Solar TiO2-photocatalysis was applied to waters from a natural wastewater treatment plant located in the Universidad de Las Palmas de Gran Canaria. Degussa P-25 TiO2 and its mixture with activated carbon (AC-TiO2) were used as catalysts. The presence of ozone and certain ions such as phosphates on the photocatalytic degradation of organic matter was also studied. Disinfection experiments have provided interesting results, particularly when using the catalyst AC-TiO2 and ozone, since total disinfection was achieved in less than 60 min. No bacterial reappearance at 24 or 48 h was observed. Additionally, this catalyst gave important TOC and some ions concentrations reductions. Studies in catalyst reuse revealed that the catalyst AC-TiO2 showed almost no deactivation.