| 题名 | 混凝-超滤工艺中的絮体调控及膜污染分析 |
| 作者 | 段淑璇 |
| 学位类别 | 硕士 |
| 答辩日期 | 2015-05 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 王东升 |
| 关键词 | 混凝-超滤联用工艺，絮体结构，膜污染，天然有机物，化学清洗，coagulation-ultrafiltration process, floc structure, membrane foulin g, nature organic matter, chemical cleaning |
| 其他题名 | The floc regulation in coagulation-ultrafiltration process and analysis of membrane fouling |
| 学位专业 | 环境工程 |
| 中文摘要 | 近年来，超滤膜技术已被广泛应用于水处理中，然而膜污染始终制约着膜技术的发展和应用，混凝与超滤联用技术在减轻膜污染方面发挥着重要的作用。本文以在线混凝-浸入式中空纤维超滤膜工艺为研究对象，探讨了絮体调控对膜通量和膜污染的影响，主要考察因素有原水中有机物特性、混凝条件等。此外，本研究还对常用化学清洗药剂清洗污染膜的效果进行了对比和分析。主要得出以下结论： （1）通过模拟大分子牛血清蛋白、中等分子腐殖酸和小分子香草酸的有机体系，考察了微絮凝与常规混凝两种预处理方式对水样处理效果、絮体结构特性及超滤膜通量变化的影响。结果表明常规混凝出水水质优于微絮凝，且在香草酸体系中较明显；常规混凝所形成的絮体更大、更致密；两种混凝形式对膜通量的影响与有机物种类、分子量有关：腐殖酸体系中常规混凝会导致更加严重的膜通量下降和膜污染，而牛血清蛋白体系和香草酸体系中，这一结果则相反；絮体分形维数和絮体尺寸均会对膜通量产生影响，絮体分形维数较大时，膜通量主要受分形维数影响，而絮体分形维数较小，膜通量主要取决于絮体尺寸。 （2）以腐殖酸为有机物主体，配制模拟水样，考察不同剪切破碎强度（350rpm、250 rpm、150 rpm）对絮体结构特性及膜通量的影响。结果表明在高剪切破碎强度下，破碎再增长后形成的絮体尺寸较小且分布均匀，结构相对松散；低剪切破碎强度下，破碎再增长后形成的絮体尺寸较大且分布不均匀，结构相对紧密。超滤膜通量的结果表明，在试验所选用的三个剪切破碎强度下，遵循着破碎强度越大膜通量越大的规律。 （3）配制同时含有腐殖酸、牛血清蛋白和高岭土的模拟水样，考察有机物种类对膜污染的影响机制。发现控制混凝剂投加量是缓解膜污染、改善出水水质的有效手段。通过对超滤出水水质特性分析，发现出水中剩余的有机物主要是腐殖酸，对污染膜表面进行表征后发现膜表面污染物主要为蛋白类有机物。 （4）通过对水厂实际超滤膜污染分析，发现造成膜污染的有机物有蛋白类、多糖类和腐殖酸类，尤其以蛋白类和多糖类为主，造成膜污染的金属元素主要为 Ca、Si、Fe、Mg。通过研究化学清洗剂对实际水厂运行膜的清洗作用，发现相对于 HCl和 NaOH，柠檬酸的清洗效果最好，且在一定范围内，清洗剂的相应酸性或碱性越强，清洗效果越好。 |
| 英文摘要 | Ultrafiltration (UF) membrane processes are widely used in water treatment,however, membrane fouling is the main problem encountered in the application of membrane technology. The coagulation-UF membrane processes play an important role in reducing membrane fouling. A in-line coagulation submerged hollow fiber UF membrane was adopted in the whole study, the effect of floc regulation on membrane flux and membrane fouling were investigated, affecting factors including natural organic matter (NOM) and coagulation condition. Besides, the performance of membrane cleaning by several chemical cleaning reagents were studied. The results were outlined as follows: (1) Macromolecular bovine serum albumin (BSA), middle molecular humic acid (HA) and micromolecule vanillic acid (VA) were used as organic matter model, the treatment performance, floc structure and membrane flux were studied and compared in microflocculation-UF and conventional coagulation-UF. Results show that conventional coagulation achieved a better effluent quality, especially in VA model; Compared to microflocculation, the flocs formed in conventional coagulation were larger and more compact. The effect of coagulation form on membrane flux were related with organics closely: in HA model, the serious decline of membrane flux happened in conventional coagulation-UF, while the results were reversed in BSA and VA model; Both the fractal dimension (Df) and floc size could affect membrane flux: when the Df value were relatively high, membrane flux may be affected by Df primarily, while the Df value were quite low, membrane flux may be depended on floc size. (2) A model water contain HA and kaolin were used to analysize the effect of share breakage rate (150 rpm, 250 rpm, 350rpm) on floc structure and membrane flux. Under the high share breakage rate, the flocs formed after regrowth were small,loose but evenly distributed. While under the low share breakage rate, the flocs were large, compact but uneven distributed. In addition, the results of membrane flux show that higher share breakage rate could achieve the higher flux. (3) HA, BSA and kaolin were dissolved in deionized (DI) water to prepare the water sample, and the effect of NOM species on membrane were investigated. The dosage of coagulant played an important role in reducing membrane fouling and improving effluent quality. The residual NOM in the effluent after coagulation-UF were HA mostly, the main organic foulant on the membrane were proteins. (4) The fouled UF membrane in the drinking water treatment plant were analyzed in our research. Proteins, polysaccharides and humic acid were the main organic foulant on the membrane, especially proteins and polysaccharides, the main metallic element on the membrane were Ca, Si, Fe, Mg. The performance of chemical cleaning reagents were studied, results show that citric acid could achieve the best performance compared to HCl and NaOH, moreover, acid solution with lower pH and alkaline solution with higher pH could achieve the better cleaning effect. |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/34322]  |
| 专题 | 生态环境研究中心_环境水质学国家重点实验室 |
| 推荐引用方式 GB/T 7714 | 段淑璇. 混凝-超滤工艺中的絮体调控及膜污染分析[D]. 北京. 中国科学院研究生院. 2015. |
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