September 20, 2023

Choosing the Right Pump: The Difference Between Sludge and Slurry

There are many factors that go into effective fluid management during bypass and dewatering operations. One of the first considerations when choosing a pump is what type of effluent will you be pumping. Factors such as fluid weight, pH level, and the presence and size of any solids play a pivotal role in ensuring the effectiveness of operations as well as safeguarding your pump from potential damage. While they may seem similar, there is a difference between sludge and slurry. Selecting the right pump not only protects your investment in equipment and but adds value through increased efficiency.

Here are key factors to consider:

• Fluid weight: a powerful determinant. A pump’s power requirement is estimated by taking the flow capacity times the density of the fluid times the gravitational constant times the vertical distance to be pumped. The weight and density of the fluid determine how powerful of a pump is needed to draw the liquid through. The difference between sludge and slurry is that thick, heavy sludge requires more force to move.
• pH: measuring the chemical impact. Understanding the pH of the fluid is essential. pH levels range from 0 to 14, with 7 being neutral. Less than 7 indicate acidity, whereas a pH greater than 7 indicates a base. The material of the internal components of the pump must be able to handle the chemical impact when pumping acidic fluids to prevent malfunction.
• Sludge: a complex viscous mixture. Sludge is a thick and soft substance, a mixture of liquids and solids such as mud. It is typically the product of municipal or industrial wastewater treatment, such as sewage. Often it includes organic components, like food waste and plant material, and inorganic compounds, such as metals and solvents. Wastewater sludge optimally is close to neutral for pH.
• Slurry: solids in suspension. Slurry is solids suspended in liquid. The solids may be larger than those in sludge and the pH level can range in alkalinity from acidic to basic. Slurry is a by-product in mining, agriculture, and renewable natural gas operations.

The difference between sludge and slurry pumps

Sludge pumps are designed to carry the thick liquid without clogging. They can withstand the high abrasion often caused by particles in the sludge. Sludge demands high powered pumps that are durable.

Slurry pumps can accommodate the large solids that are transferred by the pumped liquid. If the slurry is acidic, the pump must be corrosion resistant.

Centrifugal surface pumps like the Atlas Copco PAS range can be used for a wide range of applications including dewatering, silt and sludge removal from mines and quarries, sewage bypass, emergency water treatment, industrial effluent handling, and construction site drainage. The semi-open impeller handles liquids with solids of up to 3” in suspension. They can handle sludge and slurries.

The difference between sludge and slurry determines the design of submersible pumps like Atlas Copco’s WEDA series. WEDA sludge pumps are commonly used for pumping sewage. Used for temporary bypassing of either gravity sewer lines or pump stations, these pumps are up to the challenge.

WEDA slurry pumps can handle either clean or dirty water, even with small solids with the best performance and efficiency. WEDA’s unique aluminum alloy offers the perfect combination of strength, light weight, and corrosion resistance.

Expert solutions
Backed by Keystone Clearwater Solutions’ decades of experience in providing water transfer solutions for the natural gas industry, FieldForce brings that expertise to the municipal, industrial, and construction markets. Whether you require assistance in choosing equipment for rental or purchase or need a complete turnkey solution, FieldForce can help. We maintain a large workforce and well maintained asset base (including equipment from Atlas Copco, Pioneer, and Dominight) to meet the requirements of complex water or wastewater management projects in the mid-Atlantic region.
Photo ©Atlas Copco