Aeration means the introduction of air in a fashion to maximize its dissolving in water to provide a desired benefit. A typical example is to provide oxygen to speed the growth and metabolism of bacteria in wastewater treatment processes.
Other applications include:
- Sustaining aquatic organisms in public aquariums or in commercial fish farming
- Carbonation of soft drinks
- Enhancement of mash fermentation in beer manufacturing
- Drive off unwanted gases such as hydrogen sulfide or carbon dioxide, called decarbonation or degasification,
- Providing oxygen to oxidize contaminants such as dissolved iron or hydrogen sulfide, converting them to particles so they can be filtered from water
- Introducing other gasses such as ozone into water.
Aeration is physically accomplished in a variety of ways. A common one is to introduce air by way of diffusers, similar to the stones used in a home aquarium. Ozonation is often carried out by using dry air into which ozone gas has been introduced and bubbling the air / ozone mixture into the water.
A myriad of proprietary diffusing devices have been developed, all with the purpose of breaking air into very small bubbles, offering a high ratio of surface area, to enhance the air to water transfer. Membranes have been used in the past several years to achieve this purpose. While these are often used for degasification, the reverse application is feasible. Most methods used for degasification can also be used to aerate raw water.
Aeration is also often accomplished with venturi devices which restrict the flow of pressurized water through a restricted orifice, causing a vacuum which is effective at "sucking" air into the turbulent liquid flow. These have the advantage of being small and consuming relatively low energy (energy consumed is reflected in water pressure loss through the device).