Exam Study Guide: Identifying Water and Wastewater Treatment Processes

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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 Treatment Ponds; and Lime-Softening Alkalinity. This time, you can test your knowledge about the different kinds of wastewater and water treatment processes.

Wastewater Treatment Sample Question:

An advanced wastewater treatment plant is designed and built to remove BOD, TSS, total nitrogen and total phosphorus to very low levels prior to discharging its effluent to a river. The unit processes are arranged in the following order: primary clarification, anaerobic zone, preanoxic zone, aerobic zone, post-anoxic zone, reaeration zone, final clarifiers, filtration and disinfection. What process is described here?

A) The modified Ludzack-Ettinger (MLE) process

B) The Wuhrmann process

C) The Kraus process

D) The Bardenpho process

Answer: The answer is D, the Bardenpho process. While the other processes that are used as distractors, or incorrect choices, are indeed modifications of the activated sludge process or nutrient removing processes, only the Bardenpho uses the processes listed in the order shown. Please keep in mind that we are really only discussing the biological nutrient removal treatment processes in this question, some Bardenpho facilities to not have primary clarifiers and/or filters.

The placement of the anaerobic, anoxic and aerobic basins, and internal recycle streams give the Bardenpho process its characteristics. There are many other processes that use these types of basins, but have them in a different order, or varying numbers of the basins. Other processes similar to Bardenpho are Johannesburg process, Virginia Initiative process (VIP) and University of Cape Town (UCT) process to name just a few.

Water Treatment Sample Question: 

In the conventional filtration surface water treatment process, what unit processes would be present and in the correct order of treatment?

A) Rapid mix coagulation, flocculation, sedimentation, filtration, disinfection

B) Rapid mix coagulation, filtration, sedimentation, disinfection, flocculation

C) Rapid mix coagulation, limited flocculation, filtration

D) Rapid mix coagulation, nano-filtration, PAC addition, disinfection

Answer: The answer is A, rapid mix coagulation, flocculation, sedimentation, filtration, disinfection. A Conventional Filter treatment plant typically uses the unit processes in the order of flash mix/coagulation, flocculation, sedimentation, then filtration. These steps provide efficient removal of organic material, turbidity, color, bacteria and suspended solids. The flocculation process might include multiple stages and sedimentation might be in a two-stage series.

If source water is low in turbidity and color, and high in overall quality, then direct filtration or even in-line filtration can be looked at as options. Direct filtration eliminates the sedimentation portion of treatment and in-line filtration uses rapid mix of chemical then directly into the filter. Again, the source water quality has to be very high to allow the reduction of treatment processing.


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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