Abstract
The paper describes a thermogravimetric measurement of the free water content to predict the dewaterability of sewage sludges. Dewaterability can be described by the total solids concentration of the sludge cake and the polymer demand for conditioning. The total solids concentration depends on how water is distributed in the sludge cake. Four different types of water can be distinguished mainly by their distribution in the cake and by the intensity of their physical bonding to the solids. These types are free water, which is not bound to the particles; interstitial water, which is bound by capillary forces between the sludge floes; surface water, which is bound by adhesive forces; and intracellular water. Only the free water component can be removed during mechanical dewatering. By measuring this free water content in the sludge, it is possible to make an exact prediction of full-scale dewatering results. Polymer conditioning does not influence free water content, but it increases the velocity of the sludge water release. The percentage of excess sludge in the total sludge mass is a factor that affects the dewaterability of sewage sludge. No definite relationship could be found between volatile solids content and dewaterability. The thermogravimetric method thus shows potential in determining the full-scale dewatering result of sewage sludges.
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Kopp, J., Dichtl, N. (2000). The Influence of Free Water Content on Sewage Sludge Dewatering. In: Hahn, H.H., Hoffmann, E., Ødegaard, H. (eds) Chemical Water and Wastewater Treatment VI. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-59791-6_32
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DOI: https://doi.org/10.1007/978-3-642-59791-6_32
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