Research On The Inactivation Mehtods And Mechanism Of Cryptosporidium And Giardia In Source Water

Cryptosporidium and Giardia (they are referred as two insects) can infect humans and other species of animal, which will cause fever, abdominal pain and other symptoms, and even to cause the death of the patients whose immunity was low or lacked. Two insects can survived in the water as a long time, and they had a strong resistance to environmental factors and chlorine disinfectants, and could not be completely removed by the conventional water treatment process. In China, the water treatment process are slow, and most of the water plants can only purify the physical and microbial contamination, thus, it had the possibility of infection outbreak at largescale, which threat to our country majority of the people's health, safety and development of harmonious and stable society seriously.At present, the research in our country only concentrated on the development of detection methods, the improved recovery method and so on. So the study on the removal of water beetle is an urgent question in our country. In this study, the fluorescent staining and immune TD (pyrimidine dimer) fluorescence detect methods had been optimizd and improved, and the activity detection rate and specificity of detection had been improved. Besides, the eliminate effect of Fungicide treatment and the processing on two insects. At the same time, the primary investigation of the mechanism of disinfection through scanning electron microscopy (SEM), the protein experiments, lipid peroxidation hydrogenation reaction, polymerase chain reaction (PCR) technology and fungicide treatment. All the work carried out in this paper is to seek effective and feasible prevention and control of water, the two insects, the methods and processes for the protection of urban and rural drinking water quality and health of residents to provide strong technical support.For the current problem which is poor detection rate and inaccurate evaluate activity, the EPA1623 method, in vitro excystation and modified acid-fast staining methods, such as the detection rate, and establishment of a fluorescent activity staining method were compared. Besides, the "two worm" detection rate, the time and other factors, and the fluorescent activity staining procedure to improve were studied to get a good precision and accuracy, and to imporve that it was the reliable method for "two worms" activity detecting, which was the foundation of a further study to carry out.Study on the effect and impact factors of inactivation two insects by chemical disinfection, and found that: the inactivation of O₃ to two insects was stronger than that of ClO₂, and Cl₂ had the worst inactivation effect; the best inactivation effect conditions were as follows: the inactivation rate reached more than 99.0%, and the dosage must be above 6.3mg/L with the reaction time was over 360min. Related factors studies have shown that the turbidity and organic matter were the main factors influencing the inactivation, and the lower the turbidity and organic mater were, the better inactivation effect was. Lower temperature was not suitable for the inactivation of two insect, and pH had little effect on the inactivation of the two insects.In order to achieve the desired inactivation of two insects (inactivation rate above of 99.0%), the two insects inactivated by O₃/H₂O₂ obtained the best results, which not only reduced the initial concentration of bactericide (O₃ dosage of 2.0mg / L), but also shortened the sterilizing time (7.0min). The best H₂O₂/O₃ molar ratio is 0.8. The common ions which influenced inactivation of H₂O₂/O₃ on two insect were investigated in water. Low concentrations of Ca²⁺, Mg²⁺ and Cu²⁺ are divalent metal ions play a catalytic role for the inactivation, Na⁺ had no significant effect on disinfection, but NO₃^-, HCO₃^- and Cl^- inhibited H₂O₂/O₃ inactivation of two insects within a certain range. Photocatalytic inactivation of two insects with the amount of catalyst increased the inactivation rate gradually. When the photocatalyst is 1.0 mg/L, the Cryptosporidium and Giardia inactivation rate was 69.5% and 80.0%, respectively. As the dose increased, inactivation rate is rapidly increasing, especially when the photocatalyst was 5.0mg/L, the Cryptosporidium and Giardia inactivation rate reached 99.8% and 99.9% respectively.Physical inactivation process studies have shown that inactivation of two insects, UV method has a better ability. The higher the UV irradiation power was, the stronger the inactivation capacity was. When the UV radiation power was 4.5mW/cm², the irradiation dose increased to 13.5mJ/cm², the inactivation rate of the two insects reached 99.9%. Turbidity and the concentration of organic matter on UV inactivation of the "two bugs" is more obvious, when the turbidity (concentration of organic matter) increased, the the inactivation rate of "two worms" after radiated by UV was reduced accordingly. pH value and temperature no significant promote or inhibit effect on the UV inactivation to two insects. The actual water source experimental results show that the UV inactivation of "two worm" has a strong feasibility and value of certain applications.Scanning electron microscopy (SEM), the protein experiments, lipid peroxidation hydrogenation reaction and polymerase chain reaction (PCR) technology were used to explore a variety of water treatment chemicals and process water treatment on the inactivation process and the mechanism of "two worms". Results showed that the inactivation of "two worm" by Cl₂ and ClO₂ relied mainly on oxidation and cell membrane penetration, resulting in "two worms" cell deformation, which lost function, cell membrane permeability, and then causing inactivation or death. The inactivation of O₃ on two insects was not only relay on its strong oxidizing ability, but also had a colse relationship with the hydroxyl radicals. The mechanism of UV inactivation on two insects was the generation of intracellular nucleic acid pyrimidine dimers, which even lead to inactivation of nucleic acids, and then resulting in cell death. H₂O₂/O₃ synergies produce large amounts of hydroxyl radicals on the inactivation of the two worms, which is the most significant effective method in the inactivation of two worms.