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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
URI标识: http://ir.rcees.ac.cn/handle/311016/34322
Appears in Collections:环境水质学国家重点实验室_学位论文

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Recommended Citation:
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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