New Jersey Water Treatment Operator T1 Exam
Prep | Representative Practice Questions, Water
Treatment Operations & Certification Study Guide
(2025–2026)
Section 1: COAGULATION, FLOCCULATION & SEDIMENTATION
1. What is the main purpose of the coagulation process in drinking water
treatment?
A. Kill pathogens
B. Adjust pH levels
C. Remove dissolved gases
D. Neutralize electrical charges on suspended particles
Answer: D
Rationale: Coagulation uses chemicals to neutralize the negative charges that
repel particles, allowing them to collide and form larger flocs for easier removal .
2. Which chemical is used most widely as a primary coagulant?
A. Sodium chloride
B. Aluminum sulfate (alum)
C. Calcium carbonate
D. Potassium permanganate
Answer: B
Rationale: Aluminum sulfate (alum) is the most prevalent coagulant due to its
effectiveness and low cost .
,3. Flocculation is best described as which of the following?
A. High-speed mixing to disperse chemicals rapidly
B. Slow, gentle mixing that allows destabilized particles to collide and form larger
flocs
C. Settling particles by gravity
D. Adding chlorine to kill microorganisms
Answer: B
Rationale: Flocculation provides gentle agitation so microflocs can aggregate into
larger, settleable masses after coagulation .
4. What is the primary function of a sedimentation basin?
A. Remove dissolved organic matter
B. Settle out suspended solids and floc particles by gravity
C. Add chemicals to adjust pH
D. Kill harmful bacteria
Answer: B
Rationale: Sedimentation basins use gravity to allow heavier floc particles to
settle, reducing turbidity before filtration .
5. The optimum coagulation pH range for alum is typically:
A. 4.5 - 5.5
B. 5.5 - 7.5
C. 7.5 - 8.5
D. 8.5 - 9.5
Answer: B
Rationale: Alum operates most effectively in the pH range of 5.5 to 7.5, where the
aluminum hydroxide floc formation is optimal .
,6. A jar test is performed in a water treatment plant for what primary purpose?
A. To measure chlorine residual
B. To determine the optimum coagulant dosage
C. To check filter media cleanliness
D. To calibrate flow meters
Answer: B
Rationale: Jar tests simulate coagulation/flocculation on a small scale to find the
chemical dose that yields the best particle removal .
7. The normal operating filter rate for a conventional rapid sand filter is
approximately:
A. 0.1 gpm/ft²
B. 1–5 gpm/ft²
C. 10–20 gpm/ft²
D. 30 gpm/ft²
Answer: B
Rationale: Conventional rapid sand filters typically operate at rates of 1-5 gpm/ft²
to achieve effective particle removal .
8. Rapid sand filters remove particles mainly by which mechanism?
A. Chemical reaction
B. Straining and adsorption
C. UV radiation
D. Gravity settling
Answer: B
, Rationale: Particles are trapped within the filter media and adhere to sand grains
through straining and adsorption .
Section 2: DISINFECTION & CHLORINATION
9. What is the minimum free chlorine residual required at the point where
treated water enters the distribution system?
A. 0.05 mg/L
B. 0.2 mg/L
C. 1.0 mg/L
D. 2.0 mg/L
Answer: B
Rationale: Regulations require at least 0.2 mg/L free chlorine at the entry point to
ensure adequate protection throughout the distribution system .
10. What is the most common form of disinfection used in public drinking water
systems?
A. Ozone
B. Ultraviolet (UV) radiation
C. Chlorine
D. Chlorine dioxide
Answer: C
Rationale: Chlorine is predominant because it is effective, economical, and
provides a lasting residual to protect the distribution system .
11. What is the term for the amount of chlorine consumed by reactions with
organic matter before a stable residual appears?
Prep | Representative Practice Questions, Water
Treatment Operations & Certification Study Guide
(2025–2026)
Section 1: COAGULATION, FLOCCULATION & SEDIMENTATION
1. What is the main purpose of the coagulation process in drinking water
treatment?
A. Kill pathogens
B. Adjust pH levels
C. Remove dissolved gases
D. Neutralize electrical charges on suspended particles
Answer: D
Rationale: Coagulation uses chemicals to neutralize the negative charges that
repel particles, allowing them to collide and form larger flocs for easier removal .
2. Which chemical is used most widely as a primary coagulant?
A. Sodium chloride
B. Aluminum sulfate (alum)
C. Calcium carbonate
D. Potassium permanganate
Answer: B
Rationale: Aluminum sulfate (alum) is the most prevalent coagulant due to its
effectiveness and low cost .
,3. Flocculation is best described as which of the following?
A. High-speed mixing to disperse chemicals rapidly
B. Slow, gentle mixing that allows destabilized particles to collide and form larger
flocs
C. Settling particles by gravity
D. Adding chlorine to kill microorganisms
Answer: B
Rationale: Flocculation provides gentle agitation so microflocs can aggregate into
larger, settleable masses after coagulation .
4. What is the primary function of a sedimentation basin?
A. Remove dissolved organic matter
B. Settle out suspended solids and floc particles by gravity
C. Add chemicals to adjust pH
D. Kill harmful bacteria
Answer: B
Rationale: Sedimentation basins use gravity to allow heavier floc particles to
settle, reducing turbidity before filtration .
5. The optimum coagulation pH range for alum is typically:
A. 4.5 - 5.5
B. 5.5 - 7.5
C. 7.5 - 8.5
D. 8.5 - 9.5
Answer: B
Rationale: Alum operates most effectively in the pH range of 5.5 to 7.5, where the
aluminum hydroxide floc formation is optimal .
,6. A jar test is performed in a water treatment plant for what primary purpose?
A. To measure chlorine residual
B. To determine the optimum coagulant dosage
C. To check filter media cleanliness
D. To calibrate flow meters
Answer: B
Rationale: Jar tests simulate coagulation/flocculation on a small scale to find the
chemical dose that yields the best particle removal .
7. The normal operating filter rate for a conventional rapid sand filter is
approximately:
A. 0.1 gpm/ft²
B. 1–5 gpm/ft²
C. 10–20 gpm/ft²
D. 30 gpm/ft²
Answer: B
Rationale: Conventional rapid sand filters typically operate at rates of 1-5 gpm/ft²
to achieve effective particle removal .
8. Rapid sand filters remove particles mainly by which mechanism?
A. Chemical reaction
B. Straining and adsorption
C. UV radiation
D. Gravity settling
Answer: B
, Rationale: Particles are trapped within the filter media and adhere to sand grains
through straining and adsorption .
Section 2: DISINFECTION & CHLORINATION
9. What is the minimum free chlorine residual required at the point where
treated water enters the distribution system?
A. 0.05 mg/L
B. 0.2 mg/L
C. 1.0 mg/L
D. 2.0 mg/L
Answer: B
Rationale: Regulations require at least 0.2 mg/L free chlorine at the entry point to
ensure adequate protection throughout the distribution system .
10. What is the most common form of disinfection used in public drinking water
systems?
A. Ozone
B. Ultraviolet (UV) radiation
C. Chlorine
D. Chlorine dioxide
Answer: C
Rationale: Chlorine is predominant because it is effective, economical, and
provides a lasting residual to protect the distribution system .
11. What is the term for the amount of chlorine consumed by reactions with
organic matter before a stable residual appears?
