1. UV radiation dose
UV dose is a direct factor affecting disinfection effect. It is equal to the product of UV intensity (UV irradiance meter) and contact time. Under the same UV intensity, the contact time determines the UV dose.
If the effects of UV intensity and contact time on disinfection effect are considered separately, it can be found that the effects of the two are different for different kinds of microorganisms. In the case of the same UV dose, UV intensity has a greater effect on Escherichia coli because the repair enzymes in the cells are more sensitive to UV intensity; for eukaryotic cells, increasing contact time is more conducive to killing; of course, for more microorganisms, such as bacteriophages and spores, it is of little significance to discuss the two separately, possibly because they are in an inactive state during ultraviolet disinfection.
Therefore, the product of the two is the necessary factor affecting the effect of ultraviolet disinfection. However, if the intensity of the ultraviolet lamp tube is less than 40 uW/cm2, the disinfection effect can not be achieved for a long time, so it is required to achieve a real bactericidal effect in a short period of time. The ultraviolet radiometer must be used to measure the ultraviolet radiation intensity in the UVC band.
2. microbial species and loads
Because of the variety of bacteria and viruses, and the resistance to ultraviolet rays is different, so for different bands of ultraviolet rays, showing different disinfection effect. For example, coliform faeces and some microbes are not, they need to be killed with higher UV illumination, such as F-RNA Escherichia coli and M. aeruginosa.
Microbial load is a major factor affecting ultraviolet disinfection efficiency, and higher microbial volume must require higher ultraviolet radiation intensity. currently, in the design of uv disinfector, mainly inactivated TC( total coliform), FC( fecal coliform), E.coli( escherichia coli), streptococcus faecalis and salmonella quantities are used to estimate uv radiation intensity requirements.
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