Exam Study Guide: Duckweed Control and Hydroxide Alkalinity Calculations

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: Duckweed Control and Hydroxide Alkalinity Calculations

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 Diffusers and Motor Bearing Damage Prevention. This time you can test your knowledge about duckweed control and hydroxide alkalinity calculations.

Wastewater Treatment Sample Question

Duckweed can be a nuisance and cause problems in facultative lagoons. What is the recommended method of controlling excessive duckweed outbreaks?

A. Applying large amounts of HY-var to the influent flow
B. Adding live daphnia to the lagoon 
C. Physical removal
D. Allow the duckweed to flourish, as it will assist the algae with dissolved oxygen 

Water Treatment Sample Question

Approximately how much hydroxide alkalinity is present if the lab results indicate a total alkalinity (T) of 160 mg/L as calcium carbonate and a phenolphthalein alkalinity (P) of 90 mg/L as calcium carbonate?

A. 20 mg/L as calcium carbonate
B. 70 mg/L as calcium carbonate
C. 90 mg/L as calcium carbonate
D. 250 mg/L as calcium carbonate

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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