When faced with a licensing exam, don't struggle with test anxiety! Use the question below and others from our Exam Study Guide series to study and prepare for exam questions. Take a look at this sample water treatment licensing question along with an explanation of the correct answer.

Sample question:

How can you determine if you are past breakpoint chlorination?

A) The addition of chlorine to the treated water is proportionate to the free chlorine residual
B) The addition of chlorine to the treated water results in a decreased free chlorine residual
C) The addition of chlorine to the treated water leaves a yellow colored tint to the water
D) The addition of chlorine to the treated water causes no effect

Answer: When chlorine is added to water that contains organic and inorganic materials, it combines with those materials and a chlorine compound is formed. This is referred to as the chlorine demand of the water. If you continue to increase the amount of chlorine you will eventually satisfy the demand, which is referred to as breakpoint chlorination. Once demand is satisfied, the additional chlorine added will result in free available chlorine for disinfection.

So, the correct answer is A.

Reference: Water Treatment Plant Operation. 6th Edition, Volume l, California State University, Sacramento. Page 280

About the author
Drew Hoelscher is the program director of drinking water operations at the Environmental Resources Training Center (ERTC) in Edwardsville, Illinois.