In ultrafiltration (UF) processes, full-flow (dead-end) filtration and cross-flow filtration are two core modes, with their selection directly impacting system efficiency and energy consumption.
Full-Flow (Dead-End) Filtration
- Principle: 100% of the feed water passes through the membrane surface to become product water, with no concentrate discharge. Pollutants are removed through periodic backwashing.
- Energy Efficiency: Transmembrane pressure (TMP) typically ranges from 0.3-0.8 bar, with energy consumption as low as 0.1-0.3 kWh/m³ .
- Applicable Scenarios: Suitable for low suspended solids (SS <50 mg/L) and low turbidity (NTU <10) water sources, such as groundwater, pretreated surface water, or seawater.
Cross-Flow Filtration
- Principle: Feed water flows tangentially along the membrane surface, with a portion (5-10%) forming concentrate. High flow velocity (2-4 m/s) scours pollutants, reducing polarization layer formation.
- Energy Efficiency: TMP can reach 1.5-2.1 bar, with energy consumption of 0.5-1.2 kWh/m³, approximately 3-5 times that of full-flow filtration.
- Applicable Scenarios: High SS (>100 mg/L), high COD, or emulsified wastewater, such as petrochemical wastewater or landfill leachate.
Comparison of Filtration Modes
| Parameter | Full-Flow Filtration | Cross-Flow Filtration |
| Energy Consumption (kWh/m³) | 0.1-0.3 | 0.5-1.2 |
| Flux Range (LMH) | 40-90 (TN <5 NTU) | 50-150 (high-pollution water) |
| Recovery Rate (%) | >95 | 80-92 |
| Maintenance Cycle | Backwash every 30-60 minutes | Backwash + CEB every 6-24 hours |
