Exam Study Guide: Proper Grit Disposal; and Disinfection Profile Development

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 Organic Loading Rates; and Ion Exchange Softener Math. This time, you can test your knowledge about proper grit disposal, and disinfection profile development.

Wastewater Treatment Sample Question

What is the proper means of disposal of grit or detritus?

A.  Must be disposed of by whatever means delineated on your “503” sludge permit
B. Mixed with digester sludge and disposed of by any means
C. Burial in sanitary landfill or other type of landfill operation
D. No recommended method, maybe disposed of by any means

Answer: The answer to this question is C. Final grit disposal is by burial. It may be in either a sanitary landfill or other accepted landfill operation. The grit must be have a minimum of 6 inches (15 cm) of soil covering. This is to prevent vector attraction and odors. Grit or detritus are not covered in the 40 CFR 503 regulations for biosolid disposal. If in doubt, contact local regulatory agencies for further information on permits or approvals. Understanding procedures for disposing grit are important facts the operator must understand in his day-to-day operations.

Water Treatment Sample Question

Developing a disinfection profile for the reduction of Giardia lamblia requires the operator to know:

A. The dimensions of the basin(s) in each disinfection segment, baffling factor, water pH, peak hourly flow rate, water temperature and chlorine residual.
B. The dimensions of the basin(s) in each disinfection segment, peak hourly flow rate, water temperature and chlorine residual.
C. The dimensions of the basin(s) in each disinfection segment, water pH,  water temperature and chlorine residual.
D. T
he dimensions of the basin(s) in each disinfection segment, baffling factor, peak hourly flow rate and chlorine residual.

Answer: The correct answer is A. Disinfection profiles are developed to ensure log inactivation requirements are achieved. Calculating log inactivation credits requires the operator to know the disinfectant residual concentration and the time the concentration is in contact with the water. Once the CTCALC is established, an operator utilizes the log reduction tables created by U.S. EPA to determine the inactivation credit for Giardia lamblia. A technical guidance manual is accessible by visiting https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=20002649.txt.


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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