A Practice Exam Questions And Correct

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

1. The primary purpose of a wastewater treatment plant is to:

• Produce drinking water
• Remove solids and reduce pollutants from wastewater
• Generate electricity
• Recycle plastics
• Remove solids and reduce pollutants from wastewater

Rationale: The main function of a wastewater treatment plant is to

remove solids, organic matter, and pollutants from wastewater before discharge. 1 / 4

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

Rationale: Primary treatment typically involves physical processes like

sedimentation to remove settleable solids.

3. Biological treatment primarily removes:

• Suspended solids
• Pathogens
• Organic matter
• Heavy metals
• Organic matter

Rationale: Biological treatment uses microorganisms to break down

organic matter in wastewater.

• Which microorganism group is most commonly used in activated

sludge processes?

• Fungi
• Bacteria
• Viruses
• Protozoa 2 / 4

• Bacteria

Rationale: Bacteria are the primary organisms responsible for degrading

organic pollutants in activated sludge systems.

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

• Remove nutrients
• Promote microbial activity
• Settle solids
• Neutralize pH
• Promote microbial activity

Rationale: Aeration provides oxygen, which is required by aerobic bacteria

to degrade organic matter.

• What is the primary function of a clarifier in wastewater treatment?
• Disinfect effluent
• Settle suspended solids
• Increase pH
• Remove nutrients
• Settle suspended solids

Rationale: Clarifiers allow suspended solids to settle out of wastewater by

gravity.

7. Sludge age in an activated sludge process refers to:

• Time sludge spends in the aeration tank
• Age of microorganisms 3 / 4

• Hydraulic retention time of the plant
• Time sludge is stored before disposal
• Age of microorganisms

Rationale: Sludge age (or mean cell residence time) is the average time

microorganisms remain in the system, affecting process stability and nutrient removal.

8. Nitrification is a process that converts:

• Ammonia to nitrate
• Nitrate to ammonia
• Organic matter to chlorine
• Phosphate to ammonia
• Ammonia to nitrate

Rationale: Nitrification is the aerobic biological conversion of ammonia to

nitrate by specialized bacteria.

9. Denitrification requires:

• Oxygen
• No oxygen (anoxic conditions)
• Chlorine
• High temperature
• No oxygen (anoxic conditions)

Rationale: Denitrification is the conversion of nitrate to nitrogen gas under

anoxic conditions.

• / 4