Existing aeration tanks are among the best candidates for an MBBR retrofit because they already have the water depth, an air supply and a mixing regime broadly compatible with a moving-bed reactor. Retrofitting carriers into an aeration basin adds attached biomass to increase capacity or add nitrification. The key checks are whether the existing diffuser layout provides both oxygen transfer and enough turbulence to circulate the carriers, and whether retention screens can be installed at the outlets.
Adapting the existing aeration
A moving-bed reactor needs coarse-bubble or suitably arranged aeration to keep carriers in continuous motion, in addition to the fine-bubble transfer used for oxygenation. An existing fine-bubble grid may therefore need supplementing or reconfiguring. The oxygen supply must also cover the added biological demand created by the extra biomass. These adaptations are defined once the treatment target and carrier fill are set.
Carrier retention screens are installed on tank outlets so that carriers stay in the reactor while treated water passes through.
Aeration-Tank Retrofit Checks (site-specific — confirm per project)
| Parameter | Typical Value | Unit | Notes |
|---|---|---|---|
| Existing depth | reuse | m | Usually suitable for MBBR |
| Aeration type | review | — | Transfer + carrier mixing |
| Oxygen capacity | increase | — | For added biomass demand |
| Retention screens | add | — | On tank outlets |
Frequently Asked Questions
Why are aeration tanks good MBBR candidates?
Does the existing aeration need changing?
How are carriers kept in the tank?
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