Practice Exam Questions And Correct

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

• What is the primary purpose of a wastewater treatment plant?

a) To produce drinking water

b) To remove pollutants from wastewater before discharge

c) To store wastewater for industrial use

d) To add nutrients to water

Rationale: The primary purpose of a wastewater treatment plant is

to remove contaminants from sewage to protect public health and the environment.

• Which process primarily removes suspended solids from wastewater?

a) Aeration 1 / 4

b) Sedimentation

c) Chlorination

d) Filtration

Rationale: Sedimentation allows heavier particles to settle,

effectively removing suspended solids.

• What is the main function of a primary clarifier?

a) Biological nutrient removal

b) Sludge digestion

c) Separation of settleable solids

d) Disinfection

Rationale: Primary clarifiers are designed to remove settleable solids

from raw wastewater.

• The biological process that removes organic matter using

microorganisms is called:

a) Chlorination

b) Flocculation

c) Activated sludge process

d) Sedimentation

Rationale: Activated sludge uses microorganisms to consume and

break down organic matter.

• Which microorganism is most commonly responsible for nitrification?

a) Fungi

b) Protozoa 2 / 4

c) Bacteria (Nitrosomonas and Nitrobacter)

d) Algae

Rationale: Nitrification is carried out by bacteria such as

Nitrosomonas (ammonia to nitrite) and Nitrobacter (nitrite to nitrate).

• What is the main purpose of chlorination in wastewater treatment?

a) Reduce turbidity

b) Disinfection

c) Remove suspended solids

d) Reduce organic matter

Rationale: Chlorination is primarily used to kill pathogenic

microorganisms in treated effluent.

• Which term describes the amount of oxygen required by

microorganisms to decompose organic matter in water?

a) BOD

b) COD

c) TSS

d) BOD5

Rationale: BOD5 (Biochemical Oxygen Demand over 5 days)

measures the oxygen needed for microbial decomposition.

• In an activated sludge system, what is the purpose of the aeration

tank?

a) To supply oxygen for microorganisms to break down organic 3 / 4

matter

b) To clarify water

c) To remove nutrients

d) To disinfect effluent

Rationale: The aeration tank provides oxygen and mixing, supporting

microbial breakdown of organics.

• What is the typical range for mixed liquor suspended solids (MLSS) in

an activated sludge system?

• 10–50 mg/L
• 50–100 mg/L
• 2,000–4,000 mg/L
• 10,000–20,000 mg/L

Rationale: Typical MLSS concentrations are 2,000–4,000 mg/L,

providing adequate biomass for treatment.

• What does TSS stand for?

a) Total soluble solids

b) Total sediment saturation

c) Total suspended solids

d) Total surface solids

Rationale: TSS measures the concentration of suspended particles in

water.

• What is the first step in chemical phosphorus removal?

a) Chlorination

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