Centrifugal Pumps: What They Are & How They Improve Your System

Wastewater treatment requires continual movement to oxygenate the wastewater and allow microorganisms to do their part. For this to happen, fluid movement is key, and centrifugal pumps play an important role.

Centrifugal force is defined as “force that is felt by an object moving in a curved path that acts outwardly away from the center of rotation.” With a centrifugal pump, that rotational force plays a key role in moving fluid materials from the impellers through the discharge chute. As it uses kinetic energy (pressure) to move liquids, it’s an efficient, cost-effective solution. 

These pumps are used in many industries including HVAC, refineries, water treatment, and wastewater treatment plants. They’re also found in chemical processing plants and hydroelectric plants. It’s in a wastewater treatment plant that these pumps can make a real difference.

The Structure of a Centrifugal Pump

A centrifugal pump uses a rotary motion to move fluids from an upstream pipe to the downstream pipe. It does this by using the force of the rotation to create pressure that draws the liquids by creating suction, around the impeller, and pressure draws it up and out of the other side. 

There are four types of centrifugal pumps, too. They are:

  • Axial-Flow – Impeller rotates parallel to the pump axis and is ideal for high flow rates.
  • Multi-Stage – Multiple impellers work other and are best for high water pressure.
  • Radial-Flow – Impeller rotates perpendicular to the pump axis and is best for high water pressure.
  • Single-Stage – Pumps only have one impeller and are best for low pressure.

No matter which pump it is, the main components don’t change.

  • The impeller
  • The shaft that attaches the impeller to the electric motor
  • The motor that drives the impeller
  • The casing that holds the impeller in place and provides the watertight path for liquids to follow
  • The upstream and downstream pipe flanges where water enters and exits

How Do Centrifugal Pumps Work?

With a centrifugal pump, the electric motor turns the impeller blades. As they start to turn, it creates suction that draws fluid into the pipe flange and casing. The impeller continues turning, which keeps drawing fluid in and that creates pressure. The pressure of the water pushes it through the casing to the downstream pipe. 

What Are the Benefits of Using Centrifugal Pumps?

Centrifugal pumps have a number of benefits. First is that they are efficient. They use the transfer of kinetic energy to move water, which is more efficient. If the centrifugal pump is equipped with automated speed controls, it can reduce power consumption by as much as half. It comes down to how much speed is reduced by. A 10% reduction can reduce power consumption by 27%, while a 20% reduction is about 50%.

Sometimes your fluids might be thicker than other times. If there’s a heavy storm and your sewer system is experiencing a surge in stormwater runoff, the liquids might be more fluid than when it’s simply hauled septage and sewer water. Centrifugal pumps are versatile and can manage changes in fluid viscosities.

Maintenance is easy as a centrifugal pump is only made up of a few components. It is important to keep the components lubricated to prevent overheating. The screens on the suction head must be kept clean to ensure the flow rates don’t decrease unexpectedly. 

These pumps are designed to last and have maintenance needs minimized. Features like corrosion-resistant stainless-steel designs and sealed bearings help, too.

Finally, there are different types of centrifugal pumps. This makes it easy to choose the right fit for your plant’s needs and budget.

Are There Any Disadvantages?

Disadvantages are minimal, but there are a couple of considerations. First is that they are prone to clogging. If you use them in a wastewater or water treatment plant, make sure you have screens and trash rakes to minimize any damage or flooding caused by a clog or jam.

Second, they benefit from a steady flow of liquids. If you have times when the incoming wastewater is lower, it can become a problem. Systems that are automated to stop pumps or slow their speed during slower periods are important. If flow is decreased and ignored, it could cause problems with cavitation. That occurs when vapor pressure drops and creates air bubbles that can damage the impeller.

Where and How to Use Centrifugal Pumps for Cleaner Water

How can a centrifugal pump help with a wastewater treatment plant’s process? If you think about the basics of wastewater treatment, there are lots of steps where pumps move the wastewater around. 

  • Screening: As wastewater enters the treatment plant and is screened to remove large items and trash, centrifugal pumps help move the water around.
  • Grit Removal: Once sand, gravel, and grit are removed, these pumps move wastewater to the next stage of treatment.
  • Sludge Movement: Thicker sludge has to be compressed to remove water for additional processing, and these pumps help with the movement.
  • Chemicals: If your plant uses chemical disinfectants, these pumps can help mix them into the wastewater.

They’re great for moving fluids efficiently from one area to the next. If you accept hauled waste from pumped septic systems, you’ll need a way to transfer the septage to the screens. Water needs to go from the screens into grit removers and aeration tanks.

In some of the processes that take place in your wastewater treatment plant, you might have some of the sludge dewatered, and the water that’s pressed from the sludge needs to be moved back into tanks for treatment. Pumps are essential for all of these steps.

Things to Consider

While centrifugal pumps have plenty of benefits, they’re not always the best choice. They don’t require a lot of space, which is a benefit, but they do need space to work properly. Your plant’s current design must accommodate the pumps you select.

This is why working with professionals in wastewater and water treatment equipment is important. You might also want to consider a screw pump to see if that’s the best fit. All of this is best done by talking to an expert who has the answers you need.

Share your treatment plant’s goals with Lakeside Equipment. Our expert engineers and sales team help you determine the best solution to your facility’s goals at a price that meets your budget.