Advanced Exam Practice Questions And

Wisconsin Wastewater Operator Advanced Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of a grit chamber in a wastewater

treatment plant?

• Remove organic matter
• Remove inorganic solids and sand
• Remove pathogens
• Increase dissolved oxygen

Answer: B

Rationale: Grit chambers are designed to remove heavy inorganic particles

like sand, gravel, and grit to protect downstream equipment and processes. 1 / 4

• What is the normal range of pH for activated sludge treatment?

A. 4.5–5.5

B. 5.5–6.5

C. 6.5–8.5

D. 8.5–9.5

Answer: C

Rationale: Activated sludge operates efficiently in a near-neutral pH range

of 6.5–8.5; outside this range, microbial activity declines.

• What is the main purpose of a clarifier in wastewater treatment?
• Aerate wastewater
• Remove dissolved nutrients
• Separate solids from liquid
• Disinfect effluent

Answer: C

Rationale: Clarifiers allow suspended solids to settle, producing a clear

effluent and concentrated sludge for further processing.

• Which of the following is a common method for controlling

filamentous bacteria in activated sludge systems?

• Increasing pH
• Adjusting dissolved oxygen and sludge age
• Adding coagulants
• Reducing alkalinity 2 / 4

Answer: B

Rationale: Filamentous bulking can often be controlled by optimizing

dissolved oxygen levels and sludge age, which affects microbial population dynamics.

• What does the term “MLSS” stand for in wastewater treatment?
• Maximum Liquid Settling Solids
• Mixed Liquor Suspended Solids
• Minimum Level Settling Solids
• Mixed Liner Substrate System

Answer: B

Rationale: MLSS represents the concentration of suspended solids in the

aeration tank, including both microorganisms and non-biodegradable matter.

• Which of the following is a typical BOD5 removal efficiency for a well-

operated secondary treatment plant?

A. 20–30%

B. 40–50%

C. 85–95%

D. 100%

Answer: C

Rationale: Secondary treatment typically removes 85–95% of the five-day

biochemical oxygen demand (BOD5). 3 / 4

• What is the main function of an aeration basin?
• Remove grit
• Provide oxygen for microbial degradation of organics
• Remove nutrients
• Separate sludge from water

Answer: B

Rationale: Aeration basins supply oxygen to bacteria for breaking down

organic matter in the wastewater.

• What is the role of chlorination in wastewater treatment?
• Remove solids
• Disinfect effluent by killing pathogens
• Increase pH
• Reduce BOD

Answer: B

Rationale: Chlorination is primarily used for disinfection to control

pathogenic organisms before discharge.

• What does TSS stand for?
• Total Salt Solution
• Total Soluble Substrate
• Total Suspended Solids
• Total Sewage Solids
• / 4