Apparatus for mixing air and liquid

An improved aparatus for aeration of a body of liquid such as a body of waste water, said apparatus comprising:

• a top-mounted power drive having a rotatable shaft extending downwardly toward the surface of said body of liquid;
• and
• an impeller mounted on said shaft for rotation therewith at the surface level of said body of liquid, said impeller comprising an upwardly, outwardly flared diffusion head forming an impeller body having a lower, axial flow inducing, propeller shaped portion with a blade having a first outer diameter, said blade being mounted on the lower end of said diffusion head for drawing liquid from said body of liquid and pumping said liquid axially upward at a first velocity;
• said impeller body also having an upper, centrifugal flow inducing portion with a plurality of radially outwardly curved blades having second, outer diameters larger than said first diameter, said blades being mounted on said diffusion head for receiving therebetween said liquid pumped axially upward by said axial flow inducing portion and for centrifugally expelling said liquid outwardly from said impeller at a second velocity greater than said first velocity at a position above the surface of said body of liquid, said blade of said propeller shaped portion being gradually curved into a spiral to merge into and form one of said second plurality of blades, said centrifugal flow inducing portion having an exit diameter which is greater than that of said propeller shaped portion, whereby said liquid pumped axially upward by said axial flow inducing portion into said centrifugal flow inducing portion is continuously guided and accelerated by said blades as the direction of flow of said liquid changes gradually from axial to centrifugal before being discharged in a nearly horizontal direction from said centrifugal flow inducing portion.