Ultraviolet disinfection technology is widely used in municipal water supply, drinking water disinfection, sewage treatment, food industry, electronic industry, pharmaceutical and many other fields because of its broad-spectrum, fast, energy-saving and no residue characteristics. Toxic Substances. The rationality and quality of its use are directly related to public health and safety.

 

Overflow ultraviolet sterilizer

 

China has also formulated many standards related to UV application according to the characteristics of different industries. for example

 

1. According to CJ / t204-2000 drinking water ultraviolet sterilizer, disinfection products equipped with new lamps are required, and the measured ultraviolet radiation dose shall not be less than 12000 µ w • s / cm2. The ultraviolet radiation dose measured by the sterilizer in normal operation shall not be less than 9000 µ w • s / cm2.

 

2. According to the standard of ultraviolet disinfection equipment for urban water supply and drainage (gbt19837-2005): the ultraviolet radiation dose of urban drinking water sterilization treatment shall not be less than 40mj / cm2; Less than 20mj / cm2; The ultraviolet radiation dose of sterilization treatment of urban sewage (class I, class B and class II standards) shall not be less than 15mj / cm2.

 

3. According to the requirements of gb50014-2006 code for design of outdoor drainage, the UV radiation dose required for secondary treated effluent is 15-22mj / cm2; The ultraviolet radiation dose required for reclaimed water is 24-30mj / cm2.

 

 

 

The core parameter in the standard - ultraviolet radiation dose is the difference between the ultraviolet radiation intensity (I) of each point in the sterilizer and the residence time in the sterilizer when the water flows through the sterilizer. The integral function is usually represented by dose,

 

Namely: dose = (unit: MJ / cm2)

 

In the formula, I received that the ultraviolet radiation intensity of the lamp, the specific flow path of the water in the sterilization pot, the ultraviolet transmittance of the water, the amount of particles in the water, the transmittance and degree of the shell, and the scaling rate of the casing wall are affected by many complex factors and are not easy to calculate. In the project, we need a simple method to verify whether our design and manufacturing sterilizer meet relevant national and industrial standards, so as to achieve the expected sterilization effect.

 

 

 

Here is a brief introduction to this method - bioassay.

 

 

 

According to the requirements of GB / T 1937-2005, the specific operation methods of bioassay are as follows: 1. Firstly, the water sample to be measured is irradiated with stable ultraviolet with different radiation intensity with a parallel ultraviolet beam instrument, and different ultraviolet doses are tested. The corresponding curve between microbial inactivation rate and UV dose was obtained. 2. Continuously flow the same test water sample through the ultraviolet sterilizer, change its flow rate, monitor the residual microbial concentration at the outlet of the sterilizer at different flow rates, and obtain the corresponding curve speed between the flow rate of the sterilizer and microbial inactivation. 3. By comparing the inactivation rate measured by the parallel ultraviolet beam meter with the ultraviolet dose, we can know the equivalent ultraviolet dose that the sterilizer can provide under a certain flow rate.

 

Test method for ultraviolet dose of overflow ultraviolet sterilizer

 

If the equivalent ultraviolet dose of the sterilizer measured by bioassay under the rated flow is greater than the relevant national or industrial standards, we can know that the sterilizer can meet the sterilization requirements under the current conditions. However, due to the factors such as light intensity attenuation and scaling on the shell surface during the use of UV lamp, which will affect the transmission of UV light, we should leave enough margin for the initial UV dose. Sterilizer so that the sterilizer can be used in the lamp. At the end of the test tube life, it can still meet the requirements of sterilization efficiency. The calculation formula is:

 

 

 

ED = ND * CLH * CJG

 

 

 

In the formula:

 

ED: effective dose of ultraviolet sterilizer

 

Nd: the equivalent ultraviolet dose measured by testing the equipment with bioassay under the condition of new lamp and new shell

 

CLH: aging coefficient of ultraviolet lamp

 

CJG: casing scale factor