In which type of wastewater treatment is aeration most commonly utilized?

Aeration is most commonly utilized in secondary treatment of wastewater because this phase focuses on biologically treating the effluent to remove dissolved organic matter. Secondary treatment relies on microorganisms to digest the organic pollutants, and aeration provides the necessary oxygen for aerobic bacteria to thrive. This process facilitates the breakdown of organic material and helps to reduce biochemical oxygen demand (BOD) in the wastewater.

During secondary treatment, aeration tanks or processes such as activated sludge systems are used to ensure that the microorganisms have sufficient oxygen while they work to degrade the waste. This step is crucial for achieving a high level of treatment before the water undergoes further processing in tertiary treatment or disposal.

In contrast, primary treatment involves the physical removal of solids, enhanced treatment may include advanced biological processes but is not as focused solely on aeration, and tertiary treatment typically aims to further polish the water and remove remaining contaminants after secondary treatment.