Minnesota Water Treatment Operator
Class C Exam Practice Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
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1. The primary purpose of coagulation in a water treatment plant is to:
A. Remove dissolved oxygen
B. Destroy all microorganisms
C. Cause small particles to combine into larger particles for removal
D. Increase water hardness
The coagulation process destabilizes suspended particles so they can join
together and later be removed through sedimentation and filtration.
2. Which chemical is commonly used as a coagulant in drinking water
treatment?
A. Sodium chloride
B. Calcium carbonate
, C. Aluminum sulfate (alum)
D. Potassium permanganate
Alum is widely used because it reacts with water to form floc that captures
suspended particles.
3. The main purpose of sedimentation is to:
A. Add chlorine to water
B. Remove dissolved minerals
C. Allow suspended particles to settle out of the water
D. Increase turbidity
Sedimentation basins slow the flow of water so heavier floc particles settle
by gravity.
4. Turbidity in drinking water is a measurement of:
A. Temperature
B. Chlorine concentration
C. Cloudiness caused by suspended particles
D. pH level
Turbidity indicates the amount of suspended material that scatters light in
water.
5. A water treatment filter primarily removes:
A. All dissolved salts
, B. Remaining suspended particles and microorganisms
C. Chlorine from water
D. Water hardness only
Filtration provides additional removal of particles and pathogens that
remain after sedimentation.
6. The purpose of disinfection in drinking water treatment is to:
A. Increase alkalinity
B. Remove sand
C. Destroy or inactivate disease-causing organisms
D. Remove color only
Disinfection protects public health by controlling bacteria, viruses, and
other harmful organisms.
7. The most common disinfectant used in municipal drinking water
systems is:
A. Oxygen
B. Fluoride
C. Chlorine
D. Nitrogen
Chlorine is widely used because it is effective and provides a lasting
residual in distribution systems.
, 8. Chlorine residual in the distribution system is important because it:
A. Causes corrosion
B. Shows that disinfectant remains available to control
microorganisms
C. Removes all minerals
D. Raises turbidity
A chlorine residual indicates continued protection against microbial
regrowth after treatment.
9. The pH scale measures:
A. Water pressure
B. Hardness
C. Acidity or alkalinity of water
D. Flow velocity
pH indicates whether water is acidic, neutral, or alkaline.
10. Water with a pH below 7 is considered:
A. Hard
B. Neutral
C. Alkaline
D. Acidic
A pH below 7 indicates acidic conditions, while 7 is neutral.
Class C Exam Practice Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
1. The primary purpose of coagulation in a water treatment plant is to:
A. Remove dissolved oxygen
B. Destroy all microorganisms
C. Cause small particles to combine into larger particles for removal
D. Increase water hardness
The coagulation process destabilizes suspended particles so they can join
together and later be removed through sedimentation and filtration.
2. Which chemical is commonly used as a coagulant in drinking water
treatment?
A. Sodium chloride
B. Calcium carbonate
, C. Aluminum sulfate (alum)
D. Potassium permanganate
Alum is widely used because it reacts with water to form floc that captures
suspended particles.
3. The main purpose of sedimentation is to:
A. Add chlorine to water
B. Remove dissolved minerals
C. Allow suspended particles to settle out of the water
D. Increase turbidity
Sedimentation basins slow the flow of water so heavier floc particles settle
by gravity.
4. Turbidity in drinking water is a measurement of:
A. Temperature
B. Chlorine concentration
C. Cloudiness caused by suspended particles
D. pH level
Turbidity indicates the amount of suspended material that scatters light in
water.
5. A water treatment filter primarily removes:
A. All dissolved salts
, B. Remaining suspended particles and microorganisms
C. Chlorine from water
D. Water hardness only
Filtration provides additional removal of particles and pathogens that
remain after sedimentation.
6. The purpose of disinfection in drinking water treatment is to:
A. Increase alkalinity
B. Remove sand
C. Destroy or inactivate disease-causing organisms
D. Remove color only
Disinfection protects public health by controlling bacteria, viruses, and
other harmful organisms.
7. The most common disinfectant used in municipal drinking water
systems is:
A. Oxygen
B. Fluoride
C. Chlorine
D. Nitrogen
Chlorine is widely used because it is effective and provides a lasting
residual in distribution systems.
, 8. Chlorine residual in the distribution system is important because it:
A. Causes corrosion
B. Shows that disinfectant remains available to control
microorganisms
C. Removes all minerals
D. Raises turbidity
A chlorine residual indicates continued protection against microbial
regrowth after treatment.
9. The pH scale measures:
A. Water pressure
B. Hardness
C. Acidity or alkalinity of water
D. Flow velocity
pH indicates whether water is acidic, neutral, or alkaline.
10. Water with a pH below 7 is considered:
A. Hard
B. Neutral
C. Alkaline
D. Acidic
A pH below 7 indicates acidic conditions, while 7 is neutral.
