【作者】 付娇；

【导师】 黄君礼；

【作者基本信息】 哈尔滨工业大学 ， 环境科学与工程， 2007， 硕士

【摘要】 富营养化导致水体水质恶化,味觉和嗅觉变坏,其最大的潜在威胁是富营养化水体中存在某些优势藻类,能产生胞内毒素、肝毒素和神经毒素等,危害人类健康。微囊藻(Microcystis)是我国富营养化水体中的主要污染藻类,是富营养化水体中的优势藻并易形成“水华”,其产生的微囊藻毒素(Microcystins,MC)是一类七肽单环肝毒素,其中MC-LR是目前发现的最强的肝脏肿瘤促进剂,MC在水中的化学稳定性较好,不能被传统净水工艺有效去除。因此,微囊藻的过度繁殖及产生的微囊藻毒素已对饮用水安全构成严重威胁。ClO2是一种优良的消毒剂和强氧化剂,对水中的许多有机和无机污染物均具有较好的去除效果,而且几乎不与水中的有机物形成THMs等有机卤代物,在水处理中具有广阔的应用前景。本文以微囊藻属中的重要产毒种铜绿微囊藻和惠氏微囊藻作为目标藻种,对ClO2处理微囊藻的效果进行了研究。结果表明:ClO2对于微囊藻具有很好的杀灭效果。叶绿素去除率与ClO2投加浓度、反应时间呈正相关性,与叶绿素初始浓度呈反相关性,反应温度和pH值对于叶绿素去除率影响不明显。当ClO2投加量为2.5mg/L,温度25℃,pH=7.17时,反应15min后,惠氏微囊藻和铜绿微囊藻(905#和915#)的杀灭率分别可达到97.23%、96.2%和92.33%。本文研究了ClO2氧化去除MC-LR的效果,并采用正交试验讨论影响处理效果的因素。结果表明:ClO2对于MC-LR具有很好的去除效果。去除率与ClO2投加浓度、反应时间呈正相关性,与MC-LR初始浓度呈反相关性,反应温度和pH值对于MC-LR去除率影响不明显。当ClO2投加量为2.5mg/L,温度20℃,pH=6.47时,反应60min后,MC-LR去除率可达到95.12%。正交试验所考察的各影响因素的主次顺序为:ClO2投量→温度→反应时间→pH。将MC-LR的初始浓度降低到接近实际水体,ClO2的投量接近水厂处理的水平,结果显示MC-LR被ClO2氧化去除的剩余浓度远远低于国家标准1.0μg/L。本文对ClO2与MC-LR的反应动力学进行系统研究。结果表明,ClO2与MC-LR的反应级数对二者均为一级,总反应级数为二级。在pH=6.47、反应温度20℃的条件下,ClO2对MC-LR的反应速率常数为7.86 L/(mol?s)。考察了溶液pH和温度对反应速率常数的影响,结果表明溶液pH对反应速率有一定影响,在酸性和中性条件较碱性条件反应速率常数大一些;反应速率常数随温度的增加而增大,二者反应活化能为78.81kJ/mol,表明ClO2与MC-LR在一般水处理条件下即可发生反应。考察ClO2预氧化处理工艺与常规水处理工艺对含藻水样的处理效果,并且对微囊藻在ClO2预氧化剂作用下的破坏形态和藻毒素的释放特性进行了初探。研究结果表明:ClO2预投量为3.0mg/L时,出水叶绿素去除率达到98.5%,藻的杀灭率达到95%,浊度去除率达到89.08%。与常规水处理工艺相比,ClO2预氧化处理工艺,可以有效灭藻,降低浊度。通过对微囊藻毒素释放特性的研究显示,当ClO2大于3.0mg/L时,胞内和胞外毒素都降到一个较低的水平,可以达到控制饮用水中微囊藻毒素含量的目的,保证饮用水安全。本论文研究得出ClO2对于水中微囊藻及微囊藻毒素具有很好的去除效果,这对蓝藻“水华”的治理和饮用水安全生产提供了科学依据。更多还原

【Abstract】 Blooms in eutrophic water body had become an serious problem threatening the safe drinking water. Besides aesthetic aspects such as unattractiveness to bathers,odor, and bad taste of treated drinking water, many species or strains of cyanobacteria also produce potent cytotoxins, hepatotoxins, and/or neurotoxins. Microcystis is the mainly species in eutrophic water and easily lead to Blooms. Microcystins (MC) produced by Microcystis are hepatotoains containing cyclic heptapeptides. Microcystin-LR(MC-LR) is the most strong liver tumour promotor at present. MC are chemically stable in water and can’t be effectively removed by conventional water treatment processes. It becomes a great threaten of drinking water when Microcystis growth excessly and produce MC. As a sort of excellent disinfectant and oxidant, chlorine dioxide (ClO2) has promising future for its excellent ability in removing both organic and inorganic contaminants without forming halo-substituted organics such as trihalogenmethane (THMs).The effects of ClO2 on the degradation of two typical Microcystis including M. aeruginosa and M. wesenbergi in aqueous solution were investigated systematically and the results showed that ClO2 could effectively remove M. aeruginosa and M. wesenbergi. The removal efficiency of chlorophyll was in positive correlation to ClO2 dosage and the reaction time and in negative correlation to initial concentration chlorophyll, whereas it was affected by temperature and pH value slightly. The removal ratios of M. wesenbergi and M. aeruginosa(905#和915#)could reach to their maximum as approximately 97.23%、96.2%和92.33% respectively under the conditions as follows: the ClO2 dosage 2.5mg/L, reaction time15 min, and pH 7.17.The removal effectiveness of MC-LR oxidation by ClO2 was studied and Orthogonal experiment was used to discuss detailedly the influence factors as ClO2 dosage, reaction time, temperature and pH in removing MC-LR by ClO2 in this chapter.The results were shown as follow, ClO2 could remove MC-LR effectively, the efficiency of removal was in positive correlation to the ClO2 dosage and the reaction time and in negative correlation to the initial concentration of MC-LR, but it was affected by temperature slightly and was effictive in wide range of pH value. The significance rank of the four factors affecting degradation efficiency was the concentration of ClO2, pH, temperature, time by the orthogonal test results. The residual concentration of microcystins-LR removed by ClO2 could meet the national guideline (1.0μg/L).The research on the kinetics of MC-LR oxidation by ClO2 was systematically performed in this chapter. The results showed that the kinetics of MC-LR degradation by ClO2 followed second order reaction equation, reaction orders of the ClO2 and MC-LR were first order respectively, the reaction rate constant was 7.86 L/(mol?s) and activation energy was 78.81 kJ/mol. In conclution, ClO2 could be taken as an effective technology for removal microcystin-LR from drinking water resources in traditional drinking water supplies.Research on the differences between preoxidation treatment and conventional water treatment processes to removal of Microcystis and MC-LR .Also analyze the charateristics of the breakage of Microcystis after being oxidated by ClO2. The results were shown as follow, as the dosage of ClO2 was 3.0mg/L, removal efficiency of chlorophyll and Microcystis were 98.5% and 95% respectively and turbidity decreased to 89.08%. Compared with conventional water treatment methods,preoxidation treatment of ClO2 could effectively remove Microcystis aeruginosa, decreased turbidity and guarantee the drinking water quality. The study of the mechanism of intracellular microcystins release showed that ClO2 dosage 3.0mg/L, intracellular and extracellular microcystins had fallen to a very little level.Therefor, ClO2 is a suitable oxidant for the degradation of microcystins in drinking water treatment processes.Work of this dissertation has great theoretical and practical value as it provided enough scientific basis for the application of ClO2 in removing Microcystis and MC from aqueous solution.更多还原