Nevada Drinking Water System
Operator Grade V Certification Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. Which of the following is the primary purpose of a drinking water
treatment plant?
A. To remove all dissolved minerals
B. To reduce water hardness
C. To remove contaminants to meet safe drinking water standards
D. To increase water alkalinity
The primary purpose of a drinking water treatment plant is to remove
physical, chemical, and biological contaminants to ensure water meets
regulatory safe drinking water standards.
2. In the coagulation process, which chemical is commonly used to
destabilize particles?
A. Sodium hydroxide
B. Aluminum sulfate (alum)
C. Chlorine dioxide
D. Fluoride
Aluminum sulfate, commonly called alum, is used in coagulation to
neutralize charges on particles, allowing them to aggregate into larger
flocs for removal.
, 3. Which type of filtration is most effective for removing turbidity from
water?
A. Reverse osmosis
B. Rapid sand filtration
C. Activated carbon
D. Ion exchange
Rapid sand filtration effectively removes suspended solids and reduces
turbidity by passing water through a granular medium.
4. What is the primary disinfectant used in most U.S. drinking water
systems?
A. Ozone
B. Iodine
C. Chlorine
D. Ultraviolet light
Chlorine is widely used because it is effective against bacteria and viruses,
provides residual protection in distribution systems, and is economical.
5. The main purpose of pH adjustment in water treatment is to:
A. Improve taste only
B. Optimize chemical reactions and corrosion control
C. Increase hardness
D. Remove pathogens
Adjusting pH ensures optimal coagulation, prevents corrosion of
distribution pipes, and improves overall water stability.
6. Which of the following is considered a secondary drinking water
standard?
A. Maximum Contaminant Level for lead
B. Maximum Contaminant Level for nitrate
C. Acceptable aesthetic limits like color and taste
D. Maximum Contaminant Level for arsenic
, Secondary standards address aesthetic qualities of water such as taste,
color, and odor, which are not directly related to health risks.
7. What is the primary function of a sedimentation basin?
A. Filter dissolved metals
B. Allow flocs to settle out of water
C. Remove bacteria by chlorination
D. Increase alkalinity
Sedimentation basins allow coagulated particles and flocs to settle,
reducing turbidity before filtration.
8. In water treatment, flocculation refers to:
A. Gentle mixing to form larger flocs from destabilized particles
B. Rapid filtration
C. Disinfection
D. Chemical pH adjustment
Flocculation involves slow, controlled mixing that allows small particles to
collide and form larger, settleable flocs.
9. Which of the following factors most influences chlorine disinfection
effectiveness?
A. Hardness
B. pH and contact time
C. Water temperature only
D. Color
Chlorine effectiveness is strongly affected by water pH and the amount of
time it is in contact with the water to ensure adequate pathogen
inactivation.
10. The safe storage of chlorine gas in a water plant requires:
A. High temperatures
B. Cool, dry, and well-ventilated areas
C. Direct sunlight
D. Humid environments
Operator Grade V Certification Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. Which of the following is the primary purpose of a drinking water
treatment plant?
A. To remove all dissolved minerals
B. To reduce water hardness
C. To remove contaminants to meet safe drinking water standards
D. To increase water alkalinity
The primary purpose of a drinking water treatment plant is to remove
physical, chemical, and biological contaminants to ensure water meets
regulatory safe drinking water standards.
2. In the coagulation process, which chemical is commonly used to
destabilize particles?
A. Sodium hydroxide
B. Aluminum sulfate (alum)
C. Chlorine dioxide
D. Fluoride
Aluminum sulfate, commonly called alum, is used in coagulation to
neutralize charges on particles, allowing them to aggregate into larger
flocs for removal.
, 3. Which type of filtration is most effective for removing turbidity from
water?
A. Reverse osmosis
B. Rapid sand filtration
C. Activated carbon
D. Ion exchange
Rapid sand filtration effectively removes suspended solids and reduces
turbidity by passing water through a granular medium.
4. What is the primary disinfectant used in most U.S. drinking water
systems?
A. Ozone
B. Iodine
C. Chlorine
D. Ultraviolet light
Chlorine is widely used because it is effective against bacteria and viruses,
provides residual protection in distribution systems, and is economical.
5. The main purpose of pH adjustment in water treatment is to:
A. Improve taste only
B. Optimize chemical reactions and corrosion control
C. Increase hardness
D. Remove pathogens
Adjusting pH ensures optimal coagulation, prevents corrosion of
distribution pipes, and improves overall water stability.
6. Which of the following is considered a secondary drinking water
standard?
A. Maximum Contaminant Level for lead
B. Maximum Contaminant Level for nitrate
C. Acceptable aesthetic limits like color and taste
D. Maximum Contaminant Level for arsenic
, Secondary standards address aesthetic qualities of water such as taste,
color, and odor, which are not directly related to health risks.
7. What is the primary function of a sedimentation basin?
A. Filter dissolved metals
B. Allow flocs to settle out of water
C. Remove bacteria by chlorination
D. Increase alkalinity
Sedimentation basins allow coagulated particles and flocs to settle,
reducing turbidity before filtration.
8. In water treatment, flocculation refers to:
A. Gentle mixing to form larger flocs from destabilized particles
B. Rapid filtration
C. Disinfection
D. Chemical pH adjustment
Flocculation involves slow, controlled mixing that allows small particles to
collide and form larger, settleable flocs.
9. Which of the following factors most influences chlorine disinfection
effectiveness?
A. Hardness
B. pH and contact time
C. Water temperature only
D. Color
Chlorine effectiveness is strongly affected by water pH and the amount of
time it is in contact with the water to ensure adequate pathogen
inactivation.
10. The safe storage of chlorine gas in a water plant requires:
A. High temperatures
B. Cool, dry, and well-ventilated areas
C. Direct sunlight
D. Humid environments
