Nevada Wastewater Treatment Plant
Operator Grade I Practice Exam
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. Which of the following is the primary function of a wastewater
treatment plant?
A. Generate electricity
B. Remove contaminants from wastewater
C. Produce drinking water
D. Store wastewater
Rationale: The main purpose of a wastewater treatment plant is to remove
physical, chemical, and biological contaminants to protect public health
and the environment.
, 2. What is the first step in wastewater treatment?
A. Biological treatment
B. Preliminary treatment (screening and grit removal)
C. Disinfection
D. Sludge digestion
Rationale: Preliminary treatment removes large debris and grit to prevent
damage to downstream equipment.
3. What is the purpose of a grit chamber?
A. Remove organic matter
B. Remove sand, gravel, and other heavy particles
C. Reduce nitrogen
D. Add chemicals to wastewater
Rationale: Grit chambers allow heavy inorganic particles to settle while
letting lighter organic material continue downstream.
4. Which process is used to reduce the biological oxygen demand (BOD)
in wastewater?
A. Sedimentation
B. Aerobic biological treatment
C. Filtration
D. Chlorination
Rationale: Aerobic microorganisms metabolize organic matter, reducing
BOD levels.
, 5. Primary clarifiers are used to:
A. Remove settleable solids
B. Remove dissolved chemicals
C. Disinfect water
D. Remove nutrients
Rationale: Primary clarifiers allow solids to settle out of the wastewater by
gravity.
6. Which of the following is a sign of a properly functioning aeration
tank?
A. No foam
B. Steady sludge volume and adequate dissolved oxygen
C. Strong ammonia smell
D. Floating scum layer
Rationale: Proper aeration ensures sufficient oxygen for microbial activity,
resulting in stable sludge and odor control.
7. What does BOD stand for?
A. Biological Oxidation Demand
B. Biochemical Oxygen Demand
C. Basic Oxygen Density
D. Biochemical Oxidation Depth
Rationale: BOD measures the amount of dissolved oxygen needed by
microorganisms to decompose organic matter in water.
, 8. Which type of microorganism primarily removes ammonia in
nitrification?
A. Fungi
B. Nitrifying bacteria
C. Protozoa
D. Viruses
Rationale: Nitrifying bacteria convert ammonia to nitrite and then nitrate
during nitrification.
9. In wastewater, pH is important because:
A. It determines water temperature
B. It affects microbial activity and chemical reactions
C. It measures oxygen content
D. It indicates solids concentration
Rationale: Microorganisms and chemical treatments function optimally
within specific pH ranges.
10. Which chemical is commonly used for disinfection in wastewater
treatment?
A. Fluoride
B. Chlorine
C. Ammonia
D. Sulfate
Operator Grade I Practice Exam
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. Which of the following is the primary function of a wastewater
treatment plant?
A. Generate electricity
B. Remove contaminants from wastewater
C. Produce drinking water
D. Store wastewater
Rationale: The main purpose of a wastewater treatment plant is to remove
physical, chemical, and biological contaminants to protect public health
and the environment.
, 2. What is the first step in wastewater treatment?
A. Biological treatment
B. Preliminary treatment (screening and grit removal)
C. Disinfection
D. Sludge digestion
Rationale: Preliminary treatment removes large debris and grit to prevent
damage to downstream equipment.
3. What is the purpose of a grit chamber?
A. Remove organic matter
B. Remove sand, gravel, and other heavy particles
C. Reduce nitrogen
D. Add chemicals to wastewater
Rationale: Grit chambers allow heavy inorganic particles to settle while
letting lighter organic material continue downstream.
4. Which process is used to reduce the biological oxygen demand (BOD)
in wastewater?
A. Sedimentation
B. Aerobic biological treatment
C. Filtration
D. Chlorination
Rationale: Aerobic microorganisms metabolize organic matter, reducing
BOD levels.
, 5. Primary clarifiers are used to:
A. Remove settleable solids
B. Remove dissolved chemicals
C. Disinfect water
D. Remove nutrients
Rationale: Primary clarifiers allow solids to settle out of the wastewater by
gravity.
6. Which of the following is a sign of a properly functioning aeration
tank?
A. No foam
B. Steady sludge volume and adequate dissolved oxygen
C. Strong ammonia smell
D. Floating scum layer
Rationale: Proper aeration ensures sufficient oxygen for microbial activity,
resulting in stable sludge and odor control.
7. What does BOD stand for?
A. Biological Oxidation Demand
B. Biochemical Oxygen Demand
C. Basic Oxygen Density
D. Biochemical Oxidation Depth
Rationale: BOD measures the amount of dissolved oxygen needed by
microorganisms to decompose organic matter in water.
, 8. Which type of microorganism primarily removes ammonia in
nitrification?
A. Fungi
B. Nitrifying bacteria
C. Protozoa
D. Viruses
Rationale: Nitrifying bacteria convert ammonia to nitrite and then nitrate
during nitrification.
9. In wastewater, pH is important because:
A. It determines water temperature
B. It affects microbial activity and chemical reactions
C. It measures oxygen content
D. It indicates solids concentration
Rationale: Microorganisms and chemical treatments function optimally
within specific pH ranges.
10. Which chemical is commonly used for disinfection in wastewater
treatment?
A. Fluoride
B. Chlorine
C. Ammonia
D. Sulfate
