Influence of the free water content on the dewaterability of sewage sludges

2001 ◽  
Vol 44 (10) ◽  
pp. 177-183 ◽  
Author(s):  
J. Kopp ◽  
N. Dichtl
Keyword(s):  
Binding Energy ◽  
Sewage Sludge ◽  
Water Content ◽  
Water Distribution ◽  
Bound Water ◽  
Free Water ◽  
Binding Energies ◽  
Intracellular Water ◽  
Water Binding ◽  
Free Water Content

Dewaterabilty of sewage depends on the physical water distribution. The various types of water in sewage sludge are mainly distinguished by type and intensity of their physical bonding to the solids. In a sewage sludge suspension different types of water can be distinguished. These are free water, which is not bound to the particles, interstitial water, which is bound by capillary forces between the sludge flocs, surface water, which is bound by adhesive forces and intracellular water. Only free water can be separated during mechanical dewatering. It can be shown, that thermo-gravimteric measurement of the free water content leads to an exact prediction of full-scale dewatering results. Maximum dewatering results are reached by separating all free water during centrifugation. Furthermore on the basis of the drying curve an estimation of water binding energies can be achieved. The binding energy for free water is less than 0,28 kJ/kg water. The binding energy for bound water (sum of surface and intracellular water) is higher than 5 kJ/kg water.

Prediction of full-scale dewatering results of sewage sludges by the physical water distribution

2001 ◽  
Vol 43 (11) ◽  
pp. 135-143 ◽  
Author(s):  
J. Kopp ◽  
N. Dichtl
Keyword(s):  
Sewage Sludge ◽  
Water Content ◽  
Water Distribution ◽  
Free Water ◽  
Full Scale ◽  
Water Release ◽  
Total Solids ◽  
Solids Concentration ◽  
Free Water Content ◽  
Sludge Cake

The dewaterabilty of sewage sludge can be described by the total solids concentration of the sludge cake and the polymer-demand for conditioning. The total solids concentration of the sludge cake depends on the physical water distribution. The various types of water in sewage sludge are mainly distinguished by the type and the intensity of their physical bonding to the solids. In a sewage sludge suspension four different types of water can be distinguished. These are the free water, which is not bound to the particles, the interstitial water, which is bound by capillary forces between the sludge flocs, the surface water, which is bound by adhesive forces and intracellular water. Only the share of free water can be separated during mechanical dewatering. It can be shown, that by thermo-gravimeteric measurement of the free water content, an exact prediction of full-scale dewatering results is possible. By separation of all free water during centrifugation the maximum dewatering result is reached. Polymer conditioning increases the velocity of the sludge water release, but the free water content is not influenced by this process. Furthermore it is not possible, to replace the measuring of the water distribution by other individual parameters such as ignition loss.

scholarly journals Measurement and Modelling of Moisture Distribution and Water Binding Energy of Dredged Sludge

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3395
Author(s):  
Feiyan Mao ◽  
Yingjie Zhao ◽  
Yiping Zhang ◽  
Zhou Chen ◽  
Lu Yin
Keyword(s):  
Binding Energy ◽  
Water Distribution ◽  
Bound Water ◽  
Free Water ◽  
Moisture Distribution ◽  
Water Binding ◽  
Dredged Sludge ◽  
Urban Watercourse ◽  
Experimental Values ◽  
Stage 1

The dewatering of dredged sludge is a critical step in the minimization and reutilization of this solid waste. However, there is a lack of available literature on the fundamental drying characteristics of dredged sludge. In this work, two kinds of typical sludge dredged from an urban watercourse were tested by low-field NMR to investigate the water distribution in sludge and it was found that water contained in sludge can be classified into three categories: free water, capillary water and bound water. In addition, a novel model was proposed based on the Lennard-Jones equation and Kelvin law to quantitatively evaluate the binding energy during drying. Further, the model results were experimentally verified by thermogravimetry differential thermal analysis (TG-DTA). Results show that the trends of the model are consistent with the experimental values and the gradient of energy consumption during dehydration can be divided into three main stages. In stage 1, the total energy required for dewatering equals the latent heat of free water. In stage 2, binding energy reaches dozens to hundreds of kJ/kg accounting for capillary action. In stage 3, binding energy increases steeply reaching almost thousands of kJ/kg due to intermolecular interactions. All the discovered aspects could improve the management and disposal of dredged sludge from an energy cost perspective.

Prediction of full-scale dewatering results by determining the water distribution of sewage sludges

2000 ◽  
Vol 42 (9) ◽  
pp. 141-149 ◽  
Author(s):  
J. Kopp ◽  
N. Dichtl
Keyword(s):  
Sewage Sludge ◽  
Water Content ◽  
Water Distribution ◽  
Free Water ◽  
Full Scale ◽  
Water Release ◽  
Total Solids ◽  
Solids Concentration ◽  
Free Water Content ◽  
Sludge Cake

Dewaterability of sewage sludge can be described by the total solids concentration of the sludge cake and by the polymer-demand for conditioning. Total solids concentration of the sludge cake depends on the physical water distribution. The various types of water in sewage sludge are mainly distinguished by type and intensity of their physical bonding to the solids. In a sewage sludge suspension four different types of water can be distinguished. These are free water, which is not bound to the particles, interstitial water, which is bound by capillary forces between the sludge flocs, surface water, which is bound by adhesive forces, and intracellular water. Only free water can be separated during mechanical dewatering. It can be shown, that thermo-gravimeteric measurement of the free water content leads to an exact prediction of full-scale dewatering results. Maximum dewatering results are reached by separating all free water during centrifugation. Polymer conditioning increases the velocity of thesludge water release, but the free water content is not influenced by this process. Furthermore it is not possible, to replace the measuring of the water distribution by other individual parameters such as ignition loss.

Minimisation of Water Content in Concrete

2016 ◽  
Vol 691 ◽  
pp. 230-238
Author(s):  
Ivan Juríček ◽  
Ľudovít Fillo
Keyword(s):  
Moisture Content ◽  
Water Content ◽  
Atmospheric Pressure ◽  
Bound Water ◽  
Free Water ◽  
Point Of View ◽  
Free Water Content ◽  
Normal Atmospheric Pressure ◽  
Moisture Characteristic ◽  
Short Time

In the production of structures made of concrete it is sometimes required to make a completed structure contain a minimum amount of free water. From the point of view of effectiveness of the production process it is also preferred to dry the concrete in a short time and at a reasonable cost. Required for free water content can be limited by various factors (e.g. construction covered by flooring sensitive to humidity, frost resistance, etc.).The moisture characteristic of concrete is verified in civil engineering provided that the concrete is located in the environment with normal atmospheric pressure. By solving the project “Development of methods for structure of thermal vacuum insulated containers” we have met a requirement to produce concrete with extremely low moisture content. It was found out that information about moisture content of concrete obtained by currently used method was unsatisfactory for concrete in the environment with extremely low atmospheric pressure. The research has indicated that usual methods of concrete drying are not sufficient for concrete subjected to vacuum because they don´t eliminate physically bound water.

Determine the Moisture Distribution in Sewage Sludge by Drying Differential

2014 ◽  
Vol 665 ◽  
pp. 404-407 ◽  
Author(s):  
Wan Yu ◽  
Pei Sheng Li
Keyword(s):  
Sewage Sludge ◽  
Interstitial Water ◽  
Bound Water ◽  
Free Water ◽  
High Accuracy ◽  
Moisture Distribution ◽  
Municipal Sewage ◽  
Municipal Sewage Sludge ◽  
Hot Air ◽  
Critical Water Content

Moisture distribution in sewage sludge was considered as the essential of thermal drying. Some methods were given in literatures to test the moisture distribution, but there was no standard method to determine the critical water content between different kinds of water. The municipal sewage sludge was dried by hot air in this work. Based on the drying curve, the derivative of drying rate with respect to dry basis moisture content was brought out to analyze the moisture distribution in sewage sludge. Results show that this method can easily determine the free water, interstitial water, surface water and bound water with a high accuracy. The present work can provide new insight to determine the moisture distribution in sewage sludge, which was still lacking in the literatures.

scholarly journals Testing the effects of basic numerical implementations of water migration on models of subduction dynamics

Solid Earth ◽  
2014 ◽  
Vol 5 (1) ◽  
pp. 537-555 ◽  
Author(s):  
M. E. T. Quinquis ◽  
S. J. H. Buiter
Keyword(s):  
Upper Mantle ◽  
Water Distribution ◽  
Mantle Wedge ◽  
Bound Water ◽  
Free Water ◽  
Water Velocity ◽  
Water Migration ◽  
Creep Flow ◽  
Dehydration Reactions ◽  
Slab Dehydration

Abstract. Subduction of oceanic lithosphere brings water into the Earth's upper mantle. Previous numerical studies have shown how slab dehydration and mantle hydration can impact the dynamics of a subduction system by allowing a more vigorous mantle flow and promoting localisation of deformation in the lithosphere and mantle. The depths at which dehydration reactions occur in the hydrated portions of the slab are well constrained in these models by thermodynamic calculations. However, computational models use different numerical schemes to simulate the migration of free water. We aim to show the influence of the numerical scheme of free water migration on the dynamics of the upper mantle and more specifically the mantle wedge. We investigate the following three simple migration schemes with a finite-element model: (1) element-wise vertical migration of free water, occurring independent of the flow of the solid phase; (2) an imposed vertical free water velocity; and (3) a Darcy velocity, where the free water velocity is a function of the pressure gradient caused by the difference in density between water and the surrounding rocks. In addition, the flow of the solid material field also moves the free water in the imposed vertical velocity and Darcy schemes. We first test the influence of the water migration scheme using a simple model that simulates the sinking of a cold, hydrated cylinder into a dry, warm mantle. We find that the free water migration scheme has only a limited impact on the water distribution after 1 Myr in these models. We next investigate slab dehydration and mantle hydration with a thermomechanical subduction model that includes brittle behaviour and viscous water-dependent creep flow laws. Our models demonstrate that the bound water distribution is not greatly influenced by the water migration scheme whereas the free water distribution is. We find that a bound water-dependent creep flow law results in a broader area of hydration in the mantle wedge, which feeds back to the dynamics of the system by the associated weakening. This finding underlines the importance of using dynamic time evolution models to investigate the effects of (de)hydration. We also show that hydrated material can be transported down to the base of the upper mantle at 670 km. Although (de)hydration processes influence subduction dynamics, we find that the exact numerical implementation of free water migration is not important in the basic schemes we investigated. A simple implementation of water migration could be sufficient for a first-order impression of the effects of water for studies that focus on large-scale features of subduction dynamics.

Characterization of thin water layers in pulp by tritium exchange. Part 1: Methods development

Holzforschung ◽  
2007 ◽  
Vol 61 (2) ◽  
pp. 115-119 ◽  
Author(s):  
Frances L. Walsh ◽  
Sujit Banerjee
Keyword(s):  
Water Content ◽  
Surface Area ◽  
Tritiated Water ◽  
Bound Water ◽  
Free Water ◽  
Fiber Surface ◽  
Bulk Water ◽  
Methods Development ◽  
A Value ◽  
A New Technique

Abstract A new technique for measuring the monolayer water content of fiber is presented. Tritiated water is added to a pulp/water suspension, whereupon the tritium partitions between the bulk water and the pulp. In the pulp phase the tritium can exchange with free water, bound water, and with hydroxyl and other protons present in the pulp matrix. The free water in the pulp is then removed by displacement with acetone. The tritium remaining in the pulp is mostly associated with tightly bound water, with a small fraction being tied up with the exchangeable hydrogen in pulp. The procedure provides a value of 10% for the tightly bound water content of hardwood or softwood fiber, either bleached or unbleached. If this water is assumed to cover the fiber surface as a monolayer, then an estimate of the wet surface area of the fiber can be obtained. This estimate compares well with independent measurements of surface area.

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