CO Water Treatment Contractor Exam
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A| Instant
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1. What is the primary purpose of coagulation in conventional water
treatment?
A. To disinfect finished water
B. To increase water hardness
C. To destabilize suspended and colloidal particles
D. To remove dissolved oxygen
Rationale: Coagulation destabilizes small suspended and colloidal
particles so they can come together during subsequent flocculation and
be removed by sedimentation or filtration. Without effective
coagulation, many fine particles remain too small to settle efficiently.
2. Which chemical is commonly used as a coagulant in drinking-
water treatment?
,A. Sodium chloride
B. Aluminum sulfate
C. Calcium carbonate
D. Potassium nitrate
Rationale: Aluminum sulfate, commonly called alum, is widely used as a
coagulant. When added to water under appropriate conditions, it forms
aluminum hydroxide precipitates that help capture suspended and
colloidal material.
3. What is the primary function of flocculation?
A. Destroy pathogens
B. Remove dissolved gases
C. Raise water temperature
D. Promote the formation of larger particle aggregates
Rationale: Flocculation gently mixes coagulated water so destabilized
particles collide and form larger aggregates called flocs. These larger
particles can then be removed more effectively by sedimentation and
filtration.
4. Why is rapid mixing used immediately after a coagulant is added?
A. To cool the water
B. To remove chlorine
,C. To distribute the chemical rapidly and uniformly
D. To increase dissolved oxygen
Rationale: Rapid mixing provides sufficient turbulence to disperse the
coagulant throughout the water quickly. Uniform distribution helps the
chemical interact effectively with suspended and colloidal particles.
5. Which parameter is especially important when evaluating
coagulation performance?
A. Water color only
B. pH
C. Pipe diameter only
D. Atmospheric pressure only
Rationale: Coagulants perform differently depending on water
chemistry and pH. Maintaining the appropriate pH range is therefore
essential for effective destabilization and formation of desirable floc.
6. What is the main purpose of sedimentation in a conventional
treatment plant?
A. Increase turbidity
B. Add minerals
C. Remove settleable suspended solids
D. Sterilize all water
, Rationale: Sedimentation allows heavier particles and floc to settle
under gravity. It reduces the solids load entering downstream filtration
and improves overall treatment efficiency.
7. Which force primarily causes particles to settle in a sedimentation
basin?
A. Magnetic force
B. Electrical resistance
C. Wind pressure
D. Gravity
Rationale: Sedimentation relies primarily on gravity. Particles with
sufficient density and size move downward through the water and
accumulate as settled solids or sludge.
8. What is the primary purpose of filtration in drinking-water
treatment?
A. Add hardness
B. Remove remaining suspended particles and microorganisms
C. Increase turbidity
D. Add dissolved oxygen
Rationale: Filtration provides a physical barrier that removes particles
remaining after coagulation and sedimentation. Depending on the filter
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A| Instant
Download Pdf
1. What is the primary purpose of coagulation in conventional water
treatment?
A. To disinfect finished water
B. To increase water hardness
C. To destabilize suspended and colloidal particles
D. To remove dissolved oxygen
Rationale: Coagulation destabilizes small suspended and colloidal
particles so they can come together during subsequent flocculation and
be removed by sedimentation or filtration. Without effective
coagulation, many fine particles remain too small to settle efficiently.
2. Which chemical is commonly used as a coagulant in drinking-
water treatment?
,A. Sodium chloride
B. Aluminum sulfate
C. Calcium carbonate
D. Potassium nitrate
Rationale: Aluminum sulfate, commonly called alum, is widely used as a
coagulant. When added to water under appropriate conditions, it forms
aluminum hydroxide precipitates that help capture suspended and
colloidal material.
3. What is the primary function of flocculation?
A. Destroy pathogens
B. Remove dissolved gases
C. Raise water temperature
D. Promote the formation of larger particle aggregates
Rationale: Flocculation gently mixes coagulated water so destabilized
particles collide and form larger aggregates called flocs. These larger
particles can then be removed more effectively by sedimentation and
filtration.
4. Why is rapid mixing used immediately after a coagulant is added?
A. To cool the water
B. To remove chlorine
,C. To distribute the chemical rapidly and uniformly
D. To increase dissolved oxygen
Rationale: Rapid mixing provides sufficient turbulence to disperse the
coagulant throughout the water quickly. Uniform distribution helps the
chemical interact effectively with suspended and colloidal particles.
5. Which parameter is especially important when evaluating
coagulation performance?
A. Water color only
B. pH
C. Pipe diameter only
D. Atmospheric pressure only
Rationale: Coagulants perform differently depending on water
chemistry and pH. Maintaining the appropriate pH range is therefore
essential for effective destabilization and formation of desirable floc.
6. What is the main purpose of sedimentation in a conventional
treatment plant?
A. Increase turbidity
B. Add minerals
C. Remove settleable suspended solids
D. Sterilize all water
, Rationale: Sedimentation allows heavier particles and floc to settle
under gravity. It reduces the solids load entering downstream filtration
and improves overall treatment efficiency.
7. Which force primarily causes particles to settle in a sedimentation
basin?
A. Magnetic force
B. Electrical resistance
C. Wind pressure
D. Gravity
Rationale: Sedimentation relies primarily on gravity. Particles with
sufficient density and size move downward through the water and
accumulate as settled solids or sludge.
8. What is the primary purpose of filtration in drinking-water
treatment?
A. Add hardness
B. Remove remaining suspended particles and microorganisms
C. Increase turbidity
D. Add dissolved oxygen
Rationale: Filtration provides a physical barrier that removes particles
remaining after coagulation and sedimentation. Depending on the filter
