Exam Study Guide: Indicator Organisms; and Iron Contamination

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 Types of Bacteria, and Chemical Sequences. This time, you can test your knowledge about indicator organisms and iron contamination.

Wastewater Treatment Sample Question:

The presence of nematodes (round worms), water bears (tardigrades) and/or bristle worms is a typical indicator of what condition in an activated sludge treatment plant?

A. Young sludge
B. Mature sludge
C. Old sludge
D. Toxic condition 

Answer: The answer to this question is C, old sludge. Understanding what indicator organisms represent, when performing microscopic analysis of the mixed liquor suspended solids in the aeration tank, is a very useful tool for the operator. This allows the operator to make process control and troubleshooting decisions in a timely manner. Metazoans such as nematodes, water bears and bristle worms grow slowly and are found in older activated sludge or attached growth conditions. Most metazoans prefer environments low in ammonia; this indicates the treatment facility is well nitrified.

Water Treatment Sample Question

What is the U.S. EPA primary maximum contaminant level for iron?

A. 1.0 mg/L
B. 0.3 mg/L
C. 0.0 mg/L
Iron is not regulated by a maximum contaminant level

Answer: The correct answer is D. There is not an U.S. EPA maximum contaminant level for iron. Iron is regarded as an aesthetic issue rather than a health issue. However, the EPA does have iron listed on the secondary maximum contaminant level list as 0.3 mg/L. This is a recommended level and is not enforceable. Studies have shown that a water system typically experiences red water complaints at or above 0.3 mg/L for iron.

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.


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