Exam Study Guide: Disinfection Byproducts Rule

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When operators are faced with licensing exams, they sometimes struggle with test anxiety because they don’t understand how to study and prepare for exam questions. Here, we take a look at a sample water treatment licensing exam question and explain the correct answer.

What is the common element with the Disinfectants and Disinfection Byproduct Rules?

a. Oxygen
b. Nitrogen
c. Halogens
d. Carbon

The correct answer is D, carbon.

It is measured as Total Organic Carbon (TOC), and it is the precursor that forms trihalomethanes, which are suspected carcinogenic compounds. TOC or carbon binds up with halogens to form unstable volatile compounds that potentially pose a risk to human health.

In our application, this would be carbon and chlorine. Organic carbon can come from many natural sources in our environment, including from decaying plant life in irrigation channels or reservoirs, fallen leaves in ditches and old decaying carbon based material that is unearthed with new construction and run-off. With today’s regulations, the strategy is quite clear: Remove the source rather than control the by-product.

By reducing TOC levels in raw water, we minimize the risk of regulatory violations with the TTHM Rule. To do this, we can work upstream and do a better job of removing debris in ditches. Before activating them with a run-off flow, cut back vegetation that lines reservoirs and replace the area with rock or solid objects to minimize erosion. The current MCL for TTHM’s is .080 mg/L (total of all four species based on a running annual average).

About the Author
Mike Smith is program coordinator and lead faculty of the Water Quality Management program at Red Rocks Community College in Lakewood, Colo.

He has been in charge of the multi-faceted training program since 1996.



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