What phase of bacterial growth occurs during extended aeration wastewater treatment?

During extended aeration wastewater treatment, the endogenous phase of bacterial growth is prevalent. This phase occurs after the bacteria have utilized the readily available nutrients in the wastewater and are now in a state where they begin to utilize their own resources for energy. In the endogenous phase, bacteria experience a decline in growth or a steady state, as they are no longer multiplying significantly due to the depletion of nutrients. Instead, they focus on metabolizing their own cellular materials for survival.

The extended aeration process itself is designed to allow for longer retention times, providing conditions that favor the endogenous phase where microorganisms work efficiently to break down organic matter over an extended period. This leads to improved wastewater treatment outcomes, as the bacteria can more effectively reduce biological oxygen demand (BOD) and other contaminants.

In contrast, during the lag phase, bacteria are acclimating to the new environment and not actively dividing. The log phase is characterized by rapid growth when nutrients are abundant, and the stationary phase occurs when the nutrients are depleted and growth stabilizes. Each of these phases functions at different stages in the overall growth cycle of bacteria, with the endogenous phase being unique to extended aeration processes.