3 Types of Sewage Pumps And their advantages and Disadvantages

3 Types Of Sewage Pumps

The following 3 types of sewage pump are commonly employed for pumping of sewage/wastewater

1.  Centrifugal Pumps
2.  Reciprocating Pumps 
3.  Pneumatic ejectors or Air pressure pumps

1. Centrifugal Pumps

Centrifugal pumps are most widely used for lifting sewage. These pumps work on the principle of centrifugal force. The sewage which enters inside the pump is revolved at high speed by means of impeller and is thrown to the periphery by centrifugal force.

Thus, the velocity head is converted to pressure head. This head forces the sewage to move through the delivery Centrifugal pipe. Centrifugal pump may be of the following types: 

1.  Horizontal axis flow centrifugal pump (also known as the non-clog pump) 
2.  Disintegrating pump
3.  Volutetype 
4.  Turbine type etc.

Advantages Of Centrifugal Pumps

 The centrifugal pump has the following advantages: 

•  It requires minimum space for installation 
•  It can be easily installed.
• This pump easily transports the suspended matter present in sewage without getting clogged.
• The working is simple. 
•  It is cheap in cost. 
•  This pump can not be damaged due to high pressure.

Disadvantages Of Centrifugal Pumps

The centrifugal pump has the following disadvantages:

•  The rate of flow can not be regulated.
•  This pump can not be operated without priming. 
•  This pump has restricted suction.
•  Any air leakage on the suction side will affect the efficiency of the pump.

2. Reciprocating Pumps

Reciprocating pumps are generally not used these days. However, sometimes they may be used for pumping large quantity of sewage against low head. Reciprocating pumps used for pumping sewage are generally of two types: 

1.  Ram type. 
2.  Propeller type. 

The ram-type reciprocating pump consists of a closed cylinder in which a piston or a plunger moves to and fro by a connecting rod. The connecting rod is hinged with a wheel which is rotated by a motor. 

During the suction stroke, sewage enters the cylinder and during the delivery stroke, the sewage is forced through the delivery pipe. 

In the propeller type reciprocating pump, a propeller moves vertically inside a pump casing, causing the sewage to lift up. 

Advantages Of Reciprocating pumps

The reciprocating pump has the following advantages:

•  It gives constant discharge under variable heads.
• Durable and flexible.
•  It is suitable for pumping large quantity of sewage against low head.

Disadvantages Of Reciprocating pumps

The centrifugal pump has the following disadvantages: 

•  The initial cost is high.
•  It requires more space for installation.
•  Their maintenance is difficult.
•  The wear and tear of valves are more.
•  This pump is unsuitable for pumping sewage containing large quantity of sand, silt etc.

3. Pneumatic Ejectors or Air Pressure Pumps

These pumps are used for pumping smaller quantity of wastewater. It consists of a tight tank into which the wastewater flows by gravity. The wastewater is forced automatically whenever sufficient wastewater has accumulated to raise a float.

Advantages Of Pneumatic Ejectors

The Pneumatic ejectors or Air pressure pump has the following advantages: 

•  It requires least supervision.
•  These pumps are not likely to be clogged anywhere.
•  They are found to be economical where smaller quantities of wastewaters are required to be pumped.

Disadvantages Of Pneumatic Ejectors

The only disadvantage of Pneumatic ejectors is that they have very low efficiency (about 15%).

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