Water Treatment Operator Test Bank
Questions And Correct Answers
(Verified Answers) Plus Rationales
2026/2027 Q&A | Instant Download
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1. The primary purpose of coagulation in water treatment
is to:
• A. Kill pathogenic organisms
• B. Destabilize suspended particles
• C. Remove dissolved gases
• D. Adjust pH
Rationale: Coagulation neutralizes particle charges so they
can clump together and be removed.
2. Which chemical is most commonly used as a coagulant?
• A. Lime
• B. Chlorine
• C. Alum
• D. Ammonia
,Rationale: Alum (aluminum sulfate) is widely used to
destabilize particles during coagulation.
3. Flocculation follows which treatment process?
• A. Filtration
• B. Coagulation
• C. Disinfection
• D. Aeration
Rationale: Flocculation gently mixes water after coagulation
to form larger flocs.
4. Sedimentation removes particles by:
• A. Chemical oxidation
• B. Filtration through sand
• C. Gravity settling
• D. Air stripping
Rationale: Sedimentation relies on gravity to allow floc to
settle.
5. A rapid sand filter primarily removes:
• A. Dissolved salts
, • B. Remaining suspended particles
• C. Pathogenic bacteria only
• D. Alkalinity
Rationale: Filters physically strain out remaining suspended
solids after sedimentation.
6. Turbidity is a measure of:
• A. Color
• B. Taste
• C. Cloudiness
• D. Hardness
Rationale: Turbidity indicates the amount of suspended
material in water.
7. The unit commonly used to measure turbidity is:
• A. mg/L
• B. NTU
• C. ppm
• D. pH units
Rationale: Turbidity is measured in Nephelometric Turbidity
Units (NTU).
, 8. Which process kills or inactivates microorganisms?
• A. Filtration
• B. Coagulation
• C. Disinfection
• D. Sedimentation
Rationale: Disinfection destroys pathogens that can cause
disease.
9. The most common disinfectant used in water treatment
is:
• A. Ozone
• B. UV light
• C. Chlorine
• D. Potassium permanganate
Rationale: Chlorine is widely used due to effectiveness and
residual protection.
10. Chlorine residual is important because it:
• A. Improves taste
• B. Prevents recontamination
Questions And Correct Answers
(Verified Answers) Plus Rationales
2026/2027 Q&A | Instant Download
1. The primary purpose of coagulation in water treatment
is to:
• A. Kill pathogenic organisms
• B. Destabilize suspended particles
• C. Remove dissolved gases
• D. Adjust pH
Rationale: Coagulation neutralizes particle charges so they
can clump together and be removed.
2. Which chemical is most commonly used as a coagulant?
• A. Lime
• B. Chlorine
• C. Alum
• D. Ammonia
,Rationale: Alum (aluminum sulfate) is widely used to
destabilize particles during coagulation.
3. Flocculation follows which treatment process?
• A. Filtration
• B. Coagulation
• C. Disinfection
• D. Aeration
Rationale: Flocculation gently mixes water after coagulation
to form larger flocs.
4. Sedimentation removes particles by:
• A. Chemical oxidation
• B. Filtration through sand
• C. Gravity settling
• D. Air stripping
Rationale: Sedimentation relies on gravity to allow floc to
settle.
5. A rapid sand filter primarily removes:
• A. Dissolved salts
, • B. Remaining suspended particles
• C. Pathogenic bacteria only
• D. Alkalinity
Rationale: Filters physically strain out remaining suspended
solids after sedimentation.
6. Turbidity is a measure of:
• A. Color
• B. Taste
• C. Cloudiness
• D. Hardness
Rationale: Turbidity indicates the amount of suspended
material in water.
7. The unit commonly used to measure turbidity is:
• A. mg/L
• B. NTU
• C. ppm
• D. pH units
Rationale: Turbidity is measured in Nephelometric Turbidity
Units (NTU).
, 8. Which process kills or inactivates microorganisms?
• A. Filtration
• B. Coagulation
• C. Disinfection
• D. Sedimentation
Rationale: Disinfection destroys pathogens that can cause
disease.
9. The most common disinfectant used in water treatment
is:
• A. Ozone
• B. UV light
• C. Chlorine
• D. Potassium permanganate
Rationale: Chlorine is widely used due to effectiveness and
residual protection.
10. Chlorine residual is important because it:
• A. Improves taste
• B. Prevents recontamination
