T2 has showed more bactericidal activity compared to sample T1 under similar test conditions. This difference could be attributed to the high particle specific surface area (SSA) of T2 (200–240 m2/g) compared to T1 (50–150 m2/g). Increasing the particle surface area provides high relative OH− ion coverages for hydroxyl radical (OH·) formation which is an important ROS responsible for photocatalytic disinfection. In contrast, sample T3 with mixed phase of anatase (∼80%) and rutile (∼20%), an average particle size of ∼21 nm and relatively low SSA (35–65 m2/g) have showed highest bactericidal activity than T1 and T2.