B Exam Practice Questions And Correct

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

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

treatment plant?

• Reduce BOD
• Settle sludge
• Remove heavy inorganic solids
• Chlorinate effluent

Rationale: Grit chambers are designed to remove heavy inorganic solids like

sand, gravel, and grit before they can damage pumps and other equipment.

• Which of the following is a measure of the organic strength of

wastewater? 1 / 4

• pH

B. BOD

C. TSS

• Turbidity

Rationale: Biochemical Oxygen Demand (BOD) indicates the amount of

oxygen required by microorganisms to decompose organic matter.

• What is the primary function of aeration in activated sludge systems?
• Clarify effluent
• Provide oxygen for microorganisms
• Settle sludge
• Remove nutrients

Rationale: Aeration supplies oxygen to aerobic microorganisms to break

down organic material in wastewater.

• Which of the following processes is primarily responsible for nitrogen

removal in wastewater?

• Sedimentation
• Filtration
• Nitrification/Denitrification
• Coagulation

Rationale: Nitrification converts ammonia to nitrate, and denitrification

converts nitrate to nitrogen gas, reducing nitrogen content in effluent. 2 / 4

• What is the approximate standard pH range for typical municipal

wastewater?

A. 3–5

B. 6.5–8.5

C. 9–11

D. 4–6

Rationale: Municipal wastewater is generally near neutral, which is optimal

for biological treatment processes.

• In a primary clarifier, what type of settling is primarily occurring?
• Flocculant settling
• Discrete particle settling
• Compression settling
• Zone settling

Rationale: Primary clarifiers remove larger, discrete particles through gravity

settling.

• Which of the following is a characteristic of sludge age in activated

sludge systems?

• Average time microorganisms remain in the system
• Hydraulic retention time
• Effluent flow rate
• Oxygen transfer efficiency 3 / 4

Rationale: Sludge age, or mean cell residence time, determines the growth

and composition of the microbial population.

• Which is the most common method of disinfecting wastewater

effluent?

• Ozonation
• Chlorination
• UV radiation
• Filtration

Rationale: Chlorination is widely used due to its effectiveness and cost-

efficiency in killing pathogens.

• What is the main purpose of a trickling filter?
• Remove grit
• Provide a surface for microbial growth to degrade organic matter
• Clarify effluent
• Remove nutrients

Rationale: Trickling filters are fixed-film biological treatment units where

microbes degrade organic pollutants as wastewater passes over media.

10. Total Suspended Solids (TSS) in wastewater measures:

• Dissolved organics
• Particles suspended in water
• pH
• Oxygen demand
• / 4