Fixed aeration is normally applied in a basin with a steel or concrete floor, and retrievability, though available, is usually not an objective. Fixed diffusers can be either open (usually called coarse-bubble) or membrane (usually called fine-bubble). They can be as simple as individual diffusers with threaded connectors or saddle mounted pairs, or as sophisticated as the AerResearch oxygen panel. Design objectives can be process oxygen limited (limited by the amount of oxygen to be transferred) or mixing limited (limited by the amount of mixing energy required). Membrane diffusers can be applied to both oxygen limited and mixing limited applications. Open diffusers are usually not applied to oxygen limited applications and are often avoided because of their tendency to become plugged.

The length of individual diffusers and those mounted on saddles is limited. One limit is structural - the cantilevered load that can be applied to the diffuser attachment. The other limit is due to the pipe on which they are mounted. Thermal and other stresses on the pipe cause it to twist, and this twisting causes the diffusers be un-level from tip to tip. Because of the length limitations, individual and saddle-mounted diffusers are typically the most expensive option when compared on the basis of the total length of diffuser in the system.

Aerresearch's oxygen panel arranged for ultra-high transfer efficency with high wastewater strength.

Aerresearch's oxygen panel arranged for high transfer efficency with normal wastewater strength.

Oxygen Panels allow a high degree of floor coverage in circular tanks

In order to overcome these limitations on diffuser length, AerResearch developed the oxygen panel concept in which diffusers can have multiple supports along their length. With multiple supports, diffuser lengths up to fifteen feet are applied. Diffuser level is easy to maintain. Individual diffusers, or groups of diffusers can be isolated from long air supply pipes so that pipe twisting does not affect the diffuser level.

AerResearch has supplied oxygen panel diffusers as long as fifteen feet and at diffuser spacing of as little as six inches center to center. This is greater floor coverage, and therefore higher oxygen transfer efficiency, than any design known to AerResearch.

The oxygen panel design allows diffusers to be mounted immediately adjacent to the floor so that mixing and oxygen transfer efficiency is maximized. There are no dead areas between or beneath the diffusers. Yet the diffusers are as simple, strong, and easy to maintain as all tubular diffusers.

Oxygen panels tilted to allow easy floor cleaning

Oxygen panels in a fully retrievable configuration