The basic aerobic septic system is a system that provides a suitable oxygen rich environment for organisms that can reduce the organic portion of the waste into carbon dioxide and water in the presence of oxygen.

Aerobic septic systems are similar to septic systems in that they both use natural processes to treat wastewater. But unlike septic (anaerobic) treatment, the aerobic treatment process requires oxygen. Aerobic treatment units, therefore, use a mechanism to inject and circulate air inside the treatment tank.

Because aerobic septic systems use a higher rate process, they are able to achieve superior effluent quality. The effluent can be discharged to the subsurface as in a septic tank leach field or, in some cases, discharged directly to the surface.

The early aerobic systems consisted of little more than an aerator placed in a traditional septic tank. These were often referred to as an aeration septic system or aerator septic system.

The newer aerobic septic systems are pre-engineered and operate at a high level of efficiency.

The use of residential aerobic septic systems has been fairly limited, in part, because of the widespread use of septic systems, which are relatively inexpensive and easy to maintain. Septic systems are the most common onsite wastewater treatment systems in rural areas.

However septic systems are not suitable for all residential applications. Some homes may not have enough land area or appropriate soil conditions to accommodate the soil absorption drainfield. In some communities, the water table is too high to allow the drainfield to give adequate treatment to the wastewater before it is returned to groundwater.

One of the most common reasons to select an aerobic septic system is to replace failing septic systems, which are a major source of groundwater pollution in some areas. If a failed septic system needs to be replaced or if a site is inappropriate for a septic system, an aerobic septic system maybe a viable option.

Advantages:

• Can provide a higher level of treatment than a septic tank

• Helps protect valuable water resources where septic systems are failing

• Provides an alternative for sites not suited for septic system
• May extend the life of a drainfield

• May allow for a reduction in drain field size

• Reduces ammonia discharged to receiving waters.      

Disadvantages:

• More expensive to operate than a septic system

• Requires electricity

• Includes mechanical parts that can break down

• Requires more frequent routine maintenance than a septic tank

Most aerobic septic systems designed for individual home application include the aeration compartment, settling chamber, and in some units a pretreatment compartment. Some aerobic septic systems provide a pretreatment step to remove grease, trash and garbage grindings.

Aeration:

Oxygen is transferred to the waste stream by diffused air; low pressure air pumps force the air through diffusers on the bottom of the tank.

(show picture of aerator and pump)

Controls and Alarms:

Most aerobic septic systems are supplied with some type of alarm and control system to detect mechanical breakdown. They do not normally include devices to detect effluen quality or biomass deterioration.