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What are the differences between medium-pressure UV disinfectors and low-pressure UV disinfectors?

2021-04-06

What are the differences between medium-pressure UV disinfectors and low-pressure UV disinfectors?

In water treatment disinfection, ultraviolet (UV) disinfection has long occupied an important position. Among UV disinfection systems, the commonly used ones are the conventional low-pressure UV disinfection system and the medium-pressure UV disinfection system. But what exactly are the differences between these two? According to the National Environmental Protection Standard of the People's Republic of China HJ2522-2012—Technical Requirements for Environmental Protection Products: UV Disinfection Equipment—the UV light in these systems is generated by electron excitation of mercury vapor through arc discharge.

Medium-pressure UV sterilizer

Based on the pressure of the inert gas inside the ultraviolet lamp tube, they can be classified as low-pressure and medium-pressure.

Low-pressure UV sterilizer: In a low-pressure UV lamp, the inert gas pressure inside the lamp is lower than atmospheric pressure—approximately 0.013 MPa. Each lamp tube has a power rating of 320 W. The mercury vapor within the lamp tube is excited to emit ultraviolet light at wavelengths of 253.7 nm and 185 nm. When the 253.7-nm UV light shines on neighboring mercury atoms, it triggers a resonance absorption effect, causing the irradiated mercury atoms to further emit UV light, thereby achieving the purpose of disinfection.

Medium-pressure UV disinfection systems: In medium-pressure UV systems, the inert gas pressure inside the lamp tube is equivalent to atmospheric pressure—ranging from 0.2 MPa to 0.4 MPa, which is 100 times higher than that in low-pressure systems. Such systems can emit a broader spectrum of multi-wavelength ultraviolet light, with wavelengths spanning from 200 nm to 400 nm. This wider wavelength range enables more effective destruction of microbial organisms and prevents their replication, thereby achieving thorough disinfection. The power output of a single lamp tube ranges from 400 W to 10 kW. Low-pressure UV systems are well-suited to meet the water treatment requirements for typical flow rates and are particularly appropriate for systems that require frequent on-off operations. Low-pressure UV lamps boast high conversion efficiency, with up to 40% of their power being converted into germicidal energy. Additionally, they have low manufacturing costs, making them widely used in municipal water supply, surface water treatment, industrial water treatment, swimming pool water treatment, landscape water management, circulating cooling water systems, marine water applications, seawater desalination, and small-flow-rate water disinfection processes.

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