AWWA Water Treatment Operator
Certification Grade I Exam With Actual
Questions & Verified Answers, Plus Explained
Rationales/Expert Verified For Guaranteed
100% Pass 2026/Latest Update/Instant
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1. What is the primary purpose of coagulation in a water treatment
process?
A. Remove dissolved gases
B. Disinfect water
C. Cause small suspended particles to destabilize and form larger
particles
D. Increase water hardness
Answer: C. Cause small suspended particles to destabilize and form
larger particles
Rationale: Coagulation involves adding chemicals such as alum or
ferric chloride to neutralize particle charges, allowing particles to
combine into larger flocs that can be removed through sedimentation
and filtration.
2. Which chemical is most commonly used as a coagulant in water
treatment?
A. Chlorine
B. Alum
,C. Lime
D. Fluoride
Answer: B. Alum
Rationale: Aluminum sulfate (alum) is one of the most widely used
coagulants because it effectively destabilizes suspended particles and
promotes floc formation.
3. The process of gently mixing water after coagulation to encourage
floc formation is called:
A. Aeration
B. Sedimentation
C. Flocculation
D. Filtration
Answer: C. Flocculation
Rationale: Flocculation uses slow mixing to encourage small particles
to collide and form larger, settleable flocs.
4. What is the primary purpose of sedimentation?
A. Add oxygen to water
B. Remove suspended solids by gravity settling
C. Adjust pH
D. Destroy microorganisms
Answer: B. Remove suspended solids by gravity settling
Rationale: Sedimentation allows heavier floc particles to settle to the
bottom of a basin before filtration.
5. A filter's turbidity reading suddenly increases. The operator
should first:
,A. Increase water production immediately
B. Investigate filter performance and possible breakthrough
C. Add more fluoride
D. Stop disinfection
Answer: B. Investigate filter performance and possible breakthrough
Rationale: Increased turbidity may indicate filter breakthrough, media
problems, or operational issues requiring immediate attention.
6. Turbidity is measured in:
A. mg/L
B. NTU
C. ppm
D. psi
Answer: B. NTU
Rationale: Nephelometric Turbidity Units (NTU) measure water clarity
based on light scattering by suspended particles.
7. Which treatment process primarily removes disease-causing
microorganisms?
A. Flocculation
B. Sedimentation
C. Disinfection
D. Aeration
Answer: C. Disinfection
Rationale: Disinfection destroys or inactivates pathogens to make
water safe for consumption.
8. Chlorine demand is defined as:
, A. Total chlorine added
B. Chlorine remaining after contact time
C. Difference between chlorine applied and residual chlorine
D. Chlorine concentration in storage tanks
Answer: C. Difference between chlorine applied and residual chlorine
Rationale: Chlorine demand represents the amount of chlorine
consumed by reactions with substances in the water.
9. Free chlorine residual refers to:
A. Chlorine combined with ammonia
B. Chlorine available for disinfection after demand is satisfied
C. Chlorine in gas cylinders
D. Total chlorine dosage applied
Answer: B. Chlorine available for disinfection after demand is satisfied
Rationale: Free chlorine provides effective ongoing disinfection and
protection within the distribution system.
10. What is the primary purpose of filtration?
A. Remove dissolved salts
B. Remove suspended particles and microorganisms
C. Increase alkalinity
D. Add disinfectant
Answer: B. Remove suspended particles and microorganisms
Rationale: Filtration removes particles that remain after
sedimentation and improves water quality.
11. Head loss through a filter generally increases as:
A. The filter becomes cleaner
B. Water temperature decreases
Certification Grade I 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 a water treatment
process?
A. Remove dissolved gases
B. Disinfect water
C. Cause small suspended particles to destabilize and form larger
particles
D. Increase water hardness
Answer: C. Cause small suspended particles to destabilize and form
larger particles
Rationale: Coagulation involves adding chemicals such as alum or
ferric chloride to neutralize particle charges, allowing particles to
combine into larger flocs that can be removed through sedimentation
and filtration.
2. Which chemical is most commonly used as a coagulant in water
treatment?
A. Chlorine
B. Alum
,C. Lime
D. Fluoride
Answer: B. Alum
Rationale: Aluminum sulfate (alum) is one of the most widely used
coagulants because it effectively destabilizes suspended particles and
promotes floc formation.
3. The process of gently mixing water after coagulation to encourage
floc formation is called:
A. Aeration
B. Sedimentation
C. Flocculation
D. Filtration
Answer: C. Flocculation
Rationale: Flocculation uses slow mixing to encourage small particles
to collide and form larger, settleable flocs.
4. What is the primary purpose of sedimentation?
A. Add oxygen to water
B. Remove suspended solids by gravity settling
C. Adjust pH
D. Destroy microorganisms
Answer: B. Remove suspended solids by gravity settling
Rationale: Sedimentation allows heavier floc particles to settle to the
bottom of a basin before filtration.
5. A filter's turbidity reading suddenly increases. The operator
should first:
,A. Increase water production immediately
B. Investigate filter performance and possible breakthrough
C. Add more fluoride
D. Stop disinfection
Answer: B. Investigate filter performance and possible breakthrough
Rationale: Increased turbidity may indicate filter breakthrough, media
problems, or operational issues requiring immediate attention.
6. Turbidity is measured in:
A. mg/L
B. NTU
C. ppm
D. psi
Answer: B. NTU
Rationale: Nephelometric Turbidity Units (NTU) measure water clarity
based on light scattering by suspended particles.
7. Which treatment process primarily removes disease-causing
microorganisms?
A. Flocculation
B. Sedimentation
C. Disinfection
D. Aeration
Answer: C. Disinfection
Rationale: Disinfection destroys or inactivates pathogens to make
water safe for consumption.
8. Chlorine demand is defined as:
, A. Total chlorine added
B. Chlorine remaining after contact time
C. Difference between chlorine applied and residual chlorine
D. Chlorine concentration in storage tanks
Answer: C. Difference between chlorine applied and residual chlorine
Rationale: Chlorine demand represents the amount of chlorine
consumed by reactions with substances in the water.
9. Free chlorine residual refers to:
A. Chlorine combined with ammonia
B. Chlorine available for disinfection after demand is satisfied
C. Chlorine in gas cylinders
D. Total chlorine dosage applied
Answer: B. Chlorine available for disinfection after demand is satisfied
Rationale: Free chlorine provides effective ongoing disinfection and
protection within the distribution system.
10. What is the primary purpose of filtration?
A. Remove dissolved salts
B. Remove suspended particles and microorganisms
C. Increase alkalinity
D. Add disinfectant
Answer: B. Remove suspended particles and microorganisms
Rationale: Filtration removes particles that remain after
sedimentation and improves water quality.
11. Head loss through a filter generally increases as:
A. The filter becomes cleaner
B. Water temperature decreases
