Grade II Practice Exam Questions And

North Carolina Wastewater Operator Grade II Practice Exam Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• Which of the following is the primary purpose of a wastewater

treatment plant?

• Generate electricity
• Remove pollutants from wastewater
• Increase water temperature
• Produce drinking water

Answer: B

Rationale: The primary function of a wastewater treatment plant is to

remove pollutants from wastewater to protect public health and the environment. 1 / 4

• What is the typical pH range for activated sludge processes?

A. 4.5–5.5

B. 6.0–6.5

C. 6.5–8.5

D. 9.0–10.5

Answer: C

Rationale: Activated sludge bacteria function best in a neutral to slightly

alkaline environment, typically 6.5–8.5 pH.

• Which type of bacteria is primarily responsible for nitrification in

wastewater treatment?

• Sulfate-reducing bacteria
• Nitrosomonas and Nitrobacter
• Methanogens
• Pseudomonas

Answer: B

Rationale: Nitrosomonas oxidizes ammonia to nitrite, and Nitrobacter

oxidizes nitrite to nitrate in the nitrification process.

4. BOD stands for:

• Basic Oxidation Demand
• Biochemical Oxygen Density
• Biochemical Oxygen Demand
• Biological Oxidation Degree 2 / 4

Answer: C

Rationale: BOD measures the amount of oxygen required by microorganisms

to decompose organic matter in water.

5. The purpose of primary sedimentation is to:

• Remove dissolved nutrients
• Remove settleable solids
• Kill pathogens
• Aerate the wastewater

Answer: B

Rationale: Primary sedimentation allows heavier solids to settle out before

secondary treatment.

• Which of the following is a common coagulant used in wastewater

treatment?

• Sodium hydroxide
• Aluminum sulfate
• Calcium carbonate
• Sodium chloride

Answer: B

Rationale: Aluminum sulfate (alum) is used to coagulate and settle

suspended solids in water.

7. Sludge age is also known as:

• Hydraulic retention time 3 / 4

• Mean cell residence time
• Solids retention time
• Both B and C

Answer: D

Rationale: Sludge age refers to the mean cell residence time (MCRT), which

is equivalent to solids retention time.

• Which process is used to remove nitrogen from wastewater?
• Sedimentation
• Filtration
• Biological nitrification-denitrification
• Coagulation

Answer: C

Rationale: Nitrogen is removed biologically by converting ammonia to

nitrate (nitrification) and then nitrate to nitrogen gas (denitrification).

9. The main function of a grit chamber is to:

• Remove heavy inorganic particles
• Remove organic matter
• Aerate the wastewater
• Disinfect the effluent

Answer: A

Rationale: Grit chambers remove sand, gravel, and other heavy inorganic

particles that could damage equipment.

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