California Wastewater Treatment Operator Practice Exam

Which of the following could cause foaming in an anaerobic digester?

1. high dissolved oxygen levels

2. low organic content

3. organic overload

4. excessive alkalinity

The correct answer is: organic overload

Excessive alkalinity, or excess alkaline substances, can actually help to reduce foaming in an anaerobic digester. This is due to the buffering capacity of these substances, which can help balance the pH and prevent the formation of foam. High dissolved oxygen levels can also contribute to foaming, as it can disrupt the balance of microorganisms in the digester. Low organic content, on the other hand, would not provide enough material for the microorganisms to break down, resulting in a lack of foam. Furthermore, organic overload, while often a cause of foaming, is not the only factor that can contribute to it. Overall, the most likely cause of foaming in an anaerobic digester is organic overload, making C the correct answer.