When active sludge in an aeration tank has abundant food supply, it typically has:

When activated sludge in an aeration tank has an abundant food supply, it typically exhibits high oxygen uptake and a slow settling rate.

The high oxygen uptake is a direct result of the microorganisms present in the activated sludge consuming the available organic matter as food, which leads to enhanced respiration and thus a higher demand for oxygen. This is an important indicator of the biological activity occurring within the aeration tank.

On the other hand, the slow settling rate occurs because when the microorganisms thrive due to ample food, they tend to grow in large flocs that can become less compact and denser. As a result, these flocs may not settle quickly under sedimentation conditions compared to well-settling sludges. Effective settling is crucial for the overall efficiency of the wastewater treatment process, as it allows for better separation and removal of solids from the treated water.

This combination of high oxygen demand and slow settling illustrates the complexities of the activated sludge process, where microbial activity is heavily influenced by the availability of nutrients.