Which wavelength of UV light is required for effective disinfection of bacteria?

The effective disinfection of bacteria using ultraviolet (UV) light primarily relies on the wavelength of the light used. A wavelength around 254 nm is particularly effective for disinfection purposes because it coincides with the peak absorbance of nucleic acids, especially DNA. When UV light at this wavelength is absorbed by the DNA of bacteria, it induces the formation of thymine dimers, which interfere with DNA replication and transcription. This ultimately leads to cell death or the inability to reproduce, effectively disinfecting the water or surface being treated.

Additionally, while other wavelengths like 200 nm are absorbed strongly and can have germicidal effects, they are less effective at penetrating materials and can cause harm to humans. Wavelengths above 260 nm, such as 300 nm and 350 nm, see a decrease in efficacy as they are not optimally absorbed by microbial DNA. Thus, 254 nm is the standard in UV disinfection processes due to its balance of effectiveness and safety for practical applications.