RO Membrane Process Scheme for High-Temperature Dyeing Wastewater
10 Jun 2025
RO Membrane Process Design for High-Temperature Dyeing Wastewater
Design Highlights:
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High-Temperature Pretreatment (Core)
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Enhanced Pre-treatment
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Staged RO System Design
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Intelligent Temperature Control and Cleaning
Process Flow Diagram
A [High-Temperature Wastewater Collection Pond 60-80℃] --> B [Screening for Impurities] --> C [Cooling Tower/Plate Heat Exchanger] --> D [Regulation Pond, Temperature Controlled Below 40℃] --> E [Coagulation Sedimentation/Flotation] --> F [Hydrolysis Acidification Pond] --> G [Aerobic Biological Treatment] --> H [MBR/Secondary Sedimentation Pond] --> I [Multi-Media Filter] --> J [Activated Carbon Filter] --> K [Security Filter] --> L [RO Reverse Osmosis System] --> M [RO Permeate for Reuse/Discharge] --> N [RO Concentrate Treatment]
Key Unit Design Description
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High-Temperature Pretreatment System
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Cooling Devices:
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Plate Heat Exchanger (Series): Utilize low-temperature clear water or air for heat exchange to rapidly cool down to 40℃.
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Spray Cooling Tower: Auxiliary cooling, suitable for high-flow wastewater.
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Target Temperature: RO feed water ≤40℃ (to prevent membrane thermal degradation).
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Enhanced Pre-treatment Process
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Coagulation Sedimentation:
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Chemicals: PAC + PAM + FeCl₃ (highly effective for decolorization).
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Removal: Suspended solids, colloids, and some dye molecules.
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Biological Treatment:
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Hydrolysis acidification + contact oxidation: Degradation of organic substances (BOD/COD), enhancing biodegradability.
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Advanced Filtration:
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Multi-Media Filter: Quartz sand + anthracite, for removal of tiny particles.
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Activated Carbon Filter: Adsorption of residual dyes and organic pollutants.
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RO Reverse Osmosis System
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Membrane Selection:
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Anti-fouling spiral-wound polyamide composite membrane (e.g., DOW FILMTEC™ BW30FR-400).
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Operating pressure: 1.5~2.5 MPa.
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System Configuration:
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Single-stage, two-section design (6:4 arrangement), with a recovery rate of ≥70%.
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Concentrate recycle design to improve overall recovery rate.
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Protection Measures:
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Online pH monitoring (control within 5~7).
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Scale inhibitor (organic phosphonate) + non-oxidizing biocide dosing.
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Concentrate Treatment Scheme
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Advanced Oxidation: Fenton oxidation/ozone catalysis.
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Evaporation and Crystallization: For zero liquid discharge (ZLD) of high-salinity concentrate.
Operational Parameter Control
| Parameter | Control Range | Remarks |
|---|---|---|
| RO Feed Water Temperature | ≤40℃ | Key protection condition |
| SDI15 | ≤5 | To prevent membrane fouling |
| Residual Chlorine | <0.1 mg/L | To prevent membrane oxidation |
| Feed Water COD | ≤100 mg/L | To ensure membrane lifespan |
| Operating Pressure | 1.5~2.5 MPa | Real-time adjustment according to water quality |
Advantages and Assurance Measures
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Heat Recovery Design: Plate heat exchanger can preheat cleaning water, reducing energy consumption.
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Intelligent Control:
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PLC automatic regulation of cooling water flow and chemical dosing.
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High-temperature alarm and interlocked shutdown.
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Membrane Cleaning Scheme:
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Acid cleaning (pH=2~3): For removal of inorganic scale.
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Alkaline cleaning + surfactant (pH=10~12): For removal of organic contamination.
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Expected Treatment Results
| Indicator | Inlet Typical Value | RO Permeate |
|---|---|---|
| COD | 2000~5000 mg/L | ≤50 mg/L |
| Color | 500~1000 times | ≤5 times |
| Salinity (TDS) | 5000~15000 mg/L | ≤100 mg/L |
| Water Temperature | 60~80℃ | Ambient temperature |
Investment and Operating Costs
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Main Investment: Cooling system (30%), RO unit (40%), Pre-treatment (30%).
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Cost per Ton of Water: ≈3.5~5.0 yuan/ton (including energy consumption, chemicals, and membrane replacement).
Note: The actual design should be adjusted according to the water quality test report (such as dye types, salinity, and organic composition). It is recommended to first conduct a pilot test to verify feasibility.
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