Research On The Efficacy Of UV-LED Inactivated Escherichia Coli

Water safety issues have always been the focus of people's lives.Disinfection is an essential process in the water treatment process,it can effectively kill pathogenic microorganisms in water.Therefore,disinfection is an important part to protect people's water safety and control water pollution."Drinking water standard"(GB5749-2006)specified in the total coliform group(MPN/100mL or CFU/100mL)not detected,"cities sewage treatment plant pollutant discharge standard"(GB18918-2002)in a A standard,the number of fecal coliform is less than 103/L.In this study,the effect of CO ozonation of UVC-LED and UVA-LED on the inactivation of Escherichia coli was studied,and the mechanism of inactivation of Escherichia coli was preliminarily explored.At present,the main methods of disinfection are liquid chlorine disinfection,chlorine dioxide disinfection,ultraviolet disinfection,ozone disinfection and so on.However,from the perspective of safety,environmental protection and cost,these traditional disinfection methods have some problems.UV-LED,as a new type of ultraviolet light source,also has effective bactericidal ability,and it is no need to add chemicals,no disinfection by-products,environmental protection,no pollution,high efficiency and energy saving.UV-LED can be divided into three bands by wavelength from high to low,namely,UVA-LED(315-400nm),UVB-LED(280-315nm),and UVC-LED(200-280nm).Two kinds of light sources,UVC-LED(275nm)and UVA-LED(365nm)are selected in this experiment.The effect of UVC-LED on the inactivated Escherichia coli in water was studied.When the ultraviolet radiation dose was 24.48mJ/cm2,the inactivation of Escherichia coli was more than 4.The effects of UV-LED parameters(wavelength,UV irradiation intensity),various water quality factors(temperature,pH value,turbidity,HA and inorganic ions)on the inactivation rate of Escherichia coli were investigated.The shorter the wavelength of UV-LED,Escherichia coli inactivated effect;UVC-LED radiation intensity is stronger,the Escherichia coli inactivated effect;Temperature,pH value,turbidity and HA of Escherichia coli inactivated effect;Cu2+ is beneficial to UVC-LED inactivation of Escherichia coli;Ca2+ is not good the inactivation of Escherichia coli;Zn2+,Cl-,CO32-;SO42-to UVC-LED inactivation of Escherichia coli had no significant effect.The effect of UVA-LED on the inactivation of Escherichia coli was not good,and the effect of UVA-LED co ozonation on the inactivation of Escherichia coli was studied.UVA-LED irradiation can improve the oxidation capacity of ozone.The combined effect of UVA-LED and ozone can improve the inactivation of Escherichia coli to a certain extent.The effects of the dosage of ozone,the factors of water quality(temperature,pH,turbidity,HA and inorganic ions)on the inactivation of Escherichia coli were investigated.The higher the dosage of ozone is,the better the inactivation effect of Escherichia coli is.The temperature and turbidity have little effect on the inactivation of Escherichia coli.Decreasing pH value can promote UVA-LED to cooperate with ozone to inactivate E.coli.Within a certain range,HA will inhibit the inactivation of Escherichia coli under synergistic action.The presence of Cu2+ promoted UVA-LED synergistic ozone inactivation of Escherichia coli;Ca2+ and CO32-inhibited the inactivation of Escherichia coli.;the presence of Zn2+,Cl-and SO42-had no obvious effect on UVA-LED synergistic ozone inactivation of E.coli.The mechanism of the UVC-LED and UVA-LED co of ozonation to inactivate Escherichia coli was studied by scanning electron microscopy and system soluble protein detection.UVC-LED mainly through the destruction of E.coli nucleic acid to achieve bactericidal effect,while UVC-LED of Escherichia coli protein also has some damage.The UVA-LED synergistic ozone mainly inactivates Escherichia coli through three aspects:UVA-LED directly kill Escherichia coli by ultraviolet radiation;Ozone molecule directly oxidizes with some organelles to inactivate Escherichia coli;Ozone molecules decompose on their own or under the irradiation of UVA-LED to release active oxygen atoms,which are indirectly oxidized with various parts of organelles,eventually causing the E.coli to dissolve and die.