Exam Study Guide: Pump Hydraulics; and Calculating Non-Carbonate Hardness

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 Changing Chlorine Cylinders; and Calculating Chemical Feed. This time, you can test your knowledge about pump hydraulics and calculating noncarbonate hardness.

Wastewater Treatment Sample Question

In pump hydraulics, what condition is a measurement of the physical vertical distance between the surfaces of two fluids, but not related to how far the fluids are apart horizontally?

A. Specific gravity
B. Lift
C. Static head
D. Dynamic head

Answer: The answer to the question is C. Static head is the physical vertical distance between the surfaces of two fluids no matter the physical distance apart horizontally. Dynamic head is the theoretical distance rather than the physical distance. Both conditions are measured in feet-of-head. Understanding pump hydraulics and definitions are fundamentally important for proper plant operations.

Water Treatment Sample Question

The raw water to be treated has a total alkalinity of 275 mg/L as CaCO3 and a total hardness of 375 mg/L as CaCO3. What is the concentration of noncarbonate hardness?

A. 100 mg/L
B. 187.5 mg/L
C. 275 mg/L
D. 375 mg/L

Answer: The correct answer is A. When total hardness and total alkalinity are known, comparing the two informs an operator on the concentrations of hardness related to calcium and/or magnesium linked with bicarbonate and carbonate (CH) and hardness related to calcium and/or magnesium linked with chloride and sulfate (NCH). The table below illustrates the amount of NCH is equal to the difference between the total hardness and the total alkalinity.

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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