If foam in your aeration basin has become white and billowy, what adjustment should be made?

When foam in the aeration basin becomes white and billowy, it typically indicates an issue with the process, often related to the microbial community or the amount of activated sludge in the system. In this situation, decreasing the Waste Activated Sludge (WAS) is the appropriate adjustment to make.

Reducing the quantity of WAS allows for a better balance in the aeration system. An excess of activated sludge can lead to overpopulation of certain microorganisms, which may produce excess foam. By decreasing the WAS, you help control the biomass concentration, which can stabilize the treatment process and reduce the occurrence of this type of foam formation.

The other options, such as increasing the Aeration Liquor Ratio (ALR) or increasing WAS, may further exacerbate the issue by adding more microorganisms or nutrients that contribute to foam. Similarly, reducing the flow rate alone does not address the root cause of the foaming and may impact overall treatment efficiency. Thus, the most effective adjustment in this scenario is to decrease the WAS to regain control over the microbial balance and foam formation.