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 last time on the topics of Lagoon System Configuration; and Drinking Water Tests. This time, you can test your knowledge about TF/AS combination treatment and acid dilution preparation.

Wastewater Treatment Sample Question:

What is a benefit of using the trickling filter/activated sludge (TF/AS) combination treatment process?

Related: Case Study: Wastewater Treatment Systems

A) Less land space is required.

B) The trickling filter portion will never experience ponding or filter flies.

C) Nitrification is more effective in the activated sludge zone.

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D) Intermediate clarification is not necessary.

Answer: The answer is C, nitrification is more effective in the activated sludge zone. There are several combination systems available that use both the trickling filter and activated sludge processes. These include trickling filter/solids contact (TF/SC); roughing filter/activated sludge (RF/AS); biofilter/activated sludge (BF/AS); and trickling filter/activated sludge (TF/AS).

Out of all these systems that use trickling filters to pre-treat primary effluent wastewater prior to an activated sludge system, the TF/AS process incorporates an intermediate clarifier before the activated sludge process to settle out the trickling filter sloughings. Only the supernate from the intermediate clarifier flows to the downstream activated sludge process, which greatly reduces both the influent settleable and suspended solids loading, but also the soluble carbonaceous biochemical oxygen demand (sCBOD) loading. This reduced organic load to the AS process enhances nitrification and the production of a healthy nitrifying biomass within. With less overall organic loading to the AS process, the aeration capacity can be reduced, saving energy, equipment and treatment costs. If not properly operated, the trickling filter portion of any of these processes can experience ponding, filter flies, odors and poor treatment performance. 

Related: Exam Study Guide: Sludge Bulking

Water Treatment Sample Question: 

To prevent splashing acid on yourself or the surrounding area when preparing dilutions of acid in a laboratory, the following safety rule of thumb should be followed:

A) Always pour the dilution water into the concentrated acid solution.

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B) Rapidly add the entire amount of required acid to a small amount of heated dilution water, then top off with cold water.

C) Add equal amounts of the dilution water and concentrated acid in a separate container simultaneously.

D) Always pour the acid slowly into the dilution water.

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Answer: The answer is D, always pour the acid slowly into the dilution water. To avoid harm to yourself and others working in the lab, always add acid into the dilution water. If water is added into a concentrated acid solution, a violent reaction can take place, causing the water and acid to splatter and splash out of the container. When working around lab chemicals, or any chemicals, always wear proper personal protective equipment. This includes acid proof aprons, chemical resistant gloves, eye and face protection.


About the author: Ron Trygar is the senior training specialist for water and wastewater programs at the University of Florida’s TREEO Center. Previously, he was the wastewater process control specialist at Hillsborough County Public Utilities in Tampa, Florida. He has worked in the wastewater industry for more than 30 years in a variety of locations and positions. Trygar became a Certified Environmental Trainer (CET) in 1998 and has since provided training for associations and regulatory agencies such as Florida Department of Environmental Protection (FDEP); Florida Water and Pollution Control Operators Association Short Schools; USABlueBook; Florida Water Environment Association sponsored training events; and local school environmental programs. Working alongside the FDEP Northeast District, Trygar helped begin the Florida Rural Water Association and FDEP joint operator certification review classes that are still given around the state today. He holds a Florida Class A wastewater treatment operator’s license and a Florida Class B drinking water operator’s license.


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