Small Water System General Operation
Exam – 100 Practice Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
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1. What is the primary purpose of a water treatment plant?
A. Increase water hardness
B. Provide safe and potable water
C. Add minerals to water
D. Reduce water pressure
Rationale: The main goal of a water treatment plant is to remove
contaminants and provide water that is safe for human consumption.
2. Chlorine is commonly used in water treatment for:
A. Increasing turbidity
B. Disinfecting water
, C. Removing heavy metals
D. Adjusting pH
Rationale: Chlorine is a powerful disinfectant that kills pathogens
and prevents waterborne diseases.
3. Which of the following is considered a physical water treatment
process?
A. Coagulation
B. Chlorination
C. Sedimentation
D. Fluoridation
Rationale: Sedimentation physically removes suspended solids from
water by allowing them to settle.
4. Turbidity in water is caused by:
A. Dissolved gases
B. Heavy metals
C. Suspended particles
D. Bacteria
Rationale: Turbidity results from suspended particles such as silt,
clay, and organic matter, which make water appear cloudy.
5. The safe chlorine residual in a small water system is typically:
A. 0.01–0.05 mg/L
B. 0.1–0.2 mg/L
C. 0.2–1.0 mg/L
, D. 1.5–2.0 mg/L
Rationale: Maintaining 0.2–1.0 mg/L free chlorine ensures adequate
disinfection while minimizing taste and odor issues.
6. A common method for controlling iron and manganese in water is:
A. Chlorination
B. Oxidation followed by filtration
C. Coagulation
D. UV treatment
Rationale: Iron and manganese are oxidized and then removed via
filtration to prevent staining and taste problems.
7. Which process removes most bacteria and viruses in water?
A. Sedimentation
B. Disinfection
C. Coagulation
D. Aeration
Rationale: Disinfection, typically with chlorine or UV, is the primary
process for killing pathogens.
8. A water source is most vulnerable to contamination during:
A. Winter months
B. High water pressure
C. Low flow or drawdown periods
D. High alkalinity
, Rationale: Low flow or drawdown periods can allow contaminants to
enter or concentrate in the source.
9. pH adjustment in water is important to:
A. Remove pathogens
B. Prevent corrosion and scaling
C. Increase turbidity
D. Add chlorine
Rationale: Proper pH levels protect pipes and equipment and
improve the effectiveness of disinfection.
10. The purpose of a sedimentation basin is to:
A. Disinfect water
B. Allow solids to settle out
C. Add chemicals
D. Adjust pH
Rationale: Sedimentation allows heavier particles to settle before
filtration, improving water clarity.
11. Which is a common coagulant used in water treatment?
A. Chlorine
B. Aluminum sulfate (alum)
C. Sodium hydroxide
D. Fluoride
Rationale: Alum is widely used to cause fine particles to clump
together for easier removal.
Exam – 100 Practice Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
1. What is the primary purpose of a water treatment plant?
A. Increase water hardness
B. Provide safe and potable water
C. Add minerals to water
D. Reduce water pressure
Rationale: The main goal of a water treatment plant is to remove
contaminants and provide water that is safe for human consumption.
2. Chlorine is commonly used in water treatment for:
A. Increasing turbidity
B. Disinfecting water
, C. Removing heavy metals
D. Adjusting pH
Rationale: Chlorine is a powerful disinfectant that kills pathogens
and prevents waterborne diseases.
3. Which of the following is considered a physical water treatment
process?
A. Coagulation
B. Chlorination
C. Sedimentation
D. Fluoridation
Rationale: Sedimentation physically removes suspended solids from
water by allowing them to settle.
4. Turbidity in water is caused by:
A. Dissolved gases
B. Heavy metals
C. Suspended particles
D. Bacteria
Rationale: Turbidity results from suspended particles such as silt,
clay, and organic matter, which make water appear cloudy.
5. The safe chlorine residual in a small water system is typically:
A. 0.01–0.05 mg/L
B. 0.1–0.2 mg/L
C. 0.2–1.0 mg/L
, D. 1.5–2.0 mg/L
Rationale: Maintaining 0.2–1.0 mg/L free chlorine ensures adequate
disinfection while minimizing taste and odor issues.
6. A common method for controlling iron and manganese in water is:
A. Chlorination
B. Oxidation followed by filtration
C. Coagulation
D. UV treatment
Rationale: Iron and manganese are oxidized and then removed via
filtration to prevent staining and taste problems.
7. Which process removes most bacteria and viruses in water?
A. Sedimentation
B. Disinfection
C. Coagulation
D. Aeration
Rationale: Disinfection, typically with chlorine or UV, is the primary
process for killing pathogens.
8. A water source is most vulnerable to contamination during:
A. Winter months
B. High water pressure
C. Low flow or drawdown periods
D. High alkalinity
, Rationale: Low flow or drawdown periods can allow contaminants to
enter or concentrate in the source.
9. pH adjustment in water is important to:
A. Remove pathogens
B. Prevent corrosion and scaling
C. Increase turbidity
D. Add chlorine
Rationale: Proper pH levels protect pipes and equipment and
improve the effectiveness of disinfection.
10. The purpose of a sedimentation basin is to:
A. Disinfect water
B. Allow solids to settle out
C. Add chemicals
D. Adjust pH
Rationale: Sedimentation allows heavier particles to settle before
filtration, improving water clarity.
11. Which is a common coagulant used in water treatment?
A. Chlorine
B. Aluminum sulfate (alum)
C. Sodium hydroxide
D. Fluoride
Rationale: Alum is widely used to cause fine particles to clump
together for easier removal.
