Texas Wastewater Class B Practice Exam

What condition might an operator suspect if they observe white thick billowing sudsy foam on the aeration tank in an activated sludge system?

1. Overloaded aeration tank and or excessive sludge wasting

2. Insufficient aeration and mixing

3. Low organic loading in the tank

4. Clogged sedimentation tanks

The correct answer is: Overloaded aeration tank and or excessive sludge wasting

Observing white thick billowing sudsy foam in an aeration tank of an activated sludge system often indicates issues related to the quality of the aeration process. When an aeration tank is overloaded or there is excessive sludge wasting, the biological processes become disrupted. This can lead to a lathering effect due to the presence of surfactants produced by certain types of bacteria. In this scenario, the foam can be a result of activated sludge floc that has been destabilized, which is common when the biomass concentration exceeds the system's capacity to maintain aeration and mixing effectively. High levels of organic matter and nutrients can also condition the foaming, leading to operational challenges. Other options like insufficient aeration and mixing can relate to a different foam type or issues with general treatment performance, but are not specifically indicative of the thick sudsy foam formation seen with overloaded systems. Low organic loading would not typically result in such foam either, as the biological activity would be lower, while congested sedimentation tanks focus on the downstream processes rather than the conditions present in the aeration tank itself.