Aerobic vs. anaerobic septic systems


Septic SystemOne of the basic utilities you have to think about when you’re building on acreage is sewage. You’ll be choosing between either an anaerobic or aerobic septic system. Let’s take a look at how both of these systems work, and then I’ll give you some advantages, disadvantages and circumstances to consider.

Anaerobic septic system

Anaerobic septic systems involve the use of bacteria that don’t require oxygen to live. In an anaerobic system, you’ve got a septic tank with two main pipes. One of these goes to the house, and the other heads out into your yard. That main pipe splits into several pipes that sit just below the surface of your lawn.

Inside the septic tank, solid waste settles and is eaten by the anaerobic bacteria. Liquid waste floats to the top. Wastewater from the tank moves out to the smaller pipes under the surface, which have holes at their ends. The wastewater then filters or “percolates” out into the soil.

Aerobic septic system

The aerobic septic system involves three tanks. Waste enters the first tank and settles into layers like the anaerobic system. But when it moves to the next tank, the treatment tank, an aerator moves oxygen bubbles through the waste. This allows aerobic bacteria to consume the waste. From there, wastewater moves to a pump tank where it’s treated once more.

Then, often in the middle of the night, sprinkler heads pop up and distribute that wastewater out onto your lawn.

Comparing aerobic and anaerobic systems

The first obvious difference is cost. Typically, installing an anaerobic system is simpler and therefore less costly. Aerobic septic systems involve a more complicated system with added machinery, and are more expensive.

There are certain situations in which you might actually require an aerobic system based on your land. First, for an anaerobic system to work the soil must be able to allow for percolation. When you’re deciding on a septic system, a company will come out and do a percolation test to see how quickly water is absorbed into the soil. Depending on the land, an aerobic septic system may be more efficient.

Another case in which you’d need an aerobic septic system is if your land is very flat. Anaerobic systems require at least a gentle slope to make sure that wastewater can move out into the septic field.

Outside of these situations, you’ll most commonly see homes built with conventional anaerobic septic systems. These systems are cost effective and simple, and are used successfully in many country homes.

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