Practice Exam Questions And Correct

Ohio Water Treatment Operator Class C Practice Exam Questions And Correct Answers (Verified Answers) Plus Rationales 2025|2026 Q&A | Instant Download Pdf

1. The primary source of raw water for most municipal systems is:

• Ocean water
• Surface water
• Groundwater under the influence of surface water
• Reclaimed wastewater

Rationale: Surface water such as rivers and lakes are the most common raw

water sources for municipal systems due to availability and volume.

• Which treatment process removes suspended solids by gravity?
• Filtration 1 / 4

• Sedimentation
• Coagulation
• Disinfection

Rationale: Sedimentation allows heavier particles to settle out by gravity

before filtration.

3. The main purpose of coagulation in water treatment is to:

• Adjust pH
• Destabilize particles for aggregation
• Disinfect water
• Remove hardness

Rationale: Coagulation neutralizes particle charges so they can clump

together during flocculation.

4. Alum is commonly used as a:

• Disinfectant
• Coagulant
• pH adjuster
• Oxidizer

Rationale: Aluminum sulfate (alum) is widely used to promote coagulation

and floc formation.

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5. The term “floc” refers to:

• Fine sand used in filters
• Aggregated particles formed during treatment
• Biological growth in filters
• Chlorine residual

Rationale: Floc is the visible mass of particles formed after coagulation and

flocculation.

6. The process that removes color, taste, and odor is primarily:

• Aeration
• Activated carbon adsorption
• Sedimentation
• Fluoridation

Rationale: Activated carbon adsorbs organic compounds that cause taste,

odor, and color.

7. Chlorine is added to water for:

• Coagulation
• pH control
• Disinfection
• Softening

Rationale: Chlorine effectively kills pathogenic organisms in water. 3 / 4

8. The ideal pH range for chlorine disinfection is:

A. 4–5

B. 7–8

C. 8–9

D. 9–10

Rationale: Chlorine is most effective in the neutral to slightly basic pH range.

9. The primary purpose of filtration is to:

• Remove dissolved solids
• Remove suspended and colloidal matter
• Adjust alkalinity
• Increase hardness

Rationale: Filtration removes remaining particulates after sedimentation.

10. The backwash process in filters is designed to:

• Remove trapped solids and restore filter performance
• Disinfect filters
• Remove dissolved minerals
• Increase chlorine residual

Rationale: Backwashing cleans the filter media by reversing the flow to

remove accumulated solids.

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