AK 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 water
B. To increase water temperature
C. To destabilize suspended and colloidal particles
D. To remove dissolved oxygen
Answer: C. To destabilize suspended and colloidal particles
Rationale: Coagulation uses chemicals such as alum or ferric salts to
neutralize particle charges and destabilize fine suspended and
colloidal matter. This allows the particles to combine during
subsequent flocculation and be removed by sedimentation or
filtration.
, 2. Which treatment process is primarily responsible for allowing
destabilized particles to form larger, settleable masses?
A. Fluoridation
B. Flocculation
C. Chlorination
D. Aeration
Answer: B. Flocculation
Rationale: Flocculation gently mixes coagulated water so destabilized
particles collide and attach to one another. The resulting larger
aggregates, called floc, can then be removed more effectively through
sedimentation and filtration.
3. What is the principal purpose of sedimentation in a conventional
water treatment plant?
A. Remove settleable suspended solids
B. Add chlorine to the water
C. Increase dissolved oxygen
D. Adjust electrical conductivity
Answer: A. Remove settleable suspended solids
Rationale: Sedimentation provides sufficient detention time and
reduced flow velocity for heavier floc and other suspended particles to
,settle by gravity. This reduces the solids loading on downstream
filters.
4. Which parameter is most commonly used as an indicator of water
clarity?
A. Turbidity
B. Alkalinity
C. Hardness
D. Conductivity
Answer: A. Turbidity
Rationale: Turbidity measures the scattering of light caused by
suspended particles in water. Low turbidity generally indicates clearer
water and is especially important for evaluating filtration
performance and disinfection effectiveness.
5. What is the main purpose of filtration following sedimentation?
A. Add minerals to the water
B. Remove remaining suspended particles and microorganisms
C. Increase water pressure
D. Increase alkalinity
Answer: B. Remove remaining suspended particles and
microorganisms
, Rationale: Filtration removes particles that remain after coagulation
and sedimentation. Depending on the filter type and operating
conditions, filtration can also contribute substantially to the removal
of microorganisms.
6. Which chemical is commonly used as a disinfectant in drinking-
water treatment?
A. Sodium chloride
B. Chlorine
C. Calcium carbonate
D. Sand
Answer: B. Chlorine
Rationale: Chlorine is widely used because it can inactivate many
disease-causing microorganisms and provides a measurable residual
throughout portions of a distribution system. Proper dosing and
monitoring are essential for effective disinfection.
7. What does chlorine demand represent?
A. The amount of chlorine remaining after treatment
B. The amount of chlorine consumed by substances in the water
C. The amount of chlorine stored at the plant
D. The chlorine concentration in a chemical container
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 water
B. To increase water temperature
C. To destabilize suspended and colloidal particles
D. To remove dissolved oxygen
Answer: C. To destabilize suspended and colloidal particles
Rationale: Coagulation uses chemicals such as alum or ferric salts to
neutralize particle charges and destabilize fine suspended and
colloidal matter. This allows the particles to combine during
subsequent flocculation and be removed by sedimentation or
filtration.
, 2. Which treatment process is primarily responsible for allowing
destabilized particles to form larger, settleable masses?
A. Fluoridation
B. Flocculation
C. Chlorination
D. Aeration
Answer: B. Flocculation
Rationale: Flocculation gently mixes coagulated water so destabilized
particles collide and attach to one another. The resulting larger
aggregates, called floc, can then be removed more effectively through
sedimentation and filtration.
3. What is the principal purpose of sedimentation in a conventional
water treatment plant?
A. Remove settleable suspended solids
B. Add chlorine to the water
C. Increase dissolved oxygen
D. Adjust electrical conductivity
Answer: A. Remove settleable suspended solids
Rationale: Sedimentation provides sufficient detention time and
reduced flow velocity for heavier floc and other suspended particles to
,settle by gravity. This reduces the solids loading on downstream
filters.
4. Which parameter is most commonly used as an indicator of water
clarity?
A. Turbidity
B. Alkalinity
C. Hardness
D. Conductivity
Answer: A. Turbidity
Rationale: Turbidity measures the scattering of light caused by
suspended particles in water. Low turbidity generally indicates clearer
water and is especially important for evaluating filtration
performance and disinfection effectiveness.
5. What is the main purpose of filtration following sedimentation?
A. Add minerals to the water
B. Remove remaining suspended particles and microorganisms
C. Increase water pressure
D. Increase alkalinity
Answer: B. Remove remaining suspended particles and
microorganisms
, Rationale: Filtration removes particles that remain after coagulation
and sedimentation. Depending on the filter type and operating
conditions, filtration can also contribute substantially to the removal
of microorganisms.
6. Which chemical is commonly used as a disinfectant in drinking-
water treatment?
A. Sodium chloride
B. Chlorine
C. Calcium carbonate
D. Sand
Answer: B. Chlorine
Rationale: Chlorine is widely used because it can inactivate many
disease-causing microorganisms and provides a measurable residual
throughout portions of a distribution system. Proper dosing and
monitoring are essential for effective disinfection.
7. What does chlorine demand represent?
A. The amount of chlorine remaining after treatment
B. The amount of chlorine consumed by substances in the water
C. The amount of chlorine stored at the plant
D. The chlorine concentration in a chemical container
