Exam Study Guide - September 2020

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By Rick Lallish

Where can an operator look to find specific laboratory procedures and the proper compliance for those procedures?

A. NPDES permit

B. Wastewater textbooks, such as the Office of Water Programs, California State University, Sacramento textbook: Operation of Wastewater Treatment Plants

C. Plant standard operating procedures

D. Water Environment Federation guidelines and procedures

Answer: A. The actual source for addressing laboratory testing is the facility’s NPDES permit. Parameters are spelled out as to what is monitored and what test must be used. The laboratory testing is governed by standard procedures published by professional organizations and the various state and federal agencies. It is important for operators and lab technicians to understand these guidelines and procedures in order to properly conduct testing needed to monitor plant processes and effluent parameters. More information may be found in the Office of Water Programs, California State University, Sacramento textbook: Operation of Wastewater Treatment Plants, volume one, eighth edition, Chapter 9.


By Drew Hoelscher

At what water temperature would an operator expect the highest dissolved oxygen concentration in mg/L?

A. 50 degrees C

B. 30 degrees C

C. 10 degrees C

D. 0 degrees C

Answer: D. Introducing dissolved oxygen into the water through aeration is common practice when treating groundwater with elevated levels of carbon dioxide, hydrogen sulfide, methane, volatile organic chemicals or iron. The amount of oxygen that can remain dissolved in the water depends on the water temperature. The colder the water, the higher the dissolved oxygen concentration in mg/L. For example, at 0 degrees C, water can hold 14.621 mg/L dissolved oxygen; at 50 degrees C, it can hold only 5.477 mg/L.

About the authors

Rick Lallish is water pollution control program director and Drew Hoelscher is program director of drinking water operations at the Environmental Resources Training Center of Southern Illinois University Edwardsville. 


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