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Sludge thickening
An overview of sludge thickening − an introduction to theory and related technologies
Flotation thickeners
Dissolved air flotation (DAF) provides thickening of sludges by encouraging the solids to float to the surface, rather than allowing them to sink to the tank base as with gravity thickening, where they can be removed by a skimmer. DAF is applied when the sludge solids are neutrally buoyant (i.e. neither sink nor float) and so cannot be readily removed by conventional settling.
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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 − dissolved air flotation thickening
Dissolved air flotation thickens the sludge by encouraging solids to float to the surface by attaching to rising air bubbles
Flotation thickeners related videos
Huber DAF process (HDF)
A video to demonstrate the principles of the Huber dissolved air flotation plant.
Flotation thickeners 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
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Centrifuges
Centrifugal thickening increases sludge concentration by encouraging particles to migrate to the walls of a rapidly rotating
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Gravity belt thickeners
Gravity belt thickening thickens sludge by allowing the water to drain from the sludge under gravity through a permeable belt
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Gravity thickeners
Gravity thickening increases the solids concentration by allowing the particles to settle to the base of a vessel
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Membrane thickeners
Membrane thickeners separate suspended solids from liquid by extracting the water through a selective permeable material
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Rotary drum thickeners
Rotary drum thickening increases sludge solids concentration by agitating the solids in a cylindrical drum with porous walls
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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