NYC DEP Wastewater Treatment Plant
Operator Exam Questions With Correct
Answers (Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. What is the primary purpose of a wastewater treatment plant?
A) Produce drinking water
B) Remove contaminants from wastewater
C) Generate electricity
D) Store wastewater
Rationale: The main goal of a wastewater treatment plant is to
remove physical, chemical, and biological contaminants before
releasing water back into the environment.
2. Which stage of treatment involves the removal of large solids and
debris from incoming wastewater?
A) Secondary treatment
B) Preliminary treatment
C) Tertiary treatment
D) Disinfection
Rationale: Preliminary treatment uses screens and grit removal to
eliminate large solids and debris that could damage equipment.
3. In wastewater treatment, what is the primary function of primary
sedimentation tanks?
A) Remove dissolved nutrients
B) Settle suspended solids
C) Kill bacteria
, D) Filter water through sand
Rationale: Primary sedimentation tanks allow heavier solids to
settle out of the wastewater by gravity.
4. Which microorganism type is primarily responsible for breaking
down organic matter in activated sludge processes?
A) Viruses
B) Bacteria
C) Protozoa
D) Fungi
Rationale: Bacteria metabolize organic compounds, reducing BOD
and COD in wastewater.
5. BOD in wastewater stands for:
A) Basic Oxidation Demand
B) Biological Oxygen Deficiency
C) Biochemical Oxygen Demand
D) Bacterial Oxygen Depletion
Rationale: BOD measures the amount of oxygen required by
microorganisms to decompose organic matter in water.
6. What is the typical purpose of chlorination in wastewater
treatment?
A) Remove heavy metals
B) Reduce turbidity
C) Disinfect effluent
D) Settle solids
Rationale: Chlorination is used to kill pathogenic microorganisms
before discharge.
, 7. Nitrification in wastewater treatment refers to:
A) Removing phosphorus
B) Converting ammonia to nitrate
C) Oxidizing ammonia to nitrite and then nitrate
D) Reducing BOD
Rationale: Nitrification is a two-step biological process where
ammonia is first oxidized to nitrite and then to nitrate.
8. Denitrification is important because it:
A) Removes nitrogen from wastewater
B) Increases BOD
C) Produces methane
D) Kills bacteria
Rationale: Denitrifying bacteria convert nitrate to nitrogen gas,
preventing excess nitrogen discharge into water bodies.
9. Sludge thickening in wastewater treatment is performed to:
A) Increase water volume
B) Reduce water content and volume of sludge
C) Remove nitrogen
D) Disinfect the sludge
Rationale: Thickening concentrates the solids to make subsequent
handling and disposal easier.
10. Anaerobic digestion of sludge produces:
A) Oxygen
B) Methane and carbon dioxide
C) Chlorine
D) Nitrate
Operator Exam Questions With Correct
Answers (Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. What is the primary purpose of a wastewater treatment plant?
A) Produce drinking water
B) Remove contaminants from wastewater
C) Generate electricity
D) Store wastewater
Rationale: The main goal of a wastewater treatment plant is to
remove physical, chemical, and biological contaminants before
releasing water back into the environment.
2. Which stage of treatment involves the removal of large solids and
debris from incoming wastewater?
A) Secondary treatment
B) Preliminary treatment
C) Tertiary treatment
D) Disinfection
Rationale: Preliminary treatment uses screens and grit removal to
eliminate large solids and debris that could damage equipment.
3. In wastewater treatment, what is the primary function of primary
sedimentation tanks?
A) Remove dissolved nutrients
B) Settle suspended solids
C) Kill bacteria
, D) Filter water through sand
Rationale: Primary sedimentation tanks allow heavier solids to
settle out of the wastewater by gravity.
4. Which microorganism type is primarily responsible for breaking
down organic matter in activated sludge processes?
A) Viruses
B) Bacteria
C) Protozoa
D) Fungi
Rationale: Bacteria metabolize organic compounds, reducing BOD
and COD in wastewater.
5. BOD in wastewater stands for:
A) Basic Oxidation Demand
B) Biological Oxygen Deficiency
C) Biochemical Oxygen Demand
D) Bacterial Oxygen Depletion
Rationale: BOD measures the amount of oxygen required by
microorganisms to decompose organic matter in water.
6. What is the typical purpose of chlorination in wastewater
treatment?
A) Remove heavy metals
B) Reduce turbidity
C) Disinfect effluent
D) Settle solids
Rationale: Chlorination is used to kill pathogenic microorganisms
before discharge.
, 7. Nitrification in wastewater treatment refers to:
A) Removing phosphorus
B) Converting ammonia to nitrate
C) Oxidizing ammonia to nitrite and then nitrate
D) Reducing BOD
Rationale: Nitrification is a two-step biological process where
ammonia is first oxidized to nitrite and then to nitrate.
8. Denitrification is important because it:
A) Removes nitrogen from wastewater
B) Increases BOD
C) Produces methane
D) Kills bacteria
Rationale: Denitrifying bacteria convert nitrate to nitrogen gas,
preventing excess nitrogen discharge into water bodies.
9. Sludge thickening in wastewater treatment is performed to:
A) Increase water volume
B) Reduce water content and volume of sludge
C) Remove nitrogen
D) Disinfect the sludge
Rationale: Thickening concentrates the solids to make subsequent
handling and disposal easier.
10. Anaerobic digestion of sludge produces:
A) Oxygen
B) Methane and carbon dioxide
C) Chlorine
D) Nitrate
