Tennessee Wastewater Operator Practice Exam

Which characteristic of influent can significantly influence the biological treatment process?

1. Temperature fluctuations

2. Presence of heavy metals

3. Levels of fat, oil, and grease (FOG)

4. Pesticide residues

The correct answer is: Levels of fat, oil, and grease (FOG)

The characteristic of influent that can significantly influence the biological treatment process is the levels of fat, oil, and grease (FOG). In the context of wastewater treatment, biological processes typically rely on microorganisms to break down organic matter. High concentrations of FOG can create several challenges for these microbial communities. When FOG is present, it can form persistent layers on the surface of liquid in treatment tanks, limiting oxygen transfer and interfering with the overall biological processes. Additionally, FOG can lead to the formation of scum, which impacts the efficiency of treatment systems by hindering contact between microorganisms and substrates. This makes it difficult for the microbes to degrade organic materials effectively, potentially leading to suboptimal treatment performance and compliance issues with discharge standards. Addressing high FOG levels is essential because they can overwhelm treatment processes designed for soluble organic compounds, which can hinder the growth and activity of beneficial microorganisms critical for effective biological treatment. Implementing pre-treatment measures or employing processes specifically designed to handle FOG is often necessary to maintain a healthy, functioning biological system in wastewater treatment plants.