1. Ultraviolet dose

Ultraviolet dose is a direct factor affecting disinfection effect. It is equal to the product of ultraviolet light intensity and contact time. Under the same UV light intensity, the exposure time determines the UV dose. In large sewage treatment plants, due to the large amount of water, the contact time cannot be guaranteed, so the efficiency of ultraviolet disinfection is worse than that of small sewage treatment plants. Theoretically, the greater the UV dose, the better the disinfection. However, there is a limit value for UV disinfection. If the limit value is exceeded, additional microorganisms cannot be killed economically and effectively.

If the influence of ultraviolet light intensity and contact time on disinfection effect is considered respectively, it can be found that the influence of the two is different for different kinds of microorganisms. In the case of the same UV dose, the UV intensity has a greater impact on Escherichia coli, because the repair enzyme in the cell is more sensitive to the UV intensity; For eukaryotic yeast cells, increasing the contact time is more conducive to killing; Of course, for more microorganisms, such as bacteriophages and spores, it is not meaningful to discuss them separately. The reason may be that they are inactive in the process of ultraviolet disinfection. Therefore, it is unnecessary to determine less contact time and less UV light intensity. The product of the two is the necessary factor affecting the disinfection effect of the UV sterilizer.

2. Type and load of microorganism

Microwave electrodeless ultraviolet sterilization equipment Because there are many kinds of bacteria and viruses in sewage, and their resistance to ultraviolet radiation is different, different types of sewage show different disinfection effects. Some microorganisms are more sensitive to ultraviolet light, and the removal rate is high, such as fecal coliform, while some microorganisms are not, so they need to be killed with a higher ultraviolet dose, such as F-RNA Escherichia coli and Chaetobacillus aeruginosa. Microbial load is a major factor in the efficiency of UV disinfection, and higher microbial quantity will inevitably require higher UV dose. At present, in the design of ultraviolet sterilizer, it is mainly to inactivate the total TC coliform, FC fecal coliform, E.coli Escherichia coli, fecal streptococcus and Salmonella to estimate the ultraviolet dose demand.