A low solids content in the aeration basin is typically indicated by the presence of ___________?

A low solids content in the aeration basin is typically indicated by the presence of a white, fluffy foam. This type of foam arises when the biological activity in the aeration basin is low, which can lead to a decrease in the concentration of solids. The appearance of white, fluffy foam often suggests that there is an abundance of microorganisms reacting to the available organic material, but not enough solids to support the formation of denser foams typically seen in systems with higher solids content.

In contrast, brown, leathery foam generally indicates a more stable microbial environment where solids are more prevalent. A black color with a rotten egg odor is indicative of anaerobic conditions, suggesting that there may be excessive organic matter breaking down in a low-oxygen environment rather than a low solids condition. Floating sludge usually points to issues with solids settling properties, which can occur in systems with high solids rather than low solids. Therefore, the presence of white, fluffy foam aligns most closely with the characteristics of a low solids content in the aeration basin.