Level II Practice Exam Questions And

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

• Which microorganism is primarily responsible for nitrification in

wastewater treatment?

• Escherichia coli
• Nitrosomonas
• Clostridium
• Pseudomonas

Answer: B. Nitrosomonas

Rationale: Nitrosomonas oxidizes ammonia to nitrite in the nitrification

process, a key step in nitrogen removal.

• / 4

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

treatment plant?

• Remove organic matter
• Remove heavy inorganic solids
• Reduce BOD
• Disinfect effluent

Answer: B. Remove heavy inorganic solids

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

prevent wear on downstream equipment.

• What is the typical pH range for optimal activated sludge microbial

activity?

A. 4.5–5.5

B. 6.0–6.5

C. 6.5–8.5

D. 8.5–10.0

Answer: C. 6.5–8.5

Rationale: Most bacteria involved in wastewater treatment thrive in near-

neutral conditions; pH extremes inhibit microbial activity.

4. In the context of wastewater treatment, BOD stands for:

• Biological Oxidation Demand 2 / 4

• Biochemical Oxygen Demand
• Bacterial Oxygen Depletion
• Biological Oxide Decay

Answer: B. Biochemical Oxygen Demand

Rationale: BOD measures the amount of dissolved oxygen needed by

microorganisms to decompose organic matter in water.

5. The process of converting ammonia to nitrate is known as:

• Denitrification
• Nitrification
• Sedimentation
• Chlorination

Answer: B. Nitrification

Rationale: Nitrification is a two-step aerobic process where ammonia is

converted first to nitrite and then to nitrate.

• Which sludge treatment process reduces pathogens by raising the

temperature?

• Anaerobic digestion
• Composting
• Mesophilic digestion
• Sedimentation 3 / 4

Answer: C. Mesophilic digestion

Rationale: Mesophilic digestion operates at moderate temperatures (~95–

105°F) and reduces pathogen levels through microbial activity and heat.

• What is the primary chemical used for disinfection in most municipal

wastewater plants?

• Ozone
• Chlorine
• Fluoride
• Hydrogen peroxide

Answer: B. Chlorine

Rationale: Chlorine is commonly used to disinfect wastewater by killing

bacteria and pathogens before discharge.

• Which of the following parameters is most important for determining

aeration requirements in an activated sludge system?

A. TSS

• pH

C. BOD

• Temperature
• / 4