I'm curious what brand you are looking at. I made inquiries with www.excaliburwater.com about their equipment since I could find very little details on their site. It sounds like they may be using the same methodology and I have some of the same concerns that you have. They do however offer a two tank system as an option that should increase contact time.
Not to put too fine a point on it, but it is the oxygen supply that is crucial. The bulk of air is 78% nitrogen and has only about 21% oxygen. You could setup a greenhouse to raise the oxygen level. LOL