AZ L-84 Water Treatment Contractor
Exam Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1.What is the primary purpose of a water treatment system?
A. Increase water temperature
B. Remove contaminants and ensure water is safe for consumption
C. Add color to water
D. Reduce water flow
Rationale: The main goal of water treatment is to remove physical,
chemical, and biological contaminants to make water safe for human use.
2. Which of the following is a common chemical used in water
disinfection?
A. Sodium chloride
B. Calcium carbonate
C. Chlorine
D. Magnesium sulfate
Rationale: Chlorine is widely used to kill bacteria and other pathogens in
water systems.
3. What is the process of removing suspended solids from water called?
A. Aeration
B. Filtration
C. Chlorination
D. Sedimentation
Rationale: Filtration removes suspended solids by passing water through a
medium that traps particles.
, 4. What is the standard method to measure water hardness?
A. pH test
B. Titration with EDTA
C. Chlorine residual test
D. Turbidity test
Rationale: Water hardness is determined by measuring the concentration
of calcium and magnesium ions, commonly via EDTA titration.
5. What is the purpose of coagulation in water treatment?
A. To remove dissolved oxygen
B. To aggregate fine particles for easier removal
C. To disinfect water
D. To increase water flow
Rationale: Coagulation involves adding chemicals (like alum) to clump
small particles into larger ones called flocs, which can then be removed by
sedimentation or filtration.
6. What is the main function of a sedimentation basin?
A. To aerate water
B. To disinfect water
C. To allow flocs to settle out of the water
D. To soften water
Rationale: Sedimentation basins provide time for coagulated particles
(flocs) to settle to the bottom.
7. Which type of filter is most commonly used in municipal water
treatment plants?
A. Cartridge filter
B. Reverse osmosis membrane
C. Rapid sand filter
D. Bag filter
Rationale: Rapid sand filters are widely used for removing suspended solids
from large volumes of water.
, 8. What is the acceptable pH range for drinking water according to EPA
standards?
A. 4.5–6.5
B. 6.5–8.5
C. 8.5–10.5
D. 5.0–7.0
Rationale: Drinking water should have a pH between 6.5 and 8.5 to prevent
corrosion and maintain taste quality.
9. Which pathogen is most resistant to chlorine disinfection?
A. E. coli
B. Salmonella
C. Cryptosporidium
D. Giardia lamblia
Rationale: Cryptosporidium oocysts are highly resistant to chlorine,
requiring additional treatment methods like filtration or UV.
10. What is the purpose of aeration in water treatment?
A. Add chlorine
B. Remove turbidity
C. Remove dissolved gases and oxidize metals
D. Reduce water temperature
Rationale: Aeration helps remove dissolved gases like CO₂ and oxidizes
iron and manganese for easier removal.
11. Which chemical is commonly used for water softening?
A. Alum
B. Sodium carbonate (soda ash)
C. Chlorine
D. Fluoride
Rationale: Sodium carbonate reacts with calcium and magnesium ions,
reducing water hardness.
12. What does TDS stand for in water treatment?
A. Total Decontamination Solution
Exam Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1.What is the primary purpose of a water treatment system?
A. Increase water temperature
B. Remove contaminants and ensure water is safe for consumption
C. Add color to water
D. Reduce water flow
Rationale: The main goal of water treatment is to remove physical,
chemical, and biological contaminants to make water safe for human use.
2. Which of the following is a common chemical used in water
disinfection?
A. Sodium chloride
B. Calcium carbonate
C. Chlorine
D. Magnesium sulfate
Rationale: Chlorine is widely used to kill bacteria and other pathogens in
water systems.
3. What is the process of removing suspended solids from water called?
A. Aeration
B. Filtration
C. Chlorination
D. Sedimentation
Rationale: Filtration removes suspended solids by passing water through a
medium that traps particles.
, 4. What is the standard method to measure water hardness?
A. pH test
B. Titration with EDTA
C. Chlorine residual test
D. Turbidity test
Rationale: Water hardness is determined by measuring the concentration
of calcium and magnesium ions, commonly via EDTA titration.
5. What is the purpose of coagulation in water treatment?
A. To remove dissolved oxygen
B. To aggregate fine particles for easier removal
C. To disinfect water
D. To increase water flow
Rationale: Coagulation involves adding chemicals (like alum) to clump
small particles into larger ones called flocs, which can then be removed by
sedimentation or filtration.
6. What is the main function of a sedimentation basin?
A. To aerate water
B. To disinfect water
C. To allow flocs to settle out of the water
D. To soften water
Rationale: Sedimentation basins provide time for coagulated particles
(flocs) to settle to the bottom.
7. Which type of filter is most commonly used in municipal water
treatment plants?
A. Cartridge filter
B. Reverse osmosis membrane
C. Rapid sand filter
D. Bag filter
Rationale: Rapid sand filters are widely used for removing suspended solids
from large volumes of water.
, 8. What is the acceptable pH range for drinking water according to EPA
standards?
A. 4.5–6.5
B. 6.5–8.5
C. 8.5–10.5
D. 5.0–7.0
Rationale: Drinking water should have a pH between 6.5 and 8.5 to prevent
corrosion and maintain taste quality.
9. Which pathogen is most resistant to chlorine disinfection?
A. E. coli
B. Salmonella
C. Cryptosporidium
D. Giardia lamblia
Rationale: Cryptosporidium oocysts are highly resistant to chlorine,
requiring additional treatment methods like filtration or UV.
10. What is the purpose of aeration in water treatment?
A. Add chlorine
B. Remove turbidity
C. Remove dissolved gases and oxidize metals
D. Reduce water temperature
Rationale: Aeration helps remove dissolved gases like CO₂ and oxidizes
iron and manganese for easier removal.
11. Which chemical is commonly used for water softening?
A. Alum
B. Sodium carbonate (soda ash)
C. Chlorine
D. Fluoride
Rationale: Sodium carbonate reacts with calcium and magnesium ions,
reducing water hardness.
12. What does TDS stand for in water treatment?
A. Total Decontamination Solution
