Sludge is a byproduct of a wide range of industrial applications, from power generation to oil refining to drinking water and wastewater treatment. Due to its high liquid content, it is difficult and, consequently, expensive to store and transport for disposal in an unprocessed form. That’s why many industrial facilities invest in dewatering equipment, which is used to separate the sludge’s solid and liquid components to facilitate disposal operations.
There are many sludge dewatering methods, all of which reduce the volume and weight of the sludge to make it easier to handle and transport. Three of the most commonly used involve employing a centrifuge, a plate and frame filter press, or a belt filter press. Each piece of equipment offers distinct advantages that make it suitable for different dewatering applications. Below, we provide an overview of these three sludge dewatering systems to help readers select the right one for their needs.
Centrifuges operate under the principle of buoyancy. They use high rotational speeds—i.e., they spin—to separate components by density. Components with higher densities (e.g., sludge solids) fall to the bottom, while components with lower densities (e.g., sludge liquids) rise to the top.
The primary benefit of centrifugal dewatering operations is processing speed. They quickly produce between 25% and 35% solids by weight. They are generally used in dewatering applications where the main priority is the recovery oil rather than the quality of the solids. However, they do come with their share of faults. Centrifuges are high energy, not easy to operate on/off, and are difficult to maintain.
Plate and Frame Filter Press
Plate and frame filter presses separate liquids from solids using recessed-chamber filter plates. The filter plates combine to form a chamber, which pressurizes the sludge. The liquids are squeezed through the filter cloth that lines the chamber while the solids remain on the surface of the filter cloth. The entire process takes 4 hours for each batch.
The main benefits are that the solids are formed as stackable cakes, which makes them cost-effective to transport and the equipment does not require any special license to operate.
Belt Filter Press
Belt filter presses follow a four-stage dewatering process. The four stages are: 1) pretreatment, 2) gravity dewatering, 3) pre-pressure dewatering in the wedge zone, and 4) press dewatering.
The key benefit of belt filter press dewatering operations is high volume capacity. The continual action of the dewatering process is highly effective for processing high volumes of sludge. However, the quality of the filter cake is lower than that of filter cake produced by other methods (between 11% to 20% solids by weight).
Learn More About Sludge Dewatering From the Experts at ELODE
Sludge dewatering is an important process in many industries. By separating the liquid and solid components of sludge, it improves the cost-effectiveness of disposal operations.
Want to learn more about sludge dewatering and the various methods available? Ask the experts at ELODE! We supply second-stage dewatering systems designed to further improve the dryness and reduce the weight of sludge, which can result in significant sludge transportation, storage, and disposal cost savings. Our dewatering experience can help us answer or address any questions or concerns you may have about centrifuges, plate and frame filter presses, belt filter presses, or other dewatering systems. Additionally, we can assist you in selecting the right solution for your sludge dewatering needs.
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.
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.
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.
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.
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.
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.