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The effect of shear rate on properties of aggregates formed in the water treatment process
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SYSNO ASEP 0378896 Document Type C - Proceedings Paper (int. conf.) R&D Document Type The record was not marked in the RIV Title The effect of shear rate on properties of aggregates formed in the water treatment process Author(s) Bubáková, Petra (UH-J) SAI, ORCID, RID
Pivokonská, Lenka (UH-J) SAI, ORCID, RID
Pivokonský, Martin (UH-J) SAI, ORCID, RIDSource Title Proceedings of the 6th IWA International Conference for Young Water Professionals. - Budapest : IWA, 2012 Pages iwa-9867 Number of pages 8 s. Publication form CD-ROM - CD-ROM Action IWA International Conference for Young Water Professionals /6./ (IWA YWPC 2012) Event date 10.07.2012-13.07.2012 VEvent location Budapest Country HU - Hungary Event type WRD Language eng - English Country HU - Hungary Keywords aggregate size ; fractal dimension ; shear rate ; water treatment Subject RIV BK - Fluid Dynamics R&D Projects IAA200600902 GA AV ČR - Academy of Sciences of the Czech Republic (AV ČR) CEZ AV0Z20600510 - UH-J (2005-2011) Annotation The paper deals with the dependence of aggregate properties on the shear rate (G) at steady state. Natural raw water and ferric sulphate were aggregated in a laboratory Taylor-Couette reactor (TC) and continuous flow mixing tank (MT) with a paddle stirrer. The shear rates in the range of approximately 20-350 s-1 were used and the aggregation time corresponded to 15 min (steady state). The methods of image and fractal analysis were used to determine the aggregate size and structure, respectively. It was found that the aggregate size decreased with increasing shear rate. There was a small difference in sizes of aggregates formed in TC and MT at G < 150 s-1, but at higher shear rates, almost no difference between TC and MT was observed. The D2 fractal dimension increased with increasing shear rate indicating that the aggregates became less porous and more compact. Moreover, the very precise match in D2 values was attained for both mixing devices. The Dpf fractal dimension decreased with increasing shear rate meaning that aggregates were more regular at higher shear rates, but jagged on the surface with irregular shape at lower shear rates. Contrary to D2, aggregates formed in MT were much more irregular or jagged than those formed in TC. Workplace Institute of Hydrodynamics Contact Soňa Hnilicová, hnilicova@ih.cas.cz, Tel.: 233 109 003 Year of Publishing 2013
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