What phenomenon occurs during endogenous respiration in wastewater treatment?

Endogenous respiration is a critical process that occurs in wastewater treatment, especially during the stabilization of biomass when external nutrients and organic materials are limited. During this phase, bacteria shift from growth metabolism to maintenance metabolism, which involves utilizing stored energy reserves for their survival.

When this occurs, some bacteria may begin to break down organic matter, including the cellular components of other bacteria, in a process commonly referred to as cannibalism. This allows them to reclaim carbon and other essential nutrients from their surroundings, sustaining their metabolic functions during periods of starvation or limited resources.

This understanding aligns with the correct answer, as it highlights the survival strategy employed by bacteria to thrive under conditions where resources are scarce, enabling them to utilize available carbon sources effectively. This metabolic switch is essential for maintaining a balanced microbial community within the treatment system, ensuring that waste degradation continues even in less-than-ideal conditions.

Other processes like rapid multiplication of bacteria, nitrogen fixation, or increased dissolved oxygen production usually occur under different conditions—namely, in times when nutrients and organic carbon are abundant or in distinct biochemical scenarios not related to the endogenous respiration phase.