascribed to aging of the photocatalyst as well as due to the deposition of particles onto its surface. In cases in which incomplete disinfection resulted, a low rate of E-coli growth was observed 24 h after ending the experiment. However, pseudomones seem to be resistant to the treatment.