【作者】 缪恒锋；

【导师】 陶文沂；

【作者基本信息】 江南大学 ， 发酵工程， 2008， 博士

【摘要】 地表水体日益受到各种有机物的污染,对水环境和人类健康构成了严重的威胁。在太湖流域,许多水体面临富营养化的威胁,其中由藻类大量繁殖引起的水华和由此带来的一系列水环境问题,给地表水水质和生态系统带来了诸多影响。其中由水体生物大量死亡带来的腐殖质、藻类代谢产生的异味物质和微囊藻毒素对水体的影响尤为明显,而且常规的水处理工艺很难将这些物质去除或者存在去除效果差的问题。臭氧(O3)以及以产生自由基( ?O H)为基础的高级氧化技术(AOP)能够有效地去除水体中的这些有机污染物和对藻类进行杀灭。本文对降解和杀灭地表水体中的难降解有机物和藻细胞的高级氧化技术进行了深入研究,主要包括臭氧氧化降解腐殖酸(Humic acid)、灭活藻细胞、去除异味化合物和脱毒微囊藻毒素(Microcystins)的效能和机理,以及此过程中的条件优化。设计开发以太阳能为主要能源的地表水处理设备,为富营养化水体的处理探索新的方法和工艺。研究结果表明:(1)臭氧氧化能够有效地去除腐殖酸,提高水体的可生化性,它能使腐殖酸元素组成改变、官能团发生变化、改变其分子量分布,产生芳香族、醇酚、醛酮、酸酯等挥发性有机物。臭氧氧化腐殖酸的整体反应遵守一级动力学方程。通过对腐殖酸臭氧氧化过程中的温度、pH的优化,确定了温度为25℃和pH 7.0为合适的反应条件,购自Sigma的腐殖酸标准品的反应速率常数k为3.6×10-3 s-1,实验室分离自太湖底泥腐殖酸的k为2.9×10-3 s-1。使用叔丁醇(t-BuOH)作为自由基清除剂考察了不同条件下臭氧氧化反应的2种主要途径(直接分子氧化和自由基反应)对整个臭氧氧化反应的贡献,发现反应的直接分子氧化降解腐殖酸反应随温度的变化遵循Arrehenius方程:另外pH的升高,能大大增加自由基反应的贡献率,提高总体反应速率和效率;使用催化剂对腐殖酸的催化臭氧化考察,得到了不同的增强因子:f(Mn2+)=1.31;f(Fe2+)=1.09;f(H2O2)=1.69。(2)臭氧氧化能够破坏铜绿微囊藻细胞壁和细胞膜,使藻细胞破裂,从而使藻细胞失活,达到杀藻的效果;当溶液臭氧浓度达到3 mg L-1,臭氧处理时间30 min时,能使溶液中的藻细胞因遭受损伤而不能继续正常代谢,导致藻细胞的整体死亡。水体中的本底物质能够很大程度上影响臭氧的杀藻效率:本底DOC通过和臭氧的竞争性反应而降低藻类去除率,DOC浓度越高,臭氧杀藻效率越差;自由基清除剂通过自身对臭氧化反应间接途径的阻断,也能很大程度上降低臭氧的杀藻效果,NaHCO3作为自由基清除剂在溶液中的浓度越高,臭氧杀藻效率也越差。(3)对太湖蓝藻水华水样GC-MS分析发现的6种典型的藻类代谢异味化合物,使用臭氧氧化的方法对这些异味物质进行降解去除发现,目标异味化合物的降解符合一级动力学反应方程,反应速率由高到低为:β-紫罗兰酮(3.3×10-3 s-1)﹥β-柠檬醛(2.8×10-3 s-1)﹥2,4-癸二烯醛(2.7×10-3 s-1)﹥香叶基丙酮(2.2×10-3 s-1)﹥土味素(1.4×10-3 s-1)﹥2-甲基异莰醇(5.6×10-4 s-1)。臭氧化反应速率由目标物质的化学性质和结构决定。臭氧化反应还产生了大量醛、酮、醇和酯类小分子物质。同时,这些物质的臭氧氧化反应受水体中DOC浓度和自由基清除剂影响,这些物质的浓度越高,目标异味化合物的去除效果越差。(4)臭氧氧化降解由铜绿微囊藻代谢的微囊藻毒素(MCs)主要通过Adda途径和Mdha途径来完成对MCs的脱毒作用。臭氧氧化藻毒素的Adda途径是通过臭氧分子或者自由基对MCs上Adda侧链的进攻,断开具有活性的Adda侧链,而达到去毒的目的;臭氧氧化的Mdha途径是通过对MCs肽环上面Mdha和Ala的断键,打开环状肽链变为直链肽,使藻毒素失去/降低活性。整个臭氧化过程中Adda途径占主导作用。通过对MCs及其臭氧化副产物的蛋白磷酸酶抑制(PP1)和小鼠急性毒性试验结果,表明臭氧氧化对MCs的脱毒作用明显:PP1对MCs的检测和HPLC结果相一致,表明MCs臭氧化产物不表现毒性或者表现毒性不明显;同时小鼠急性毒性表明,MCs臭氧化产物对小鼠肝毒性不显著。说明了臭氧氧化作用做MCs脱毒的可靠性。(5)根据实验室研究结果开发以臭氧氧化技术为主要手段的地表水处理系统,设备以臭氧投加量为5 g t-1、臭氧/空气曝气比例为1:5对现场富营养化的地表水体处理一周期(15 d)的效果为:COD去除率78.9%,叶绿素a去除率为49.0%,NH3-N去除率为50.6%;同时使水体DO达到6.2,恢复水体的自净化能力。表明了该设备对富营养化水体污染物具有很好的去除率和针对性。针对水处理系统能量要求来设计太阳能地表水处理设备的发电系统,通过计算得到处理水量为3 t h-1的水处理设备的太阳能光伏发电系统的配置要求:3.24 KW的太阳能电池方阵、48 V/5 KW的逆变器、24个48 V的蓄电池并联。综上所述,本文研究表明臭氧氧化技术对地表水污染可以起到很好的控制作用,可以有效地去除水体有机物、杀灭藻细胞并降解其代谢产物,保障饮用水安全。更多还原

【Abstract】 Organic pollution in water gradually become a serious threaten to water environment and human health. Especially, the eutrophication of water in Taihu Lake Basin leads to excessive growth of algae and formation of blooms. These bring out many problems in water ecosystem such as humic substance from the death of vegetable substances, odorous organic compounds and microcystins from metabolism of algae. They are difficult to be eliminated with routine processes of water treatment. Ozonation and AOPs, which could produce ?O H, perform powerfully in the removal of these pollutions. The investigation focused on the effect of ozonation to NOM and algae with its metabolites in surface wates, which mainly includes mechanism study and condition optimization of humic acids (HAs) degradation, algae killing, odorous compounds removal and microcystins (MCs) detoxification. Finally, a surface water treatment system powered by solar energy was designed and developed for eutrophication water. Research results of this thesis are as follows.(1) Ozonation with its direct and indirect reaction pathways can not only rearrange molecular structures of HA and convert it to more hydrophilic forms but partition the HA macromolecules into small fractions. The reaction of HA ozonation followed a pseudo-first order model, rate constant of HA bought from Sigma is 3.6×10-3 s-1 and HA extracted from Taihu Lake 2.9×103 s-1. The proper condition of ozonation of HA was optimized as 25℃and pH 7.0. The contributions of two pathways (molecular ozone attack and .OH attack) to HA ozonation could be traced using tert-butanol as the radical scavenger at different pH, temperature, and the results showed that .OH oxidation are more sensitive to operating variables than molecular ozone oxidation and exerted a contribution of approximately 50-60% to the overall reaction at the different operating parameters. And molecular ozone attack was found followed Arrehenius equation under different temperature, Catalytic ozonation of HA by different catalyst was further investigated, enhancement factor was calculated as follows: f(Mn2+)=1.31;f(Fe2+)=1.09;f(H2O2)=1.69.(2) The ozonation of M. Aeruginosa led to the damage of cell wall and celluar cytoplasm release from the cells, which caused the DOC increase in solution and odorous organic compounds production. A the ozone dosage of 3 mg L-1 and reaction time of 30 min could seriously damage the cells, which led to the death of algae. Further investigation found out that DOC and radicals scavenger (NaHCO3) exerted an important influence on the ozonation of algae. High concentration of these compounds leds to low efficiency of algae killing.(3) Ozonation was applied to investigate the removal efficiency of 6 odorous organic compounds in eutrophic water from Taihu Lake. The results showed that the ozonation process could be described by first order kinetic model and the overall kinetic rates of the odorous compounds were determined by their chemical characteristic and structure, which could be ranked:β-Ionone (3.3×10-3 s-1)﹥β-Cyclocitral (2.8×10-3 s-1)﹥2,4-Decadienal (2.7×10-3 s-1)﹥Neryl Acetone (2.2×10-3 s-1)﹥Geosmin (1.4×10-3 s-1)﹥2-Methylisoborneol (5.6×10-4 s-1). Ozonation of eutrophic water led to the formation of a series of aldehydes, ketones, alcohols and esters. The influence of DOC and radicals scavenger (NaHCO3) on odorous compounds ozonation were further investigated, results showed that the radicals scavenger could restrain the effect of ozonation by cutting down the radical pathway and DOC in the water by competition with target compounds.(4) The decomposition of MCs by ozonation appears to involve substitution and cleavage of the Adda conjugated diene structure, cleavage of the peptide bond between Mdha and Ala, and attack of the Adda benzene ring. The degradation rate of MC-RR was a little slower than that of MC-LR, which lead to more byproducts from Adda side chain cleavage in our study. The Adda moiety, which is important in MCs toxicity, is readily oxidized and destroyed by ozonation. It is apparent from this study that Adda degradation pathway is the major destruction pathway of both MC-LR and MC-RR. The heptotoxity of MCs expressed as inhibition of PP1 and damage in mouse liver was greatly reduced or eliminated by the ozonation process.(5) The surface water treatment system was developed as the output of equipment was 3 t h-1. The system was applied to eutrophication water in Taihu Lake and obtained the results as COD removal of 78.9%, Chl-a 49.0%, NH3-N 50.6%. Simultaneously, DO of water increased to 6.2 mg L-1. The device was equipped with the solar cell array of 3.24 KW, an inverter of 48 V/5 KW and 24 parallel connection of 48 V storage battery.In conclusion, the results indicate that ozonation was found an innovative and prospective method in surface water treatment. The application of ozonation was including organic compounds decomposition, algae and its metabolites killing and removal for dringking water security.更多还原