Operator Level 3 Exam Practice

New Brunswick Wastewater Treatment Operator Level 3 Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of a wastewater treatment plant?
• Produce drinking water
• Reduce wastewater volume
• Protect public health and the environment
• Generate electricity

Rationale: Wastewater treatment plants remove pollutants to protect public

health and prevent environmental contamination.

• Which of the following is a typical indicator of organic pollution in

wastewater?

• Chloride 1 / 4

• Biochemical Oxygen Demand (BOD)
• Nitrate
• pH

Rationale: BOD measures the amount of oxygen microorganisms need to

decompose organic matter.

• What is the primary function of primary sedimentation tanks?
• Remove dissolved nutrients
• Remove settleable solids
• Remove pathogens
• Aerate wastewater

Rationale: Primary sedimentation allows heavier solids to settle, reducing

the load on secondary treatment.

• In activated sludge systems, what is the role of the return activated

sludge (RAS)?

• Remove scum from the surface
• Aerate the incoming wastewater
• Maintain a sufficient concentration of microorganisms in the

aeration tank

• Disinfect the effluent

Rationale: Returning activated sludge ensures adequate microbial

population for biological treatment. 2 / 4

• What does the term “sludge age” refer to?
• The time sludge spends in storage
• The average time microorganisms remain in the system
• The age of the treatment plant
• The time between sludge removal and disposal

Rationale: Sludge age, or mean cell residence time, affects system stability

and nutrient removal.

• Which nutrient is typically limiting in municipal wastewater treatment

for biological growth?

• Sodium
• Phosphorus
• Calcium
• Potassium

Rationale: Phosphorus is often the limiting nutrient for microbial growth in

wastewater treatment.

• What is the typical range for dissolved oxygen in an aeration tank?
• 0.1–0.5 mg/L
• 1–2 mg/L
• 2–4 mg/L
• 6–8 mg/L

Rationale: Maintaining DO between 2–4 mg/L ensures aerobic microbial

activity without excessive energy use. 3 / 4

• Which of the following is a common method of sludge stabilization?
• Filtration
• Chlorination
• Anaerobic digestion
• Coagulation

Rationale: Anaerobic digestion reduces sludge volume, stabilizes organic

matter, and can produce biogas.

9. Nitrification in wastewater treatment involves converting:

• Nitrite to ammonia
• Ammonia to nitrate
• Nitrate to nitrogen gas
• Organic nitrogen to ammonia

Rationale: Nitrification is a two-step aerobic process converting ammonia to

nitrite and then nitrate.

10. Denitrification requires:

• High oxygen concentration
• Anoxic conditions and carbon source
• Ultraviolet light
• Chlorination

Rationale: Denitrifying bacteria convert nitrate to nitrogen gas under anoxic

conditions using organic carbon.

• / 4