Abstract: An air lift diffuser for use in the aeration of a body of water including an air lift tube and a gas diffuser located a distance below the open bottom end of the air lift tube. The distance in question is sufficiently large that there is substantially no obstruction to the passage of water from the space surrounding the air lift diffuser into the space between the air lift tube and the diffuser, but at the same time is not so large that rising air bubbles are likely to escape and flow outside the air lift tube. In one embodiment, a cylindrical return tube is provided around the air lift tube that directs the water stream and gas bubbles entrained therein downward, after they have risen in the air lift tube, so as to return the aerated water to the lower levels of the body of water being aerated.

Abstract: A fluid diffuser for dispersing gas bubbles or liquid droplets into a body of receiving liquid in a tank. The diffuser includes a fluid-emitting member for communication with the body of receiving liquid, which member defines a fluid plenum. A portion of at least one of the walls of the fluid-emitting member is porous and has a foraminous outer surface, to permit the passage of fluid from the plenum into the body of liquid. A slot-forming chamber has a wall that defines a narrow, elongated slot extending parallel to the foraminous outer surface of the plenum-defining wall of the fluid-emitting member, with the foraminous outer surface lying primarily outside the slot. Fluid supplied under pressure to the plenum flows out through the porous wall portion to produce small nascent fluid spheroids on the foraminous surface of that portion.