Aerobic Treatment Units (ATU's)

Aerobic Treatment Units (ATU) are a special kind of wastewater disposal system that are more efficient at processing waste.

They are highly versatile and efficient systems and have many advantages including: 

• Ability to be installed in a place where a conventional system could be installed (due to soil quality or site conditions, or
• Providing the ability to build a larger house on a smaller lot (ATUs require a smaller drain field size than conventional systems). 

ATU reduces the amount of biological material that enters the owner/user drain field. This may extend the lifespan of the drain field and is more environmentally friendly than a conventional system.

The closure of the construction permit transitions to the opening of the annual operating system.

Requirements to Maintain an ATU System

The homeowner must maintain a current operating permit for the life of the system.

• The operating permit must be renewed every two years.
• The fee is $175.00, payable to the Florida Department of Health.
• Pay online by visiting MyFloridaEHPermit.com.
  
  

The homeowner must maintain a valid maintenance contract with an approved maintenance entity for the life of the system.   

• The maintenance contract on new construction will initially be good for two years.
• Subsequent renewals must be good for at least a one-year term for the life of the system.
• The maintenance entity is required to inspect/service the ATU at least two times per year.
• Inspection reports must be submitted to the Department of Health in Lee County (DOH-Lee).
• DOH-Lee must inspect the maintenance and performance of the ATU at least once per year.

*To check the status of a septic permit application or inspection use our new Septic Online Services page for quick access to the information. 

How ATU Works

ATU force compressed air through the liquid effluent in the tank to create a highly oxygenated (aerobic) environment for bacteria. Bacteria that thrive in oxygen-rich environments work to break down and digest the wastewater inside the ATU. 

ATU come in a variety of sizes and shapes. They can be made of concrete, fiberglass, or polyurethane.

Pretreatment

Some ATU have a step before the actual aeration begins. This is a pretreatment that helps reduce the number of solids and other materials that go into the system and the bacteria cannot degrade.

These solids include grease, oil, toilet paper, and other substances that go down the drain or flushed into the system. This stage may take place in a separate tank or in a compartment of the ATU itself. 

Aerobic Treatment Unit

The ATU consists of a pump, pipes, and diffusers. 

• The pump compresses the air that flows into the chamber.
• The pipes carry the air from the aerator to the diffusers.
• The diffuser forces air into the water in the form of bubbles which introduces oxygen into There are two main types of ATU:
  • Suspended growth units– The most common type of ATU. They work by mixing air with the sewage to feed the free-floating bacteria without the use of any type of medium.
  • Attached growth units- The bacteria are attached to some type of medium located inside the ATU itself.

Settling Chamber

The settling chamber is a calm area which allows settling to occur with the use of gravity. This is the area where the clear, treated water is separated from the bacteria that have been treating the sewage and other solids before they leave the system and travel to the drain field.

Drain Field

After the treatment is complete, the effluent is discharged into unsaturated soil and allowed to filter through the sand and continue further treatment.

The effluent from ATU can be discharged into a variety of different drain field systems.

• Gravel systems
• Chamber systems
• Pipe systems
• Dripline systems.