AR WT Water Treatment Contractor
Exam Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. Which of the following is the primary purpose of a water treatment
system?
A) Increase water hardness
B) Improve water quality for consumption and use
C) Add color to water
D) Increase water turbidity
Rationale: The main goal of water treatment is to make water safe
and suitable for its intended use by removing contaminants.
2. What is the typical pH range for treated drinking water?
A) 4.0–5.0
B) 5.5–6.5
C) 6.5–8.5
D) 8.5–10.0
Rationale: Drinking water is generally maintained between pH 6.5
and 8.5 to prevent corrosion and scaling and ensure safety.
3. Chlorination in water treatment is primarily used to:
A) Remove turbidity
B) Soften water
C) Disinfect water
D) Remove heavy metals
Rationale: Chlorine is a disinfectant that kills pathogenic
microorganisms in water.
4. The removal of suspended solids from water is achieved mainly
through:
, A) Filtration
B) Sedimentation
C) Both A and B
D) Aeration
Rationale: Sedimentation allows solids to settle, while filtration
removes remaining suspended particles.
5. Hard water is characterized by:
A) High microbial content
B) High calcium and magnesium concentrations
C) Low pH
D) High chlorine content
Rationale: Hardness is caused by dissolved calcium and magnesium
ions.
6. Reverse osmosis primarily removes:
A) Suspended solids only
B) Dissolved salts and minerals
C) Turbidity
D) Chlorine
Rationale: Reverse osmosis uses a semi-permeable membrane to
remove dissolved salts and impurities.
7. A coagulant commonly used in water treatment is:
A) Sodium hydroxide
B) Aluminum sulfate (alum)
C) Chlorine gas
D) Activated carbon
Rationale: Alum is used to coagulate and aggregate fine particles for
easier removal.
8. The main function of a sedimentation basin is to:
A) Disinfect water
B) Allow suspended particles to settle
C) Adjust pH
D) Add minerals
Rationale: Sedimentation allows gravity to remove larger suspended
solids before filtration.
9. Water turbidity is primarily caused by:
A) Chlorine
B) Fluoride
, C) Suspended particles and colloids
D) Dissolved oxygen
Rationale: Turbidity is a measure of cloudiness caused by particles in
water.
10. Softening water reduces:
A) pH
B) Calcium and magnesium ions
C) Chlorine
D) Nitrate levels
Rationale: Water softening replaces hardness-causing ions with
sodium or potassium ions.
11. The safe level of residual chlorine in drinking water is generally:
A) 0.01–0.05 mg/L
B) 0.1–0.2 mg/L
C) 0.2–0.5 mg/L
D) 1–2 mg/L
Rationale: Maintaining residual chlorine at 0.2–0.5 mg/L ensures
disinfection without causing taste issues.
12. Activated carbon in water treatment is used to:
A) Soften water
B) Remove organic compounds and odors
C) Kill bacteria
D) Adjust pH
Rationale: Activated carbon adsorbs dissolved organics, chlorine, and
other contaminants.
13. Aeration in water treatment is primarily used to:
A) Add chlorine
B) Remove dissolved gases such as CO₂ and H₂S
C) Remove suspended solids
D) Adjust pH
Rationale: Aeration helps release unwanted gases and oxidize iron
and manganese.
14. The most common method for controlling microbial
contamination in water is:
A) Sedimentation
B) Filtration
C) Disinfection
Exam Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. Which of the following is the primary purpose of a water treatment
system?
A) Increase water hardness
B) Improve water quality for consumption and use
C) Add color to water
D) Increase water turbidity
Rationale: The main goal of water treatment is to make water safe
and suitable for its intended use by removing contaminants.
2. What is the typical pH range for treated drinking water?
A) 4.0–5.0
B) 5.5–6.5
C) 6.5–8.5
D) 8.5–10.0
Rationale: Drinking water is generally maintained between pH 6.5
and 8.5 to prevent corrosion and scaling and ensure safety.
3. Chlorination in water treatment is primarily used to:
A) Remove turbidity
B) Soften water
C) Disinfect water
D) Remove heavy metals
Rationale: Chlorine is a disinfectant that kills pathogenic
microorganisms in water.
4. The removal of suspended solids from water is achieved mainly
through:
, A) Filtration
B) Sedimentation
C) Both A and B
D) Aeration
Rationale: Sedimentation allows solids to settle, while filtration
removes remaining suspended particles.
5. Hard water is characterized by:
A) High microbial content
B) High calcium and magnesium concentrations
C) Low pH
D) High chlorine content
Rationale: Hardness is caused by dissolved calcium and magnesium
ions.
6. Reverse osmosis primarily removes:
A) Suspended solids only
B) Dissolved salts and minerals
C) Turbidity
D) Chlorine
Rationale: Reverse osmosis uses a semi-permeable membrane to
remove dissolved salts and impurities.
7. A coagulant commonly used in water treatment is:
A) Sodium hydroxide
B) Aluminum sulfate (alum)
C) Chlorine gas
D) Activated carbon
Rationale: Alum is used to coagulate and aggregate fine particles for
easier removal.
8. The main function of a sedimentation basin is to:
A) Disinfect water
B) Allow suspended particles to settle
C) Adjust pH
D) Add minerals
Rationale: Sedimentation allows gravity to remove larger suspended
solids before filtration.
9. Water turbidity is primarily caused by:
A) Chlorine
B) Fluoride
, C) Suspended particles and colloids
D) Dissolved oxygen
Rationale: Turbidity is a measure of cloudiness caused by particles in
water.
10. Softening water reduces:
A) pH
B) Calcium and magnesium ions
C) Chlorine
D) Nitrate levels
Rationale: Water softening replaces hardness-causing ions with
sodium or potassium ions.
11. The safe level of residual chlorine in drinking water is generally:
A) 0.01–0.05 mg/L
B) 0.1–0.2 mg/L
C) 0.2–0.5 mg/L
D) 1–2 mg/L
Rationale: Maintaining residual chlorine at 0.2–0.5 mg/L ensures
disinfection without causing taste issues.
12. Activated carbon in water treatment is used to:
A) Soften water
B) Remove organic compounds and odors
C) Kill bacteria
D) Adjust pH
Rationale: Activated carbon adsorbs dissolved organics, chlorine, and
other contaminants.
13. Aeration in water treatment is primarily used to:
A) Add chlorine
B) Remove dissolved gases such as CO₂ and H₂S
C) Remove suspended solids
D) Adjust pH
Rationale: Aeration helps release unwanted gases and oxidize iron
and manganese.
14. The most common method for controlling microbial
contamination in water is:
A) Sedimentation
B) Filtration
C) Disinfection
