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      Thixotropic behaviour of thickened sewage sludge

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          Abstract

          The aim of the work is a description of the rheological behaviour of thickened sewage sludge. The sample of thickened sludge was collected from the wastewater treatment plant, where pressure flotation unit is used for a process of thickening. The value of dry matter of collected sample was 3.52%. Subsequently the sample was diluted and the rheological properties of individual samples were obtained. Several types of rheological tests were used for the determination of the sample. At first the hysteresis loop test was performed. The next test was focused on the time-dependency, i.e. measurement of dependence of dynamic viscosity on the time at constant shear rate. Further dependence dynamic viscosity on the temperature was performed. Then the activation energy was obtained from measured values. Finally, the hysteresis areas were counted and measured values were evaluated with use of Herschel-Bulkley mathematical model.

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          Most cited references22

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          Influence of clays on the rheology of cement pastes

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            Chemical and physical control of the rheology of concentrated metal oxide suspensions

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              The rheological behaviour of anaerobic digested sludge.

              Producing biogas energy from the anaerobic digestion of wastewater sludge is one of the most challenging tasks facing engineers, because they are dealing with vast quantities of fundamentally scientifically poorly understood and unpredictable materials; while digesters need constant flow properties to operate efficiently. An accurate estimate of sludge rheological properties is required for the design and efficient operation of digestion, including mixing and pumping. In this paper, we have determined the rheological behaviour of digested sludge at different concentrations, and highlighted common features. At low shear stress, digested sludge behaves as a linear viscoelastic solid, but shear banding can occur and modify the apparent behaviour. At very high shear stress, the behaviour fits well to the Bingham model. Finally, we show that the rheological behaviour of digested sludge is qualitatively the same at different solids concentrations, and depends only on the yield stress and Bingham viscosity, both parameters being closely linked to the solids concentration. Copyright © 2011 Elsevier Ltd. All rights reserved.
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                Author and article information

                Contributors
                Journal
                J Environ Health Sci Eng
                J Environ Health Sci Eng
                Journal of Environmental Health Science and Engineering
                BioMed Central
                2052-336X
                2014
                23 April 2014
                : 12
                : 72
                Affiliations
                [1 ]Department of Agricultural, Food and Environmental Engineering, Mendel University in Brno, Zemedelska 1, 613 00 Brno, Czech Republic
                Article
                2052-336X-12-72
                10.1186/2052-336X-12-72
                4013819
                5f11e874-3c11-4f3a-862b-24d4f4c71f6e
                Copyright © 2014 Trávníček and Junga; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.

                History
                : 26 April 2013
                : 12 April 2014
                Categories
                Research Article

                rheology,mathematical model,herschel-bulkley,sewage sludge,pressure flotation

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