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Sludge separation − gravitation/sedimentation
Gravitation (sedimentation or settlement) is the separation of particles from water on the basis of their weight
Thickening, dewatering & drying
Sludge drying refers to processes where moisture is removed from sludge as water vapour. These processes often require pre-treatment ('conditioning'). With sludge thickening or dewatering, moisture is removed as a liquid.
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Sludge separation − centrifugation
The theory of centrifugation relates to sedimentation theory as it acts to enhance gravity through the centrifugal force
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Sludge separation − filtration
Filtration theory defines the way in which water flows through the bed, which is formed of the sludge solids (cake)
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Sludge conditioning
An overview of sludge conditioning − chemical and thermal
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Introduction to sludge conditioning
Thickening and dewatering processes often need pre-treatment (conditioning) to help separate the water from the solids
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Chemical sludge conditioning
The chemical pre-treatment of sludge helps remove water upstream of thickening and dewatering processes
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Thermal sludge conditioning
Thermal processes are used to condition sludges upstream of anaerobic digestion as well as pre-treating sludge for dewatering
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Sludge thickening
An overview of sludge thickening − an introduction to theory and related technologies
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Introduction to sludge thickening
Processes which act to remove water from the sludge to reduce its volume are called thickening and dewatering
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Sludge treatment − gravity thickening
Gravity thickening increases the solids concentration by allowing the particles to settle to the base of a vessel
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Sludge treatment − dissolved air flotation thickening
Dissolved air flotation thickens the sludge by encouraging solids to float to the surface by attaching to rising air bubbles
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Sludge treatment − gravity belt thickening
GBT thickens the sludge by allowing the water to drain from the sludge under gravity through a permeable moving belt
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Sludge treatment − rotary drum thickening
Rotary drum thickening thickens the sludge by agitating the solids in a slowly-rotating vessel with porous walls
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Sludge treatment − centrifugal thickening
Sludge concentration increases as particles are encouraged to migrate to the walls of a rapidly rotating cylindrical vessel
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Other sludge thickening processes
Other processes include membrane thickening − water is extracted through a membrane, increasing the solids concentration
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Sludge dewatering
An overview of sludge dewatering − an introduction to sludge dewatering theory and technologies
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Introduction to sludge dewatering
Dewatering processes provide a concentrated, consolidated product along with a diluted stream which is predominantly water
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Belt filter presses for sludge dewatering
These presses dewater sludges to produce a cake with a dry solids content of 30% or more in the case of primary sludge
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Screw presses for sludge dewatering
A screw press is a dewatering technology based on a slowly-rotating (~5 RPM) Archimedean screw within a cylindrical screen
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Filter presses for sludge dewatering
The filter press forces water from the sludge by applying high pressures to sludge layers held between rectangular plates
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Rotary presses for sludge dewatering
This technology removes water by passing the sludge through a narrow, rotating parallel-flow channel with porous walls
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Centrifugal sludge dewatering
Centrifugation is used for thickening and dewatering sewage sludge − dewatered sludge has a higher dry solids concentration
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Sludge drying beds and lagoons
Drying beds dewater sludge by allowing the liquid to drain and to evaporate. Lagoons provide dewatering through evaporation
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Other sludge dewatering processes
Electro-dewatering technology provides enhanced removal by non-mechanical means through the application of an electric field
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Sludge drying
An overview of sludge drying − an introduction to sludge drying theory and technologies
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Introduction to sludge drying
Processes where moisture is removed from sludge as water vapour are known as 'sludge drying'
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Sludge treatment − properties of drying sludge
When sludge dries, it goes through three different phases as the water evaporates
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Sludge treatment − sludge drying operation
Sludge drying processes operate at solids temperatures of 60-93 °C to encourage water to evaporate and leave a solid residue
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Sludge treatment − sludge dryer configurations
Sludge drying processes are generally configured as convective, conductive, or as solar dryers
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Sludge treatment − conductive sludge dryers
Conductive drying indirectly heats sludge by bringing the sludge particles into contact with an externally-heated surface
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Sludge treatment − convective sludge dryers
Convective sludge dryers are the most commonly used type of dryer for sewage sludge
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Sludge treatment − solar dryers
Solar dryers make use of renewable solar energy to dry sludge and need a larger footprint to allow for increased drying times
Thickening, dewatering & drying related videos
Benenv's Wave Separator for sludge and waste thickening and dewatering
Film to demonstrate the Benenv Wave Separator for sludge and waste thickening and dewatering.
The Wave Separator is a self-cleaning, solid−liquid separation machine, with thickening and dewatering functions. The Wave Separator can be used for various applications and industries, including for food waste, biological sludge and paint waste.
Thickening, dewatering & drying features and blogs
Feature
Co-processing of sewage digestate by hydrothermal carbonisation
Hydrothermal carbonisation (HTC) can be used to co-process anaerobic digestion (AD) digestate and lignocellulosic (or plant-based) feedstocks to improve the the hydrochar product quality. This AD waste co-processing route has been studied at bench scale. Read article
More Thickening, dewatering & drying topics…
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Conditioning
Conditioning is the pretreatment of sludge upstream of thickening and dewatering to promote solid-liquid separation
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Thickening
Thickening processes concentrate the sludge by removing part of the free water, such that the product can still be pumped
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Dewatering
Dewatering processes mechanically remove a significant proportion of the sludge water to produce a 15-45% cake product
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Drying
In sludge drying the sludge moisture is removed as water vapour by heating, generating a pelleted or powdered product
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Conditioning
Conditioning is the pretreatment of sludge upstream of thickening and dewatering to promote solid-liquid separation
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Thickening
Thickening processes concentrate the sludge by removing part of the free water, such that the product can still be pumped
-
Dewatering
Dewatering processes mechanically remove a significant proportion of the sludge water to produce a 15-45% cake product
-
Drying
In sludge drying the sludge moisture is removed as water vapour by heating, generating a pelleted or powdered product
More process and operation topics…
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Sludge stabilisation
Sludge stabilisation − alkaline stabilisation, lime and solids dosing, plus anaerobic and aerobic digestion
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Thermochemical processes
Thermochemical methods are used to either significantly reduce the sludge solids content or pre-treat sludge upstream of AD
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Sludge quality
Sludge is the main waste stream from the treatment of wastewater