Grade III Practice Exam Questions And

New Hampshire Wastewater Operator Grade III Practice Exam Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

1. The primary purpose of a wastewater treatment plant is to:

• Produce drinking water
• Remove pollutants from wastewater before discharge
• Generate electricity
• Pump sewage to landfills

Rationale: Wastewater treatment plants are designed to remove

contaminants from sewage and industrial effluent to protect public health and the environment.

• The most common type of biological treatment used in secondary

wastewater treatment is: 1 / 4

• Sand filtration
• Chlorination
• Activated sludge
• Membrane distillation

Rationale: Activated sludge uses microorganisms to biologically degrade

organic matter in wastewater.

• Which parameter measures the amount of oxygen consumed by

microorganisms to decompose organic matter?

A. TDS

B. BOD

C. COD

D. TSS

Rationale: Biochemical Oxygen Demand (BOD) indicates the oxygen required

by microorganisms to break down organic matter over a specified period.

4. Total Suspended Solids (TSS) in wastewater refers to:

• Dissolved salts
• Particles suspended in water that can be filtered out
• Gaseous emissions
• Microorganisms only

Rationale: TSS is a measure of particulate matter that remains after

filtration or settling. 2 / 4

5. The purpose of primary sedimentation is to:

• Remove settleable solids from raw wastewater
• Remove dissolved organics
• Kill pathogens
• Increase oxygen levels

Rationale: Primary sedimentation allows solids to settle by gravity, reducing

the load on secondary treatment.

6. The typical detention time for a primary clarifier is:

• 5–10 minutes
• 15–20 minutes
• 1–2 hours
• 6–8 hours

Rationale: Primary clarifiers generally allow 1–2 hours for solids to settle

effectively.

• Which of the following is the primary function of aeration in secondary

treatment?

• Remove heavy metals
• Supply oxygen to microorganisms for biological treatment
• Filter solids
• Neutralize pH

Rationale: Aeration ensures sufficient oxygen for aerobic bacteria to

metabolize organic pollutants. 3 / 4

8. Nitrification is the process by which:

• Ammonia is converted to nitrate
• Nitrite is converted to ammonia
• Ammonia is converted to nitrite and then nitrate
• Nitrate is removed as gas

Rationale: Nitrification is a two-step aerobic process where ammonia is

oxidized to nitrite and then to nitrate.

9. Denitrification occurs under:

• Aerobic conditions
• Anoxic conditions
• Anaerobic sludge digestion
• High pH conditions

Rationale: Denitrification is the microbial reduction of nitrate to nitrogen gas in the absence of oxygen.

• Which is a primary reason for chlorination of wastewater

effluent?

• Remove BOD
• Remove TSS
• Disinfect and kill pathogens
• Reduce nitrogen

Rationale: Chlorination is used to disinfect wastewater to meet public health

standards.

• / 4