An apparatus (12) for treating water, in particular for removing surfactants from waste water, includes a vessel (14), defining an inlet (16) for receiving waste water containing air bubbles, and an outlet (20) for the exit of water, following treatment. Inside the vessel there is at least one tubular member (50) having a lower open end (52) into which the flow of waste water from the inlet may be directed in use. The tubular member (50) extends from the inlet towards a top of the vessel where an upper exit (54) from the tubular member is defined. In use, most un-aerated water entering the vessel through the inlet can exit the tubular member at the lower open end. Foam formed in the water by the air bubbles may travel up the tubular member to the upper exit, which is preferably located above the water level (60) in the vessel.