Exam Study Guide: Rotifers in Activated Sludge Systems and Arsenic Regulations

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.

Exam Study Guide: Rotifers in Activated Sludge Systems and Arsenic Regulations

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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 Types of Pumps and Chemical Reactions. This time you can test your knowledge about rotifers in activated sludge systems and arsenic regulations.

Wastewater Treatment Sample Question

Operators and lab personnel look for rotifers in the system as an indicator of how well the activated sludge process is working. What role (if any) does the rotifer actually do in the activated sludge process?

A. Reduce ammonia-nitrogen 
B. Promote endogenous respiration
C. Reduce BOD
D. None, the rotifers are only used as indicators

Water Treatment Sample Question

What is the MCL for arsenic in tap water?

A. 1 ug/L
B. 10 ug/L
C. 10 mg/L
D. 50 ug/L

To see answers for both of the above questions, click this link.

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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