Sterilization system using an ozone-air mixture for treatment of a water-intake finger (6) and an air space (10) of a water source bottle (9) of a water dispenser in which the bottle (9) is installed with its neck downwards for gravitation discharge of water from the bottle (9) into a water reservoir (11) located inside the dispenser and having an air space (8), the system includes a cone (7) for holding the bottle (9) in vertical position, the water-intake finger (6) for water delivery from the bottle (9) into the water reservoir (11), an ozone generator (2), and a control device (13). Two longitudinal channels (20, 21) are made in the water-intake finger (6) for separate water delivery from the bottle (9) into the water reservoir (11) and ozone-air mixture delivery into the bottle (9). The water-intake finger (6) is provided with a preventive cup (19) adapted to prevent from air penetration into the bottle (9) from the air space (8) of the water reservoir (11), the preventive cup (19) being provided with an inlet channel (18) connected to the ozone generator (2) for ozone-air mixture delivery into the preventive cup (19) during water off-take from the water reservoir (11) when water poured out of the bottle (9) is replaced with the ozone-air mixture delivered from the ozone generator (2).
