Water Treatment Methods and Principles: Ultraviolet Disinfection

Ultraviolet (UV) disinfection is a commonly used method. Its sterilization mechanism involves destroying the genetic material of bacteria's nucleic acids, preventing them from multiplying. The most significant reaction is the conversion of pyrimidine groups within the nucleic acid molecule into dimers. It typically uses artificial 253.7nm wavelength UV energy from low-pressure mercury discharge lamps. The principle of UV germicidal lamps is the same as that of fluorescent lamps, except that the lamp tube is not coated with fluorescent material, and the tube material is quartz glass with high UV transmittance. UV devices are generally classified according to their application as irradiation, immersion, and flow-through types.

In hemodialysis, the UV light used for dilution water is placed in the pipeline between the water storage tank and the dialysis machine. This means that all dialysis water is irradiated with UV light before use to achieve thorough sterilization. Pseudomonas aeruginosa and Escherichia coli are most sensitive to UV light; conversely, Bacillus subtilis spores are more resistant. Because UV disinfection is safe, economical, has low selectivity for bacteria, and does not alter water quality, this method has been widely used in recent years, for example, for drinking water on ships.