Industry Applications
One. Principle of UV disinfection technology
Ultraviolet light (UV) destroys the DNA/RNA structure of microorganisms, making them lose their ability to replicate, thereby achieving the purpose of inactivating pathogens such as bacteria, viruses, and parasites. The main effective band is UV-C (200-280nm), especially 254nm wavelength has the best effect.
Two. Core application scenarios in sewage treatment
1. Municipal sewage treatment plant
- Application stage: Disinfection of effluent after secondary treatment (biochemical treatment).
- Advantages:
- Meet the fecal coliform group limit of the "Pollutant Discharge Standard for Urban Sewage Treatment Plants" (GB 18918-2002).
- Replace traditional chlorine disinfection to avoid the toxicity of residual chlorine to water ecology.
- Applicable scale: Large flow continuous treatment (single device can reach tens of thousands of tons/day).
2. Industrial wastewater treatment
- Typical industries:
- Food processing (containing high-organic wastewater)
- Pharmaceutical/chemical wastewater (containing antibiotics, chlorine-resistant pathogens)
- Electronics industry (ultrapure water pretreatment)
- Special needs:
- Pretreatment is required (such as removing suspended matter, adjusting turbidity) to increase UV transmittance (UVT).
- UV dose needs to be increased for highly resistant microorganisms (such as Bacillus).
3. Hospital and medical wastewater
- Key goals: Inactivate high-risk pathogens such as multi-drug resistant bacteria, coronavirus, HIV, etc.
- Regulatory requirements: Comply with the "Medical Institution Water Pollutant Discharge Standard" (GB 18466-2005), and require multi-stage disinfection (often in conjunction with ozone/chlorine).
4. Recycled water reuse system
- Scenario:
- Landscape water (river water replenishment, fountain)
- Industrial cooling water
- Agricultural irrigation (avoid chemical residues)
- Standard: Must meet the "Urban Sewage Recycling Water Quality Standard" (GB/T 18920-2020).
5. Rural and decentralized sewage treatment
- Applicable scenarios: Small village sewage treatment stations, ecological wetland effluent disinfection.
- Advantages: Modular equipment, no need for chemical transportation and storage, suitable for remote areas.
Three, key parameters for technology selection
1. UV dose (mJ/cm²): Determines the inactivation efficiency, municipal sewage usually requires 30-40 mJ/cm², and hospital wastewater requires ≥80 mJ/cm².
2. Lamp type:
- Low-pressure mercury lamp: Suitable for low flow and intermittent operation.
- Medium pressure mercury lamp: high intensity, suitable for large flow continuous processing.
3. System design:
- Open channel (large flow) vs closed reactor (compact).
- Automatic cleaning device (to deal with scaling problems).
Fourth, compared with other disinfection technologies
| Disinfection method | Advantages | Disadvantages |
| Ultraviolet light | No chemical residue, immediate effect, broad-spectrum sterilization | No sustained disinfection effect, greatly affected by water quality |
| Chlorine disinfection | Low cost, sustained disinfection ability | Produces DBPs (carcinogenic byproducts), ecotoxicity |
| Ozone | Strong oxidizing, decolorization and deodorization | High energy consumption, complex equipment, possible generation of bromate |
Five, precautions and maintenance
1. Water quality pretreatment:
- Suspended solids (SS) needs to be <10 mg/L, UV transmittance (UVT) >65%.
- Hard water needs to prevent quartz sleeve scaling (can be cleaned or softened with acid).
2. Maintenance cost:
- The lamp life is about 8,000-12,000 hours and needs to be replaced regularly.
- The failure rate of electronic ballast is high (redundant design is recommended).
Sixth, future trends
1. UV-LED technology: more energy-saving and mercury-free, but the current cost is high.
2. Intelligent monitoring system: real-time monitoring of UV intensity and dosage, and linkage with water quality sensors to optimize operation.
Ultraviolet disinfection balances efficiency and environmental protection needs in sewage treatment, and is particularly suitable for scenarios that are sensitive to chemical agents (such as ecologically sensitive areas and recycled water reuse). In practical applications, comprehensive selection should be combined with water quality, flow rate, and cost.
