A tightening effluent ammonia limit is a frequent trigger for an upgrade, because ammonia removal depends on nitrification — the slowest and most sensitive part of the biological process. An MBBR ammonia upgrade adds a nitrifying stage, often as a tertiary polishing reactor after existing secondary treatment, to drive effluent ammonia down to the required level. Ammonia removal by nitrification is the same underlying mechanism as a nitrification upgrade; the framing here is compliance with an ammonia consent.
Meeting an ammonia consent
A tertiary MBBR polishing stage receives already-treated, low-BOD water and is dedicated to converting the remaining ammonia. Because the nitrifiers are held on carriers, the stage delivers stable ammonia removal even when the upstream plant experiences peaks. The stage is sized for the ammonia load at the coldest design temperature and requires adequate dissolved oxygen and alkalinity.
Where total nitrogen must also be reduced, a nitrification upgrade is combined with a denitrification step; where only ammonia is limited, the nitrifying stage alone may suffice.
Ammonia Upgrade Design Context (indicative — confirm per project)
| Parameter | Typical Value | Unit | Notes |
|---|---|---|---|
| Stage position | tertiary polish | — | After secondary treatment |
| Upstream BOD | low | — | Favours nitrifiers |
| Sizing basis | ammonia load @ min T | — | Cold-weather governs |
| Dissolved oxygen | ≥ ~2 | mg/L | Needed for nitrification |
Frequently Asked Questions
How does MBBR help meet an ammonia limit?
Is an ammonia upgrade the same as a nitrification upgrade?
Does an ammonia upgrade also remove total nitrogen?
Related Pages
Need MBBR Design Support?
Submit your wastewater data for a preliminary MBBR engineering assessment. Our team reviews every submission within 2 business days.