What does anaerobic mean in terms of molecular oxygen and other compounds?

Anaerobic refers to a condition in which molecular oxygen is not present. In the context of wastewater treatment, anaerobic processes are characterized by the absence of oxygen, as well as the absence of other electron acceptors such as nitrate or nitrite. This environment promotes the growth of anaerobic bacteria that can utilize other compounds for metabolic processes.

The correct choice highlights the absence of both molecular oxygen and nitrate or nitrite, emphasizing the exclusive nature of anaerobic environments. In these settings, organisms rely on fermentation or other anaerobic respiration pathways, allowing them to survive and thrive without oxygen. This is a critical aspect of anaerobic digestion, which is important for treating wastewater and reducing organic matter.