Tennessee Wastewater Operator Practice Exam

What role do polyphosphate accumulating organisms play in wastewater treatment?

1. They inhibit bacterial growth

2. They accumulate excess nutrients

3. They are responsible for nitrogen removal

4. They convert organic matter into sludge

The correct answer is: They accumulate excess nutrients

Polyphosphate accumulating organisms (PAOs) play a crucial role in wastewater treatment by accumulating excess nutrients, specifically phosphorus. In biological wastewater treatment processes, these organisms are part of a process known as enhanced biological phosphorus removal (EBPR). During specific phases of the treatment cycle, PAOs uptake and store phosphorus in the form of polyphosphate, which allows for the efficient removal of phosphorus from the wastewater. The presence of PAOs contributes to the overall balance of nutrients in the treatment system, helping to mitigate the risks associated with nutrient loading in receiving waters, such as algal blooms and eutrophication. Their ability to accumulate phosphorus is essential for achieving regulatory compliance regarding nutrient discharges and maintaining ecological health in surface waters. In contrast, the other options do not accurately describe the primary function of PAOs. They do not inhibit bacterial growth, as they are themselves a type of bacteria; while they may indirectly affect nitrogen levels through processes associated with other organisms, they are not directly responsible for nitrogen removal; nor do they convert organic matter into sludge; that function is primarily carried out by other types of microorganisms in the treatment process.