Tubular Ultrafiltration (TUF) Membrane Process Design for Landfill Leachate Treatment
04 Aug 2025
Here is the professional English translation of the Tubular Ultrafiltration (TUF) Membrane Process Design for Landfill Leachate Treatment:
Project Background
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Water Characteristics:
- COD: 5,000–60,000 mg/L │ NH₃-N: 1,000–3,000 mg/L │ SS: 500–5,000 mg/L
- Contains heavy metals (Zn, Pb, Cr), oils, and refractory organics
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Treatment Targets:
- Effluent compliant with Standard for Pollution Control on the Landfill Site of Municipal Solid Waste (GB 16889-2008)
- TUF permeate: SDI₃≤5, SS≤10 mg/L (qualified feedwater for subsequent RO/NF)
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Process Positioning:
"Biological Treatment + Tubular UF" core process, replacing traditional secondary clarifiers for zero sludge discharge
Full Process Flow
graph TB
A[Raw Leachate Equalization Tank] --> B[Coagulation-Sedimentation Pretreatment]
B --> C[Anaerobic Reactor]
C --> D[Aerobic MBR Tank]
D --> E[Tubular UF System]
E --> F[TUF Permeate Tank]
E --> G[Sludge Thickening & Dewatering]
F --> H[Advanced Treatment Units]
I. Core Unit Specifications
1. Pretreatment System
| Unit | Parameters | Function |
|---|---|---|
| Coagulation-Sedimentation | PAC + PAM (PAC 300 ppm, PAM 1 ppm) | Remove colloids/SS, reduce membrane fouling |
| DAF (Dissolved Air Flotation) | HRT=20 min | Separate oils and light suspended solids |
| pH Adjustment | H₂SO₄/NaOH → pH 6.5–7.8 | Protect microbial activity & membrane materials |
2. Biological Treatment
- Anaerobic Process: IC reactor (organic loading: 10–15 kg COD/m³·d)
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Aerobic Process: MBBR + Tubular UF integrated MBR (DO=2–4 mg/L, MLSS=12–18 g/L)
Innovation: Secondary clarifier eliminated; sludge directly recycled to TUF system
3. Tubular UF System (Core Unit)
| Parameter | Value/Specification |
|---|---|
| Membrane Material | PVDF (acid/alkali/oxidant resistant) |
| Pore Size | 0.02–0.1 μm |
| Diameter/Length | Φ8–12 mm × 3–6 m (standard module) |
| Operation Mode | Cross-flow (velocity: 3–5 m/s) |
| Flux | 40–70 LMH (L/m²·h) |
| TMP (Transmembrane Pressure) | 0.2–0.5 MPa |
| Cleaning Frequency | Physical backwash every 2h; CIP every 7–15 days |
Cleaning Protocol:
- Physical Cleaning: Combined air-water backwash (compressed air + permeate)
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Chemical Cleaning:
- Alkaline: 0.5% NaOH + 0.3% NaClO (remove organics/biofilm)
- Acidic: 1% oxalic/citric acid (remove inorganic scaling)
II. Key Equipment Selection
| Equipment | Specifications | Qty |
|---|---|---|
| Tubular UF Modules | Membrane area 40 m²/module, 0.6 MPa | 6 modules |
| Recirculation Pump | Q=50 m³/h, H=25 m, plastic-lined | 2 sets (1W+1S) |
| Backwash Pump | Q=30 m³/h, H=40 m | 1 set |
| CIP Cleaning Skid | Acid/alkali tanks + heater (40°C) | 1 set |
| Sludge Dewatering Press | Filter press (moisture ≤60%) | 1 set |
III. Anti-fouling Strategies
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Flow Channel Optimization:
- High cross-flow velocity (>3 m/s) scours membrane surface
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Intelligent Pulsed Backwash:
- Auto air-water backwash every 30min (0.3 MPa air + 0.4 MPa water)
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Sludge Concentration Control:
- Maintain MLSS=15 g/L in MBR; auto-discharge excess sludge to dewatering
IV. Performance & Economics
| Parameter | Treatment Efficiency |
|---|---|
| TUF Permeate SS | ≤5 mg/L |
| COD Removal (Bio + TUF) | ≥98% (40,000 mg/L → 800 mg/L) |
| Ammonia-N Removal | ≥99% (2,500 mg/L → 15 mg/L) |
| Operating Cost | 4.5–5.3 USD/m³ (energy/chemicals/depreciation) |
Cost Breakdown:
- Energy: 8–10 kWh/m³ (mainly recirculation pumps)
- Chemicals: PAC/PAM/cleaners ≈ 1.7 USD/m³
- Membrane replacement: 0.7 USD/m³ (5-year lifespan)
V. Concentrate Treatment Options
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TUF Reject Stream Management:
- Recycle to anaerobic reactor (enhance carbon utilization)
- Evaporation-crystallization (MVR evaporator → mixed salts)
- Advanced oxidation: Fenton (H₂O₂/Fe²⁺) or catalytic ozonation
Process Advantages
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Tolerance for Extreme Feed:
- Handles shock loads: SS≤20,000 mg/L, oils≤500 mg/L
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Extended Operation Cycles:
- 50% fewer CIPs vs. spiral-wound membranes; lifespan ≥5 years
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Modular Scalability:
- Single unit capacity: 50–200 m³/d; parallel scaling for large projects
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Sludge Minimization:
- Zero excess sludge discharge (full recycling + dewatering)
Applications:
- Municipal landfill sites │ Waste-to-energy plants │ Hazardous waste facilities
- Particularly suitable for aged landfill leachate (high salinity, low biodegradability)
Note: Design parameters (e.g., flux, MLSS) must be adjusted based on leachate age (fresh/medium/stable). Pilot testing is essential to optimize protocols. For RO feedwater hardness reduction, add an ion-exchange softener post-TUF. All emissions comply with ISO 14001 and EPA 503 standards.
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