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The Effect of UV Radiation on Microorganisms
UV radiation disrupts the DNA / RNA of microorganisms and prevents these organisms from affecting living things. With UV radiation, results can be obtained against all kinds of microorganisms, but this result is not the same for every living thing. In general, UV (UV-C) radiation is most effective against viruses, while fungi are more resistant to UV radiation. Therefore, when designing the system, the target microorganism should be known and the amount of radiation and contact time should be determined accordingly.
Figure 3. UV Radiation Power 
Basic Terms Related to UV Lamps
Irradiance (W / m2): Electromagnetic radiation power per unit area
UVGI: It stands for germicidal effect (Ultraviolet Germicidal Irradiation). It can also be defined as UV radiation that kills harmful microorganisms.
UV Dose (J / m2): It indicates the amount of radiation that comes to the surface or microorganism during the contact period. (UV exposure dose or fluence) is indicated by the letter D and is generally calculated as the dose that will destroy 90% of microbes (D90). Another dose is the dose that destroys 99% of the microbes stated as D99.
UV Dose = Radiation X calculated as contact time.
Microorganism Specific UV Sensitivity Coefficient (m2 / Joule): UV radiation coefficient that will kill the organism determined by experiments for each microorganism. This coefficient is given separately for air, water and surface disinfection.
Irradiation Time (seconds): Refers to the contact time of UV light with microorganism.