We talk a lot about aerobic bacteria on this website and how much better they are than anaerobic bacteria for resolving septic tank problems. The reason lies in the aerobic bacteria’s faster metabolism and respiration rates.

When talking about these terms, it is helpful to review their classic definitions:

Metabolism: the sum of the physical and chemical processes in an organism by which its material substance is produced, maintained, and destroyed, and by which energy is made available.

Aerobic Respiration: the sum total of the physical and chemical processes in an organism by which oxygen is conveyed to tissues and cells, and the oxidation products, carbon dioxide and water, are given off.

Anaerobic respiration: A form of cellular respiration that occurs when oxygen is absent or scarce.  The process of generating energy by the oxidation of nutrients and using an external electron acceptor other than oxygen.

Both aerobic and anaerobic respiration processes have to have an electron transfer occur in order to have subsequent reactions occur.  This electron transfer occurs because an oxidizer, an atom or ion that is likely or probable to accept an electron, is readily available within the environment.

In aerobic respiration, the oxidizing agent is oxygen, which has one of the highest propensities in nature to accepting an electron. As a result, aerobic respiration processes occur readily and abundantly as long as oxygen is present.

Anaerobic respiration, however, relies on atoms and ions that are less prone to accept an electron. As a result, the respiration chemical reactions are less spontaneous. So, although respiration occurs, it proceeds at a considerably slower rate when compared to aerobic respiration.

Septic tanks normally do not have a steady supply of oxygen available. The tank and the rest of the septic system are buried underground, sealed off from the atmosphere. Anaerobic bacteria and its weak oxidizing agents dominate the environment.

Consequently, the amount of nutrient breakdown occurring within the septic tank is predictably low. High percentages of nutrients are not broken down within the time that they are in the septic tank and are exported into the drainfield where they become part of the biomat, the most commonly occurring septic tank problem people face.

Once oxygen is carefully introduced and controlled in the septic tank,however, aerobic bacteria are able to generate much higher rates of nutrient consumption when compared to anaerobic bacteria. This means that the wastewater leaving the septic tank contains far less organic material, which results in less organic material contributing to the growth of the biomat.

Aerobic bacteria and residual dissolved oxygen are also exported from the septic tank into the drainfield. The aerobic bacteria will thrive in this environment until their chief food source, the biomat, is completely consumed and the septic tank problem is resolved.