What outcome is expected when low dissolved oxygen conditions are paired with high organic loading?

When low dissolved oxygen conditions are paired with high organic loading, an increase in filamentous organisms is expected. This outcome occurs because the lack of oxygen creates an anaerobic environment that is less favorable for typical aerobic bacteria, which would normally thrive under higher dissolved oxygen conditions. Instead, some filamentous organisms, particularly certain types of bacteria that can thrive in low-oxygen environments, tend to dominate.

In these conditions, filamentous bacteria can proliferate due to their ability to utilize organic matter in the absence of sufficient oxygen. These organisms can form mats or clumps, which can sometimes lead to operational issues in wastewater treatment, such as increased scum formation or poor settling in sedimentation processes.

While other outcomes might also be anticipated under different circumstances, the growth of filamentous organisms is a direct consequence of the combination of low dissolved oxygen and high organic loading, making it the most pertinent outcome in this scenario.