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Challenges with Difficult Sludge: Meet the PWTech Volute Duo

Dealing with sludge is a common challenge in various industries, such as wastewater treatment plants, mining, and chemical processing facilities. The dewatering process removes the water from sludge, which is important for proper disposal and resource recovery. However, some types of sludge possess unique characteristics that require unique dewatering approaches and technologies. In this blog, we will explore the problems associated with dewatering difficult sludge and discuss potential solutions.

Belt filter press in operation at a Wisconsin municipality.

High Moisture Content

Difficult sludge often exhibits high moisture content, making dewatering a challenging task. The extra water content increases the sludge's viscosity, reducing the effectiveness of conventional dewatering methods. To tackle this problem, certain dewatering technology that extracts water more efficiently will help create better cake.

Low Solid Concentration

Certain types of sludge have low solid concentrations, which makes dewatering more complex. Low solids concentration results in less efficient separation of water and solids during the dewatering process. Chemical conditioning techniques, such as flocculation and coagulation, can be applied in this situation to enhance solid-liquid separation. By introducing coagulants or polymers, the sludge particles can agglomerate, improving the dewaterability and removing the water from the sludge.

PWTech Dewatering Press pilot unit, testing cake consistency.

High Viscosity

Sludge with high viscosity poses significant challenges during dewatering. Sludge that is thick and sticky in nature hinders the separation of water, leading to longer dewatering times and reduces overall efficiency. Pre-treatment methods like thermal conditioning or the use of chemical additives can help reduce viscosity. If you raise the sludge temperature or introduce specific chemicals, the viscosity decreases and allows for faster and more effective dewatering.

Presence of Toxic Substances

Sludge in certain industries might contain toxic substances, such as heavy metals, harmful chemicals, or pathogens. The presence of these substances complicates the dewatering process and raises concerns about the potential release of pollutants in wastewater. Advanced treatment methods like electrocoagulation, activated carbon adsorption, or biological treatments might be necessary to remove or immobilize these contaminants prior to dewatering.

Biological wastewater treatment.

Maintenance and Operational Challenges

Dewatering difficult sludge often requires specialized equipment and expertise, leading to higher maintenance costs and operational challenges. Regular maintenance and monitoring of the dewatering equipment are essential to ensure optimal performance. Training operators and implementing preventive maintenance programs can help overcome these challenges, reducing downtime and increasing the efficiency of the dewatering process.

Processing sludge from wastewater treatment plants processing raw, primary sludge or sludge with excessive alum, ferric, or lime can cause problems with traditional dewatering equipment. Agricultural and industrial applications that dewater pulp, raw manure, or land remediation applications can also run into mechanical and quality issues.

When dewatering difficult sludge with standard screw press technology, the final cake product needs to be malleable enough to extrude from the end of the screw press (or dewatering drum). Dewatered sludges that contain high concentrations of fibrous, inorganic, or adhesive material can form a compacted cake that is too hard to extrude from the screw press. This plugs the press, which makes it difficult to pass solids or it may require lower cake solids performance to allow for continuous operation.

The PWTech® Volute DUO is designed with a smaller footprint than the standard Volute Dewatering Press. It takes the original Volute dewatering drum concept and adapts it for the dewatering of difficult sludges. It utilizes twin counter-rotating screws inside a single drum to break up and move all material for dewatering. This makes it possible for full mechanical dewatering of more difficult sludges without the performance being compromised.

The DUO uses a separate drive mechanism so that the moving rings don’t contact the screws as they move. That prevents wear points on the press, which can result in many years of maintenance-free operation. Since the mechanism is completely enclosed, it minimizes odor and noise.

Dewatering difficult sludge presents several challenges due to factors like high moisture content, low solid concentration, high viscosity, presence of toxic substances, and maintenance issues.

However, with the advancements in technology and the implementation of specialized techniques, these challenges can be addressed effectively. It is crucial for industries to understand the nature of their sludge and adopt appropriate strategies to optimize the dewatering process, enabling efficient sludge management and disposal. By overcoming these problems, industries can achieve cost-effective and sustainable sludge management solutions.

PWTech Volute DUO presentation and announcement of the DUO pilot unit.


If you are interested in piloting the PWTech Volute DUO on your difficult sludge, please contact PWTech or the ICS Group.

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