Wastewater Treatment Plants: Pumps for Efficiency & Conservation - Research Paper

Introduction

Wastewater treatment plants have become increasingly important in residential and industrial complexes due to the need for water conservation and usage efficiency. Wastewater treatment plays a critical role in ensuring that large volumes of wastewater that are discharged daily are converted into a useful state. Industries such as food processing, manufacturing, chemical among others have installed treatment plants to satisfy government regulations. This paper aims to discuss the type of pumps that are used in a sewage water treatment plant. The paper will also look at how the pumps work, their efficiency, their importance, and their performance levels.

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The treatment process is divided into three different phases that include the primary, secondary, and tertiary levels. The type of treatment process used is determined by the kind of contaminants in the wastewater and the level of purity and quality needed in the end product. The type of wastewater pump used in a treatment plant depends on the specific treatment process required (Thakur, 2014). In general, these pumps collect the wastewater from different parts of the industry and assist in moving the sludge from the collection point to the treatment plant. The pumps are also used to move the treated water to a storage tank or back into the industrial system so that it can be reused in the industry.

The type of wastewater pump used is determined by the treatment technique employed and the force that is required in the process. There are different types of pumps that are common in a wastewater treatment plant such as the centrifugal, positive displacement, submersible, high-pressure, and progressive cavity, among others. Each type of pump offers its advantages and usefulness depending on the application and the concentration of the sludge that is required to be moved.

Centrifugal Pumps

Centrifugal pumps are designed to apply centrifugal force to create sufficient power that is required to displace the wastewater through the treatment system. The pumps are fitted with rotating impellers that resemble and function similarly as the mechanical fans. The pump is characterized by a relatively small inlet and a large outlet to create the required velocity (Sintech Pumps, 2018). The pumps are ideal for pumping liquids with low viscosity at constant discharge pressure. It is a more economical choice to use the centrifugal pumps because they offer reliable service when used to perform simple pumping applications.

The centrifugal pumps have several highlights that make them appropriate and ideal for use in sewage water treatment processes. First, they have a simple structural design that renders them practical and easy to operate. Second, the moving parts of the pump are durable, and thus, they can last for a long time without replacement. Lastly, the pumps require less maintenance due to the simple design. The centrifugal pumps have different typical applications since they can be used to move raw wastewater, effluent sewage water, primary and secondary sludge. The pumps can also be used in moving flush, spray and seal water.

Positive Displacement Pumps

Positive displacement pumps are fitted with impellers, gears, and rollers that serve to displace the sludge through the treatment system. The pumps have to cavities on both ends that enhance the flow of wastewater. The suction side has a cavity that expands to allow fluids to flow into the pump while the discharge end has a decreasing cavity that collapses to permit the wastewater to flow out of the treatment plant (Engineer Toolbox, 2003). Positive displacement pumps are available in different types, which include the piston, the rotary gear, the rotary pump, and the diaphragm pump, which is the most popular.

The key characteristics of the diaphragm pumps are that they have a diaphragm membrane and a chamber which has discharge valves. The discharge side has a relief valve on which act as a safety precaution. The typical application of the pumps is in moving hazardous and toxic liquids and slurries that contain numerous solid particles. The pumps are also used to move primary, thickened and digested sludges. The moving parts of the pumps are highly durable and thus can be able to withstand the chemical feed applications without much corrosion.

Progressive Cavity Pump

The typical main application of the progressive cavity pumps is in sewage water that contains a lot of abrasive solids. Other wastewater pumps such as the centrifugal pumps cannot pump solids due to be a high possibility of clogging because of their close tolerances and their all metallic designs. The design of the progressive cavity pumps with rotor and stator makes them suitable to use for abrasive applications (Elsey, 2017). The pumps are fitted with a rubber stator that allows for more flexibility and thus reduces abrasion.

The progressive cavity pumps are mainly used in treatment processes where the fluids have a higher viscosity than water. The pumps are ideal for pumping wastewater with higher viscosity because of the increased mechanical efficiency, thus reducing power consumption. It is also suitable because of its volumetric efficiency that translates to more flow of discharge fluids. Also, the progressive cavity pumps can be fitted with variable frequency drives which regulate the pump speed and hence they can be used when the viscosity of the fluids is variable.

Pump Stations

A pump station houses all the necessary systems and equipment that are used in the treatment of sewage water. A pump station has several fundamental essentials which include wet wells, wastewater pumps, pipes fitted with valves and filters, motors among others. There are several systems installed in the pump station, such as the power supply, the alarm control, the odor control, and the ventilation systems. Custom designed pump stations are installed on site and are therefore made to meet the specific needs and requirement of the user, and they can have much higher capacity than the pre-fabricated pump stations (Paschke, 1997). The operations of pump stations are customarily automated and thus require minimal inspections to establish any possible malfunctioning and defects. The operations and maintenance costs vary according to the capacity of the pump station. These costs include labor and power costs, which account for almost ninety percent.

Conclusions

In conclusion, the type of pump that is used in a sewage water treatment plant is determined by several factors. The key factors to consider include the ability to withstand the abrasion that is caused by the slurry, the level of viscosity of the fluids, and the velocity required. The pumps used in the treatment of wastewater must be durable and have a heavy-duty design to handle large volumes of the sludge effectively. The pump station houses all the necessary equipment and systems required in the treatment process and thus it is important to have frequent checks to ensure efficiency in operations.

References

Elsey, J. (2017, June 12). A Beginner's Guide to Progressive Cavity Pumps. Retrieved from Pumps and Systems: https://www.pumpsandsystems.com/progressing-cavity/june-2017-beginner-s-guide-progressive-cavity-pumps

Engineering Toolbox, (2003). Positive Displacement Pumps. [online] Available at: https://www.engineeringtoolbox.com/positive-displacement-pumps-d_414.html

Paschke N.W. Pump Station Basics - Design Considerations for a Reliable Pump Station. Operations Forum, Vol. 14, No. 5, 15-20, May 1997.

Sintech Pumps. (2018, May 11). Types of Water Treatment Pumps. Retrieved from Sintech Pumps: http://www.sintechpumps.com/wastewater-pumps/

Thakur, K. (2014, May 20). Know About Pumps Used for Waste Water Treatment Plants. Extracted from Effluent Treatment Plants: https://effluenttreatmentplants.wordpress.com/2014/05/20/know-about-pumps-used-for-waste-water-treatment-plants/