High Efficiency Diffusers vs. Surface Aerators

Key elements in the comparison of diffusers versus surface aerators are to get the performance on a common basis. Items that are important to evaluate are as follows:

• Surface aerators typically have limited standby capacity. It is important when comparing surface aerators and diffusers to have a similar standby capacity. Diffusers will typically have 50% or 100% standby capacity of the blower systems. Similar standby capacities or spare capacity should be considered with surface aerators as well.
• With the diffusers, the cost of a blower building may be included for the diffusers. There are two important issues to remember:
  • Most of the blower systems can also be installed outside with little if any protection. The cost of a blower building is optional and not a direct cost comparison for the diffuser system versus surface aerators.
  • If a blower building or shelter is employed, it is critical to recognize that cost of an office for the plant operator, housing for other components in the treatment plant, storage space for spare parts, etc which are typically employed inside a blower building and operations building are really not associated with diffusers, but are the convenience for the total plant operation. Those costs should not be assigned to diffusers in a comparison of diffusers versus surface aerators.
• Electrical switch gear items need to be compared for total systems as well. Blowers will typically have less electrical components as all starters and electrical controls are in one location. The cost for the electrical components that are distributed around the treatment plant or lagoon are part of the surface aerator system cost.

It should also be noted that on the electrical controls, when there is a 50% to 100% standby of blowers provided there should be an accounting for a similar electrical switch for capability on the surface aerators.

In general, mechanical aerators have been considered as the lowest first cost of most systems. In reality when total system cost are considered on a similar design criteria and similar design basis, diffusers and surface  aerators can be very similar in capital cost.

Once the capital cost issue has been addressed, the operating savings from diffused aeration systems will typically pay for complete abandonment of new surface aeration systems and converting to fine bubble diffusers with less than 3 year pay back. When comparing surface aerators with diffusers for new construction, comparing them on an equal scope of supply basis will show that the diffusers are very close to the same first cost and if the first year’s operation cost are incorporated, the installed cost of diffusers are less! Beyond that point, savings of energy is huge and is contributing to the owner or to the operating entity.

For convenience, a quick checklist of operating and performance characteristics of high efficiency diffusers versus surface aerators is below for reference and use.

EDI HIGH EFFICIENCY DIFFUSERS VS SURFACE AERATORS