【作者】 刘芳；

【导师】 马军；

【作者基本信息】 哈尔滨工业大学 ， 市政工程， 2010， 博士

【摘要】 由于溶气气浮工艺对低温低浊水、高藻水、高色度水均有较好的处理效果,得到人们的高度关注。近年来我国水污染严重,水源水质较差,微污染水的处理成为急需解决的问题。而以往人们主要关注气浮工艺除颗粒物的效能,对于气浮除有机物的效果缺乏系统的研究工作。研究溶气气浮除污染效能并强化其运行的稳定性具有很重要的现实意义,使之能更好地应用于受污染水处理中。在溶气气浮除污染效能及影响因素的研究中,发现采用适当提高混凝剂投量、较短的絮凝时间及较强的絮凝强度、pH值为中性、投加Ca2+离子及少量高岭土等均可作为气浮工艺强化去除有机物的手段。溶气气浮对腐殖酸的去除率均在80%左右,对硝基苯的去除效果随着pH值和TOC值增加而降低,随着Ca2+离子浓度提高而增加,随着浊度升高先增加而后降低,最高去除率为50%。腐殖酸在水中的存在形态随水质特征而发生变化,进而影响其对硝基苯的吸附效果,也影响混凝阶段对气浮工艺去除硝基苯的效果。在研究气浮工艺处理有机物的机理过程中,利用三维荧光手段证明随着pH值增大,腐殖酸分子荧光强度发生变化,腐殖酸与铝离子络合反应减弱,更多铝盐水解成高分子聚合体,通过网捕作用使大量腐殖酸形成有利于气浮工艺去除的絮体。并且随着pH值升高,腐殖酸在云母表面的覆盖率明显降低,在酸性条件下观测到的分子半径相对于中性和碱性条件下较小,聚集体结构在碱性条件下较为松散。金属阳离子Ca2+在腐殖酸分子聚集方面发挥重要的作用,少量Ca2+离子(10mg/L CaCl2)的加入就会导致大的聚集现象发生,促进腐殖酸的吸附。扫描电镜检测结果进一步表明,随着pH值增大,絮体聚集现象明显,形成的絮体更容易与微气泡粘附形成密度小于1的泡絮结合体,靠浮力上升而被去除,进一步证明了三维荧光扫描中的结论。在优化分离区内部结构以提高气浮工艺运行稳定性的研究中,发现气浮池集水系统及分离区内加入的竖板装置均对气浮池运行效果和稳定性有一定影响,采用穿孔板集水系统及在分离区底部加入小板距竖板装置强化了气浮工艺的稳定性。使竖板气浮池随着水力负荷变化,出水效果基本不变,并且能够在水力负荷18m/h的情况下运行,与传统气浮池相比,浊度去除率提高50%,有机物去除率提高29%。并且竖板气浮池对回流比等参数变化的适应性很强,更利于运行管理。竖板气浮池对水质特点的改变也有很好的适应性,在低温低浊、低温中浊及低温高浊等几种情况下运行时,随着水力负荷的变化,出水中浊度及有机物的含量基本保持稳定,即使水力负荷达到18m/h,浊度及有机物的去除率依然保持在很高的水平上,没有出现恶化情况。竖板气浮池分离区内流场特性随运行水力负荷和回流比的变化而产生变化。随水力负荷和回流比的增大,气泡层厚度增加。水力负荷过大或者回流比过小时,分离区内出现三维漩涡,影响运行效果。提出了沉淀—溶气气浮高适应性联用工艺,并在某水厂进行了生产性试验。结果表明,沉淀—溶气气浮联用工艺对有机物、藻类、氨氮、嗅味等均有很好的处理效果。质谱分析结果表明,气浮工艺对水中烷类、酮、杂环类有机污染物有很好的去除效果。该技术解决了高藻水絮凝后产生絮体太轻不易沉降而堵塞后续滤池的问题,使藻类严重爆发期间滤池反冲洗周期从最短的四小时延长到十几小时,恢复了水厂正常的产水量,大大地降低了水厂的自用水量。该水厂原水的水资源费用为每吨1元,在生产性实验中发现,虽然加入气浮工艺有一部分耗电量的增加,但生产用水和投药量都有所降低,生产成本也降低。采用沉淀—溶气气浮联用工艺对平流沉淀池进行改造,具有工期短、工程简单,投资小而且出水效果好、产水量高等特点。解决了传统工艺处理高藻水难的问题。并且为将气浮池改造成气浮池分离区内部加入竖板装置的竖板气浮池的二期工程,以应对产水量进一步提高的实际情况做好了准备。更多还原

【Abstract】 Water treatment process with dissolved air flotation is concerned because of its better treatment effectiveness on low temperature and low turbidity water, high algae-laden water and high-colour water. In recent years, the water pollution was critical while the water quality and quantity were worse in China. The treatment of micro-contaminated source water becomes an urgent problem. However, the ability of air flotation process to remove particulate matter was mainly concerned in the past, the research work on the enhanced treatment of organic matter was limited. In order to apply dissolved air flotation process in the treatment of micro-contaminated source water, the study on the pollutant removal efficiency and the enhancement of operation stability is of great practical significance.The treatment efficiency and influencing factors of micro-polluted water by air flotation process were studied. It was found that appropriate increase in coagulant dosage, shorter flocculation time, stronger flocculation intensity, neutral initial pH value, addition of Ca2+ ions and small amount of kaolin added could be used as the means for enhanced coagulation of organic matter by air flotation process. The average humic acid removal by coagulation and air flotation was about 80%. The effectiveness of nitrobenzene removal by coagulation and air flotation process was decreased with the increase of initial pH value and TOC value, increased with the increase of Ca2+ ion concentration, firstly increased and then decreased with the increase of turbidity while the maximum removal rate was 50%. The occurrence of this phenomenon is a consolidated results,which depend on the variations of humic acid microstructure under different water conditions and the effectiveness of nitrobenzene adsorption and removal by air flotation process at coagulation stage was studied.The mechanism of organic matter treatment by air flotation process was studied. The three-dimensional fluorescence detection results showed that the humic acid molecule fluorescence intensity changed with the increase of initial pH value, the complexation reaction of humic acid with aluminum ion was weakened. It inferred that more aluminum salt decomposed into high polymer, a large number of humic acid formed conducive flocs for air flotation process with capture mechanism. With the increase of pH value, the coverage of humic acid on the mica surface decreased. Under acidic conditions, the observed molecular radius being smaller than neutral and alkaline conditions while aggregate structure was looser under alkaline condition. Ca2+ ion played an important role in humic acid molecular aggregation. A small amount of Ca2+ ions addition would result in great aggregation phenomenon to improve humic acid adsorption. Scanning electron microscopy results further showed that the phenomenon of floc clusters was obvious as the initial pH value was increased. The flocs were more easily adhered with micro-bubbles to form foam-floc combination, which could be removed by buoyant force because the density of combination was less than 1. It proved the conclusions in three-dimensional fluorescence scanning above.The effects of internal structure of optimized separation zone on air flotation process stability were studied. It was found that both the water collection system of air flotation tank and vertical plates in separation zone influenced the operation effectiveness and the stability of air flotation tank. By using perforated plates collection system and adding vertical plates with small space length in the bottom of separation zone, the stability of air flotation tank was enhanced. The effects of effluent water were basically constant with the variation of hydraulic loading for vertical plates air flotation tank which could operate at hydraulic loading of 18m/h. Under the same hydraulic loading conditions, the effect of the vertical plates air flotation tank was better than the traditional air flotation tank for both turbidity removal and organic matter removal. The vertical plates air flotation tank had a high adaptability with the variation of parameters such as recycled ratio and was easy for operation management. As well, the vertical plates air flotation tank also had a great adaptability with changes of water quality, operation under the conditions of low temperature low turbidity, low temperature medium turbidity and low temperature high turbidity achieved good results on the removal of turbidity and organic matter at hydraulic loading of 18m/h. The flow field feature of separation zone in vertical plates air flotation tank changed with the flow rate and recycled rate. As the hydraulic loading and recycled ratio increased, the bubble layer thickness increased. The three-dimensional vortex appeared in separation zone influenced the operation effect when the hydraulic loading was too large or recycled ratio was too small.Full scale experiment on the combined sedimentation with dissolved air flotation was performed. The experimental results showed that the effects of combined treatment technology on the removal of organic matter, algae, ammonia nitrogen and odor were excellent. Since the solution of problem in the difficulty of flocs settlement and the block of filter after the flocculation of high algae bearing water, the backwash cycle of filters extended from a minimum of four hours to more than ten hours during serious outbreak of algae, the water plant resumed normal production of water, greatly reduced the water consumption. It was found that the flotation part added the increase in power consumption, but the production water consumption and the coagulant dosage reduced, so that the cost of water production reduced. By using high adaptable technology combined sedimentation with dissolved air flotation, the sedimentation tank reformation had the advantages of low cost, low investment, high qualified water and high water production. This process could solve the water treatment difficulty in traditional high algae-laden seasons. The second phase project by adding vertical plates in separation zone of air flotation tank was prepared for the actual situation of further improvements in water production.更多还原