Short answer: The MBBR process itself is biological and does not consume chemicals to remove COD or nitrify. However, depending on the wastewater and treatment targets, supporting chemicals may be needed for alkalinity supplementation, pH adjustment, phosphorus precipitation, carbon dosing (denitrification) or polymer addition (solids separation).
When chemicals are needed
Typical chemical requirements (indicative — confirm per project)
| Parameter | Typical Value | Unit | Notes |
|---|---|---|---|
| Alkalinity (NaOH, Na₂CO₃, lime) | Nitrification | — | Nitrification consumes 7.14 mg CaCO₃ per mg NH₄-N oxidised. |
| pH adjustment (NaOH or H₂SO₄) | If pH outside 6.5–8.5 | — | Nitrifiers need pH above 6.5; acidic industrial waste may need neutralisation. |
| Iron/aluminium salt | Phosphorus removal | — | Chemical P precipitation when permit requires TP removal. |
| External carbon (methanol, ethanol, acetate) | Denitrification | — | Only when influent COD:N ratio is too low for biological denitrification. |
| Polymer | Solids separation | — | Optional; improves clarifier or DAF performance in some cases. |
| Antifoam | Rarely | — | Some industrial wastewaters generate foam during aeration. |
When NO chemicals are needed
Many MBBR applications run without any chemical addition:
- Pure COD/BOD removal with well-buffered wastewater and no P limit: the biology does all the work.
- Nitrification with sufficient natural alkalinity: some wastewaters (e.g. certain food-industry streams) have enough bicarbonate to buffer the acid produced by nitrification without supplementation.
- Roughing applications: MBBR used as a high-rate pre-treatment step before further biological treatment often needs no chemicals.
Frequently Asked Questions
Is chemical cost a major OPEX item for MBBR?
It depends on the application. For simple COD removal with no P limit and sufficient alkalinity, chemical cost is zero. For nitrification with low alkalinity plus P removal, chemical cost can be 20–40 % of total OPEX. An engineering assessment quantifies this for a specific project.
Can I reduce chemical consumption?
Yes. Strategies include: using simultaneous nitrification-denitrification (SND) to recover alkalinity, optimising chemical dosing with online control, using waste carbon sources instead of purchased methanol, and selecting the most cost-effective metal salt for P removal.
Does activated sludge need the same chemicals?
Largely yes. Alkalinity, pH adjustment, P precipitation and external carbon are needed in activated-sludge plants under the same conditions. The chemical requirements are driven by the wastewater and the permit, not by the biological technology choice.
Related Pages
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