Apparatus for diffusion in bodies of liquid

A floating aerator for a sewage lagoon or the like, said aerator comprising a floating diffuser dome of generally disc-shaped configuration and having a closed upper face disposed above the liquid level of the lagoon, said dome having an underface which is concave over a central portion of its total surface area and of flat planar configuration over the marginal area, said marginal surface area being below said liquid level and encircling said concave surface portion, said concave surface thus providing a trapped air pocket under said dome, a draft tube supported by said dome and depending vertically below the center of said concave portion of the dome surface with the upper end of the draft tube spaced therefrom, and an air supply tube accessible from the outer surface of said dome and extending through said draft tube to terminate at a diffuser adjacent the draft tube's lower end, whereby the upper flow of the air-liquid mixture induced in the draft tube by the injection of air through the diffuser initially impacts on said concave surface portion then flows radially outwardly along said planar marginal surface of the dome.