Apparatus for establishing contact between a liquid and a gas

An apparatus for aeration of water poor in oxygen and for purification of water in a lake or a water course contaminated with organic matter, comprising a cylindrical container which is packed with hollow filling bodies and mounted for rotation about a horizontal axis, at least the circumferential wall of the cylindrical container being perforated so that the liquid and the gas can flow therethrough, the hollow filling bodies being of sufficiently light weight to support the cylindrical container when said container is partially immersed in the liquid, and a plurality of pipes parallel with the horizontal axis of the cylindrical container and symmetrically distributed about the circumferential wall of the cylindrical container, said pipes having openings of lesser size than the peripheral dimensions of the hollow filling bodies so as to prevent passage of said filling bodies through said openings into said pipes, said openings directed substantially in the direction of rotation of the cylindrical container for raising the liquid and for entraining air into the liquid.