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 Calculation and Soil Types. This time you can test your knowledge about types of wastewater treatment processes and gravity filters.

Wastewater Treatment Sample Question

Aeration reactors using buoyant free-floating biofilm carriers in an activated sludge process are known as what sort of treatment?

A. Rotating Biological Contactors 
B. Moving Bed Biological Reactors
C. Trickling Filters
D. Sequencing Batch Reactors

Water Treatment Sample Question

A facility has a 500,000-gallon backwash holding tank and 10 gravity filters. The gravity filters are 20 feet wide and 30 feet long. How many filter(s) can be backwashed before refilling the tank, if the backwash rate is 20 gpm/ft2 for 15 minutes? 

A. One filter
B. Two filters
C. Three filters
D. Four filters

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.