New Jersey Wastewater Treatment Operator S-2
Exam – 300 Practice Questions and answers|2026
updates |with complete solutions.
Section 1: Preliminary & Primary Treatment (Questions 1-30)
1. What is the primary purpose of screening in preliminary wastewater treatment?
A) Remove dissolved solids
B) Remove large floating and suspended debris
C) Add chemicals for coagulation
D) Aerate the wastewater
Correct Answer: B
Rationale: Screening removes large objects and debris that could damage
subsequent treatment equipment or clog pipes. This is the first physical treatment
step in wastewater treatment .
---
,2. Which type of screen is most suitable for removing rags and sticks from
influent?
A) Fine screen
B) Bar screen
C) Drum screen
D) Microstrainer
Correct Answer: B
Rationale: Bar screens consist of parallel bars spaced typically 1-2 inches apart and
are designed to remove large debris such as rags, sticks, and other coarse
materials from the incoming wastewater flow .
---
3. What is the primary function of a comminutor in wastewater treatment?
A) Aerate the water
B) Grind and shred large solids
C) Remove grit
D) Add chemicals
Correct Answer: B
,Rationale: Comminutors grind and shred large solids into smaller pieces without
removing them from the flow. This prevents clogging and protects downstream
processes while eliminating the need for screenings handling .
---
4. Grit chambers are primarily designed to remove which material?
A) Organic solids
B) Settleable solids
C) Fats, oils, and grease
D) Inorganic sand and gravel
Correct Answer: D
Rationale: Grit chambers use velocity control to remove inorganic materials like
sand, gravel, and eggshells that are abrasive and can damage pumps and
mechanical equipment .
---
5. Which of the following is NOT a typical type of grit removal system?
, A) Aerated grit chamber
B) Vortex grit chamber
C) Sedimentation tank
D) Horizontal flow grit chamber
Correct Answer: C
Rationale: Sedimentation tanks are primary clarifiers, not grit removal systems.
The typical grit removal types are aerated, vortex, and horizontal flow grit
chambers .
---
6. The primary clarifier typically removes what percentage of suspended solids?
A) 10–20%
B) 25–35%
C) 50–70%
D) 80–90%
Correct Answer: C
Rationale: Primary clarification typically achieves 50–70% TSS removal through
sedimentation. It also removes 25–40% of influent BOD (mostly particulate BOD) .
Exam – 300 Practice Questions and answers|2026
updates |with complete solutions.
Section 1: Preliminary & Primary Treatment (Questions 1-30)
1. What is the primary purpose of screening in preliminary wastewater treatment?
A) Remove dissolved solids
B) Remove large floating and suspended debris
C) Add chemicals for coagulation
D) Aerate the wastewater
Correct Answer: B
Rationale: Screening removes large objects and debris that could damage
subsequent treatment equipment or clog pipes. This is the first physical treatment
step in wastewater treatment .
---
,2. Which type of screen is most suitable for removing rags and sticks from
influent?
A) Fine screen
B) Bar screen
C) Drum screen
D) Microstrainer
Correct Answer: B
Rationale: Bar screens consist of parallel bars spaced typically 1-2 inches apart and
are designed to remove large debris such as rags, sticks, and other coarse
materials from the incoming wastewater flow .
---
3. What is the primary function of a comminutor in wastewater treatment?
A) Aerate the water
B) Grind and shred large solids
C) Remove grit
D) Add chemicals
Correct Answer: B
,Rationale: Comminutors grind and shred large solids into smaller pieces without
removing them from the flow. This prevents clogging and protects downstream
processes while eliminating the need for screenings handling .
---
4. Grit chambers are primarily designed to remove which material?
A) Organic solids
B) Settleable solids
C) Fats, oils, and grease
D) Inorganic sand and gravel
Correct Answer: D
Rationale: Grit chambers use velocity control to remove inorganic materials like
sand, gravel, and eggshells that are abrasive and can damage pumps and
mechanical equipment .
---
5. Which of the following is NOT a typical type of grit removal system?
, A) Aerated grit chamber
B) Vortex grit chamber
C) Sedimentation tank
D) Horizontal flow grit chamber
Correct Answer: C
Rationale: Sedimentation tanks are primary clarifiers, not grit removal systems.
The typical grit removal types are aerated, vortex, and horizontal flow grit
chambers .
---
6. The primary clarifier typically removes what percentage of suspended solids?
A) 10–20%
B) 25–35%
C) 50–70%
D) 80–90%
Correct Answer: C
Rationale: Primary clarification typically achieves 50–70% TSS removal through
sedimentation. It also removes 25–40% of influent BOD (mostly particulate BOD) .
