State Water Treatment Operator Class C
Licensing Exam 100 Practice Questions
And Correct Answers (Verified Answers)
Plus Rationales 2026 Q&A | Instant
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1. What is the primary purpose of coagulation in water treatment?
A. Reduce taste and odor
B. Remove dissolved minerals
C. Destabilize suspended particles
D. Produce chlorine residual
Coagulation adds chemicals that neutralize particle charges, allowing them
to clump together for removal.
2. Alum is most commonly used as a:
A. Disinfectant
B. Coagulant
C. Corrosion inhibitor
,D. pH booster
Alum (aluminum sulfate) is the most widely used coagulant in drinking
water treatment.
3. The most effective pH range for alum coagulation is typically:
A. 3.0–4.0
B. 5.0–6.0
C. 6.0–7.5
D. 8.5–10.0
Alum works best in slightly acidic to neutral conditions.
4. The main purpose of flocculation is to:
A. Add chlorine
B. Remove hardness
C. Promote particle collisions
D. Disinfect water
Gentle mixing promotes formation of larger, heavier floc particles.
5. Sedimentation removes particles primarily by:
A. Filtration
B. Gravity settling
C. Chemical oxidation
D. Air flotation
Sedimentation relies on gravity to settle floc particles.
6. Turbidity is measured in:
, A. ppm
B. mg/L
C. NTU
D. mL/min
Turbidity is expressed in nephelometric turbidity units.
7. A normal turbidity level entering filters should be:
A. >10 NTU
B. <1–5 NTU
C. 20–30 NTU
D. 50 NTU
Low turbidity improves filter performance and disinfectant effectiveness.
8. The most common filtration media used in rapid sand filters is:
A. Gravel only
B. Activated carbon only
C. Sand and anthracite
D. Clay
Dual-media filtration increases efficiency and capacity.
9. Backwashing filters is necessary to:
A. Add chlorine
B. Remove accumulated solids
C. Increase alkalinity
Licensing Exam 100 Practice Questions
And Correct Answers (Verified Answers)
Plus Rationales 2026 Q&A | Instant
Download Pdf
1. What is the primary purpose of coagulation in water treatment?
A. Reduce taste and odor
B. Remove dissolved minerals
C. Destabilize suspended particles
D. Produce chlorine residual
Coagulation adds chemicals that neutralize particle charges, allowing them
to clump together for removal.
2. Alum is most commonly used as a:
A. Disinfectant
B. Coagulant
C. Corrosion inhibitor
,D. pH booster
Alum (aluminum sulfate) is the most widely used coagulant in drinking
water treatment.
3. The most effective pH range for alum coagulation is typically:
A. 3.0–4.0
B. 5.0–6.0
C. 6.0–7.5
D. 8.5–10.0
Alum works best in slightly acidic to neutral conditions.
4. The main purpose of flocculation is to:
A. Add chlorine
B. Remove hardness
C. Promote particle collisions
D. Disinfect water
Gentle mixing promotes formation of larger, heavier floc particles.
5. Sedimentation removes particles primarily by:
A. Filtration
B. Gravity settling
C. Chemical oxidation
D. Air flotation
Sedimentation relies on gravity to settle floc particles.
6. Turbidity is measured in:
, A. ppm
B. mg/L
C. NTU
D. mL/min
Turbidity is expressed in nephelometric turbidity units.
7. A normal turbidity level entering filters should be:
A. >10 NTU
B. <1–5 NTU
C. 20–30 NTU
D. 50 NTU
Low turbidity improves filter performance and disinfectant effectiveness.
8. The most common filtration media used in rapid sand filters is:
A. Gravel only
B. Activated carbon only
C. Sand and anthracite
D. Clay
Dual-media filtration increases efficiency and capacity.
9. Backwashing filters is necessary to:
A. Add chlorine
B. Remove accumulated solids
C. Increase alkalinity
