A capacity upgrade increases the load a plant can treat without adding tank volume. In an MBBR upgrade this is achieved by introducing biofilm carriers, which add a large protected surface for biomass on top of any suspended-growth biomass already present. The additional attached biomass raises the treatable organic or nitrogen load. The achievable increase depends on the carrier fill ratio, the available surface area and whether aeration and solids separation can support the higher duty.
How added capacity is created
Each carrier provides protected surface area on which biofilm grows. Adding carriers therefore adds biomass independent of the clarifier return, which is what allows more load to be treated in the same tank. When the same tank is partly filled with carriers and still retains suspended biomass, the configuration is an IFAS system; when it operates on attached growth alone it is a pure MBBR.
The required added capacity sets the carrier volume; aeration must then supply the extra oxygen demand and keep the carriers moving.
Capacity Upgrade Levers (indicative — confirm per project)
| Parameter | Typical Value | Unit | Notes |
|---|---|---|---|
| Carrier fill ratio | up to ~65 | % | Higher fill, more biomass surface |
| Added surface area | per media type | m²/m³ | Protected area drives capacity |
| Aeration | increase | — | Extra oxygen + carrier mixing |
| Config | MBBR or IFAS | — | Attached-only vs hybrid |
Frequently Asked Questions
How much extra capacity can MBBR add?
What is the difference between MBBR and IFAS in an upgrade?
Does a capacity upgrade need more aeration?
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