Influence Of Algae Organic Matter(AOM) On Viruses Inactivation By Ultraviolet Light And Its Inactivation Mechanism

The control of pathogens has always been one of the core issues that guarantee the safety of drinking water.At present,most of the water plants in China use lake(reservoir)water as the source of drinking water.Due to the release of nutrient elements such as nitrogen and phosphorus,many lakes and reservoirs have experienced various levels of eutrophication.These eutrophic waters not only contain natural organic matter,suspended solid particles,and inorganic nutrients,but also contain many algal cells and algae organic matter.These more complex water conditions will affect the inactivation of viruses in natural water bodies and disinfection units ofwater treatment plant.In this study,the indicator virus MS2 of enterovirus in water and the enterovirus rotavirus in water were selected.The algae extracellular organic matter(EAOM)and algae intracellular organic matter(IAOM)extracted from the cultured Microcystis aeruginosa were selected as the algal source.The effect of different organic matter on the inactivation of phage MS2 in natrual water bodies under simulated sunlight conditions be studied.The effects of algae organic matter on the phage MS2 and rotavirus inactivation under different ultraviolet wavelengths and its inactivation mechanism,the main conclusions are as follows:(1)Under simulated sunlight conditions,the concentrations of reactive oxygen species produced by different organic substances are different.The concentration of hydroxyl radicals detected by SEW was 1.36±0.80 fM,and the concentration of singlet oxygen radicals was 70±30 fM.The concentration of hydroxyl radicals detected by the secondary effluent(CSEW)in the wastewater treatment plant was 0.26±0.004 fM,the concentration of singlet oxygen radicals was 61.3±0.02 fM.The radical did not be detected out in water containing EAOM.In simulated solar inactivation MS2 experiments,the presence of algal extracellular organisms increased the inactivation logarithm of phage MS2 by 0.5 log10.The secondary effluent from different wastewater treatment plants increased the inactivating logarithm of bacteriophage MS2 1.75~2 log10.The generation of reactive oxygen radicals under simulated sunlight conditions can increase the inactivation of phage MS2.(2)Radical measurement under UV radiation from algae organic matter.Under UV220 nm radiation,single-oxygen free radicals(727±314 fM)and hydroxyl radicals(9.25±1.55 fM)were detected when extracellular organic matter was present.When the organic matter in the algal cells was present,no singlet oxygen radicals or hydroxyl radicals were detected.Under ultraviolet 254 nm radiation,no singlet oxygen radical or hydroxyl radical was detected when algae organic matter was present.(3)The presence of algae organic matter has different effects on the inactivation of phage MS2 at different wavelengths of UV radiation.Under UV220 nm,the presence of extracellular organisms in the algae greatly increased the inactivating logarithm of phage MS2,the presence of organic matter in the algal cells,and did not significantly increase the inactivating logarithm of phage MS2.The presence of algal intracellular/external organic matter did not significantly increase the inactivating logarithm of phage MS2 at UV wavelengths of UV254 nm.In combination(2),it was found that the production of reactive oxygen radicals can increase the inactivation of phage MS2.The study also found that when algae-derived organic matter is present,compared with UV254 nm,using UV220 nm can reduce the UV dose by 2 times,and the inactivation rate of phage MS2 can reach 99.99%.(4)The presence of algae-derived organic matter has different effects on inactivated rotavirus(OSU and ST3)under different ultraviolet wavelengths of radiation.At UV wavelengths of UV220 nm,the presence of algal extracellular organisms greatly increased the inactivating logarithms of rotavirus(OSU and ST3).At UV wavelengths of UV254 nm,the presence of algal extracellular organisms did not significantly increase the logarithm of the rotavirus(OSU and ST3)inactivation.By comparing the sensitivities of the three viruses to ultraviolet radiation,it was found that the presence of algal extracellular organisms does not affect the sensitivity of the virus to ultraviolet radiation.Different ultraviolet wavelengths affect the sensitivity of the three viruses.Under the condition of UV254 nm,the sensitivity of the three viruses was ST3<OUS?MS,while under UV220 nm,the sensitivity of the three viruses was OSU?ST3<MS2.(5)The linear correlation between the loss of infectivity of MS2 detected by reverse transcription-quantitative polymerase chain reaction(RT-qPCR)and the loss of genomic fragment replication in the study of the mechanism of inactivation of UV radiation bacteriophage MS2 : In the presence of algae organisms under ultraviolet radiation,the main inactivation mechanism of MS2 is gene damage.In the study of the inactivation mechanism of the UV radiation rotavirus OSU,the results of the binding experiments showed that the spike VP4 of the rotavirus OSU did not break.