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Aerobic Septic System Tanks InspectAPedia®  -     This article discusses size and design requirements for aerobic septic tanks. Here are designs and products for aerobic septic treatment units (ATUs) for onsite waste disposal, also called fine bubble aeration systems. We address aerobic septic system design, features, inspection, repair, and maintenance. Product sources are also listed.

Aerobic Treatment Unit Tank Size Requirements

Typically a residential aerobic septic treatment unit does not run continuously, just as inflow to it is not continuous. ATU size or capacity is determined as for a conventional septic system, by allowing 50 to 100 gallons of wastewater per day per building occupant. Some jurisdictions require that the system minimum capacity accept 500 gallons of wastewater daily.

Safe aerobic treatment tank size advice

A "safe" design size for an aerobic treatment tank that allows for temporary power outage (and thus loss of the aeration pump) is an aerobic treatment tank at least as large as the conventional tank that would have been required for a given site.

Aerobic treatment tanks in cold climates

If your ATU tank is being installed in a cold climate, it may be necessary to insulate the treatment tank (use 2" solid foam panels) to keep the tank temperature high enough (above 54 degF) for the aerobic processing to continue in cold weather. (Some thermophilic microorganisms require temperatures as high as 131 to 149 degF.)

ATU Flow: Continuous or Intermittent Design Alternatives for Aerobic Septic Systems

Two basic ATU designs provide for intermittent or continuous flow through the system.

Intermittent flow aerobic septic systems

Just as most residential septic systems do not receive wastewater continuously but rather intermittently, the ATU may be designed to turn the aerator and agitator on and off as needed. Intermittent flow septic systems, including aerobic or aeration treatment designs are also called a "batch system" septic design approach.

Continuous flow aerobic treatment system designs

Other aerobic or aeration septic treatment systems, particularly aerobic systems which have to serve a larger facility where wastewater inflow may be continuous, may themselves operate continuously. Obviously these designs are called "continuous flow" aerobic treatment systems.

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