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.

Circles/uneven strata of different blues from light blue/yellow on the outside to dark blue/black at the centre

Topic

Sludge separation − centrifugation

The theory of centrifugation relates to sedimentation theory as it acts to enhance gravity through the centrifugal force

Cake being discharged from a sludge dewatering belt filter press

Topic

Sludge separation − filtration

Filtration theory defines the way in which water flows through the bed, which is formed of the sludge solids (cake)

Topic Home

Sludge dewatering

An overview of sludge dewatering − an introduction to sludge dewatering theory and technologies

Topic

Introduction to sludge dewatering

Dewatering processes provide a concentrated, consolidated product along with a diluted stream which is predominantly water

Topic

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

Topic

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

Sludge filter press, comprising a series of vertical filter plates fitted with a porous cloth though which water travels when it is squeezed out from the sludge under a high applied pressure.

Topic

Filter presses for sludge dewatering

The filter press forces water from the sludge by applying high pressures to sludge layers held between rectangular plates

Rotary press dewatering technology, consisting of two rotating disc-shaped screens which form a narrow channel through which the sludge travels. Water drains through the screens as the sludge as it travels around the channel in a circular motion.

Topic

Rotary presses for sludge dewatering

This technology removes water by passing the sludge through a narrow, rotating parallel-flow channel with porous walls

Whispy swirls of blue on a black background

Topic

Centrifugal sludge dewatering

Centrifugation is used for thickening and dewatering sewage sludge − dewatered sludge has a higher dry solids concentration

Topic

Sludge drying beds and lagoons

Drying beds dewater sludge by allowing the liquid to drain and to evaporate. Lagoons provide dewatering through evaporation

Caterpillar electrode detail of the ELODE electroosmotic dewatering device from Bluewin (Korea)

Topic

Other sludge dewatering processes

Electro-dewatering technology provides enhanced removal by non-mechanical means through the application of an electric field

Dewatering related videos

Solid bowl decanting centrifuge, Alfa Laval Source: Alfa Laval / YouTube

Solid bowl decanting centrifuge, Alfa Laval

Alfa Laval's decanter centrifuge for sludge thickening and dewatering in operation − for use in 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