Tennessee Wastewater Operator Practice Exam

After a major process change in an activated sludge system, how long should it be monitored for stabilization?

1. At least 1 day

2. At least 1 week

3. At least 2-3 weeks

4. At least 1 month

The correct answer is: At least 1 week

After a major process change in an activated sludge system, monitoring for stabilization should typically span at least one week. This duration allows for the assessment of how the biological treatment process adjusts to the new conditions introduced by the change. During this period, key performance indicators such as biochemical oxygen demand (BOD), chemical oxygen demand (COD), mixed liquor suspended solids (MLSS), and effluent quality can be observed to ensure that the system is recovering and functioning effectively. Stabilization is crucial because it helps to confirm that the microorganisms within the activated sludge are adapting to any new operational parameters or influent characteristics. Shorter monitoring periods, such as one day, may not provide a comprehensive view of system responses to changes, as the biological community needs time to adjust. Monitoring for two to three weeks or one month might be excessively cautious given that many systems generally stabilize within a week after changes, depending on the nature of the adjustments made. Therefore, a one-week monitoring period strikes a balance that is often sufficient to gauge stabilization effectively.