Aerator
Wastewater treatment with surface aeration mixes and stirs the wastewater while spraying it into the air. This helps the wastewater get more contact with air, which improves aeration. In this type of aeration, the aerator is placed on a platform outside the wastewater tank, with only its impeller submerged at a certain depth in the fluid. Aerators stir the wastewater with force, preventing the settling of suspended solids and increasing the contact surface between the wastewater and air.
By receiving sufficient oxygen in the aeration basin, microorganisms break down the organic and unstable compounds in the wastewater, converting them into stable, non-putrefying substances (inorganic compounds).
Role of Aeration in Treatment of Wastewater
Aeration is the most critical part of an activated sludge treatment system. A well-designed aeration system has a direct impact on the quality of wastewater treatment. Properly uniform distribution of oxygen and an adequate source of oxygen within this aeration system are vital for quick, durable, economical, and effective wastewater treatment.
Fixed Surface Aeration
The surface aerator system plays an important role in the oxygenation and removal of pollutants in wastewater. The system works via an electric motor and rotating blades that inject air into the wastewater, increasing the interface area between the water and air.
This process oxygenates the water, reducing the concentration of pollutants in the wastewater. Furthermore, the water temperature declines as a result of the turbulence of air and water, decreasing the growth of detrimental bacteria in the wastewater.
Fixed surface aerators for wastewater can be categorized into two types based on rotational speed:
High-Speed Surface Aerator
As a water treatment method, it plays an indispensable role in improving wastewater quality and removing organic and nitrogenous pollutants. This technique provides the required oxygen for the bacteria that break down wastewater pollutants by producing high amounts of air and mixing it with the wastewater.
Using a high-speed surface aerator causes the wastewater surface to move like a crust, automatically activating the majority of the oxygen needed to decompose wastewater pollutants, resulting in much faster removal of pollutants such as BOD and COD. Additionally, high-speed surface aerators increase the production of active sludge and improve the efficiency of the activated system. This method also reduces wastewater treatment costs and extends the useful life of the treatment system.
Advantages of High-Speed Surface Aeration:
- High efficiency in oxygen transfer and absorption
- Elimination of the gearbox from the aeration system
- Easy installation and maintenance without the need to empty the basin
- Usable in both fixed and floating states
- Corrosion resistance
Low-Speed Surface Aerator
Both low-speed and high-speed surface aeration are methods for oxygenating wastewater, but they differ in air flow speed and water turbulence intensity. In low-speed surface aeration, the air flows slowly and gently into the wastewater tank. This method is suitable for activating bacteria and increasing their activity. In contrast, high-speed surface aeration involves stronger air flow and more intense turbulence, making it suitable for removing semi-pure substances and eliminating odors in open spaces. The main difference between the two methods lies in the air flow intensity and water turbulence level.
Advantages of Low-Speed Surface Aeration:
- Easy installation, operation, and maintenance
- Cost-effectiveness
- Highly proper for wastewater treatment
- Long lifespan owing to low-speed operation
- High efficiency in oxygen transfer
Floating Surface Aeration
Another type of wastewater aeration system is the floating surface aeration system. Like fixed surface aerators, this system operates on the upper layers of the effluent. However, unlike fixed types, these devices are floating. Components of these aerators include a floating structure, shaft and impeller, a cone-shaped pipe for effluent suction, a rain hood, and an electric motor.
Floating surface aeration is used as an oxygenation method in wastewater treatment. In this method, air is directly injected into the wastewater through air diffusers. The injected air forms large bubbles on the water’s surface, increasing the contact area between the water and air and, consequently, enhancing the rate of oxygenation into the solution.
In this technique, air diffusers typically float on the water surface; these devices force air into the water using rotating pumps. The substantial volume of air injected into the system significantly raises oxygen absorption in the wastewater, which aids in removing organic materials and improves the efficiency of the treatment process. In general, Floating surface aeration is a basic but effective method of oxygenating wastewater, leading to better treatment results and reduced operating expenses.
Importance of Aeration in Wastewater Treatment
Aeration is the most critical component of an activated sludge treatment system. A well-designed aeration system has a direct impact on the quality of wastewater treatment. Even oxygen distribution and a sufficient oxygen source in the aeration system are key to fast, durable, economical, and effective wastewater treatment.
Key Applications of Aeration Systems:
Oxygenation and aeration of aquaculture ponds
Aeration and oxygenation of municipal wastewater treatment plants
Advantages of Using Aerators in Wastewater Treatment:
- High efficiency in oxygen transfer and absorption
- Elimination of the gearbox from the aeration system
- Easy installation and maintenance without the need to empty the basin
- Cost-effective maintenance and repair process
- Usable in both fixed and floating states
- Corrosion resistance
