Abstract: Apparatus for contacting a liquid, in a tank containing a body of same, with a gas from a gas space overlying the body of liquid. A generally tubular draft member is disposed in the tank, having a cylindrical main body portion and an outwardly flared conical inlet upper section forming a liquid inlet at its upper end. Enclosing walls of the conical inlet section form an angle with the draft member central axis of from 5.degree. to 35.degree. and the conical inlet section has a vertical height of from 0.25 to 1.25 times diameter of the draft member. A rotatable axial pumping impeller is provided in the draft member for rotational vortex entrainment of gas in downwardly flowing liquid pumped through the draft member. Baffle means are positioned in the conical inlet section of the draft member to prevent bulk rotation of liquid in the tank during rotation of the impeller.