Aerobic septic system design and size requirements

Aerobic septic system design and size requirements

Aerobic septic system design and size requirements

Aerobic Septic System Design and Size Requirements

Septic systems are an essential part of any residential or commercial property that is not connected to a municipal sewer system. Among the various types of septic systems available, aerobic septic systems are gaining popularity due to their efficiency and environmental friendliness. This article will delve into the design and size requirements of aerobic septic systems, providing valuable insights for homeowners, builders, and environmental enthusiasts alike.

Understanding Aerobic Septic Systems

Aerobic septic systems, also known as aerobic treatment units (ATUs), are wastewater treatment systems that use oxygen and aerobic bacteria to break down waste. Unlike traditional septic systems that rely on anaerobic bacteria and a lack of oxygen, aerobic systems introduce oxygen into the system to promote the growth of aerobic bacteria. These bacteria are more aggressive and faster at breaking down waste, making aerobic systems more efficient and effective.

Design of Aerobic Septic Systems

The design of an aerobic septic system is more complex than that of a traditional septic system. It typically consists of three main components:

  • Pretreatment tank: This is where the raw wastewater from the house is collected. The solids settle at the bottom, and the liquid flows to the next chamber.
  • Aeration chamber: In this chamber, air is pumped in to promote the growth of aerobic bacteria. These bacteria break down the waste in the wastewater.
  • Clarification chamber: Here, the treated wastewater is allowed to settle. The remaining solids settle at the bottom and are returned to the aeration chamber for further treatment. The clarified water is then discharged to the drain field.

Size Requirements of Aerobic Septic Systems

The size of an aerobic septic system is determined by several factors, including the number of bedrooms in the house, the soil type, and the local regulations. Here are some general guidelines:

  • Number of bedrooms: The size of the septic tank is usually based on the number of bedrooms in the house. For example, a three-bedroom house typically requires a 1,000-gallon tank, while a four-bedroom house requires a 1,250-gallon tank.
  • Soil type: The size of the drain field is determined by the soil type. Sandy soil, which drains quickly, requires a larger drain field than clay soil, which drains slowly.
  • Local regulations: Local health departments and environmental agencies often have specific requirements for the size of septic systems. It’s important to check with these agencies before designing and installing a system.

Benefits of Aerobic Septic Systems

Aerobic septic systems offer several benefits over traditional septic systems. They are more efficient at breaking down waste, which results in cleaner effluent. This can be beneficial in areas with strict environmental regulations or sensitive ecosystems. Additionally, aerobic systems can be a good choice for properties with limited space, as they require smaller drain fields than traditional systems.

Considerations for Aerobic Septic Systems

While aerobic septic systems have many benefits, they also have some considerations. They require electricity to operate, which can increase operating costs. They also require more maintenance than traditional systems, including regular pumping and inspection. Furthermore, the installation cost of aerobic systems is typically higher than that of traditional systems.

Case Study: Aerobic Septic System in a Coastal Community

A coastal community in Florida was facing challenges with their traditional septic systems due to the high water table and sandy soil. The community decided to switch to aerobic septic systems. The new systems were able to handle the high water table and sandy soil, and they produced cleaner effluent that was less harmful to the local ecosystem. The community reported a significant reduction in septic system failures and an improvement in water quality.


Aerobic septic systems are an efficient and environmentally friendly alternative to traditional septic systems. Their design involves a pretreatment tank, an aeration chamber, and a clarification chamber. The size of the system is determined by factors such as the number of bedrooms in the house, the soil type, and local regulations. While aerobic systems offer many benefits, they also require electricity and more maintenance than traditional systems. However, as the case study shows, they can be an effective solution in challenging environments.


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