Licensure Exam Practice Test Questions

Certified Water Treatment Operator Licensure Exam Practice Test Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of coagulation in water treatment?
• Remove dissolved gases
• Destabilize suspended particles
• Adjust pH levels
• Disinfect the water

Rationale: Coagulation involves adding chemicals like alum to destabilize

and aggregate fine suspended particles, making them easier to remove during flocculation and sedimentation.

• Which of the following chemicals is most commonly used as a

coagulant? 1 / 4

• Chlorine
• Lime
• Aluminum sulfate (alum)
• Activated carbon

Rationale: Aluminum sulfate, known as alum, is the most commonly used

coagulant due to its effectiveness and low cost.

• What is the ideal pH range for coagulation with alum?

A. 3.0–4.5

B. 5.5–7.5

C. 8.0–9.0

D. 9.5–11.0

Rationale: Alum works best in slightly acidic to neutral conditions, typically

between pH 5.5 and 7.5.

4. The term “floc” refers to:

• A disinfectant gas
• Aggregated particles formed during treatment
• A corrosion inhibitor
• A sedimentation basin

Rationale: Floc is the larger mass of particles formed during flocculation

when smaller particles stick together after coagulation. 2 / 4

• The process used to remove dissolved minerals such as calcium and

magnesium is:

• Filtration
• Chlorination
• Softening
• Aeration

Rationale: Water softening removes hardness ions like calcium and

magnesium, typically using lime or ion exchange methods.

• What is the main purpose of sedimentation?
• Allow suspended solids to settle out
• Disinfect microorganisms
• Remove dissolved gases
• Adjust alkalinity

Rationale: Sedimentation allows heavier particles to settle by gravity

before filtration, improving clarity.

• Which of the following is a physical water treatment process?
• Filtration
• Chlorination
• Coagulation 3 / 4

• Fluoridation

Rationale: Filtration is a physical process that removes suspended solids

from water by passing it through porous media.

• In rapid sand filtration, what is the usual filter media?
• Gravel only
• Anthracite only
• Sand and anthracite layers
• Activated carbon only

Rationale: Rapid sand filters use layered media—coarse anthracite on top

of fine sand—to improve filtration efficiency.

9. Backwashing a filter is done to:

• Add chlorine
• Remove coagulants
• Clean and restore filter media
• Add disinfectant residual

Rationale: Backwashing reverses flow through a filter to remove trapped

solids and clean the media.

• What is the primary purpose of chlorination?
• Remove hardness
• / 4