Exam Practice Questions And Correct

Missouri Wastewater Operator Class A 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?
• Generate electricity
• Remove pollutants from wastewater
• Supply drinking water
• Irrigate crops

Rationale: The main goal of wastewater treatment is to remove

pollutants to protect public health and the environment.

• Which stage of treatment primarily removes settleable solids?
• Secondary treatment
• Tertiary treatment 1 / 4

• Primary treatment
• Advanced treatment

Rationale: Primary treatment involves sedimentation tanks that

allow solids to settle.

• What is the most common method for biological treatment of

wastewater?

• Chlorination
• Activated sludge process
• Filtration
• Sedimentation

Rationale: The activated sludge process uses microorganisms to

digest organic matter in wastewater.

4. In wastewater treatment, BOD stands for:

• Biological Oxidation Demand
• Basic Organic Density
• Biochemical Oxygen Demand
• Biological Oxygen Diffusion

Rationale: BOD measures the amount of oxygen required by

microorganisms to decompose organic matter.

5. The primary purpose of aeration in wastewater treatment is to:

• Heat the water
• Supply oxygen to microorganisms
• Settle solids 2 / 4

• Filter pathogens

Rationale: Aeration introduces oxygen to support the aerobic

bacteria that break down organic matter.

• Which of the following is considered a physical treatment process?
• Activated sludge
• Trickling filter
• Sedimentation
• Nitrification

Rationale: Sedimentation is a physical process that separates solids

from liquids by gravity.

• What does TSS stand for in wastewater terminology?
• Total Soil Solids
• Total Sedimentation Standard
• Total Suspended Solids
• Total Soluble Substances

Rationale: TSS measures the concentration of particles suspended in

water.

• Which microorganism is primarily responsible for nitrification?
• E. coli
• Nitrosomonas and Nitrobacter
• Clostridium
• Bacillus 3 / 4

Rationale: Nitrosomonas oxidizes ammonia to nitrite, and

Nitrobacter oxidizes nitrite to nitrate.

9. The term “sludge age” refers to:

• Age of plant equipment
• Age of incoming wastewater
• Average time microorganisms stay in the system
• Time sludge remains in clarifiers

Rationale: Sludge age is important in maintaining a healthy

population of microorganisms in biological treatment.

10. The pH of typical municipal wastewater is usually:

A. 2–4

B. 4–5

C. 6.5–8.5

D. 9–10

Rationale: Wastewater is typically near neutral, slightly acidic to

slightly basic.

• What is the function of a grit chamber?
• Remove organic matter
• Remove sand, gravel, and other heavy particles
• Chlorinate wastewater
• Promote bacterial growth

Rationale: Grit chambers remove heavy inorganic particles that could

damage equipment.

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