Exam Study Guide - November 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

What term is defined as a measurement of how much acid can be added to water before there is a big change in pH?

A. Conductivity

B. Turbidity

C. Acidity

D. Alkalinity

Answer: D. Alkalinity is discussed in aerobic and anaerobic digestion. Biological treatment works best when the pH is maintained in the 6.5 to 9.0 range and there is enough residual alkalinity to keep it there. Alkalinity is expressed as mg/L as CaCO3. Understanding some chemistry in aerobic and anaerobic digestion and the wastewater process will help in achieving higher certifications. Learn more in the WEF Textbook, Wastewater Fundamentals II – Solids Handling and Support Systems, Chapter 3.


By Drew Hoelscher

Which chemical reaction represents the precipitation of noncarbonate hardness?

A. CaSO4 + Na2CO3    CaCO3  + Na2SO4

B. Ca(HCO3)2 + Ca(OH)2    2CaCO3  + 2H2O

C. Mg(HCO3)2 + Ca(OH)2    CaCO3  + MgCO3 + 2H2O

D. MgCO3 + Ca(OH)2    CaCO3  + Mg(OH)2

Answer: A. Carbonate hardness (temporary hardness) and noncarbonate hardness (permanent hardness) contribute to total hardness. To reduce noncarbonate hardness, calcium hydroxide (lime) and sodium carbonate (soda ash) are introduced to the treatment process. This chemical reaction produces an insoluble calcium carbonate precipitate. Sodium hydroxide (caustic soda) could be used in place of calcium hydroxide and sodium carbonate, but the increase in chemical cost usually limits this practice.

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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