WATER TREATMENT OPERATOR CLASS
B LICENSING EXAM QUESTION AND
CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2026 Q&A
INSTANT DOWNLOAD PDF
1. Which process is primarily used to remove suspended solids from raw
water?
A. Disinfection
B. Aeration
C. Filtration
D. Coagulation and flocculation
Answer: D
Rationale: Coagulation and flocculation destabilize and aggregate
suspended particles so they can be removed by sedimentation and
filtration.
2. What chemical is most commonly used as a coagulant in water treatment?
A. Lime
B. Aluminum sulfate (alum)
C. Chlorine
D. Sodium fluoride
Answer: B
Rationale: Alum is widely used to neutralize particle charges and form
floc.
3. The purpose of flocculation is to:
A. Kill pathogens
B. Adjust pH
C. Gently mix water to form larger particles
, D. Remove taste and odor
Answer: C
Rationale: Slow mixing allows small particles to collide and form
settleable floc.
4. Sedimentation basins are designed to remove:
A. Dissolved gases
B. Settleable solids
C. Dissolved minerals
D. Bacteria only
Answer: B
Rationale: Sedimentation allows heavier floc to settle by gravity.
5. What is the primary function of filtration?
A. Chemical oxidation
B. Remove remaining suspended particles
C. Increase alkalinity
D. Add disinfectant
Answer: B
Rationale: Filters capture fine particles not removed during
sedimentation.
6. Rapid sand filters differ from slow sand filters because they:
A. Do not require backwashing
B. Use biological action only
C. Operate at higher filtration rates
D. Remove dissolved solids
Answer: C
Rationale: Rapid sand filters have much higher loading rates and require
backwashing.
7. What is the main purpose of backwashing a filter?
A. Disinfect the filter
B. Remove accumulated solids
C. Replace filter media
D. Adjust pH
, Answer: B
Rationale: Backwashing cleans the filter media to restore capacity.
8. Which disinfectant provides a residual in the distribution system?
A. Ozone
B. UV light
C. Chlorine
D. Aeration
Answer: C
Rationale: Chlorine leaves a measurable residual to protect water in
distribution.
9. The CT concept in disinfection refers to:
A. Chlorine temperature
B. Contact tank size
C. Concentration × contact time
D. Chlorine turbidity
Answer: C
Rationale: CT is used to determine effective pathogen inactivation.
10.Increasing water temperature generally:
A. Decreases disinfection efficiency
B. Has no effect
C. Increases disinfection efficiency
D. Stops chlorine demand
Answer: C
Rationale: Higher temperatures enhance chemical reaction rates.
11.Which factor most affects chlorine demand?
A. Pipe diameter
B. Organic matter in water
C. Pump speed
D. Tank height
Answer: B
Rationale: Organic and inorganic compounds consume chlorine.
12.pH affects chlorine disinfection because:
A. Chlorine evaporates
B LICENSING EXAM QUESTION AND
CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2026 Q&A
INSTANT DOWNLOAD PDF
1. Which process is primarily used to remove suspended solids from raw
water?
A. Disinfection
B. Aeration
C. Filtration
D. Coagulation and flocculation
Answer: D
Rationale: Coagulation and flocculation destabilize and aggregate
suspended particles so they can be removed by sedimentation and
filtration.
2. What chemical is most commonly used as a coagulant in water treatment?
A. Lime
B. Aluminum sulfate (alum)
C. Chlorine
D. Sodium fluoride
Answer: B
Rationale: Alum is widely used to neutralize particle charges and form
floc.
3. The purpose of flocculation is to:
A. Kill pathogens
B. Adjust pH
C. Gently mix water to form larger particles
, D. Remove taste and odor
Answer: C
Rationale: Slow mixing allows small particles to collide and form
settleable floc.
4. Sedimentation basins are designed to remove:
A. Dissolved gases
B. Settleable solids
C. Dissolved minerals
D. Bacteria only
Answer: B
Rationale: Sedimentation allows heavier floc to settle by gravity.
5. What is the primary function of filtration?
A. Chemical oxidation
B. Remove remaining suspended particles
C. Increase alkalinity
D. Add disinfectant
Answer: B
Rationale: Filters capture fine particles not removed during
sedimentation.
6. Rapid sand filters differ from slow sand filters because they:
A. Do not require backwashing
B. Use biological action only
C. Operate at higher filtration rates
D. Remove dissolved solids
Answer: C
Rationale: Rapid sand filters have much higher loading rates and require
backwashing.
7. What is the main purpose of backwashing a filter?
A. Disinfect the filter
B. Remove accumulated solids
C. Replace filter media
D. Adjust pH
, Answer: B
Rationale: Backwashing cleans the filter media to restore capacity.
8. Which disinfectant provides a residual in the distribution system?
A. Ozone
B. UV light
C. Chlorine
D. Aeration
Answer: C
Rationale: Chlorine leaves a measurable residual to protect water in
distribution.
9. The CT concept in disinfection refers to:
A. Chlorine temperature
B. Contact tank size
C. Concentration × contact time
D. Chlorine turbidity
Answer: C
Rationale: CT is used to determine effective pathogen inactivation.
10.Increasing water temperature generally:
A. Decreases disinfection efficiency
B. Has no effect
C. Increases disinfection efficiency
D. Stops chlorine demand
Answer: C
Rationale: Higher temperatures enhance chemical reaction rates.
11.Which factor most affects chlorine demand?
A. Pipe diameter
B. Organic matter in water
C. Pump speed
D. Tank height
Answer: B
Rationale: Organic and inorganic compounds consume chlorine.
12.pH affects chlorine disinfection because:
A. Chlorine evaporates
