Domestic sewage is a medium-strength wastewater dominated by biodegradable organics, ammonia from nitrogenous compounds, and suspended solids. Its flow and load follow a strong daily pattern — peaking in the morning and evening — which a biological process must absorb without losing performance. MBBR does this by holding biomass on the carriers, so treatment capacity does not depend on maintaining a settleable sludge.
Treating the Daily Load Cycle
Sewage treatment must cope with peak flows several times the average and with dilution during wet weather. Because the MBBR biofilm is fixed, it is not washed out by hydraulic peaks the way a suspended-growth system can be. Preliminary treatment — screening and grit removal — protects the carriers and aeration system, and primary treatment can be included upstream to reduce the organic load reaching the reactor.
For sewage, an MBBR is typically designed for combined BOD removal and nitrification where an ammonia consent applies, with the reactor either staged or sized to achieve both duties.
Sewage Treatment Design Context (indicative literature ranges — confirm per project)
| Parameter | Typical Value | Unit | Notes |
|---|---|---|---|
| Typical influent BOD | 150 – 400 | mg/L | Site-specific — confirm per project |
| Typical influent NH₄-N | 25 – 60 | mg/L | Site-specific — confirm per project |
| Peak factor (flow) | 2 – 4 × | of average | Diurnal + wet weather |
| SALR — combined duty | 5 – 15 | g BOD/m²·d | Lower where nitrification required |
Pre-treatment and Solids Separation
Effective screening and grit removal are essential to protect the carriers and the aeration grid. Downstream, a solids-separation step removes the biofilm that sloughs from the carriers to produce a clarified effluent. The overall train is simple and well suited to community-scale plants.
Frequently Asked Questions
Does MBBR handle peak sewage flows?
Is primary treatment needed before MBBR?
Can one MBBR remove both BOD and ammonia?
Related Pages
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