Physical Properties of UV Light

UV light is part of electromagnetic radiation, the relationship between frequency, wavelength, and light speed can be expressed as  

254 nm), low-pressure high-output (LPHO) mercury lamp, and medium-pressure (MP) mercury lamp are the most frequently used in water disinfection owing to their high radiation absorbance by pathogens. 

As discussed previously, DNA and RNA have their basic elements of adenine, guanine, cytosine, thymine, and uracil. They can strongly absorb UV light however, the damage with pyrimidines (C, T and U) is more serious. Absorbed UV light induces several types of damage and alteration in the DNA and RNA with varying levels of effectiveness dependent on UV dose (12). 

When the UV dose is several orders higher than that used in the conventional UV disinfection, the DNA and RNA can be broken. At the same time, the DNA-DNA cross-linkage is formed between two different strands of DNA. For some germs, protein-DNA cross-linkage can be established between a protein and a DNA strand, which eventually changes the DNA structure. 

In addition to the alteration in the DNA or RNA structures, photochemical oxidation is another mechanism that must be taken into consideration in the disinfection process. 

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