Digestate ultrafiltration with UltraFlux™
UltraFlux™ separates permeate from the retainable fraction of digestate. The design coordinates solids concentration, pumping capacity and the destination of both streams.
- Technology
- Outside-in cross-flow UF
- Objective
- Concentrate the retainable fraction
- Integration
- Evaporation or dewatering
What ultrafiltration concentrates
The membrane barrier retains solids and colloids according to its cut-off. Selection of the feed point considers fibres, coarse particles, fats and digestate variability to define pretreatment and protect the circuit.
Salts, ammonium and some soluble organic matter may remain in the permeate. The balance therefore distinguishes suspended solids, dissolved solids and soluble COD: reducing concentrate volume does not remove the entire load from the water.
| Aspect | Project criterion |
|---|---|
| Concentrate | A fraction enriched in the retained components. |
| Permeate | Separated stream for recovery or further treatment. |
| Recirculation | Membrane surface sweeping and control of sustainable concentration. |
Integration with downstream stages
UltraFlux™'s outside-in configuration combines high active area per module with a low reference cross-flow velocity. The layout is adapted to plant capacity and available space.
Sizing considers the complete treatment system. A reduced flow can relieve a downstream stage, provided the separated permeate has a defined destination and the target concentration is achieved consistently.
| Aspect | Project criterion |
|---|---|
| Evaporation | Preconcentrate the retainable fraction and calculate the thermal duty reaching the evaporator. |
| Dewatering | Coordinate flow and solids load with centrifugation, pressing or other equipment. |
| Water reuse | Characterise the permeate and define the polishing required for its intended use. |
Solids balance and operating point
For a given component, the balance is: feed Q × feed C = concentrate Q × concentrate C + permeate Q × permeate C. Q is flow rate and C is the concentration of the same component in each stream.
Achievable concentration depends on viscosity, composition, fouling and recirculation demand. Testing establishes sustainable flux, retentate concentration and permeate quality, together with cleaning sequences.
| Aspect | Project criterion |
|---|---|
| Permeate flow | Stable production over the cycle, including the effect of cleaning. |
| Concentration | Retentate solids content, viscosity and pumpability. |
| Availability | Cycle duration and permeability recovery after cleaning. |
Data for an initial assessment
- Digestate origin and existing separation layout.
- Flow, total and suspended solids, and load variability.
- Available data on fibres, fats, particle size distribution and viscosity.
- Total and soluble COD, ammonium, salinity, pH and temperature.
- Concentrate destination, permeate use and available installation space.