The Upflow Anaerobic Sludge Blanket (UASB) reactor is the workhorse of high-rate anaerobic treatment. Wastewater flows up through a dense bed of granular sludge that converts soluble COD to biogas, while a gas–liquid–solid separator at the top retains the biomass — giving high treatment rates with a small footprint and energy recovery.
The features that define its performance
Self-immobilising granules of anaerobic biomass settle into a dense, fast-settling bed that holds a very high active-organism concentration.
An even upflow through a floor distribution system fluidises the bed just enough to maximise contact between substrate and biomass without washing granules out.
The GLSS (three-phase separator) at the top decouples biogas, treated water and granules — the feature that lets the reactor run at high rate while retaining its biomass.
Two numbers govern a UASB. The organic loading rate, OLR = Q·S0/V (kg COD/m³·day), sets how much substrate the granule bed must process — typically 5–15 for a UASB. The upflow velocity, v = Q/A, must be high enough to keep the bed expanded and well-mixed but low enough that granules are not carried into the separator (commonly ~0.5–1.5 m/h on soluble effluent). Granule quality and the GLSS design are what let a UASB hold both numbers in band — which is why start-up, granular acclimation and even flow distribution matter as much as the vessel itself.
Indicative figures — confirmed by treatability testing on your effluent
| COD Loading | 5 – 15 kg/m³·day |
| COD Removal | 75 – 85% |
| HRT | 6 – 12 hours |
| Best For | Soluble COD, moderate TSS |
Reynolds & Bauhm selects and designs the anaerobic reactor that fits your effluent — confirmed by treatability testing and delivered with biogas handling and energy recovery.
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