Exam Practice Questions And Correct

Wastewater Operator Class I Licensing 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?
• Generate electricity
• Remove contaminants from wastewater
• Increase water hardness
• Produce drinking water

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

remove physical, chemical, and biological contaminants from wastewater before discharging it into the environment.

• Which of the following is considered a physical treatment process?
• Chlorination 1 / 4

• Sedimentation
• Biological filtration
• Aeration

Rationale: Sedimentation is a physical process that removes suspended

solids by allowing them to settle under gravity.

3. In wastewater terminology, BOD stands for:

• Biological Oxidation Demand
• Biochemical Oxygen Determination
• Biochemical Oxygen Demand
• Biological Oxidation Depth

Rationale: BOD measures the amount of dissolved oxygen needed by

microorganisms to break down organic matter in water.

• Which unit process is primarily used to remove suspended solids?
• Disinfection
• Aeration
• Filtration
• Sedimentation

Rationale: Sedimentation removes suspended solids from wastewater by

gravity settling.

• What is the typical range of BOD in domestic wastewater?
• 10–50 mg/L
• 50–100 mg/L 2 / 4

• 200–300 mg/L
• 500–800 mg/L

Rationale: Domestic wastewater usually contains BOD levels between 200–

300 mg/L.

• Which of the following is a characteristic of primary treatment?
• Biological nutrient removal
• Removal of settleable solids
• Advanced filtration
• Chemical coagulation

Rationale: Primary treatment focuses on removing settleable solids and

floating material.

7. Chlorination is used primarily for:

• Disinfection
• Sedimentation
• Biological treatment
• Filtration

Rationale: Chlorination kills or inactivates pathogens in wastewater to

reduce disease risk.

8. Sludge digestion is primarily intended to:

• Remove heavy metals
• Stabilize organic solids 3 / 4

• Reduce chlorine demand
• Increase BOD

Rationale: Sludge digestion stabilizes organic matter in sludge, reducing

odors and pathogen content.

• Which of the following is NOT a type of wastewater?
• Domestic
• Industrial
• Stormwater
• Groundwater

Rationale: Groundwater is naturally occurring water below the surface,

not wastewater.

• What is the main function of an aeration basin in secondary

treatment?

• Remove grit
• Provide oxygen for biological processes
• Settle solids
• Filter water

Rationale: Aeration basins supply oxygen to microorganisms to biodegrade

organic pollutants.

• Which microorganism is commonly used in activated sludge

systems?

• Virus
• / 4