Tennessee Wastewater Operator Practice Exam

What do phosphorous accumulating organisms use volatile fatty acids (VFAs) for in the anaerobic zone?

1. To generate energy

2. To convert internal storage products

3. To produce oxygen

4. To enhance microbial activity

The correct answer is: To convert internal storage products

Phosphorus accumulating organisms (PAOs) utilize volatile fatty acids (VFAs) primarily for the purpose of converting internal storage products. During the anaerobic phase of wastewater treatment, PAOs uptake VFAs, which serve as an energy source and a carbon source for enhancing their metabolism. The process involves the breakdown of stored polyphosphate as PAOs convert it into energy and subsequently utilize that energy to ferment the VFAs. This action allows them to store energy in the form of poly-β-hydroxybutyrate (PHB) and internal polyphosphate reserves. This conversion process is crucial for the nutrient removal capabilities of PAOs during the subsequent aerobic phase, where they can then take up phosphates from the wastewater. The other options, while related to microbial processes, do not accurately describe the primary role of VFAs in the anaerobic zone concerning PAOs. Generating energy is a general function but doesn't specifically address the transformation of internal storage, producing oxygen is not applicable in an anaerobic zone, and while enhancing microbial activity is beneficial, it doesn’t pinpoint the mechanism by which PAOs utilize VFAs directly.