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Revisiting Hydraulic Flocculator Design for Use in Water Treatment Systems with Fluidized Floc Beds

机译:再谈液压絮凝器设计,用于带有流化絮凝床的水处理系统

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摘要

In water treatment, flocculation creates aggregated particles or flocs large enough to be removed by downstream processes of sedimentation and filtration. Fluidized beds of flocs (floc blankets) are sometimes included in upflow sedimentation processes because they can significantly improve sedimentation tank particle removal when plate or tube settlers are used. Overall performance of a sedimentation tank containing a floc blanket is influenced by the characteristics of incoming flocs fromthe flocculator. Floc blankets provide an additional opportunity for aggregation of colloidal particles that enables a reduction in the size of the flocculators, while improving particle removal efficiency. In this study, laminar flow flocculators varying in velocity gradient (G) and residence time (theta) were tested in a laboratory scale water treatment systemwith a floc blanket. Results indicate that increasing G (range of 74-251 s(-1)), while decreasing residence time from 269 to 80 s, and maintaining a constant G theta (similar to 20,000) improved particle removal. These results indicate that velocity gradients greater than existing design recommendations may be used to reduce flocculator residence times (and associated construction costs) when upflow sedimentation with a floc blanket and overlying lamellar plate or tube settlers are employed subsequent to flocculation. Further reduction of the residence time to 24 s with a G of 251 s(-1) resulted in a settled water turbidity of 14 nephelometric turbidity unit (NTU). When varying theta at a constant G of 72 s(-1), an apparentminimum in settled effluent turbidity at 0.15 NTU was observed at the middle residence time tested (theta = 211 s), suggesting that long hydraulic flocculator residence times may be suboptimal.
机译:在水处理中,絮凝会产生聚集的颗粒或絮凝物,其大小足以被下游的沉淀和过滤过程除去。絮凝物(絮凝毯)的流化床有时包含在上流沉降过程中,因为当使用板式或管式沉降器时,它们可以显着提高沉降池中颗粒的去除率。包含絮凝毯的沉淀池的整体性能受絮凝器传入絮凝物的特性影响。絮凝毯为胶体颗粒的聚集提供了额外的机会,从而可以减小絮凝器的尺寸,同时提高颗粒去除效率。在这项研究中,层流絮凝器的速度梯度(G)和停留时间(θ)有所变化,是在实验室规模的带絮凝毯的水处理系统中进行测试的。结果表明,增加G(74-251 s(-1)的范围),同时将停留时间从269减少到80 s,并保持恒定的G theta(类似于20,000)可以改善颗粒去除效果。这些结果表明,在絮凝之后采用絮凝毯和上层薄板或管式沉降器进行上流沉降时,可以使用大于现有设计建议的速度梯度来减少絮凝器的停留时间(和相关的建造成本)。 G值为251 s(-1)进一步将停留时间减少到24 s,使沉淀水浊度为14浊度浊度单位(NTU)。当以72 s(-1)的恒定G改变theta时,在测试的中间停留时间(theta = 211 s)观察到在0.15 NTU的沉降出水浊度有一个最小的值,这表明较长的液压絮凝器停留时间可能不是最佳的。

著录项

  • 来源
    《Environmental Engineering Science》 |2017年第2期|122-129|共8页
  • 作者单位

    Cornell Univ, Sch Civil & Environm Engn, 220 Hollister Hall, Ithaca, NY 14853 USA|AEESP, Butte, MT 59702 USA;

    Cornell Univ, Sch Civil & Environm Engn, 220 Hollister Hall, Ithaca, NY 14853 USA|AEESP, Butte, MT 59702 USA;

    Cornell Univ, Sch Civil & Environm Engn, 220 Hollister Hall, Ithaca, NY 14853 USA|AEESP, Butte, MT 59702 USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    coagulant; flocculation; fluid mechanics; sedimentation;

    机译:混凝剂;絮凝;流体力学;沉降;
  • 入库时间 2022-08-17 13:28:31

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