Exam Study Guide - September 2021

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Licensing exams can be challenging. Our Exam Study Guide helps you prepare by presenting questions similar to those on an actual exam. You can find many more sample questions on the TPO website at  www.tpomag.com/study.


By Rick Lallish

When selecting a polymer for dewatering on a belt-filter press, what performance requirement should you conduct before making a choice?

A. Time to filter test

B. pH and acidity analysis

C. Jar test

D. Emulsion standards analysis

Answer: C. Selecting the proper polymer for dewatering is very important. Polymers matched to your plant’s sludge characteristics can make a huge difference. Too much conditioning can be costly and fail to meet your needs, and too little can result in ineffective dewatering and possible excess costs in handling and land application. Jar tests are effective means of testing different types or concentrations of polymers at the same time. Learn more in the WEF textbook, Wastewater Fundamentals II ­— Solids Handling and Support Systems, Chapter 1.


By Drew Hoelscher

The backwash rate for a granular activated carbon filter should be sufficient to achieve a bed expansion of about what percent?

A. 15

B. 30

C. 50

D. 75

Answer: C. It is essential to follow proper backwashing procedures to ensure adequate filtration and adsorption. If the media is not properly cleaned, the effectiveness of both filtration and adsorption is lost, and mudballs may develop. Polymers fed as filter aids may also contribute to mudballs if the media is not expanded to about 50% during a backwash. It is also important to note that the density of granular activated carbon is less than that of other filter media, so it can be easily washed out if the backwash rate is excessive.

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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