Aerobic vs. Anaerobic: How a Septic System Works

Anyone that builds a home outside city limits quickly learns that city services are limited once you cross into the country. County services often don’t include water or septic facilities, so smart homeowners use the old methods of building wells and creating septic tanks. You can choose from an aerobic and anaerobic septic system for your home. Each breaks the waste down, and both do it slowly in an underground tank. Here is how it all works.


The aerobic uses oxygen to break down the tank’s waste and an “aerator” that pumps oxygen from the outside into the tank. The oxygen speeds the bacterial consumption up, but it once was too cost-prohibitive for most home systems. With improvements to the design and aerators, homeowners that want sustainable houses and environmentally friendly constructions are turning to this system.


The anaerobic septic system works with a drainage field that surrounds the tank. While it doesn’t use oxygen, some structures do rely on an added chemical to help the tank’s contents keep from backing up and overflowing. The bacteria colonies must remain within a noted beneficial range and common household chemicals can destroy their helpful nature. To keep bacteria flourishing, the industry has developed special chemicals that can be added to the system once or twice a year, depending on household size.


The anaerobic septic system creates methane gas as the bacteria works to break down human waste. The tank can discharge a disgusting and foul odor with other natural smells associated with that waste. The aerobic tank has a more earthy smell that people say reminds them of the outdoors after a rainstorm. Some aerobic system owners do add cleaners to their tanks to maintain the number of beneficial enzymes and bacteria.

There are positive and negative aspects to both septic systems. So, if you are building a home outside city limits, check with your contractor about which style of septic tank is best for your area.