Class C Exam Practice Test Questions

Water System Operations Specialist Class C Exam Practice Test Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of a water treatment plant?
• Increase water hardness
• Improve taste only
• Remove contaminants to make water safe for consumption
• Store water for firefighting

Rationale: The main goal of water treatment is to remove harmful

microorganisms, chemicals, and physical impurities to ensure the water is safe for human use.

• Which of the following is considered a surface water source?
• Well 1 / 4

• Spring
• River
• Aquifer

Rationale: Surface water comes from sources above ground, such as rivers,

lakes, and reservoirs.

• What is the most common disinfectant used in water treatment?
• Ozone
• Chlorine dioxide
• Chlorine
• Ultraviolet light

Rationale: Chlorine is widely used due to its effectiveness, cost efficiency,

and residual protection in the distribution system.

4. Coagulation in water treatment primarily serves to:

• Bind particles together for easier removal
• Kill bacteria
• Adjust pH
• Increase water hardness

Rationale: Coagulants like alum cause small suspended particles to clump

together, forming larger particles (floc) that can be removed by sedimentation.

5. Sedimentation in a treatment plant is used to:

• Filter water through sand 2 / 4

• Allow floc to settle by gravity
• Disinfect water
• Remove dissolved minerals

Rationale: Sedimentation allows larger particles, formed during coagulation,

to settle out of the water, reducing turbidity.

6. The purpose of filtration in a water treatment plant is to:

• Remove dissolved salts
• Remove remaining suspended particles
• Adjust pH
• Kill microorganisms

Rationale: Filtration through media like sand or anthracite removes fine

particles that did not settle during sedimentation.

• Which of the following is an indicator of possible microbial

contamination in water?

• Hardness
• Color
• Presence of coliform bacteria
• Turbidity

Rationale: Total coliform bacteria are commonly tested because their

presence indicates potential contamination by pathogens.

• What is the primary function of a water distribution system?
• Treat water 3 / 4

• Increase pressure
• Deliver safe water to consumers
• Store water

Rationale: Distribution systems are designed to convey treated water to

customers efficiently while maintaining quality and pressure.

• Which water quality parameter is most affected by corrosion in pipes?
• Turbidity
• pH and metal concentration
• Temperature
• Dissolved oxygen

Rationale: Corrosion can release metals like iron or lead into the water and

alter the pH, impacting taste and safety.

• A water system operator notices an unusually high chlorine

residual at the end of the distribution system. This could indicate:

• Over-chlorination at the treatment plant
• Pipe leakage
• Low water demand
• Inadequate filtration

Rationale: High residuals often occur when chlorine doses are too high or

contact time is excessive.

• What is the primary cause of turbidity in surface water sources?
• Dissolved salts
• / 4