Types of Mechanical Aerators
There are two types of mechanical aerators, which are popular and widely used in the wastewater treatment processes. These two aerators are :
Mechanical surface aerators are widely used in wastewater treatment applications. Their primary function is to supply oxygen to water. They are also used for controlling taste and odor problems in water treatment. These aerators are usually installed at a reservoir rather than at the treatment plant.
Construction:
The major components of the mechanical surface aerators are Motor, Gear box and Impeller. More commonly these components come combinedly, but for the purpose of maintenance they can be easily separated. The impellers are constructed from cast iron, steel, noncorrosive alloys, and fiberglass. Reinforced plastic are used to shake the wastewater vigorously. It causes a rapid change in the air - water interface, which facilitates the dissolution of the air in water. These aerators consist of partially submerged or submerged impellers, which are attached to motors mounted on fixed structures or pontoons. The mechanical surface aerators commonly consist of an electric motor suspended on a float provided with a driveshaft operating a propeller located at a short distance below the water surface. The blade is used to draw up water and then the water is thrown into the air in tiny droplets so that the water may pick up oxygen. They facilitate the dissolution of air into wastewater by vigorously shaking up the water in its contact.
Variations:
The mechanical surface aerator units come in two variations. They can be offered in fixed and floating aeration options. The floating aeration unit includes the device supported on three floating pontoons. These pontoons are interconnected through a steel frame forming floating platform around the aerator.
Surface aerators can also be classified according to the speed of rotation of the impeller or the type of impeller used. The low speed category of impellers include centrifugal impellers, while the axial-flow impeller type aerators operate at higher speed. The impeller, in low speed aerators, is driven through a reduction gear by an electric motor.
Industries:
Mechanical aerators are used in a number of industries for the treatment of wastewater and sewages. Some of them are :
- Municipal Wastewater Treatment
- Wine and Beverage Manufacturing
- Chemical Processing
- Pulp and Paper Mills
- Leachate Treatment
- Textile Industries
- Dairies
Submerged aerators are another type of mechanical aerators. They operate in the reverse of surface aerators. The submerged blades draws water downwards and also draws air in the process. The air is diffused into the water. These aerators operate in relatively calm and still water at the surface compared with surface aerators. They are considered best for increasing the level of dissolved oxygen.