In the process of inactivating microorganisms, it is mainly the ultraviolet light of 240 ~ 260 nm band that plays a role [10, 11]. Common ultraviolet disinfection products are mainly based on ultraviolet light output from low-pressure mercury lamps [12]. With the development of nitride material technology, UV LED based on high Al nitride component has attracted much attention. By comparing the characteristics of the two kinds of light sources, it is helpful to realize the difference of performance between the solid-state light source and ultraviolet mercury lamp in disinfection field.
The efficiency of ultraviolet disinfection technology is mainly affected by the output wavelength and ultraviolet radiation dose of the light source. In 2011, a research team at the technical university of Berlin designed and prepared a UV LED light module based on 269 nm and 282 nm, and inactivated bacillus subtilis in water using these two different wavelengths of ultraviolet solid-state light. The results showed that the inactivation effect of 269 nm on bacillus subtilis was more complete under the same ultraviolet irradiation dose [13]. In 2016, a research team from Seoul university in South Korea studied the inactivation efficiency of UV LED and low-pressure mercury lamps on escherichia coli and salmonella [14]. The results show that under the same radiation dose, the killing rate of UV LED with peak wavelength of 266 nm is much higher than that of low-pressure mercury lamp. The above experimental results show that a wavelength with the highest efficiency exists for the inactivation of a specific microorganism by ultraviolet light.
The output wavelength of UV LED can be set by adjusting the component of the material in the active region, and the half-peak width is relatively narrow, about 10 nm. Therefore, the output wavelength of UV LED is arbitrarily adjustable between 200 and 365 nm, covering the range from UVA to UVC. For ultraviolet mercury lamps, this source has a wide spectrum and cannot be adjusted. For example, low-pressure ultraviolet mercury lamps mainly output ultraviolet near 253.7 nm