Research On Inactivation Of Cryptosporidium By UV And UV Synergisyic US

As the spread and outbreak of the pathogenic protozoa disease in the world, the infection of Cryptosporidium in drinking water has become a subject of widespread concern of public health and health problems. In 2006, China promulgated the new water quality standard and made corresponding provisions of cryptosporidium concentration in drinking water.After conventional water treatment process of "pretreatment, coagulation,sedimentation, filtration", most of the Cryptosporidium can be removed, and the Cryptosporidium unremoved can be inactivated by the distinfection process. Most Cryptosporidium oocysts are protected by thick wall from killing by the traditional water treatment disinfectant. The ultraviolet light can be used for disinfection in the water treating plant, and does not produce any disinfection by-products. Ultrasonic technology can effectively kill the protozoa in water, and it has a broad application prospect in the field of disinfection. The research studys the effect of single UV and UV synergistic US inactivating Cryptosporidium in drinking water, and also the inactivati--ng mechanism was preliminarily discussed in this thesis.The research studys using single ultraviolet(simulating parallel light style and immersion style) inactivating the Cryptosporidiumin drinking water,and the inactivating rate of 14 W UV lamp(immersion style) in 120 min reaches 99.99%. The effect of water quality factor(pH, temperature, turbidity, HA and inorganic ion) on the inactivation rate of the Cryptosporidium was studied. The pH value had little effect on the inactivation rate of the Cryptosporidium. The higher the temperature, the higher the inactivation rate;high turbidity restrained the inactivation rate, the Cryptosporidiumin ensconce in particulate matter reducing the ultraviolet radiation on the Cryptosporidium.; HA is a strong absorber of UV, and it inhibited the UV inactivation; HCO3-, SO42-, Ca2+, Cl-and CO32- had no obvious effect on the inactivation rate, Fe3+ and Mn2+ had antagonistic effect on the Cryptosporidium inactivation by UV inactivation; Ag+ synergistic UV on the effect of Cryptosporidium inactivation.It is difficult to achieve good effect on the inactivation of Cryptosporidium bysingle UV, so the research studys the effect of Cryptosporidium inactivation by ultravoit synergistic ultrasonic. We studyed three different combinations of investigation, and found that the UV coupled ultrasonic mode had the highest inactivation rate, and the inactivation rate was significantly higher than that of a single ultrasound.The pH value had little impact on the coupling inactivation rate; raising the temperature of the water can promote the inactivation rate; turbidity and humic acid(HA) can reduce the coupling inactivation rate. Cl-had little effection on the Cryptosporidium inactivation rate; CO32- and Fe3+ can lead the Cryptosporidium inactivation rate decreased; Ag+ played a positive role in promoting on the coupling inactivating rate.The research studyed the mechanism of UV and UV synergistic US by scanning electron microscopy(SEM) observation, the protein experiment and agarose gel electrophoresis imaging experimental. For single UV inactivating the Cryptosporidium,the effect of short time's UV irradiation is poor, long time of UV irradiation can lead to the death of the Cryptosporidium. There are two aspectsfor the Cryptosporidium's death reasons: on the one hand the nucleic acid of Cryptosporidium was damaged, and the longer, more serious damage; on the other hand ultraviolet irradiation produced free radicals in water which damaged the surface structure of Cryptosporidium. For the UV coupling ultrasonic inactivating the Cryptosporidium oocysts, the Cryptosporidium's death is mainly due to the oocyst's surface stucture damage caused by ultrasonic cavitation, at the same time the DNA of the Cryptosdium has also been some damaged by the UV irradiation.