AWWA Water Treatment Operator
Certification Grade II Exam With Actual
Questions & Verified Answers, Plus Explained
Rationales/Expert Verified For Guaranteed
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1. What is the primary purpose of coagulation in water treatment?
A. To disinfect pathogens
B. To remove dissolved gases
C. To destabilize suspended particles
D. To increase alkalinity
Answer: C. To destabilize suspended particles
Rationale: Coagulation neutralizes the electrical charges on
suspended particles, allowing them to clump together during
flocculation and settle more easily during clarification.
2. Which chemical is most commonly used as a coagulant in
conventional water treatment?
A. Sodium chloride
B. Aluminum sulfate (alum)
C. Sodium bicarbonate
D. Calcium carbonate
Answer: B. Aluminum sulfate (alum)
,Rationale: Alum is widely used because it effectively destabilizes
colloidal particles and promotes floc formation.
3. A sudden increase in filtered water turbidity is most likely caused
by:
A. Proper filter ripening
B. Filter breakthrough
C. Excess chlorine residual
D. High alkalinity
Answer: B. Filter breakthrough
Rationale: Filter breakthrough occurs when particles pass through the
filter media, causing elevated turbidity in the effluent.
4. What is the primary purpose of flocculation?
A. Oxidize metals
B. Increase pH
C. Promote particle collisions and floc growth
D. Add disinfectant
Answer: C. Promote particle collisions and floc growth
Rationale: Gentle mixing allows destabilized particles to collide and
form larger flocs that can be removed through settling or filtration.
5. Which parameter is most critical when optimizing coagulation?
A. Water color only
B. Turbidity only
C. Jar test results
D. Chlorine demand
Answer: C. Jar test results
,Rationale: Jar testing helps determine the optimal coagulant dosage
and treatment conditions for changing raw water quality.
6. What is the typical purpose of sedimentation basins?
A. Increase chlorine residual
B. Remove settled floc particles
C. Add fluoride
D. Increase dissolved oxygen
Answer: B. Remove settled floc particles
Rationale: Sedimentation allows heavy floc particles to settle by
gravity before filtration.
7. A filter run should generally be terminated when:
A. Turbidity decreases
B. Head loss and turbidity reach operational limits
C. pH exceeds 7.0
D. Water temperature drops
Answer: B. Head loss and turbidity reach operational limits
Rationale: Excessive head loss or turbidity indicates the filter is
becoming ineffective and requires backwashing.
8. Which disinfectant leaves a lasting residual in the distribution
system?
A. Ozone
B. UV radiation
C. Chlorine
D. Aeration
Answer: C. Chlorine
, Rationale: Chlorine provides a residual that continues protecting
water from microbial contamination throughout distribution.
9. The primary function of a clearwell is to:
A. Store sludge
B. Provide disinfection contact time and storage
C. Add coagulants
D. Remove hardness
Answer: B. Provide disinfection contact time and storage
Rationale: Clearwells allow sufficient contact time for disinfection
while providing treated water storage.
10. Which factor significantly affects chlorine disinfection
efficiency?
A. Water velocity only
B. CT value
C. Pipe diameter only
D. Filter media size
Answer: B. CT value
Rationale: CT is the product of disinfectant concentration and contact
time and is essential for pathogen inactivation.
11. What does "head loss" across a filter indicate?
A. Water quality improvement
B. Energy loss due to flow resistance
C. Chlorine consumption
D. Increased alkalinity
Answer: B. Energy loss due to flow resistance
Certification Grade II Exam With Actual
Questions & Verified Answers, Plus Explained
Rationales/Expert Verified For Guaranteed
100% Pass 2026/Latest Update/Instant
Download Pdf
1. What is the primary purpose of coagulation in water treatment?
A. To disinfect pathogens
B. To remove dissolved gases
C. To destabilize suspended particles
D. To increase alkalinity
Answer: C. To destabilize suspended particles
Rationale: Coagulation neutralizes the electrical charges on
suspended particles, allowing them to clump together during
flocculation and settle more easily during clarification.
2. Which chemical is most commonly used as a coagulant in
conventional water treatment?
A. Sodium chloride
B. Aluminum sulfate (alum)
C. Sodium bicarbonate
D. Calcium carbonate
Answer: B. Aluminum sulfate (alum)
,Rationale: Alum is widely used because it effectively destabilizes
colloidal particles and promotes floc formation.
3. A sudden increase in filtered water turbidity is most likely caused
by:
A. Proper filter ripening
B. Filter breakthrough
C. Excess chlorine residual
D. High alkalinity
Answer: B. Filter breakthrough
Rationale: Filter breakthrough occurs when particles pass through the
filter media, causing elevated turbidity in the effluent.
4. What is the primary purpose of flocculation?
A. Oxidize metals
B. Increase pH
C. Promote particle collisions and floc growth
D. Add disinfectant
Answer: C. Promote particle collisions and floc growth
Rationale: Gentle mixing allows destabilized particles to collide and
form larger flocs that can be removed through settling or filtration.
5. Which parameter is most critical when optimizing coagulation?
A. Water color only
B. Turbidity only
C. Jar test results
D. Chlorine demand
Answer: C. Jar test results
,Rationale: Jar testing helps determine the optimal coagulant dosage
and treatment conditions for changing raw water quality.
6. What is the typical purpose of sedimentation basins?
A. Increase chlorine residual
B. Remove settled floc particles
C. Add fluoride
D. Increase dissolved oxygen
Answer: B. Remove settled floc particles
Rationale: Sedimentation allows heavy floc particles to settle by
gravity before filtration.
7. A filter run should generally be terminated when:
A. Turbidity decreases
B. Head loss and turbidity reach operational limits
C. pH exceeds 7.0
D. Water temperature drops
Answer: B. Head loss and turbidity reach operational limits
Rationale: Excessive head loss or turbidity indicates the filter is
becoming ineffective and requires backwashing.
8. Which disinfectant leaves a lasting residual in the distribution
system?
A. Ozone
B. UV radiation
C. Chlorine
D. Aeration
Answer: C. Chlorine
, Rationale: Chlorine provides a residual that continues protecting
water from microbial contamination throughout distribution.
9. The primary function of a clearwell is to:
A. Store sludge
B. Provide disinfection contact time and storage
C. Add coagulants
D. Remove hardness
Answer: B. Provide disinfection contact time and storage
Rationale: Clearwells allow sufficient contact time for disinfection
while providing treated water storage.
10. Which factor significantly affects chlorine disinfection
efficiency?
A. Water velocity only
B. CT value
C. Pipe diameter only
D. Filter media size
Answer: B. CT value
Rationale: CT is the product of disinfectant concentration and contact
time and is essential for pathogen inactivation.
11. What does "head loss" across a filter indicate?
A. Water quality improvement
B. Energy loss due to flow resistance
C. Chlorine consumption
D. Increased alkalinity
Answer: B. Energy loss due to flow resistance
