Exam Study Guide: Lagoon System Configuration; and Drinking Water Tests

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Exam Study Guide: Lagoon System Configuration; and Drinking Water Tests

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 Soluble Organic Contaminant Removal, and the Langelier Index. This time, you can test your knowledge about lagoon system configuration, and drinking water tests.

Wastewater Treatment Sample Question:


Effluent quality improves in lagoon systems that are operated in which configuration?

A) Parallel arrangement

B) Series arrangement

C) Anaerobic only

D) Aerobic only

Answer: The answer is B, series arrangement. Lagoons operated in series configuration tend to produce higher quality effluent as the waste stream passes from lagoon to lagoon. Series operation means that the lagoon system piping is configured so that the influent of the second lagoon in series is actually the treated effluent of the first lagoon. The influent of a third lagoon in line is the treated effluent from the second lagoon, and so on. Lagoons operated in parallel essentially run side by side, and the influent wastewater is split equally to two or three lagoons, while the outlets of all three are combined into one effluent.

Series configuration allows for improved treatment of the waste stream since the influent of each downstream lagoon has considerably less strength and loading with respect to BOD and TSS.

Lagoons can be operated in combinations of anaerobic, aerobic or facultative modes, but will still produce higher quality effluent if operated in series.

Granular activated carbon (GAC) can be used in the filtering process as a layer of the filter media or in a separate treatment contact unit where soluble organic material is adsorbed and removed from the water flowing through the unit. As the GAC continues to adsorb organics, it becomes exhausted and measurable COD begins to rise in the effluent. Once the service life of the GAC is reached, the GAC can be removed from the filter unit as a slurry, dried and regenerated by heating the GAC in a furnace. The organic material is released during the heating process and further destroyed in an afterburner unit. The GAC can now be reused in the treatment process.

Water Treatment Sample Question: 

The following is a description of what test? “First, measure the pH, alkalinity and hardness of the water. Into a ½-liter sample of the same water, add 0.5 g of crushed calcium carbonate, and stir for 5 minutes. Filter the water, and again measure the pH, alkalinity and hardness.” – adapted from Cal. State Sacramento, Water Treatment Plant Operation, Volume I, sixth ed., section 8.42.

A) The marble test

B) Zinc orthophosphate demand test

C) Ryznar Index test

D) Aggressive Index test

Answer: The answer is A, the marble test. There is a little more to actually running the marble test, but essentially that’s the basic description. The idea of the marble test is to see if the initial water sample is under- or over-saturated with calcium carbonate. By adding calcium carbonate (crushed chalk, or crushed marble) to a water sample, allowing it to dissolve into the water and measuring the effect of that calcium addition, one can determine if the initial water is corrosive or scale forming.

If the initial water sample is already high in calcium hardness, such as a hard water source, its ability to hold any more calcium in solution is very limited. In fact, if the water is at a point of being super-saturated with calcium, the addition of extra calcium might actually cause a miniature lime-softening reaction in the sample bottle. The calcium hardness will decrease as a result of the over-saturation and precipitation of the excess calcium will occur. This indicates to the water operator that the initial water sample is scale forming.

Conversely, if the initial water sample is under-saturated with calcium hardness, the water will retain the excess calcium and the measurable calcium hardness will increase. This indicates the water is under-saturated or corrosive. Think of deionized or distilled water with little mineral content. It is said to be aggressive, or corrosive, and lacking the calcium ions needed to stabilize the water.

If the calcium hardness, alkalinity and pH show no real change in measurement after adding the 0.5g of crushed calcium carbonate, the water is said to be stable, or just at saturation.

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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