Removal Efficiency Of Microcystins And Cryptosporidium Oocysts In Water By Chlorine Dioxide And Toxic Effect Of The Byproduct

Along with the development of agriculture and industry, water body has been suffered serious pulution that threatened the water safety. People also demand higher quality water followed by the improvement of the living standard. Microcystins (MCs) and Cryptosporidium are of great concern under this background. Chlorine dioxide has been considered as an ideal substitution of chlorine in potable water treatment, however chlorite produced in the disinfection process has been an issue.Enzyme-linked immunosorbent assay, HPLC-MS/MS method, intravital staining and quantum chemistry method were used to invesgated the efficiency, influence factors and reaction mechanism of chlorine dixoide removing microcystins and Cryptosporidium oocysts in water. Treatment efficiencies of chlorine dioxide proixidation, coagulation, sedimentation, filtration and disinfection on algae-laden water were studied by simulative processes. In addition, the neurotoxicity of chlorite in prolonged exposure was preliminarily investigated by the methods of ethology and neuroanatomy assay in three generation rat pups. A series of original conclusions were drawn through this thesis.Performance of chlorine dioxide removing MCs were studied. And the recction mechanism and products between MCs and chlorine dioxide were also determined. The results showed that chlorine dioxdide can degrade MC-LR, MC-RR and MC-YR effectively. The reactions follow similar pattern and affected greatly by chlorine dioxide concertration and reaction time while slightly by pH and temperature. In the reactions, carbon atoms at the end of Adda groups were attacted, and then Adda groups were oxidated followed by dihydroxy substituendums formated.Treatment effect of algea-laden water by conventional drinking water treatment processes was investigated in the general. It was found that coagulation and sedimentation can hardly remove microcystins but can remove large amount of algae. The filter contained higher ratio of blind coal resulted in better effluent. In the disinfection process, more microcystins can be removed by adding chlorine dioxide before filtration than after. However, higher removal rates of potassium permanganate index and turbidity and lower chlorite formation can be abtained when adding chlorine dioxide after filtration. Satisfactory water quality can be gotten at the condition that: proxidation by 2.5 mg/L chlorine dioxide for 40 min, coagulation at 60 r/min for 20 min, sedimentation for 30 min,addition 0.8 mg/L chlorine dioxide for disinfection and then filtration at 10 m/L with the ratio of blind coal and quartz sand of 2:1.Performance of chlorine dioxide inactivating Cryptosporidium oocysts in water was studied. The results showed that chlorine dioxide can kill Cryptosporidium oocysts effectively. Inactivate rate affected mostly by chlorine dioxide dosage, reaction time and temperature. And it decreased at high turbidity and high potassium permanganate index. The Cryptosporidium oocysts inactivated by chlorine dioxide is still remained integrality in shape.The neurotoxicology performance of chlorite was proposed. It is found that prolonged exposure to excessive chlorite for three generations can cause damage in cerebellum for rat pups in the second and the third generation, which leading to adverse impact on physical ability. And the learning memory ability seemed also impaired. The no observed adverse effect level of neurotoxicology for three generation Wistar rat is 30 mg/L.The results obtained in the paper not only provide theoretical basis for controlling microcystins and Cryptosporidium oocysts in potable water, but also bring out a feasible way of chlorine dioxide proxidation for water treatment, which is of important theory and application value. Furthermore, the toxicity of chlorite has also been complemented and can be references for extending the application of chlorine dioxide and standard developing.