Have a look at this paper:
http://aquanic.org/systems/recycle/docu ... tingVT.pdf

Check out the U-Tube diffuser. They have a U tube that goes down 40'. They inject air at the top and have water flow high enough to carry the air with the water. The water goes down with the bubbles and back up and exists with the water oxygen saturated. The system I saw was similar, but injected the air at the bottom of the U-Tube and was used as an air-lift water circulator. It requires a little more air pressure.