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题名: 水处理滤池两段式过滤颗粒物截留机制及工艺优化
作者: 耿 欣1
学位类别: 博士
答辩日期: 2017-05
授予单位: 中国科学院大学
授予地点: 北京
导师: 王东升
关键词: 过滤工艺,停留时间分布,计算流体力学,改性滤料,光催化 ; Filtration Technology, Residence Time Distribution, Computational FluidDynamics, Modified Filter Media, Photocatalytic reaction
其他题名: Particle Retention Mechanism and Process Optimization ofTwo Stage Filtration in Water Treatment Filter
学位专业: 环境工程
中文摘要: 传统过滤工艺由于出水稳定、节约能耗等优点在我国广泛的运用,是常规水 处理工艺的核心单元。随着生活水平的不断提高,人们对水量、水质的要求也不 断提升;而社会的发展使得水体污染日益严重,越来越多的新兴污染物排入水体 中,使得传统过滤工艺无法有效应对。 为了能够有效提高传统过滤工艺的出水水量和水质,本论文采用停留时间分 布(RTD)和计算流体力学(CFD)的方法,对小试实验滤柱和水厂传统滤池中 的流态情况进行分析,为新型的两段式过滤装置的设计和滤料组合提供指导;对 传统水处理过滤工艺的优化升级,采用新型的两段式高速过滤装置,考察了滤料 的搭配组合对出水水质的影响,通过现场对比实验,考察了其长期运行效果;通 过对传统滤料的表面改性考察了其对污染物的去除效果;最后通过与光催化氧化 的组合工艺技术,考察了其对滤池中难以降解的污染物的去除效果。得出了以下 主要结论: 本论文通过对实验室小试滤柱装置的示踪粒子实验,来测定滤柱中示踪粒子 的停留时间分布曲线,并计算得到实际的水力停留时间。结果发现,随着滤速的 增大,推流过程越明显,而短流程度也越严重。而增大粒径可使得过滤过程中的 水力混合现象更明显。采用CFD 多孔介质模型对小试装置进行模拟分析,计算 得到的停留时间分布与实测数据相吻合。通过CFD 对小试装置的模型分析发现, 滤料孔隙率的增大,将使得各断面的压力变化呈指数倍的增大。而滤料球形度的 减少,将使得各断面的压力变化呈倍数的增大。在不同粒径滤料搭配组合的研究 中,随着上层粗粒径滤料的比重增大,上层断面的压力逐渐变小。整个滤柱压力 成比例减小。通过对水厂滤池的CFD 模拟发现,在水厂滤池的滤上水部分及承 托层下面部分的区域紊流现象较为明显,而在上层粗粒径滤料的表层,有轻微的 湍流出现,而滤池滤层中的流态则为稳定的推流。中试装置进行CFD 模型研究 发现,通过上层粗粒径滤料的加入,使得滤柱的压力明显减小。而对比三种规模 下的滤池发现,随着滤池规模的增大,推流作用减弱,而混合作用增强。 采用两段式高速过滤技术用于水处理中,这种新型滤池采用两段滤柱的设计, 可以防止在反冲洗过程中,不同滤料间的混合,这点是传统的双层滤池不能达到 的。在出水浊度、UV254 和水头损失与传统滤池一致的情况下,滤速可提高至传 统滤池的 2 到 3 倍,而反冲洗水率仅为传统滤池的 1/3。通过对五种粗粒径滤 料的比选,发现60cm 的无烟煤滤料和柱状活性炭滤料的出水浊度始终低于 1.2 NTU,在过滤速度为 20 m/h 的情况下,水头损失的增加在可接受的范围内,最 终被确定为纳污段滤柱的滤料,进行下面的实验。在第二部分的实验中,研究了十二组滤料组合和填料高度,最终确定 60 cm 柱状活性炭+ 40 cm 细石英砂滤料 为两段式高速过滤滤池的最优组合。采用上述滤料组合作为新型滤池滤料时,在 整个 48 小时的过滤过程中,出水浊度始终低于 0.2 NTU,出水 UV254 值低于 0.030,滤层的总水头损失也在可接受的范围内。通过一个月的现场实践研究发 现,以实际水厂沉后水为进水的条件下,两段式过滤工艺在浊度,DOCMn,UV254 和氨氮去除上均明显优于实际水厂的传统滤池工艺。 通过羟基铁表面改性石英砂滤料的方法来从本质上提高滤池对污染物的去 除。改性后的滤料表面负载了化学稳定性良好的Fe2O3,负载的铁含量为8.685 mg Fe /g 砂。石英砂滤料在进行表面改性之后,其表面形成了网状多孔结构,有 效的增加了滤料的比表面积。改性后的石英砂滤料的Zeta 电位向碱性范围内移 动,等电点处于pH 值8.0–9.0 之间,有利于对带负电的有机污染物的吸附。通 过对污染物去除实验,发现羟基铁改性后的石英砂滤料对浊度和腐殖酸的去除效 果有明显的提高,较未改性石英砂的平均去除率分别提高9.1%和24.9%。而对于 表面带正电荷的罗丹明B 的去除效果反而下降了8.1%。 通过光催化工艺与滤料工艺的组合进一步提高过滤工艺对污染物的降解。选 取砂滤工艺难以去除的罗丹明B 为目标污染物,研究表明,通过铁掺杂的溴氧铋 颗粒比表面积增加,并对可见光的吸收增强,有利于其在可见光下对罗丹明B 的 降解去除效果。在可见光类芬顿反应中,对罗丹明的降解过程中,在30 分钟的 吸附-解吸平衡后,吸附能力最强的催化剂为 0.2-FBB,吸附效率为43%。可见 光类芬顿反应中,对罗丹明的降解过程中,0.2-FBB 催化剂的催化活性最强。在 两个小时的光催化反应,对罗丹明B 的去除率达99%。通过光催化-过滤组合工 艺对罗丹明B 的去除效果较好,光催化过程对罗丹明B 的去除起决定作用,而 过滤工艺可以有效分离回收水中的光催化颗粒,经过光催化-过滤组合工艺,使 用未改性砂为滤料时,对罗丹明B 的去除率在79.3%以上;而使用改性砂的去除 率则在78.5%以上。光催化颗粒强化滤料的方式对罗丹明B 的去除率很低,仅有 44.4% - 59.9%,其中光催化的作用仅占1.7% - 3.6%,这主要是由于光催化的反 应时间太短。最后,通过循环实验可以看出,0.2-FBB 催化剂的催化活性较稳定。
英文摘要: The traditional filtration process has been widely used in China because of its stable effluent quality and energy saving. As the continuous improvement of living standards, the quantity and quality of drinking water gradually improved. However, more and more pollutants are discharged into the water. Water pollution is becoming increasingly serious because of the development of the society. The traditional filtering technology become ineffective deal with the emerging organic pollutants. In order to improve water quantity and water quality of the traditional filtration technology, flow pattern in experimental filter column and traditional filter was analyzed by Residence Time Distribution (RTD) and Computational Fluid Dynamics (CFD). The results can guide the design of new two stage filtration equipment and the combination of filter media. The optimization and upgrading of traditional water treatment filter technology, two stage high-speed filter device, investigates the combinations of effluent water quality of the filter material, through the contrast experiment, surveying the long running effect; The effect of the removal of pollutants by the surface modification of the traditional filter is investigated. Finally, the removal effect of the difficult degradable pollutants in the filter is investigated by combining process technology with photocatalytic oxidation. It is concluded as following: This article based on the test in the laboratory column devices of tracer particles experiment, to determine the filter column on residence time distribution curve of tracer particles, and the actual hydraulic retention time is calculated. The results showed that as the filtration rate increased, the flow was more pronounced and the short flow was severe. Increasing the size of the particle can make the water in the filtration process more obvious. Using CFD porous media model, the simulation analysis of the small test device was carried out, and the time distribution of the calculation was consistent with the measured data. According to the CFD model analysis of the small test device, the pore rate increase of the filter material will increase the pressure variation in the various sections. However, the reduction of filter sphericity will increase the variation of pressure in each section. In the study of different particle size filter combinations, the pressure of the upper section is getting smaller as the proportion of the filter material increased. The whole filter pressure is reduced in proportion. CFD simulation of filter found that, turbulence phenomenon is more obvious in free water and below bearing layer, and in the surface layer of the upper coarse particle filter material, has a slight turbulence, and the flow pattern in the filter filter layer is stable flow. It is found from the study of the CFD model that the pressure of the filter column decreased significantly with the addition of the upper coarse particle size filter. Compared to three sizes of filter as mentioned, the effect of the filter was decreased with the filter size increasing, and the mixing effect increased. This research is conducted to innovative two-stage high speed filtration technology used in water treatment. The new type of filter is designed to be connected with two down-flow filter columns in series. The two filter columns can be backwashed separately, thus different filter media cannot be mixed like the traditional dual filter. The performances, with respect to the removal of turbidity, UV254 and development of head loss, are similar to other more conventional filters with the exception that filtration rate is 2 to 3 times more than that of other filters and the backwash water rate is only 1/3 of those of other filters. Comparisons of five types of coarse particle filter, effluent turbidity of 60 cm thick anthracite or columnar activated carbon was consistently below 1.2 NTU, with acceptable head loss at a high filtration rate of 20 m/h, so that anthracite and columnar activated carbon were identified as the presupposed filter material of receiving pollution stage column. In the second part of the experiment, 12 combinations of filter media and packing height were studied, the combination of 60 cm columnar activated carbon + 40 cm fine quartz sand was regarded as the optimal filtration media. When the above combination was used as the filter media, effluent turbidity was consistently low than 0.2 NTU, and UV254 was lower than 0.030, head loss developed acceptably during entire 48 hours’ filter run. One month later, in the condition of settled water as inlet, in the water treatment plant, the two-phase filtration process is significantly better than the traditional filter technology in the turbidity, DOCMn, UV254 and ammonia nitrogen removal. The removal ability of emerging organic pollutants in the filter is enhanced by the iron-surface-modified quartz sands filter material. After surface modification, Fe2O3 could stably exist on the surface of quartz sands under different pH conditions, and the iron content of the load-oxides is 8.685 mg Fe /g sand. After the surface modification of quartz sand, a lot of porous structure is formed on the surface of the sand filter material, which effectively increases the specific surface area of filter material. The Zeta potential of the modified quartz sand filter material moves to the alkaline range after modification, and the iso-electric point is at pH = 8.0 – 9.0, which is beneficial to the adsorption of organic pollutants with the negatively charged surface. Based on pollutants removal experiment, found that the iron of the modified quartz sand filter material removal rate of turbidity and humic acid is an obvious increase, less modified quartz sand, the average removal rate increased by 9.1% and 24.9%, respectively. But removal of Rhodamine B decreased by 8.1%. The degradation of pollutants by the combination of photocatalytic process and filter technology is improved. Selection of sand filtration process is difficult to remove Rhodamine B as the goal pollutant, studies show that iron doped by bromine oxygen bismuth particle specific surface area increased, and the absorption of visible light, it is helpful to degradation of Rhodamine B in the visible light. In visible light type of fenton reaction, in the process of the degradation of Rhodamine B, after 30 minutes of adsorption - desorption equilibrium adsorption capacity of the strongest catalyst is 0.2- FBB, the adsorption efficiency of 43%. The catalytic activity of the 0.2-FBB catalyst was the most active in the process of degradation of Rhodamine B. In the two hours of photocatalytic reaction, the removal rate of Rhodamine B was 99%. Through combination photocatalytic - filtration process better removal effect of Rhodamine B, photocatalytic process of Rhodamine B decide to remove, and filtering technology can effectively separate recycling the photocatalytic particles in the water, after combination photocatalytic - filtration process, using unmodified sand as filter material, the removal rate of Rhodamine B in more than 79.3%; The removal rate of modified sand was more than 78.5%. Removal rate of Photocatalytic particle enhanced filter media for Rhodamine B is very low, only 44.4% - 59.9%, among them photocatalytic role only 1.7% - 3.6%, this is mainly caused by the catalytic reaction time is too short. Finally, the catalytic activity of the 0.2-FBB catalyst is stable by the cyclic experiment.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/38623
Appears in Collections:环境水质学国家重点实验室_学位论文

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作者单位: 1.中国科学院生态环境研究中心

Recommended Citation:
耿 欣. 水处理滤池两段式过滤颗粒物截留机制及工艺优化[D]. 北京. 中国科学院大学. 2017.
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