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NYC DEP WASTEWATER TREATMENT PLANT OPERATOR
GRADE ONE CERTIFICATION EXAM 2026/2027 COMPLETE
(150) CURRENT TESTING QUESTIONS AND CORRECT
ANSWERS WITH DETAILED RATIONALES.
WASTEWATER
Prepare effectively for the NYC DEP Wastewater Treatment Plant Operator Grade One
Certification Exam with this focused practice resource. It supports review of
wastewater treatment processes, plant operations, water quality, equipment
maintenance, safety procedures, and regulatory requirements. Use the material to
reinforce your technical knowledge, practice key concepts, and identify areas that
may require additional study. This resource is suited for wastewater treatment
operators, environmental professionals, plant technicians, and candidates preparing
for NYC DEP Grade One certification examinations.
MULTIPLE CHOICE.
SECTION 1: WASTEWATER TREATMENT PROCESSES (Questions 1–45)
1. What is the primary purpose of a wastewater treatment plant?
(A) To increase water hardness
(B) To remove pollutants and contaminants from wastewater before discharge
(C) To add chemicals to drinking water
(D) To generate electricity from wastewater
Answer: (B) To remove pollutants and contaminants from wastewater
before discharge
Rationale: Wastewater treatment plants are designed to remove physical,
chemical, and biological pollutants from wastewater to protect human health
and the environment before the treated effluent is discharged to receiving
waters.
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2. What is the primary purpose of preliminary treatment in a wastewater
treatment plant?
(A) To remove dissolved organic matter
(B) To remove large solids and grit
(C) To disinfect the influent
(D) To convert sludge into biogas
Answer: (B) To remove large solids and grit
Rationale: Preliminary treatment aims to remove large solids, grit, and debris
to protect downstream equipment and processes from damage and clogging.
3. Which equipment is commonly used to remove large solids during
preliminary treatment?
(A) Chlorine contact chamber
(B) Clarifiers
(C) Bar screens
(D) Aeration tanks
Answer: (C) Bar screens
Rationale: Bar screens are used to filter out large solids and debris from the
influent wastewater during preliminary treatment. They are the first line of
defense in the treatment process.
4. What is the main function of a grit chamber?
(A) To remove oil and grease
(B) To settle out grit and heavy inorganic particles
(C) To remove dissolved organic matter
(D) To disinfect the wastewater
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Answer: (B) To settle out grit and heavy inorganic particles
Rationale: Grit chambers are designed to settle out heavy inorganic particles
(grit) such as sand, stone, and other inorganic materials that can damage
equipment if not removed.
5. What is the main goal of primary clarification?
(A) To remove dissolved nutrients
(B) To settle and remove settleable solids
(C) To disinfect the wastewater
(D) To reduce biochemical oxygen demand (BOD)
Answer: (B) To settle and remove settleable solids
Rationale: Primary clarification aims to settle and remove settleable solids
from wastewater by gravity. This process is a physical treatment step.
6. Which process follows preliminary treatment in a typical wastewater
treatment sequence?
(A) Disinfection
(B) Secondary biological treatment
(C) Primary clarification
(D) Grit removal
Answer: (C) Primary clarification
Rationale: After preliminary treatment (bar screens and grit removal), primary
clarification is the next step to remove settleable solids.
7. What is the function of aeration in secondary treatment?
(A) To remove heavy metals
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(B) To provide oxygen for microorganisms
(C) To settle sludge
(D) To remove chlorine
Answer: (B) To provide oxygen for microorganisms
Rationale: Aeration supplies oxygen to microorganisms that biologically
degrade organic matter in wastewater. This is essential for the activated
sludge process.
8. Which of the following is a common method used in secondary
biological treatment?
(A) Trickling filters
(B) Chlorination tanks
(C) Grit chambers
(D) Sedimentation tanks
Answer: (A) Trickling filters
Rationale: Trickling filters are a common biological secondary treatment
method that uses biofilms to remove organic matter. Other methods include
activated sludge and rotating biological contactors.
9. What does Biochemical Oxygen Demand (BOD) measure?
(A) Total suspended solids
(B) The amount of oxygen required by microorganisms to decompose organic
matter
(C) Dissolved oxygen concentration
(D) Toxicity of wastewater
NYC DEP WASTEWATER TREATMENT PLANT OPERATOR
GRADE ONE CERTIFICATION EXAM 2026/2027 COMPLETE
(150) CURRENT TESTING QUESTIONS AND CORRECT
ANSWERS WITH DETAILED RATIONALES.
WASTEWATER
Prepare effectively for the NYC DEP Wastewater Treatment Plant Operator Grade One
Certification Exam with this focused practice resource. It supports review of
wastewater treatment processes, plant operations, water quality, equipment
maintenance, safety procedures, and regulatory requirements. Use the material to
reinforce your technical knowledge, practice key concepts, and identify areas that
may require additional study. This resource is suited for wastewater treatment
operators, environmental professionals, plant technicians, and candidates preparing
for NYC DEP Grade One certification examinations.
MULTIPLE CHOICE.
SECTION 1: WASTEWATER TREATMENT PROCESSES (Questions 1–45)
1. What is the primary purpose of a wastewater treatment plant?
(A) To increase water hardness
(B) To remove pollutants and contaminants from wastewater before discharge
(C) To add chemicals to drinking water
(D) To generate electricity from wastewater
Answer: (B) To remove pollutants and contaminants from wastewater
before discharge
Rationale: Wastewater treatment plants are designed to remove physical,
chemical, and biological pollutants from wastewater to protect human health
and the environment before the treated effluent is discharged to receiving
waters.
, Page 2 of 59
2. What is the primary purpose of preliminary treatment in a wastewater
treatment plant?
(A) To remove dissolved organic matter
(B) To remove large solids and grit
(C) To disinfect the influent
(D) To convert sludge into biogas
Answer: (B) To remove large solids and grit
Rationale: Preliminary treatment aims to remove large solids, grit, and debris
to protect downstream equipment and processes from damage and clogging.
3. Which equipment is commonly used to remove large solids during
preliminary treatment?
(A) Chlorine contact chamber
(B) Clarifiers
(C) Bar screens
(D) Aeration tanks
Answer: (C) Bar screens
Rationale: Bar screens are used to filter out large solids and debris from the
influent wastewater during preliminary treatment. They are the first line of
defense in the treatment process.
4. What is the main function of a grit chamber?
(A) To remove oil and grease
(B) To settle out grit and heavy inorganic particles
(C) To remove dissolved organic matter
(D) To disinfect the wastewater
, Page 3 of 59
Answer: (B) To settle out grit and heavy inorganic particles
Rationale: Grit chambers are designed to settle out heavy inorganic particles
(grit) such as sand, stone, and other inorganic materials that can damage
equipment if not removed.
5. What is the main goal of primary clarification?
(A) To remove dissolved nutrients
(B) To settle and remove settleable solids
(C) To disinfect the wastewater
(D) To reduce biochemical oxygen demand (BOD)
Answer: (B) To settle and remove settleable solids
Rationale: Primary clarification aims to settle and remove settleable solids
from wastewater by gravity. This process is a physical treatment step.
6. Which process follows preliminary treatment in a typical wastewater
treatment sequence?
(A) Disinfection
(B) Secondary biological treatment
(C) Primary clarification
(D) Grit removal
Answer: (C) Primary clarification
Rationale: After preliminary treatment (bar screens and grit removal), primary
clarification is the next step to remove settleable solids.
7. What is the function of aeration in secondary treatment?
(A) To remove heavy metals
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(B) To provide oxygen for microorganisms
(C) To settle sludge
(D) To remove chlorine
Answer: (B) To provide oxygen for microorganisms
Rationale: Aeration supplies oxygen to microorganisms that biologically
degrade organic matter in wastewater. This is essential for the activated
sludge process.
8. Which of the following is a common method used in secondary
biological treatment?
(A) Trickling filters
(B) Chlorination tanks
(C) Grit chambers
(D) Sedimentation tanks
Answer: (A) Trickling filters
Rationale: Trickling filters are a common biological secondary treatment
method that uses biofilms to remove organic matter. Other methods include
activated sludge and rotating biological contactors.
9. What does Biochemical Oxygen Demand (BOD) measure?
(A) Total suspended solids
(B) The amount of oxygen required by microorganisms to decompose organic
matter
(C) Dissolved oxygen concentration
(D) Toxicity of wastewater
