What condition must be met for wastewater to be categorized as septic?

For wastewater to be categorized as septic, the condition of complete depletion of oxygen is the key factor. In a septic environment, the absence of oxygen leads to anaerobic conditions where bacteria that thrive without oxygen, known as anaerobes, dominate. These bacteria break down organic matter in the absence of oxygen, resulting in the production of gases such as methane and hydrogen sulfide, which characterize septic conditions.

While the presence of high levels of bacteria and excessive nutrients can contribute to the overall quality and treatment processes of wastewater, they do not solely define septic conditions. High temperatures may affect the rates of microbial activity or chemical reactions but are not prerequisites for wastewater to be considered septic. Thus, the defining feature is the complete lack of oxygen, which is crucial for creating the anaerobic environment associated with septic wastewater.