WATER TREATMENT OPERATOR CLASS C
LICENSING EXAM QUESTION AND
CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2026 Q&A
INSTANT DOWNLOAD PDF
1. Which process removes suspended solids by gravity?
A. Filtration
B. Coagulation
C. Sedimentation
D. Disinfection
Sedimentation allows heavier particles to settle out of water under
gravity.
2. The primary purpose of coagulation is to:
A. Kill pathogens
B. Destabilize particles
C. Remove taste and odor
D. Adjust pH
Coagulation neutralizes particle charges so they can clump together.
3. Which chemical is commonly used as a coagulant?
A. Sodium chloride
B. Chlorine
C. Alum
D. Lime
Aluminum sulfate (alum) is a widely used coagulant.
4. Flocculation occurs after which process?
A. Filtration
B. Coagulation
, C. Disinfection
D. Aeration
Flocculation gently mixes water after coagulation to form floc.
5. The primary purpose of filtration is to:
A. Kill bacteria
B. Adjust alkalinity
C. Remove remaining particles
D. Add fluoride
Filtration removes fine particles that did not settle.
6. Rapid sand filters operate primarily by:
A. Chemical reaction
B. Gravity settling
C. Physical straining
D. UV radiation
Rapid sand filters remove particles by straining and adsorption.
7. Which disinfectant provides a residual in the distribution system?
A. UV light
B. Ozone
C. Chlorine
D. Heat
Chlorine maintains a disinfectant residual.
8. The CT concept relates to:
A. Chemical toxicity
B. Contact time and concentration
C. Temperature and turbidity
D. Chlorine type
CT is the product of disinfectant concentration and contact time.
9. A high turbidity in filtered water indicates:
A. Effective filtration
B. Filter breakthrough
C. Proper coagulation
D. Adequate disinfection
High turbidity after filtration suggests filter problems.
, 10.Which unit measures turbidity?
A. ppm
B. mg/L
C. NTU
D. psi
Turbidity is measured in Nephelometric Turbidity Units.
11.pH affects:
A. Color only
B. Odor only
C. Coagulation and disinfection
D. Flow rate
pH influences chemical reactions and disinfectant effectiveness.
12.Optimal pH for chlorination is generally:
A. Above 9
B. Below 8
C. Exactly 7
D. Above 10
Lower pH improves chlorine disinfection efficiency.
13.Which chemical raises pH?
A. Alum
B. Lime
C. Chlorine
D. Carbon dioxide
Lime increases alkalinity and pH.
14.Alkalinity is important because it:
A. Causes corrosion
B. Buffers pH changes
C. Increases turbidity
D. Removes bacteria
Alkalinity resists rapid pH changes.
15.Which parameter indicates corrosive water?
A. High alkalinity
B. High hardness
LICENSING EXAM QUESTION AND
CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2026 Q&A
INSTANT DOWNLOAD PDF
1. Which process removes suspended solids by gravity?
A. Filtration
B. Coagulation
C. Sedimentation
D. Disinfection
Sedimentation allows heavier particles to settle out of water under
gravity.
2. The primary purpose of coagulation is to:
A. Kill pathogens
B. Destabilize particles
C. Remove taste and odor
D. Adjust pH
Coagulation neutralizes particle charges so they can clump together.
3. Which chemical is commonly used as a coagulant?
A. Sodium chloride
B. Chlorine
C. Alum
D. Lime
Aluminum sulfate (alum) is a widely used coagulant.
4. Flocculation occurs after which process?
A. Filtration
B. Coagulation
, C. Disinfection
D. Aeration
Flocculation gently mixes water after coagulation to form floc.
5. The primary purpose of filtration is to:
A. Kill bacteria
B. Adjust alkalinity
C. Remove remaining particles
D. Add fluoride
Filtration removes fine particles that did not settle.
6. Rapid sand filters operate primarily by:
A. Chemical reaction
B. Gravity settling
C. Physical straining
D. UV radiation
Rapid sand filters remove particles by straining and adsorption.
7. Which disinfectant provides a residual in the distribution system?
A. UV light
B. Ozone
C. Chlorine
D. Heat
Chlorine maintains a disinfectant residual.
8. The CT concept relates to:
A. Chemical toxicity
B. Contact time and concentration
C. Temperature and turbidity
D. Chlorine type
CT is the product of disinfectant concentration and contact time.
9. A high turbidity in filtered water indicates:
A. Effective filtration
B. Filter breakthrough
C. Proper coagulation
D. Adequate disinfection
High turbidity after filtration suggests filter problems.
, 10.Which unit measures turbidity?
A. ppm
B. mg/L
C. NTU
D. psi
Turbidity is measured in Nephelometric Turbidity Units.
11.pH affects:
A. Color only
B. Odor only
C. Coagulation and disinfection
D. Flow rate
pH influences chemical reactions and disinfectant effectiveness.
12.Optimal pH for chlorination is generally:
A. Above 9
B. Below 8
C. Exactly 7
D. Above 10
Lower pH improves chlorine disinfection efficiency.
13.Which chemical raises pH?
A. Alum
B. Lime
C. Chlorine
D. Carbon dioxide
Lime increases alkalinity and pH.
14.Alkalinity is important because it:
A. Causes corrosion
B. Buffers pH changes
C. Increases turbidity
D. Removes bacteria
Alkalinity resists rapid pH changes.
15.Which parameter indicates corrosive water?
A. High alkalinity
B. High hardness
