Minnesota Wastewater Systems
Engineering Certification Exam Practice
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the primary purpose of wastewater treatment?
A. Produce drinking water
B. Remove contaminants before discharge
C. Increase water hardness
D. Add disinfectants only
Rationale: Wastewater treatment removes physical, chemical, and
biological contaminants before release into the environment.
2. Which process is typically the first step in wastewater treatment?
A. Aeration
B. Chlorination
C. Screening
D. Filtration
, Rationale: Screening removes large solids and debris at the
preliminary stage.
3. What does BOD measure?
A. Heavy metals
B. Oxygen required by microorganisms to decompose organic matter
C. Turbidity
D. pH level
Rationale: BOD (Biochemical Oxygen Demand) indicates organic
pollution strength.
4. Which microorganism group is most important in activated sludge
systems?
A. Viruses
B. Bacteria
C. Algae
D. Helminths
Rationale: Bacteria are responsible for organic matter
decomposition.
5. What is the purpose of primary clarifiers?
A. Disinfection
B. Settling of suspended solids
C. Nutrient removal
D. Oxygen production
Rationale: Primary clarifiers allow solids to settle out by gravity.
, 6. What gas is commonly produced in anaerobic digestion?
A. Oxygen
B. Nitrogen
C. Methane
D. Chlorine
Rationale: Methane is a key byproduct of anaerobic digestion.
7. What does MLSS stand for?
A. Mixed Liquid Sludge Supply
B. Mixed Liquor Suspended Solids
C. Mechanical Level Sludge System
D. Managed Liquid Settling Solution
Rationale: MLSS refers to suspended solids in aeration tanks.
8. Which process removes nitrogen biologically?
A. Sedimentation
B. Screening
C. Nitrification-denitrification
D. Coagulation
Rationale: Nitrogen is removed through biological conversion
processes.
9. What is the main function of aeration tanks?
A. Sludge storage
B. Provide oxygen for microbial activity
C. Chemical mixing
Engineering Certification Exam Practice
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the primary purpose of wastewater treatment?
A. Produce drinking water
B. Remove contaminants before discharge
C. Increase water hardness
D. Add disinfectants only
Rationale: Wastewater treatment removes physical, chemical, and
biological contaminants before release into the environment.
2. Which process is typically the first step in wastewater treatment?
A. Aeration
B. Chlorination
C. Screening
D. Filtration
, Rationale: Screening removes large solids and debris at the
preliminary stage.
3. What does BOD measure?
A. Heavy metals
B. Oxygen required by microorganisms to decompose organic matter
C. Turbidity
D. pH level
Rationale: BOD (Biochemical Oxygen Demand) indicates organic
pollution strength.
4. Which microorganism group is most important in activated sludge
systems?
A. Viruses
B. Bacteria
C. Algae
D. Helminths
Rationale: Bacteria are responsible for organic matter
decomposition.
5. What is the purpose of primary clarifiers?
A. Disinfection
B. Settling of suspended solids
C. Nutrient removal
D. Oxygen production
Rationale: Primary clarifiers allow solids to settle out by gravity.
, 6. What gas is commonly produced in anaerobic digestion?
A. Oxygen
B. Nitrogen
C. Methane
D. Chlorine
Rationale: Methane is a key byproduct of anaerobic digestion.
7. What does MLSS stand for?
A. Mixed Liquid Sludge Supply
B. Mixed Liquor Suspended Solids
C. Mechanical Level Sludge System
D. Managed Liquid Settling Solution
Rationale: MLSS refers to suspended solids in aeration tanks.
8. Which process removes nitrogen biologically?
A. Sedimentation
B. Screening
C. Nitrification-denitrification
D. Coagulation
Rationale: Nitrogen is removed through biological conversion
processes.
9. What is the main function of aeration tanks?
A. Sludge storage
B. Provide oxygen for microbial activity
C. Chemical mixing
