Organic matter removal is the collective term for reducing the carbonaceous pollutant load in wastewater — quantified as BOD and COD — by biological oxidation. In an MBBR, heterotrophic bacteria on the carriers convert biodegradable organics to carbon dioxide, water and new biomass. It is the most established MBBR application and the basis on which nutrient-removal duties are added.
The Biology of Carbon Removal
Heterotrophic organisms use organic carbon as both energy and carbon source, consuming dissolved oxygen in the process. Because they grow quickly, they establish an active biofilm rapidly and dominate the carrier surface wherever organic load is high. This makes carbon removal fast and resilient, but it also means that where nitrogen removal is required, the organic load must be managed so that nitrifiers are not crowded out.
The two standard measures — BOD (biodegradable, oxygen-demanding fraction) and COD (total chemically oxidisable matter) — together describe the organic load and its treatability. BOD and COD removal are treated in dedicated pages; this page frames how they relate as one treatment objective.
Organic Matter Removal at a Glance (indicative — confirm per project)
| Parameter | Typical Value | Unit | Notes |
|---|---|---|---|
| Responsible organisms | heterotrophs | — | Fast-growing biofilm |
| Measured as | BOD & COD | — | Biodegradable & total |
| Typical SALR | 5 – 15 | g BOD/m²·d | Objective dependent |
| Position in train | first stage | — | Ahead of nitrification |
Where It Fits in the Train
Organic matter removal is normally the first biological stage. As a standalone objective it produces a well-treated carbonaceous effluent for discharge or reuse; as a preparatory stage it reduces the organic load so that a downstream nitrification stage can operate at the low loading nitrifiers require. Either way it is followed by solids separation to remove the biofilm sloughed from the carriers.
Frequently Asked Questions
What does “organic matter removal” cover?
Which organisms perform carbon removal in MBBR?
Why is carbon removal usually the first stage?
Related Pages
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