Method and installation for bringing ozone into contact with a flow of liquid, in particular a flow of drinking water or wastewater

An installation comprising:

• an inflow channel (2) for a liquid stream to be treated,
• a descending vertical pipe (3) forming a shaft toward an end of the inflow channel, the descending vertical pipe being directly joined, at a bottom of the vertical pipe, to an approximately horizontal pipe (4),
• pumping means (11) being provided for withdrawing a tapped-off fraction of the liquid stream upstream of the descending vertical pipe and for directing the tapped-off stream toward a mixing assembly (14), receiving a gas—air and/or oxygen—laden with ozone;
• and producing a two-phase trapped off stream, wherein:
• the mixing assembly (14) is placed at the top of a vertical injection tube (16) which is immersed in the descending vertical pipe (3), which pipe is free of any obstacles so that a descending vertical flow (3a) forms a continuous liquid column;
• and
• the vertical injection tube (16) includes, near a lower end, a static mixer (19i) for keeping bubble diameters below a predetermined value, and its lower end includes at least one opening (16a) for reintroducing the two-phase tapped-off stream into the descending vertical flow in the form of at least one jet (25) having a downwardly vertical velocity component (VZ),
• the length of the injection tube (16) and the outlet opening (16a) of the jet both being provided so that the reintroduction takes place below a liquid height (H) and with a downwardly vertical velocity component (VZ) that are sufficient for the gas bubbles to be entrained downward, without them rising in the descending vertical flow of the liquid stream.