The Internal Circulation (IC) reactor stacks two UASB-type compartments in a tall vessel with a built-in gas-lift that recirculates the liquor internally. That self-powered circulation lets it carry very high-strength effluent at organic loading rates and upflow velocities a single-stage UASB cannot reach — in a remarkably compact footprint.
The features that define its performance
A high-load lower compartment does the bulk of the conversion; a polishing upper compartment captures the remaining COD and retains fine biomass.
Biogas from the lower stage drives a gas-lift that pumps liquor up and back down internally — mixing and diluting the feed without any mechanical pump.
The internal recirculation and tall geometry let the IC reactor run at very high loading on a small plan area, ideal for strong, space-constrained streams.
A UASB is limited by upflow velocity: push too much flow and the granules wash out. The IC reactor breaks that limit by recirculating liquor internally via a gas-lift, so the lower compartment sees a high effective upflow and intense mixing while the net throughput stays manageable. This internal circulation — often several times the influent flow — dilutes shock loads, evens out the pH and lets the organic loading rate reach 15–30 kg COD/m³·day at hydraulic retention times of only 2–4 hours. The trade is a taller, more sophisticated vessel, which is why IC reactors are chosen specifically for the strongest distillery, brewery and food streams.
Indicative figures — confirmed by treatability testing on your effluent
| COD Loading | 15 – 30 kg/m³·day |
| COD Removal | 80 – 90% |
| HRT | 2 – 4 hours |
| Best For | Very high-strength effluent |
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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