Process Flow of Hollow Fiber Ultrafiltration Membrane Cooling Water System Water Supply

1. Raw Water Pretreatment Stage
   • Mechanical Filtration
     • Multimedia Filter: Removes suspended solids (SS), silt, rust, etc. The filter media are quartz sand and anthracite coal, with a filtration accuracy of ≤50μm.
     • Self-Cleaning Filter (Optional): Fully automatic backwashing to protect the ultrafiltration membrane from large particle impacts.
   • Water Quality Adjustment
     • Disinfection and Algae Control: Add sodium hypochlorite (1-3mg/L) or non-oxidizing biocides to inhibit microbial growth.
     • pH Adjustment: If the raw water is acidic (e.g., pH<7), add NaOH to adjust to neutral (pH 6.5-7.5) to reduce membrane fouling.
2. Ultrafiltration Membrane Treatment Stage
   • Membrane Module Selection
     • Material: Hollow fiber membranes made of polyvinylidene fluoride (PVDF) or polyethersulfone (PES), which are resistant to oxidation and fouling.
     • Pore Size: 0.01-0.1μm, capable of retaining bacteria (99.99%), colloids, and large molecular organic substances (such as humic acid).
     • Membrane Flux: Design flux of 50-100LMH (liters/square meter·hour), with a conservative value chosen based on water quality.
   • Operation Mode
     • Full Flow Filtration/ Cross Flow Filtration: For low-pollution water quality, full flow filtration is used (recovery rate ≥90%); for high-pollution water quality, cross flow filtration is used (recovery rate 70-85%).
     • Backwashing: Every 30-60 minutes, combined air and water backwashing (0.1-0.3MPa, lasting 30 seconds) is performed to restore membrane flux.
   • Key Parameters
     • Operating Pressure: 0.1-0.3MPa
     • Inlet Water Temperature: 5-40℃ (to avoid membrane aging due to high temperature)
     • Transmembrane Pressure Difference (TMP): ≤0.15MPa (chemical cleaning is triggered when exceeded)
3. Post-Treatment and Recirculation
   • Scale and Corrosion Inhibition Treatment
     • Scale Inhibitor Addition: Add scale inhibitors (such as polyacrylic acid) to the ultrafiltration product water to prevent scaling in the recirculating cooling water system (CaCO₃, CaSO₄).
     • Corrosion Inhibitor Addition: Add corrosion inhibitors (such as molybdates) to protect the metal surfaces of pipes and heat exchangers.
   • Recirculating Water System
     • The ultrafiltration product water enters the cooling tower or heat exchanger for recirculation. The concentrate (backwash drainage) is discharged to the wastewater treatment system or reused.
4. Maintenance and Management
   • Chemical Cleaning
     • Frequency: Every 3-6 months or when TMP increases by 20%.
     • Cleaning Agents: 0.1% NaOH + 0.05% NaClO (for removing organic matter and biological contamination); 0.2% citric acid (for removing inorganic scale).
   • Membrane Lifespan: Under normal maintenance, the lifespan is 3-5 years, with a flux attenuation rate of ≤10%/year.
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Brief Scheme Design

• Pretreatment Unit: Multimedia filter, dosing equipment (biocides, pH adjusters)
• Ultrafiltration System:
  • PVDF hollow fiber ultrafiltration membrane modules (e.g., SFP-2660 type)
  • Backwashing pump, compressed air system, PLC automatic control system
• Post-Treatment Unit: Scale inhibitor dosing pump, corrosion inhibitor dosing equipment
• Recirculation System: Cooling tower, heat exchanger, recirculation pump

• High-Efficiency Retention: Thoroughly removes suspended solids, colloids, and microorganisms, reducing the risk of scaling and corrosion in the cooling water system.
• Low Energy Consumption: Low operating pressure (0.1-0.3MPa), with lower operating costs compared to reverse osmosis.
• Automation: PLC control can achieve automatic backwashing, dosing, and fault alarms.

• Water Quality Monitoring: Real-time monitoring of SDI, TOC, and residual chlorine to avoid damage to membrane materials from excessive oxidants.
• Concentrate Water Treatment: Backwash drainage contains high concentrations of pollutants and should be included in the plant's wastewater system for treatment.
• Freeze Protection: In cold regions, insulation of membrane modules and pipes is required to prevent freezing and cracking.