Aeration is the process of adding air into wastewater to allow. Aerobic bio-degradation of the pollutant components. Unlike chemical treatment, aeration enhances biological treatment, uses micro-organisms that occur naturally in wastewater to degrade wastewater contaminants. Aeration brings water and air in close contact in order to A) add a gas such as oxygen and also to B) remove dissolved gases (such as carbon dioxide) and C) oxidizes dissolved metals such as iron, hydrogen sulfide, and volatile organic chemicals (VOCs). Aeration is the first major process at the treatment plant. Constituents are removed or modified before they can interfere with the treatment processes. The efficiency of aeration depends on the amount of surface contact between air and water, which is controlled primarily by the size of the air bubble. Constituents commonly affected by aeration are: VOCs, such as benzene, trichloroethylene, dichloroethylene, and perchloroethylene, Ammonia, Hydrogen sulfide stripping, Chlorine, Carbon dioxide, Methane, Iron and Manganese

Water aeration is often required in water bodies that suffer from low oxygen conditions. Caused by sewage discharges, agricultural run-off, or heavy rain. During heavy rain enormous masses of rain water fills up rivers and water courses and increases the BOD (Biological Oxygen Demand) and COD (Chemical Oxygen Demand) of the water. The result is that the oxygen levels in the water decreases endangering the aquatic life and releasing chemical substances. Aeration provides oxygen to bacteria for treating and stabilizing the wastewater. Oxygen is needed by the bacteria to allow bio-degradation. The O2 is used by bacteria in the water to break down organic matter containing carbon. Without sufficient dissolved oxygen, degradation occurs and the biological process convert hydrogen and sulfur to form hydrogen sulfide and methane.