What is a characteristic of anaerobic bacteria in a septic system?

Anaerobic bacteria are a key component of septic systems because they play a vital role in the decomposition of organic matter in environments devoid of oxygen. One of the primary characteristics of these bacteria is their ability to produce methane gas as a byproduct of their metabolic processes, particularly during the breakdown of organic material. This methane is a significant component of biogas, which can be harnessed for energy in some systems.

Anaerobic bacteria thrive in environments where activities occur without free oxygen, such as the lower regions of a septic tank. Their efficiency in utilizing organic matter under these conditions leads to the generation of soluble nutrients and gases, including methane. This process is essential for maintaining the health of the septic system and ensuring proper treatment of wastewater.

The other choices relate to conditions or requirements not typical for anaerobic bacteria. For example, anaerobic bacteria do not require sunlight and can function in completely dark environments, and while they may tolerate a range of pH levels, they do not necessarily prefer acidic conditions. They are also known to thrive in water-saturated environments, but the production of methane gas specifically highlights their metabolic activity and is a defining characteristic of their function within a septic system.