Secondary Clarification Practice Questions for Level 4 · Expert

1. Question 1

   Filamentous bulking increases after internal recycle is moved ahead of the selector. Selector DO rises, readily biodegradable carbon is unchanged, and total aeration capacity is adequate. Which trial best tests the suspected cause?

   1. Raise final-zone DO for one week
   2. Increase RAS concentration by settling
   3. Move the recycle past the selector
   4. Reduce wasting until the blanket falls
   Show the answer

   Answer: C. Move the recycle past the selector

2. Question 2

   A cold-weather ammonia increase begins after one train loses biomass during maintenance. The other train has complete nitrification and spare aeration, but its clarifier is near the plant's blanket limit. What is the best recovery plan?

   1. Send all influent to the stable train
   2. Stop wasting from both trains
   3. Raise airflow in the damaged train only
   4. Seed the train within loading limits
   Show the answer

   Answer: D. Seed the train within loading limits

3. Question 3

   Settling worsened after a second selector cell was placed in service and influent and RAS were split equally between the cells. Selector F/M fell by half, low-F/M filaments increased, and aeration-basin DO, SRT, and total active volume stayed within target. One cell can carry the full selector flow within its mixing limit. Which trial best tests the suspected cause?

   1. Increase RAS flow through both selector cells
   2. Raise DO in both aeration basins
   3. Reduce WAS to increase the total SRT
   4. Route all selector flow through one cell
   Show the answer

   Answer: D. Route all selector flow through one cell

Operator Master has 3 Level 4 · Expert secondary clarification questions, free.

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