Exam Study Guide - June 2021


By Rick Lallish

Even though there are many ways to determine wasting amounts, what is the main purpose of wasting?

A. Maintain acceptable sludge blanket depth

B. Maintain proper facultative levels in the lagoon

C. Maintain effluent total suspended solids requirements

D. Maintain a sludge age that produces the best effluent

Answer: D. One of the best ways to have successful process control is to have proper wasting procedures and calculations. By wasting, you maintain control of your food/microorganism levels and median cell retention time, or sludge ages. There are many ways to waste; each when correctly performed will achieve a sludge age that produces the best effluent possible for your treatment system. One rule of thumb is generally accepted: You should never vary your wasting amount by more than 10%-15% on a daily basis. This will allow you to make changes without shocking your system. More information may be found in the Office of Water Programs, California State University, Sacramento textbook: Operation of Wastewater Treatment Plants Vol. 2 (Seventh ed.), Chapter 11.


By Drew Hoelscher

The U.S. EPA Lead and Copper Rule revision requires which liter of water to be collected when the sample location has a known lead service line?

A. First

B. Fifth

C. 10th

D. 15th

Answer: B. The recent revisions to the Lead and Copper Rule are the first major changes since the original rule issued in 1991. The updated rule provides an opportunity to further reduce lead and copper contamination in public water supplies. One of the many updates is the required fifth-liter collection of water from a sample location with a known lead service line. The fifth liter of water collected is more likely to be the water that was sitting stagnant in the service line, where the first-liter sample would represent the stagnant water within the premise plumbing.

About the authors

Rick Lallish is water pollution control program director and Drew Hoelscher is program director of drinking water operations at the Environmental Resources Training Center of Southern Illinois University Edwardsville.  


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