Aerobic Treatment Unit Septic System

Aerobic Treatment Units (ATUs) or aerobic septic systems are popular septic systems because the wastewater effluent leaving the septic tank is treated to a higher standard. Aerobic Treatment Units are often used for small lot sizes (ATU use a smaller leach field footprint) where a conventional septic system would not work due to for example inadequate soil types or a high water table (close to water). Also, families sometimes like that the wastewater coming out of the system is teated with either ultraviolet light or chlorine tablets.

How do aerobic septic systems work?

Aerobic septic systems use oxygen forced into the aeration chamber with the use of an air blower or compressor. If your property is on solar power, it is a good idea to add a timer on your blower/ compressor so it only operates during sunlight hours. This will also reduce the noise from the septic tank during the night.

The additional oxygen stimulates natural bacterial activity within the system, which in turn aids in the treatment of nutrients in the effluent. Many aerobic systems have a pre-treatment tank before the aerobic unit or may have a pretreatment tank within the unit to allow solids and sludge to settle before the effluent wastewater enters the ATU. The last stage of treatment is a disinfection stage is to treat wastewater with either a chlorine tablet or ultraviolet light to reduce harmful pathogens as it is leaving the entire aerobic septic system.

What are the benefits of an aerobic system over a conventional system?

The benefits of an aerobic treatment unit system are:

• Can be used on smaller sized lots as drain field size is smaller
• Can be used on lots with poor or inappropriate soil conditions (see perc test)
• Can be used on lots with a high water table or close to a body of water like lake, river or creek.

What are the negatives to an aerobic treatment unit

• Expect regular maintenance for the lifetime of the system, specifically to service the blower and change chlorine tablets regularly
• Noise from the churning of the system and blower can be high (recommend a timer so only runs during the day)
• Installation costs can be higher than conventional septic systems
• High water usage can negatively affect the system
• Not suitable for cold weather climates unless the system is insulated

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