Wastewater aeration involves a method of adding fresh oxygen into wastewater that promotes aerobic bio-degradation of pollutant components. Aeration is an essential step for the majority of wastewater biological treatment systems. Chemical treatments involve the use of specific chemicals to stabilize and react contaminants present in wastewater while biological treatments make use of microorganisms naturally occurring in the wastewater in order to degrade the contaminants.
When Is Aeration Used?
Activated sludge processes are among the more common options under secondary treatments used in both industrial and municipal wastewater treatment. Aeration in activated sludge processes involves pumping fresh oxygen into the tank. The introduction of air into the wastewater promotes microbial growth. The microbes then feed on organic materials which form flocs that are then easy to settle out. Once the flocs settle into a settling tank, the bacteria that forms the “activated sludge” flocs are circulated back continually to an aeration basin. This process increases the decomposition rate.
How Does Aeration Work?
Bacteria present in wastewater require fresh oxygen for biodegradation to occur successfully. Aeration is a process that provides the bacteria with oxygen for stabilizing and treating the wastewater. Bacteria present in the water break down organic matter that contains carbon that results in water and carbon dioxide using the supplied air. Without enough oxygen, the bacteria are not able to biodegrade the organic matter fast enough.
The two most common water aeration types include Subsurface and Surface:
What Is Subsurface Aeration?
Subsurface is the more common aeration type. Wastewater plants located in urban areas often use this method. Subsurface aeration involves the use of porous devices positioned below the surface of the liquid. These submersible aerators or diffusers sit below the fluid or water where compressed air releases bubbles. This technique is effective in delivering sufficient amounts of oxygen into the wastewater. At the same time, this also ensures that oxygen and water are mixed thoroughly.
What Is Surface Aeration?
Surface aeration involved surface aerators that push the water from beneath the surface up and out into the air. The water droplets drop back down into the wastewater, mixing in fresh oxygen. The water jets break the water’s surface with different levels of force.
How Does Fresh Oxygen Improve Wastewater Treatment?
The use of pure oxygen helps to achieve the highest levels of “dissolved oxygen” when compared to the more conventional approach of using just air. There are multiple potential advantages when using “pure oxygen” to enhance air systems in secondary treatments. Some of these include:
– Improved sludge settling
– Reduction in odors
– Increased loading (oxygen/BOD demand)
– Reduced volatile chemicals
– Maintain system health
– Increased flexibility in the system operation (for example turndown, blower, etc.)
– Increase the capability to match high production or peak demands
– Assist with meeting permit limits such as NPDES
– Assist in an emergency situation such as aerator failure
The Importance Of Aeration For Wastewater Treatment
Aeration (the introduction of oxygen) is a highly critical component when it comes to treatment systems that use activated sludge processes. Aeration is also important to eliminate seasonal problems including stratification or algae growth.
A sufficient supply of transferred oxygen happens to be key for every type of secondary treatment operation. There are numerous ways that fresh oxygen can assist to make sure these systems are operating correctly.
Well-designed aeration systems have a significant and direct impact on the overall levels of wastewater treatments achieved. An oxygen supply that is evenly distributed in aeration systems is integral to economically viable, effective, and rapid wastewater treatment.
Joe Cadieux is the Senior Biologist for Midwestponds.com. Joe grew up fishing, hunting, and camping with his family in the Midwest. At home he helped out on the hobby farm with the chickens, rabbits, and goats … and one goose (Gracie).