Exam Study Guide: Anaerobic Digester Classifications and Water Hardness 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: Anaerobic Digester Classifications and Water Hardness 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 Solids Retention Time and Total Trihalomethanes. This time you can test your knowledge about anaerobic digester classifications and water hardness calculations.

Wastewater Treatment Sample Question

Which classification of anaerobic digester is the most efficient at pathogen reduction, increased volatile solids reduction and decreased detention times?

A. Heterophilic 
B. Mesophilic
C. Thermophilic

Water Treatment Sample Question

Using the data below, what is the approximate magnesium concentration in mg/L?

Total hardness = 470 mg/L as CaCO3

Calcium = 136 mg/L

Elements and atomic weights: Ca, 40.078; Mg, 24.304; C, 12.0096; O, 15.999

A. 3
B. 32
C. 147
D. 334

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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