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 Odor Control and Repeat Sampling for Bacteria Contamination. This time you can test your knowledge about ORP readings and basin perimeter calculations.

Wastewater Treatment Sample Question

Oxidation-reduction probes read changes in potential when dissolved oxygen is present and not present. ORP readings of -200 mV typically indicate what condition?

A. Anoxic conditions 
B. Aerobic conditions
C. Anaerobic conditions
D. Fouled probe tip/sensor

Water Treatment Sample Question

An operator needs to order safety railing for a large rectangular basin. The rectangular basin has a perimeter of 750 feet and the length is two times the width. What is the length and width of the basin?

A. Length 400 feet, width 350 feet
B. Length 350 feet, width 400 feet
C. Length 375 feet, width 375 feet
D. Length 250 feet, width 125 feet

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

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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.