California Water Treatment Operator
Certification Exam T5 Questions With Correct
Answers (Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. What is the primary purpose of coagulation in water treatment?
a) Disinfect the water
b) Remove dissolved salts
c) Aggregate suspended particles into larger flocs
d) Adjust pH
Coagulation causes fine particles to clump together into flocs,
making them easier to remove in sedimentation and filtration.
2. Which chemical is commonly used as a coagulant in water
treatment?
a) Chlorine
b) Aluminum sulfate (alum)
c) Sodium hydroxide
d) Ozone
Alum is widely used to destabilize suspended particles, aiding floc
formation.
3. The process of removing dissolved gases, such as carbon dioxide,
from water is called:
a) Coagulation
b) Sedimentation
c) Aeration
d) Filtration
, Aeration allows gases to escape from water by physical contact
with air.
4. What is the main function of a rapid sand filter?
a) Disinfect water
b) Remove suspended solids
c) Adjust water hardness
d) Remove dissolved gases
Rapid sand filters trap and remove suspended particles after
coagulation and sedimentation.
5. Which of the following is the primary purpose of chlorination?
a) Sedimentation
b) Coagulation
c) Disinfection
d) Filtration
Chlorination kills pathogens to make water safe for consumption.
6. The optimal pH range for coagulation with alum is typically:
a) 4.0–5.0
b) 6.0–7.5
c) 8.5–9.5
d) 10.0–11.0
Alum works best in slightly acidic to neutral water to form effective
flocs.
7. Turbidity in water is caused by:
a) Dissolved minerals
b) Suspended particles
c) High temperature
d) Chlorine residual
, Turbidity measures the cloudiness caused by particles suspended
in water.
8. What is the primary mechanism of sedimentation in water
treatment?
a) Chemical oxidation
b) Gravity settling of flocculated particles
c) Filtration through sand
d) UV radiation
Sedimentation allows heavier floc particles to settle out of the
water by gravity.
9. In water treatment, “flocculation” refers to:
a) Disinfection of bacteria
b) Removal of dissolved salts
c) Gentle mixing to grow flocs
d) Aeration of water
Flocculation gently stirs water so that coagulated particles collide
and form larger flocs.
10. Which type of filter requires frequent backwashing due to
high clogging potential?
a) Slow sand filter
b) Rapid sand filter
c) Activated carbon filter
d) Membrane filter
Rapid sand filters trap large amounts of suspended solids,
necessitating regular backwashing.
11. What is the purpose of adding lime in water treatment?
a) Coagulation
Certification Exam T5 Questions With Correct
Answers (Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. What is the primary purpose of coagulation in water treatment?
a) Disinfect the water
b) Remove dissolved salts
c) Aggregate suspended particles into larger flocs
d) Adjust pH
Coagulation causes fine particles to clump together into flocs,
making them easier to remove in sedimentation and filtration.
2. Which chemical is commonly used as a coagulant in water
treatment?
a) Chlorine
b) Aluminum sulfate (alum)
c) Sodium hydroxide
d) Ozone
Alum is widely used to destabilize suspended particles, aiding floc
formation.
3. The process of removing dissolved gases, such as carbon dioxide,
from water is called:
a) Coagulation
b) Sedimentation
c) Aeration
d) Filtration
, Aeration allows gases to escape from water by physical contact
with air.
4. What is the main function of a rapid sand filter?
a) Disinfect water
b) Remove suspended solids
c) Adjust water hardness
d) Remove dissolved gases
Rapid sand filters trap and remove suspended particles after
coagulation and sedimentation.
5. Which of the following is the primary purpose of chlorination?
a) Sedimentation
b) Coagulation
c) Disinfection
d) Filtration
Chlorination kills pathogens to make water safe for consumption.
6. The optimal pH range for coagulation with alum is typically:
a) 4.0–5.0
b) 6.0–7.5
c) 8.5–9.5
d) 10.0–11.0
Alum works best in slightly acidic to neutral water to form effective
flocs.
7. Turbidity in water is caused by:
a) Dissolved minerals
b) Suspended particles
c) High temperature
d) Chlorine residual
, Turbidity measures the cloudiness caused by particles suspended
in water.
8. What is the primary mechanism of sedimentation in water
treatment?
a) Chemical oxidation
b) Gravity settling of flocculated particles
c) Filtration through sand
d) UV radiation
Sedimentation allows heavier floc particles to settle out of the
water by gravity.
9. In water treatment, “flocculation” refers to:
a) Disinfection of bacteria
b) Removal of dissolved salts
c) Gentle mixing to grow flocs
d) Aeration of water
Flocculation gently stirs water so that coagulated particles collide
and form larger flocs.
10. Which type of filter requires frequent backwashing due to
high clogging potential?
a) Slow sand filter
b) Rapid sand filter
c) Activated carbon filter
d) Membrane filter
Rapid sand filters trap large amounts of suspended solids,
necessitating regular backwashing.
11. What is the purpose of adding lime in water treatment?
a) Coagulation
