Topic
Sludge separation − centrifugation
The theory of centrifugation relates to sedimentation theory as it acts to enhance gravity through the centrifugal force
Dewatering
Dewatering processes mechanically remove a significant proportion of the sludge water content to produce a concentrated sludge product, with a dry solids concentration generally between 15 and 45%. At this concentration the product, referred to as a cake, is not free-flowing and instead forms lumps which can only be transported by a conveyor belt, mechanical earth-moving equipment, or spade.
Topic
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 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
Dewatering related videos
Belt filter press Alfa Laval
Animation to demonstrate the operating process of the Alfa Laval AS-H G3 belt press for sludge dewatering. This belt press can handle high volumes, and is used in both municipal and industrial wastewater treatment.
Dewatering 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 Dewatering topics…
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Belt filter presses
A belt filter press (BFP) dewaters sludge by pressing it between two revolving permeable belts to squeeze out the water
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Centrifuges
Centrifugal dewatering consolidates sludge by encouraging particles to migrate to the walls of a rapidly rotating cyclinder
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Drying beds
Drying beds dewater sludge by allowing the liquid to both drain from the sludge under gravity and evaporate from its surface
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Filter presses
A filter press dewaters sludge by pressing it between a series of porous plates at high pressure to squeeze out the water
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Lagoons
A lagoon is a large shallow reservoir filled with sludge, which settles and stabilises over an extended time period
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Rotary press
A rotary press dewaters sludge by passing it along a channel formed between two slowly-rotating circular permeable screens
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Screw presses
A screw press dewaters sludge by passing it along the inside of an inclined permeable cylinder using an Archimedean screw
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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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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
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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
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