Level IV Exam Practice Questions And

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

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

treatment plant?

• Remove dissolved nutrients
• Remove large solids and debris
• Reduce BOD
• Disinfect wastewater

Answer: B

Rationale: Preliminary treatment removes large solids and debris to prevent

damage to downstream equipment and ensure efficient operation of the treatment process. 1 / 4

• Which of the following best describes BOD5?
• The total suspended solids in 5 hours
• The amount of oxygen consumed by microorganisms in 5 days
• The total chemical oxygen demand in 5 days
• The biochemical oxygen demand at 25°C

Answer: B

Rationale: BOD5 measures the oxygen consumed by microorganisms over

five days at 20°C, reflecting the amount of biodegradable organic matter in the wastewater.

3. The ideal pH range for activated sludge bacteria is:

A. 4.0–5.0

B. 6.0–6.5

C. 6.5–8.5

D. 8.5–10.0

Answer: C

Rationale: Most bacteria in activated sludge systems thrive in a pH range of

6.5–8.5; outside this range, microbial activity and treatment efficiency decrease.

• Which of the following is the primary purpose of chlorination in

wastewater treatment?

• Remove solids
• Disinfect effluent 2 / 4

• Increase BOD
• Neutralize pH

Answer: B

Rationale: Chlorination kills pathogenic microorganisms in the treated

wastewater to ensure it is safe for discharge.

5. The Sludge Volume Index (SVI) is used to:

• Measure effluent BOD
• Determine dissolved oxygen levels
• Evaluate settleability of activated sludge
• Measure influent flow rate

Answer: C

Rationale: SVI indicates the volume occupied by 1 gram of sludge after 30

minutes of settling, reflecting sludge settleability in the secondary clarifier.

6. Nitrification in wastewater treatment converts:

• Nitrogen gas to ammonia
• Ammonia to nitrate
• Nitrate to ammonia
• Organic nitrogen to nitrogen gas

Answer: B

Rationale: Nitrifying bacteria convert ammonia (NH3) into nitrite (NO2-) and

then nitrate (NO3-) in the biological treatment process. 3 / 4

7. Denitrification in wastewater treatment requires:

• Oxygen-rich conditions
• Anoxic conditions and a carbon source
• High pH
• UV radiation

Answer: B

Rationale: Denitrification occurs under anoxic conditions where nitrate is

reduced to nitrogen gas, often using a carbon source as an electron donor.

8. The primary purpose of a grit chamber is to:

• Remove dissolved organics
• Remove heavy inorganic solids
• Aerate wastewater
• Disinfect effluent

Answer: B

Rationale: Grit chambers remove sand, gravel, and other dense particles to

prevent damage and abrasion to pumps and downstream equipment.

• Which of the following is the main source of phosphorus in

wastewater?

• Rainwater
• Industrial cooling water
• Detergents and human waste
• Agricultural runoff
• / 4