Providing air for aeration is among the most expensive processes at a sewage treatment plant. Mechanical aerators are typically the most expensive while fine bubble diffusers are the least expensive to operate. Significant savings in energy cost can also be achieved by insuring that tanks are not over aerated.

If a certain amount of air is divided into large bubbles, while an equal amount of air is divided into small bubbles, the smaller bubbles will enable a greater transfer ratio of oxygen into the water. This is so due to the fact that the smaller bubbles will contain the same volume of air in a greater number of air bubbles. As the number of bubbles increase, so does the available surface area over which air can be transferred into water. Fine bubbles are much more efficient at transferring air because they create a larger transfer surface area per unit volume of added air. While coarse bubble diffusion efficiency may have an OTE of 0.75% per foot of pond depth, fine bubble systems may have an OTE of up to 2% per foot. This means that twice as much air can be transferred from the same air volume using fine bubbles as could occur using coarse bubbles.