This post is dedicated to answer several questions raised why TiO2 being a popular photocatalyst and thus often being used for photocatalysis and photodegradation any unwanted compounds or chemicals including microorganism, organic particles.
I just found in a paper of Weimin Xi (2001), he stated that TiO2 is having considerable photocatalytic activity. Honestly I do not know what does that mean by photocatalytic activity. It has high stability, non-environmental impact and low cost. Despite that not all those factors I know, but I ever read somewhere in journals, probably by Katsofidou, that the presence of TiO2 of course coupled with ultraviolet (UV) irradiation has produced non hazardous stream of product water as a result of transformation of organics treated by photocatalysis.