The type of equipment that it has is what constitutes a successful and fully functioning wastewater treatment plant, be it the capacity, efficiency, technology, or even the speed at which it works. However, in the case of wastewater biological treatment, the selection of the appropriate pump for your water treatment plant is what determines the amount of water that can be treated, the duration of time that it will take, and its effectiveness in modifying its pH levels. Centrifugal pumps v/s positive displacement pumps are the most popular options of pumps to use in this, and each has its own advantages and disadvantages, so it is up to you to decide which one fits your plant better after considering all the aspects required.

So now we will explore all that you should know before making your decision on the correct pump to use in your wastewater treatment plant, the explanation, the factors that differentiate them, the applications of both, and finally, the reasons that lead you to the correct pump to use in your wastewater treatment plant.

The Two Most Common Water Pumps that are used in Wastewater Biological Treatment Plants

Talking of biological treatment, the type of pumps you use directly depends on the volume and pressure that they treat the wastewater, hence the importance of knowing the two types. The two primary categories of pumps utilized in biological treatment are centrifugal pumps vs. positive displacement pumps, and the following are the reasons why they are the most popular pumps to use in treating wastewater:

1. Centrifugal Pumps

Centrifugal pumps are most effective in high flow rates or when the liquids to be treated are of low viscosity, like sewage, with the use of a spinning impeller to generate kinetic energy in the fluid. The other feature is that these pumps are capable of transporting large amounts of wastewater using a few but high-efficiency moving components, which are large enough to avoid being damaged or clogged by solids and floating debris, making it a prominent name under wastewater treatment trends.

2. Positive Displacement Pumps

Positive Displacement Pumps are used where the wheel is concerned in passing high viscosity liquids, but in a fixed volume to prevent overloading or failure. This is so because the passing spaces and components of PD pumps, such as rotors, stators, and gear teeth, are normally tight and designed to regulate the amount of fluid that enters the pump. But in the case of large or rough solids, the positive displacement pumps fail miserably, since it is simple to be damaged or affected by the wear and tear of the solids or debris in the wastewater.

The Decision of Choosing Centrifugal Pumps Vs. Positive Displacement Pumps

The decision between centrifugal pumps v/s positive displacement pumps is not determined by their objective properties, but rather by the application you make of them, in the volume of liquid, viscosity, and quantity of solids in the liquid, in the following way:

1. Fluid Viscosity

The consistency and viscosity of the fluid in wastewater biological treatment differ significantly, and, therefore, centrifugal pumps are the most suitable in high-viscosity fluids like sludges or pastes, whereas positive displacement pumps are the most appropriate in low-viscosity liquids.

2. Flow Rate

When you want to pump large quantities of wastewater, and that too, quickly and efficiently, then centrifugal pumps are the way to go because they can perform this task with ease. But when you are interested in pumping controlled and metered volumes of water at a constant rate, positive displacement pumps will do it well.

3. Pressure Requirements

Although both pumps are effective in the biological treatment of wastewater, the selection of the pump is solely based on the kind of pressure that you require to push the wastewater, since the positive displacement pumps generate more pressure, whereas centrifugal pumps are effective within a given range of pressure.

4. Flow Consistency

You have a choice of positive displacement and centrifugal pumps, depending on the storage capacity of all your equipment, because the former provides a constant flow, regardless of the change in pressure within the system, whereas the flow rate provided by the latter changes with the change in pressure within the system.

5. Quantity and Dimensions of Current Solids

In the case of wastewater with a large proportion of abrasive solids, a centrifugal pump would be preferable since it is not damaged or jammed by them, whereas a positive displacement pump is your solution, considering the new developments and innovations in water treatment technology. However, if your goal is to remove the solid parts beforehand, the use of a Smith & Loveless pista grit is greatly beneficial, and is something your pumps and equipment will thank you for.

6. Shear Sensitivity

To maintain the biological colonies and life in the wastewater biological treatment, you should use a positive displacement pump rather than a centrifugal pump that runs at high speed impellers, which are destructive to the colonies.

7. Initial Cost and Maintenance

Positive displacement pumps are not the best option where centrifugal pumps can work, and are easier to install and maintain, and the cost of installation is low.

Selection of Centrifugal and Positive Displacement Pumps

The kind of pumps you desire to use in the wastewater biological treatment in your plant must be solely based on the volume, speed, and pressure of the water to be treated, and also on the quantity and nature of solids in the wastewater to be treated. Finally, the choice of centrifugal v/s positive displacement pumps to use in your water treatment plant is entirely subjective and is determined by the waste to be treated.