As the manufacturing sector grows in India, the environmental footprint is becoming a significant problem. Moreover, wastewater production and releasing untreated water are pressing issues.
However, as the government makes wastewater discharge rules stringent, industries and municipalities need to partner with plant manufacturers to install wastewater treatment plants mandatorily. Treatment plant manufacturers install several technologies and processes in the facility depending on the wastewater quality to meet the end goal.
Many treatment methods involve the use of chemicals, high energy, and more cost, which can leave a significant environmental footprint. Thus, one of the eco-friendly methods used widely in wastewater treatment plants is the aeration system.
What is the purpose of aeration?
Aeration is the process of infusing air into the wastewater, which is then mechanically mixed to disperse air bubbles across the water. It is used to promote aerobic biodegradation of organic matter.
Generally, there are two types of aerators: surface aspirator aerator and subsurface aerators.
However, the most commonly used and effective are surface aspirator aerator.
What is surface aeration?
surface aspirator aerators are employed on the surface of the water. They push water from the bottom up into the air where oxygen is mixed in it, and then the water droplets fall back down. They are generally used for shallow waters and when oxygen is needed immediately in water.
What are the types of surface aerators in wastewater treatment plants?
Fixed surface aerators
Fixed aerators are installed on metal or concrete bridges and are designed based on the turbine rotation speed and wastewater quality. There is no conical pipe in fixed type, unlike floating type aerators, and water is not sprinkled upwards like a fountain.
Here, the blades are rotated on the water’s surface to create turbulence. Due to turbulence, water comes in contact with air, and oxygen is transferred.
A significant factor considered during designing fixed aerators for a wastewater treatment plant is the speed of the rotation or equipment speed. Based on the speed, fixed aerators are of two types:
- High-speed surface aerators
In high-speed surface aerators, the impeller is directly connected to the electromotor shaft and does not require a gearbox to reduce the speed. Moreover, rain caps are used to prevent water from entering the coil.
This type of aerator creates high turbulence and oxygenation and is suitable for large industrial wastewater treatment plants. Moreover, the equipment is made with fiberglass or stainless steel to avoid corrosion and decay caused by the organic matter present in wastewater.
- Slow speed surface aerators
In slow-speed surface aerators, a gearbox is used to control the speed of the impeller. As a result, the speed of the rotation of the impeller is slow and less turbulence is created compared to fast-speed aerators.
These aerators are highly suitable for dissolving sewage in aeration tanks and lagoons. Moreover, as the equipment speed is low, the life of the device is increased and is easy to maintain.
Floating surface aerators
Floating surface aerators extract water down a couple of feet from the water bodies, but instead of pushing water up in the air, they disrupt the water at the surface. They are powered by on-shore electricity. However, they cannot circulate oxygen to more than a 3 meters radius and also leave the bottom portion unaffected.
There are two types of floating surface aerators:
An electric motor powers the impeller in fountains, which pulls water from a few feet and pushes it into the air. The water then falls as droplets, and oxygen is transferred through them.
Though fountains are favorable because of their aesthetic appearance, they cannot transfer oxygen to a large quantity of water. Moreover, as electricity runs through the water, it can be a safety hazard.
- Paddlewheel aerators
Paddlewheel aerators also work on the ‘water into the air’ principle. It contains a hub with paddles attached to it and is powered by an electric motor or gas engine, and the electricity facilities the paddles to churn and turn water and allows oxygen transfer.
Though surface aerators are commonly used and come in a wide range, there are certain pros and cons of surface aeration.
- Easy installation
- Better performance in shallow water
- Surfactant resistant
- High maintenance
- Ineffective in deep water
- Cannot stand cold weather
Aeration is beneficial in wastewater treatment plants because it eliminates the need for chemicals and treats water biologically. Therefore, they are used in various industries like food & beverages, petrochemical, paper & pulp, etc., for wastewater treatment. Moreover, surface aspirator aerator are used in lakes and ponds to keep the water circulating and odor-free.