Tennessee Wastewater Operator Practice Exam

What happens to a sludge sample if it is not analyzed within 10 minutes of collection?

1. It remains unchanged

2. pH may increase

3. Volatile solids will decrease

4. It's no longer usable

The correct answer is: pH may increase

Analyzing a sludge sample promptly after collection is crucial for ensuring accurate results. If a sludge sample is not analyzed within 10 minutes, certain properties, such as pH, can be affected. Specifically, biological activity within the sludge may continue after collection, leading to changes in composition. The microorganisms present can produce metabolic byproducts that may cause the pH of the sample to increase over time, as these organisms metabolize available nutrients and alter the sludge's chemical environment. In terms of the other options, the sludge sample will not typically remain unchanged due to ongoing biological processes. While volatile solids are a measure of the organic matter that can be lost upon heating, if the analysis is delayed, they could either stay the same or change, not necessarily decreasing. Lastly, while a sample that is not analyzed might become less reliable over time, the statement suggesting it becomes entirely unusable is not wholly accurate—though it may not provide the information needed for effective analysis, it does not mean it can no longer be utilized at all.