Sewage pumps are pumps for transferring sewage and wastewater. They are used in the sewage treatment plants of towns and cities. Besides sewage treatment plants, they are also used in private homes and buildings which, due to topography, cannot be connected to the city sewage plant or municipal sewer. Sewage pumps are installed at the lowest point of a sewage basin, from where they pump waste to the septic tank or sewer system. Since they are submerged, they are also called submersible sewage pumps.
There are different kinds of sewage pumps such as, the centrifugal pumps, the reciprocating Pumps, and the pneumatic ejectors or air pressure pumps.
Centrifugal pumps are used for lifting sewage. As its name implies, the centrifugal pump utilizes the centrifugal force. Sewage, on entering the pump, is revolved at high speeds by impellers. The velocity of the rotation creates a pressure that moves the sewage through the delivery pipes.
Centrifugal pumps are affordable, easy to install, can withstand high pressures, and are quite resistant to clogging. However, the pump's flow rates cannot be regulated, and they cannot run without priming.
The second type of pump listed, the reciprocating pump, is used for pumping large quantities of sewage at a low pressure. The advantages of the reciprocating pump are that it is durable, and able to pump huge quantities at low pressure. The disadvantages are its high cost of installation and maintenance. It is unsuitable for transferring wastewater with high levels of solid content.
The third type of sewage pump listed, the pneumatic ejector or air pressure pump, is used for pumping small quantities of wastewater. It is fitted with a tight tank into which flows the wastewater under gravity. When the wastewater has reached sufficiently high levels such that it raises a float, the wastewater is flushed out.
The pneumatic ejector pump is not easily clogged, it requires little supervision while in operation, and it is affordable for sewage disposal involving small quantities of wastewater. Its disadvantage, however, is that its efficiency is low, about 15%.
There are also different kinds of sewage pumps based on the kinds of impellers they have. There are pumps for dry installation with a single-vane impeller, submersible
motor pumps with a single-vane impeller, close-coupled pumps, torque flow pumps with a free-flow impeller, and sewage Pumps with a diagonal impeller.
To maintain and keep sewage pumps in proper running condition, clogging must be prevented. It is essential, even when solid materials are high in the slurry, to keep the pump from clogging. The impellers, the single-vane and diagonal-vane impellers are designed to keep this from happening.
It is also important that sewage pumps are wear-resistant. To make sure of this, sewage lifting units are fitted with replaceable wear-resistant components like the casing wear ring, wear plate, and the impeller wear ring. The types of wear-resistant components added to the pumps depend on the kind of slurry (precisely, the level of solid content in the wastewater) being transported.
Sewage pumps have several benefits. Apart from pumping wastewater to the sewer system, they also prevent flooding, damp and mildew.