Exam Study Guide: Activated Sludge Troubleshooting

Exam Study Guide: Activated Sludge Troubleshooting
Foaming and light brown color in the activated sludge process indicate that you have a “young” sludge and it’s probably overloaded with flagellates.

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When operators are faced with licensing exams, they sometimes struggle with test anxiety because they don’t fully understand how to properly study and prepare for exam questions. Here we take a look at a sample wastewater treatment licensing exam question, how to solve the problem, and the correct answer. 

Sample Question:

While monitoring the activated sludge process on your shift, you notice that a lot foaming is developing on top of the aeration basins — every basin is affected.

You also notice that the color of the activated sludge contents has changed to a light brown. 

Clearly something is wrong. What should you do to correct the problem?

a. Collect a sample and analyze it with a microscope
b. Reduce the recirculation rate
c. Reduce the airflow
d. Add seeding chemicals 

Conditions are continually changing in the activated sludge process because natural flow dynamics change often. With an activated sludge process, simple procedures are rarely established to correct problems because so many different factors can create the same problems. With this particular situation, the foaming and light brown color would indicate that you have a “young” sludge and it’s probably overloaded with flagellates. 

However, just because this situation would lead an experienced operator to assume these conditions doesn’t mean it is the correct assessment. Hydraulic overloading will cause the same affect but both conditions require two different corrective actions. 

As with any science-based operation, having correct and accurate information is critical when making troubleshooting repairs or adjustments. Never assume from previous operations that the remedy will be same. Always, always, always study your situation and the conditions at the time of the problem. With this situation, take a few minutes and confirm the condition. 

Therefore, the correct answer is a) Collect a sample and analyze it with a microscope.

If it is confirmed that you have a young sludge and a high population of flagellates, you will need to increase both the incoming airflow maintaining a DO concentration of 0.5 to 1.0 mg/L and the return rate from the secondary clarifier to add some age to the activated sludge system. Hosing the foam with cold water will keep it under control until the advanced microorganisms can populate the system and increase your sludge age. 

About the Author

Mike Smith is program coordinator and lead faculty of the Water Quality Management program at Red Rocks Community College in Lakewood, Colo.

He has been in charge of the multi-faceted training program since 1996.


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