Abstract: An apparatus for dispersing a gas into a fluid stream. The apparatus has a generally annular body disposed to define an orifice in the fluid stream, a plurality of inwardly depending apertures formed in the body and in fluid communication with a supply of pressurized gas. Each of the apertures defines a localized injection point for dispersion of the pressurized gas into the fluid stream. The orifice includes a restricted throat section adapted to progressively reduce the effective cross-sectional flow area of the fluid downstream of the apertures, such that resultant velocity and pressure differentials enhance dissolution of the gas in the fluid.