Level III Exam Practice Questions And

Wyoming Wastewater Treatment Operator Level III Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of a clarifier in a wastewater treatment

plant?

• Aeration
• Sedimentation
• Disinfection
• Sludge digestion

Rationale: Clarifiers are designed to remove suspended solids from

wastewater through sedimentation.

• Which microorganism is primarily responsible for nitrification?
• Escherichia coli
• Nitrosomonas and Nitrobacter 1 / 4

• Clostridium
• Bacillus subtilis

Rationale: Nitrosomonas oxidizes ammonia to nitrite, and

Nitrobacter oxidizes nitrite to nitrate.

• The maximum allowable BOD for effluent under Wyoming regulations

is generally:

• 5 mg/L
• 10 mg/L
• 30 mg/L
• 50 mg/L

Rationale: State standards commonly limit BOD in treated effluent to

around 30 mg/L to protect water quality.

• What does MLVSS stand for in wastewater treatment?
• Mixed Low-Volume Suspended Solids
• Maximum Level Volatile Soluble Substrate
• Mixed Liquor Volatile Suspended Solids
• Medium Level Volatile Suspended Sludge

Rationale: MLVSS measures the organic portion of suspended solids

in activated sludge.

• Which process reduces nitrogen in wastewater through

denitrification?

• Ammonia stripping
• Conversion of nitrate to nitrogen gas 2 / 4

• Aeration
• Coagulation

Rationale: Denitrification converts nitrate (NO3-) into nitrogen gas

(N2) under anoxic conditions.

6. The purpose of a bar screen is to:

• Remove dissolved solids
• Remove large debris
• Clarify water
• Oxidize ammonia

Rationale: Bar screens remove rags, sticks, and other large solids

before primary treatment.

• Which of the following is a common method for sludge stabilization?
• Sedimentation
• Filtration
• Anaerobic digestion
• Chlorination

Rationale: Anaerobic digestion biologically reduces organic matter

and pathogens in sludge.

8. The term “MLSS” refers to:

• Maximum Liquid Suspended Solids
• Medium Level Soluble Solids
• Mixed Liquor Suspended Solids
• Minimum Level Sludge Solids 3 / 4

Rationale: MLSS measures total suspended solids in the aeration

tank.

9. The main purpose of aeration in activated sludge systems is:

• Reduce sludge volume
• Provide oxygen for microorganisms
• Remove large solids
• Settle solids

Rationale: Aeration supplies oxygen for aerobic microbes to

metabolize organic matter.

• Which chemical is commonly used for phosphorus removal in

wastewater treatment?

• Chlorine
• Alum (Aluminum sulfate)
• Lime
• Sodium hydroxide

Rationale: Alum precipitates phosphorus, forming insoluble

compounds that can be removed by sedimentation.

• What is the ideal dissolved oxygen (DO) range in an aeration

tank for activated sludge?

• 0.5–1 mg/L
• 1–2 mg/L
• 2–4 mg/L
• 5–8 mg/L
• / 4