Grade I Exam Practice Questions And

New Hampshire Wastewater Operator Grade I Exam Practice 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
• Protect public health and the environment by treating wastewater
• Increase sewer flow
• Reduce industrial costs

Rationale: Wastewater treatment plants are designed to remove

pollutants to protect public health and prevent environmental contamination.

2. The term BOD stands for:

• Basic Oxygen Demand 1 / 4

• Biochemical Oxygen Demand
• Biological Oxidation Duration
• Bacterial Oxygen Depletion

Rationale: BOD measures the amount of oxygen microorganisms consume

while decomposing organic matter in water.

• What is the typical range of BOD for domestic wastewater?
• 5–20 mg/L
• 50–100 mg/L
• 200–300 mg/L
• 500–800 mg/L

Rationale: Domestic wastewater usually contains 200–300 mg/L BOD,

reflecting typical organic load from households.

4. Total Suspended Solids (TSS) are:

• Soluble minerals
• Particles suspended in water that can be removed by filtration
• Dissolved organic matter
• Gaseous contaminants

Rationale: TSS represents particles that remain in suspension and

contribute to turbidity.

5. The first step in the treatment of wastewater is:

• Biological treatment
• Disinfection 2 / 4

• Preliminary treatment (screening and grit removal)
• Sludge digestion

Rationale: Preliminary treatment removes large solids and grit to prevent

damage to downstream equipment.

6. Screens in preliminary treatment:

• Remove dissolved organics
• Remove large debris such as rags, sticks, and plastics
• Neutralize pH
• Reduce BOD

Rationale: Screens prevent large objects from entering pumps and

treatment units.

7. Grit chambers are designed to:

• Remove organic solids
• Remove sand, gravel, and other heavy inorganic particles
• Neutralize wastewater
• Treat pathogens

Rationale: Grit is heavy and settles quickly, preventing abrasion of

equipment.

8. The purpose of primary sedimentation tanks is to:

• Remove dissolved nutrients
• Settle suspended solids and remove floatable material 3 / 4

• Kill bacteria
• Oxidize ammonia

Rationale: Primary tanks remove settleable solids and scum, reducing load

on secondary treatment.

9. Activated sludge process relies on:

• Chemical precipitation
• Microorganisms to degrade organic matter
• Filtration
• Chlorination

Rationale: Activated sludge uses aerobic bacteria to biologically treat

wastewater.

10. The term “MLSS” refers to:

• Maximum Liquid Sludge Solids
• Mean Load Suspended Solids
• Mixed Liquor Suspended Solids
• Microbial Load Solids Standard

Rationale: MLSS is the concentration of suspended solids, primarily

microorganisms, in the aeration tank.

11. The main function of secondary clarifiers is to:

• Remove grit
• Separate treated wastewater from biological solids
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