The Influence of Free Water Content on Sewage Sludge Dewatering

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.

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

Water Science & Technology ◽

10.2166/wst.2001.0613 ◽

2001 ◽

Vol 44 (10) ◽

pp. 177-183 ◽

Cited By ~ 39

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.

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

Water Science & Technology ◽

10.2166/wst.2000.0191 ◽

2000 ◽

Vol 42 (9) ◽

pp. 141-149 ◽

Cited By ~ 40

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.

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Free Water Content and Sludge Retention Time: Impact on Oxygen Transfer in Activated Sludge

Environmental Science & Technology ◽

10.1021/es901559f ◽

2009 ◽

Vol 43 (22) ◽

pp. 8561-8565 ◽

Cited By ~ 22

Author(s):

Jochen Henkel ◽

Peter Cornel ◽

Martin Wagner

Keyword(s):

Activated Sludge ◽

Water Content ◽

Retention Time ◽

Oxygen Transfer ◽

Free Water ◽

Sludge Retention Time ◽

Free Water Content

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Fermentation Problem in Spanish North-Coast Honey

Journal of Food Protection ◽

10.4315/0362-028x-58.5.515 ◽

1995 ◽

Vol 58 (5) ◽

pp. 515-518 ◽

Cited By ~ 17

Author(s):

SUSANA SANZ ◽

GLORIA GRADILLAS ◽

FUENCISLA JIMENO ◽

CONSUELO PEREZ ◽

TERESA JUAN

Keyword(s):

Water Content ◽

Water Activity ◽

Microbiological Quality ◽

Free Water ◽

High Water ◽

North Coast ◽

High Water Content ◽

Free Water Content ◽

Cantabrian Coast ◽

Mold And Yeast

Twenty-one samples from the Cantabrian coast were analyzed to establish their microbiological quality and fermentation tendency. In a food with a very low free-water content like honey, microbiological growth is only possible when there is an increase in water activity. Since most of the samples studied were not extensively granulated, the risk of fermentation is mostly due to high water content. Among our samples, only two had a water content below 17.1% (no risk of fermentation), whereas the high water activity of the rest of the samples indicates the possibility of microbial growth. In fact, four of the samples analyzed showed a moisture content over the Spanish maximum legal limit, which means a high risk of fermentation. The absence of Enterobacteriaceae, coliforms, and Escherichia coli in our samples indicates an appropriate cleanliness during extractions and handling of honey. No Salmonella or Shigella were found. The relationship between water activity and mold and yeast counts found for the honeys analyzed allowed us to divide our samples in two groups: honeys with a high or a low risk of fermentation. Changes observed during storage of the samples confirmed this classification.

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Short-Term Snow Melt and Ablation Derived from Heat- and Mass-Balance Measurements

Journal of Glaciology ◽

10.1017/s0022143000032093 ◽

1973 ◽

Vol 12 (65) ◽

pp. 275-289 ◽

Cited By ~ 27

Author(s):

Paul M. B. Föhn

Keyword(s):

Mass Balance ◽

Water Content ◽

Free Water ◽

Liquid Water Content ◽

Snow Melt ◽

Snow Pack ◽

Density Profiles ◽

Run Off ◽

Free Water Content ◽

Meteorological Observations

AbstractThe daily snow melt calculated from meteorological observations is compared with detailed mass-balance measurements taking into account internal changes in density and free water content in the surface layers of a glacier snow-pack. The energy balance is calculated from measurements obtained by a meteorological station at the experimental site. In addition to the standard ablation measurements the run-off from the melting snow-pack was obtained for a few days. The snow-density profiles were measured with a portable gamma-transmission probe and the liquid-water content of snow was determined by a calorimetric method.Agreement between the melt calculated by the heat-balance method and the mass changes observed in the mass-balance measurements is fair for daily periods. It appears that about 20% of the daily snow melt takes place internally as a result of penetration of solar radiation.

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