Exam Study Guide: Activated Sludge Conditions; and Well Screens

Maintaining your education is important, especially in a career that demands licensing exams. Prove you’re an expert operator by answering these questions and others from our Exam Study Guide Series.

Welcome back to TPO magazine's Exam Study Guide Series, which offers a pair of water/wastewater study questions with in-depth explanations of the answers. Last time, we covered a set of wastewater and drinking water treatment questions on the topics of RBC Troubleshooting; and Noncarbonate Hardness. This time, you can test your knowledge about Activated Sludge Conditions, and Well Screens.

Wastewater Treatment Sample Question

What condition occurs when the sludge age advances and there is less food available per bacteria?

A. Flocculation
B. Nocardia filaments 
C. Excessive white foam
D. Endogenous respiration 

Answer: The answer to this question is D. A portion of the bacteria can be lost due to endogenous respiration at high sludge ages. This is due to the lack of food available or an unbalanced F/M ratio. The bacteria will consume their own cell mass and exopolymer to survive. This will also provide food for the other bacteria as well. Understanding the natural cycle of life and conditions in an activated sludge treatment process allows the operator knowledge for troubleshooting his/her treatment facility.

Water Treatment Sample Question

A well with an encrusted screen:

A. Can cause the specific capacity in gpm/ft of drawdown to decrease.
B. Can cause the specific capacity in gpm/ft of drawdown to increase.
C. Can cause the drawdown to decrease.
D. Can cause the static level to increase. 

Answer: The correct answer is A. Over time, well screens become plugged due to dissolved minerals in the water coming out of solution and collecting on the well screen openings. Calcium and magnesium carbonate will precipitate out of the water rather easily under high velocity and low-pressure conditions. 

This is one reason well drillers/engineers design a well to limit the velocity of the water entering the well to 0.1 feet per second or less. As the screen plugs, water is restricted from entering the well, which increases the drawdown and ultimately decreases the gallon per minute per foot of drawdown (specific capacity).


About the authors: Rick Lallish is the Water Pollution Control program director at the Environmental Resources Training Center (ERTC) of Southern Illinois University Edwardsville. He provides training for entry-level operators in the wastewater field and operators throughout the state looking to further their education. Lallish was also named the 2017 Illinois Operator of the Year and 2018 president of the Illinois Association of Water Pollution Control Operators.

Drew Hoelscher is the program director of drinking water operations at the Environmental Resources Training Center in Edwardsville, Illinois.



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