The effect of UV disinfection is significantly affected by water quality, equipment selection, operating parameters and other factors. In the application of secondary water supply scenarios, the following technical points must be strictly controlled to ensure qualified disinfection.
1. Water Quality Pretreatment Requirements
UV rays have weak penetration. Suspended solids (SS), turbidity, chromaticity, and dissolved organic matter in water will block or absorb UV energy, reducing sterilization efficiency. Therefore, before applying UV disinfectors in secondary water supply systems, supporting pretreatment processes are required to control the influent SS at ≤20 mg/L, turbidity at ≤5 NTU, and organic matter content below 10 μg/L, so as to avoid microorganisms being wrapped by suspended solids to form a "protective barrier" and ensure that UV rays can effectively irradiate the microorganisms themselves. For secondary water supply systems with poor water quality, coagulation, sedimentation, and filtration devices can be added to optimize influent water quality.
2. Equipment Selection Specifications
Equipment selection must comply with the requirements of "Ultraviolet Disinfectors for Drinking Water" (CJ/T204) and "Hygienic Safety Evaluation Specifications for Drinking Water Disinfectants and Disinfection Equipment": Priority should be given to low-pressure high-intensity amalgam germicidal lamps with preheated electronic ballasts, ensuring that the UV intensity at 253.7 nm is not less than 70 μW/cm² (measured at 220V voltage, 20℃ environment, and 60% relative humidity); Determine the equipment power according to the water supply flow to ensure an irradiation dose of ≥40 mJ/cm² (under the working conditions of end-of-life and peak flow). For Cryptosporidium and Giardia that may exist in secondary water supply, it is recommended to increase the irradiation dose to more than 300 J/m² to avoid photoreactivation. In addition, equipment with mechanical automatic cleaning function can be selected to reduce the frequency of manual maintenance.
3. Operation Parameter Control
During operation, real-time monitoring of UV intensity is required, and the lamp tube should be replaced immediately when the intensity drops below 70% of the standard value; Control the water flow rate evenly to avoid irradiation shadow areas and ensure sufficient UV irradiation of water; The ambient temperature should be maintained at 20-40℃, and the irradiation time should be appropriately extended when the temperature is too high or too low; When used for tank disinfection, reflectors (such as polished aluminum plates) can be matched to improve UV utilization rate and ensure no disinfection dead corners inside the tank.
