Exam Study Guide: Plastic-Media Trickling Filters; and Activated Alumina

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 on the topics of Effluent Coliform Count; and Enteric Virus Removal. This time, you can test your knowledge about plastic-media trickling filters and activated alumina.

Wastewater Treatment Sample Question:

What is an advantage of using plastic media in place of traditional rock-type media in a trickling filter?

A) Ponding and filter fly occurrences are eliminated.

B) Higher surface area allows more biofilm growth.

C) The media is less aerobic.

D) Odor complaints are reduced.

Answer: The answer is B, higher surface area allows more biofilm growth. New versions of plastic, trickling-filter media allow many more times the square feet of surface area for microorganisms to attach and grow on. More biomass equates to more wastewater that can be treated per day and better effluent quality. In some instances, portions of the filter media get better aeration, becoming more aerobic, which can help reduce odors and increase treatment efficiency.

Unfortunately, filter flies can still breed and be a nuisance if the filter is not operated properly. 

Water Treatment Sample Question: 

The use of media columns that contain activated alumina are effective in removing what contaminant from groundwater?

A) Lead

B) Total coliform

C) Arsenic

D) Iron

Answer: The answer is C, arsenic. Typically arranged in a two-column sequence, activated alumina will allow adsorption of arsenic on the media. The first (primary) column provides the main arsenic removal, while the secondary column provides polishing. Once the primary column is exhausted (cannot remove more arsenic), the media in the primary column is replaced and the flow reversed so that the secondary column now becomes the primary until it is exhausted.

Sources of arsenic in drinking water can come from the resulting ash from wildfires, volcanic activity and leaching from soil. Human activities contribute to arsenic in water from mining and agricultural use, and arsenic can be found in treated wood products (preservatives) and dyes and paint products. 

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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