Tennessee Wastewater Operator Practice Exam

Approximately how long does it take for PAO to complete the uptake of Volatile Fatty Acids (FVAs) in an anaerobic zone?

1. 5-15 minutes

2. 15-45 minutes

3. 30-60 minutes

4. 1-2 hours

The correct answer is: 15-45 minutes

Polyphosphate-accumulating organisms (PAOs) play a crucial role in the biological treatment of wastewater through a process called enhanced biological phosphorus removal (EBPR). During this process, these organisms preferentially uptake volatile fatty acids (VFAs), which are short-chain organic acids produced during the anaerobic degradation of organic matter. The timeframe for PAOs to complete the uptake of volatile fatty acids in an anaerobic zone is typically around 15-45 minutes. This duration is significant because it reflects the metabolic processes of the PAOs, which thrive in environments rich in VFAs. The uptake phase is essential for their growth and phosphorus accumulation, making the efficiency and timing of this uptake critical for effective wastewater treatment. Understanding this timeframe is important for operators managing anaerobic zones in wastewater treatment plants. If the contact time with VFAs is too short, PAOs may not assimilate enough carbon, potentially compromising the subsequent biological phosphorus removal processes. This highlights the necessary balance between retention time, VFA concentration, and the overall efficiency of the wastewater treatment operation.