In water treatment applications, different types of pumps are selected based on criteria such as:
- System requirements
- Flow capacity requirements
- Discharge pressure requirements
- Availability of space
The pumps most commonly used in water distribution systems are centrifugal, vertical turbine, and submersible pumps.
1. Centrifugal pumps
“Centrifugal pumps are the most common types of pumps used in water distribution,” says a water industry specialist working for the Woodhams Group. A circular fan or turbine-shaped impeller is mounted on a centrally supported shaft that is rotated by a motor that can be powered by diesel fuel or electricity. When water enters at the center suction a high velocity is imparted by the rotating impeller that circulates the water, throwing it outward.
2. Vertical turbine pumps
Generally used in raw water intakes and at booster stations in a water distribution system. The water is channeled through a cross-sectional, uniform area. A central impeller is situated along the axis with blades shaped in a way that allows the water to flow in a radial direction.
3. Submersible pumps
Submersible pumps are used mostly to pump groundwater from wells and are placed below the water level. It is a multi-stage centrifugal pump with impellers mounted on a vertical shaft. An electric motor that drives the pump and constructed for use in submerged operations is positioned adjacent to the pump.
Pumping pure water is very different from pumping waste water. Wastewater often contains contaminants in the form of long fibres or other abrasive solids. A lot of aggressive chemicals are used in water treatment operations. Water treatment plants usually make use of continuous flow operations with points in the process for additional treatments such as filtration, dosing of chemicals, disposal of treated sludge, sedimentation, and storage. Some water treatment operations have periodic processes that run only once a day or once a week.
In a professional waste treatment plant a number of processes are involved including:
- Physical – filtration and flotation
- Chemical – chlorination, and coagulation
- Biological – aerobic and activated sludge processes.
- A combination of all three
Chemical Dosing Pumps
These are positive displacement pumps used for feeding chemicals into the water supply system at various stages of the treatment process. They are suitable for handling fluids with varying viscosities and abrasive fluids such as viscous liquids and acids and for applications that require high pressure. There are two types:
1. Reciprocating pumps
A piston moving back and forth in an enclosing cylinder pushes the water into the cylinder with the help of check valves.
2. Rotary pumps
A rotary pump has an impeller in the shape of a screw, gear, or lobe that rotates within an enclosed cylinder, imparting energy to the water.
Industrial Water Pumps
Industrial water pumps are designed for pumping wastewater with high reliability and efficiency through all stages of water treatment. They are suitable for the following applications:
- Sludge treatment – pumping and treatment of dewatered, stabilized, thickened, primary, secondary, and tertiary sludge.
- Wastewater treatment – pumping,