Archive: Apr 2021

What is Sludge Dewatering?

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What Is Sludge vs. Sludge Cake?

Sludge dewatering is a process in which a sludge slurry (sludge) is made more solid by removing water from its contents to form a sludge cake. A wide variety of municipal and industrial processes will create sludge cake after it is dewatered using various presses to form higher solids content versus a watery sludge slurry. While dewatering does not in itself treat the sludge, separating the components ultimately makes it easier and more cost-effective to treat the waste products, as the liquid and solid components will often require separate treatments due to separate contaminants. In this blog, we will discuss the advantages of further sludge dewatering, as well as the technologies behind this important process.

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Why Is Sludge Dewatering Necessary?

Sludge dewatering is a reliable and efficient method of concentrating waste into high solid filter cakes, thus making them significantly easier to dispose of. It also prevents mudslides at the landfills, which is hazardous to the landfill operators, as well as preventing the contamination of groundwater due to leachate. This process can also serve an important role in a company’s sustainability initiatives. Simplifying the sludge disposal process is important for both public and private sectors, as regulatory agencies require companies to dispose of this substance in an approved way that is both environmentally safe and in line with company requirements. Regulations are starting to prevent the disposal of organic waste in landfills.


The Benefits of Sludge Dewatering

Waste Volume Reduction

By removing the moisture from the slurry, sludge dewatering reduces both the weight and volume of the final waste product. This significantly lowers the ultimate cost of disposal. It also further reduces the leachate production in a landfill and lowers the dangers of a landslide caused by high moisture sludge cake. Recently this has caused a sharp increase in tipping cost by the landfill operators.

Reduced Transportation Costs

Dewatered high solid cakes are lightweight and compact. As such, this process helps manage sludge accumulation and reduces the cost of transportation and storage.

Lower Risk of Spilling/Leaking

In addition to being more lightweight, dry high solid cakes are much less likely to spill or leak onto the road during transportation. This is especially beneficial when transporting waste products through residential areas.

Wastewater Recycling

Sludge dewatering makes wastewater recycling much easier. Once the wastewater has gone through treatment, local industries and communities may be able to reuse it. This cuts down on the carbon footprint by reducing the number of trucks on the road.

Environmentally Friendly

As it reduces the volume of waste to a more compact size, sludge dewatering is an eco-friendly process of waste disposal. The dry, high-solid cakes are also environmentally friendly due to the fact that the sludge cake may be reusable. You cannot incinerate a low solid cake from mechanical presses unless additional fuel is added. However, a much drier sludge cake can be incinerated or used as a fuel source.

An infographic explaining the benefits of sludge dewatering

Types of Technologies for Sludge Dewatering

To separate the liquid and solid components of sludge, there are three distinct types of dewatering techniques.


Using a high rotational speed, a centrifuge is able to separate components of varying densities. Components of lower densities will rise to the top of the mixture, while high-density components will fall to the bottom. This uses high energy, has a long startup process, and is an expensive major overhaul of the core working component needed.

Belt Filter Press

Although it cannot produce a high-quality filter cake, a belt filter press is excellent for high volume waste streams that require a large production of filter cake at lower qualities. More specifically, this process provides a continual action that is ideal when the high moisture content in the filter cake is acceptable. Municipal wastewater treatment plants will often utilize belt filter presses.

Screw Press

Using a slow speed, low energy process with less maintenance to dewater sludge, the screw press is gaining popularity. It is more compact but has a lower capacity than belt filter press due to the drain filter surface area of the filter screen.

Sludge Dewatering With ELODE

Sludge dewatering is an efficient and environmentally friendly process that ultimately facilitates the treatment of municipal and industrial organic sludges. Our ELODE non-thermal sludge dryer is a second-stage dewatering machine that will further reduce the moisture content of filter cakes while saving significant amounts of energy.

Mechanical presses are limited in the amount of water they can remove from sludge no matter how slow or hard you press them. If a heated thermal dryer is used to dry the sludge cake, valuable organic properties of the sludge cake will be lost to the hot gas and you will only have useless ash left. To learn more about our sludge dewatering capabilities, contact us today.

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