Exam Practice Questions And Correct

Wisconsin Wastewater Operator Basic 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
• Remove pollutants from wastewater
• Generate electricity
• Irrigate crops

Rationale: The main goal of wastewater treatment is to remove

contaminants to protect public health and the environment.

• Which of the following is a common primary treatment method?
• Biological nutrient removal 1 / 4

• Activated sludge
• Sedimentation
• Disinfection

Rationale: Sedimentation allows solids to settle out of wastewater as part of

primary treatment.

• What is the typical pH range for wastewater entering a treatment

plant?

A. 2–4

B. 9–11

C. 6–9

D. 11–14

Rationale: Most municipal wastewater has a near-neutral pH, usually

between 6 and 9.

• The process of removing large solids at the beginning of treatment is

called:

• Filtration
• Coagulation
• Screening
• Chlorination 2 / 4

Rationale: Screening removes rags, sticks, and other large debris before it

can damage equipment.

• What is the main function of aeration in secondary treatment?
• Remove grit
• Provide oxygen for microorganisms
• Settle solids
• Neutralize pH

Rationale: Aeration supplies oxygen needed for aerobic bacteria to break

down organic matter.

• Which unit process removes fine suspended solids after primary

treatment?

• Screening
• Secondary clarification
• Grit removal
• Disinfection

Rationale: Secondary clarifiers allow biological flocs to settle, removing fine

solids.

• Which of the following microorganisms is commonly used in activated

sludge systems? 3 / 4

• Virus
• Bacteria
• Protozoa
• Algae

Rationale: Bacteria are the primary agents that digest organic matter in

activated sludge.

8. BOD stands for:

• Biotic Oxygen Demand
• Biochemical Oxygen Demand
• Biological Oxidation Device
• Basic Oxygen Dissolution

Rationale: BOD measures the amount of oxygen required by microorganisms

to decompose organic matter.

9. A high BOD in influent wastewater indicates:

• Low organic content
• High chlorine content
• High organic pollution
• Low nitrogen content

Rationale: BOD reflects the amount of biodegradable organic matter in the

wastewater.

• / 4