What is an Aeration System and How Does it Work?

According to Central Pollution Control Board, India treats only one-third of wastewater generated. Moreover, the treatment systems are not evenly distributed across the nation. For example, Maharashtra, Gujarat, Uttar Pradesh, Delhi, and Karnataka account for 60% of India's total installed wastewater treatment capacity. On the contrary, some states like Assam, Arunachal Pradesh, Manipur, etc., do not have treatment plants.

Nowadays, wastewater treatment is no longer an option but the need of the hour. However, wastewater treatment plants require high amounts of energy and chemicals, increasing the cost of industries. 

In its wake, a more feasible approach has made its way in industries: aeration systems. The use of aeration has multiplied over the years, making it a central part of wastewater treatment because of its eco-friendliness.

What is aeration wastewater treatment?

Aeration is one of the wastewater treatment processes that treat water through the air.

Here, air bubbles are released in wastewater, and they come in contact with impurities like gas, dissolved metals, suspended solids, and volatile organic compounds. Then the air bubbles rise to the surface and facilitate the removal of pollutants. Moreover, aeration effectively oxidizes iron and hydrogen sulfide, as air is a very fast oxidizer.

How does the aeration system work?

Aeration for wastewater treatment can be accomplished in two fundamental ways: passing air in the water or passing water in the air.

• Passing air in the water

Here, the air is introduced into wastewater through fine pores that create tiny air bubbles. The air bubbles are allowed to attach with impurities and float to the surface. After some time, the surface air bubbles with pollutants are skimmed, and clean water is further passed for treatment. 

This type of aerator is widely used in wastewater treatment plants are is effective in removing volatile organic compounds, ammonia, chlorine, carbon dioxide, etc.

For example,

• Pressure aerators
• Centrifugal aerators
• Air stripping
• Passing water in the air

Here, water is sprayed into the environment, allowing it to mix with the surrounding air. 

This type of aerator is widely used for ponds, lakes, and lagoons. It is effective in oxidizing iron, manganese, and hydrogen sulfide. Moreover, it is also efficient in removing dissolved gases.

For example,

• Spray aerators
• Cascade aerators
• Cone aerators
• Draft aerators

Challenges during operation of aeration systems

• High amounts of dissolved oxygen results in corrosion of equipment. Here, the quantity of aeration required depends on the type of plant, wastewater constituents, and current season.
• When the dissolved oxygen is more, water will release some oxygen in the filters as it passes through, resulting in false clogging of filters. Here, the spaces between the filter media get clogged with air, called air binding, and behaved like they need backwashing.
• The physical scrubbing action of aeration is efficient in removing hydrogen at pH six or less. However, high pH will ionize the hydrogen sulfide barring its removal.

To overcome the challenges as mentioned earlier during aeration wastewater treatment, following control tests can be beneficial,

• Monitor dissolved oxygen in wastewater
• Identify the pH of the water to ensure the efficient removal of heavy metals
• Maintain optimum temperature because the decreased temperature will increase dissolved oxygen levels.

List of different types of aeration system

• Gravity aeration systems
• Spray aeration systems
• Diffused air aeration sys
• Mechanical aerators

Factors to consider before selecting the right aeration system

• Location of the plant
• The climate of the plant area
• The volume of wastewater to be treated
• Investment and maintenance budget
• Tank size of the aeration system
• Oxygen requirement in wastewater
• Energy and efficiency requirement of the plant

Aeration is central to wastewater treatment because its proper implementation will effectively remove algae growth and improve nutrient-oxygen balance. Moreover, when oxygen is evenly distributed in optimum quantity in aeration wastewater treatment, it directly affects the treated water quality. In addition, it is crucial for economically viable, rapid, and efficient treatment.