CPO Disinfection and Sanitizers Questions and Answers

Question 1

A pool operator at an outdoor facility notices a rapid depletion of free chlorine levels on sunny days, despite regular dosing. Which of the following is the most likely cause and appropriate chemical to add?

Accepted Answer

UV degradation; add cyanuric acid.

Answer

Cyanuric acid (CYA), also known as a stabilizer or conditioner, is used in outdoor pools to protect free chlorine from being destroyed by the sun's ultraviolet (UV) rays. Without an adequate level of CYA (typically 30-50 ppm), chlorine will be rapidly consumed by sunlight, making it difficult to maintain a proper disinfectant residual.

Question 2

Breakpoint chlorination is performed on a swimming pool to primarily address which of the following water quality issues?

Accepted Answer

High levels of combined chlorine (chloramines).

Answer

Breakpoint chlorination is the process of adding a significant amount of an oxidizing agent (typically chlorine) to the water to destroy combined chlorine (chloramines). Chloramines are formed when free chlorine reacts with nitrogen-containing compounds from swimmers (like sweat and urine) and are responsible for the 'chlorine' odor and eye irritation.

Question 3

A CPO is managing a 50,000-gallon pool and needs to choose between sodium hypochlorite (liquid) and calcium hypochlorite (granular) for routine sanitization. The facility is in an area with very hard source water, leading to chronically high calcium hardness levels. Which sanitizer is the better choice and why?

Accepted Answer

Sodium hypochlorite, because it does not add calcium to the water, helping to prevent scaling.

Answer

Sodium hypochlorite (liquid chlorine) is the better choice in this scenario because it does not add calcium to the pool water. Since the source water already contributes to high calcium hardness, using calcium hypochlorite would exacerbate the problem, increasing the risk of scale formation on surfaces and equipment.

Question 4

Which of the following statements is TRUE regarding the use of Polyhexamethylene Biguanide (PHMB) as a pool sanitizer?

Accepted Answer

It requires the regular addition of hydrogen peroxide to act as an oxidizer.

Answer

PHMB (biguanide) is a sanitizer but not an oxidizer. Therefore, it must be used in conjunction with a separate oxidizing product, most commonly hydrogen peroxide, to break down organic contaminants. PHMB is incompatible with chlorine and its efficacy is not dependent on pH.

Question 5

Ozone is increasingly used as a secondary disinfection system in aquatic facilities. What is a primary benefit of using an ozone system?

Accepted Answer

It is a powerful oxidizer that destroys chloramines and other organic contaminants.

Answer

Ozone is a very powerful oxidizer and disinfectant that is highly effective at destroying organic matter, bacteria, viruses, and, importantly, breaking down irritating chloramines. However, it has a very short half-life and does not create a lasting residual in the main body of water, which is why a primary sanitizer like chlorine is still required.

CPO (Certified Pool Operator Exam) Practice Test

CPO (Certified Pool Operator Exam) Practice Test

CPO Disinfection and Sanitizers Questions and Answers