Which of the following is NOT one of the causes of white billowing foam?

White billowing foam in wastewater treatment processes can be influenced by several factors, and understanding these causes is important for effective management of foam occurrences.

The correct choice is that a lack of nutrients is not typically identified as a cause of white billowing foam. Foam typically forms when there is a combination of surfactants and microbubbles that stabilize the aerobic conditions in treatment systems. While nutrient levels are crucial for microbial health and activity, a lack of nutrients generally leads to reduced microbial growth and activity, which would not promote the formation of foam. Instead, foam is more likely to occur during specific operational conditions where microbes proliferate, leading to an abundance of extracellular polymeric substances (EPS), which trap air and create foam.

In contrast, plant start-up can lead to foam because during this phase, the system may not yet have reached equilibrium, allowing for fluctuating microbial populations and resultant foam formation. Improper return can exacerbate foam issues by disrupting the recirculation of activated sludge, potentially allowing for conditions that lead to foam generation. Hydraulic washout, resulting from high flow conditions, can wash out settled solids and create a scenario for bubble formation and foam.

Understanding these dynamics helps in addressing and managing foam in wastewater treatment facilities effectively.