Michigan Wastewater Treatment
Operator Level 2 Exam Practice
Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. Which of the following best describes the primary purpose of
wastewater treatment?
A. Increase solids concentration
B. Produce potable water
C. Protect public health and the environment
D. Generate energy
Primary treatment processes remove pollutants to protect
downstream receptors and comply with regulations.
2. The Biochemical Oxygen Demand (BOD) test measures:
A. pH change over time
B. Total suspended solids
C. Oxygen consumed by microorganisms
D. Chemical contaminants present
BOD quantifies organic matter by measuring oxygen consumption
during microbial decomposition.
3. Primary treatment primarily removes which type of material?
A. Dissolved nutrients
B. Pathogens
C. Settleable solids
D. Gases
Primary clarifiers settle heavy particles out of the wastewater.
,4. Activated sludge treatment is classified as:
A. Chemical settling
B. Trickling filtration
C. Biological treatment
D. Disinfection
Activated sludge uses microbes in aerated conditions to degrade
organic matter.
5. The Mixed Liquor Suspended Solids (MLSS) refers to:
A. Settled sludge only
B. Clarified effluent
C. Biomass concentration in aeration basin
D. Sludge in digesters
MLSS measures the suspended solids that include microorganisms in
the aeration tank.
6. Aeration basins are primarily used to:
A. Remove grit
B. Supply oxygen to microorganisms
C. Clarify treated water
D. Disinfect effluent
Aeration introduces oxygen to sustain the biological oxidation of
pollutants.
7. pH control in wastewater treatment is important because:
A. Higher pH kills pathogens only
B. It improves color
C. It increases odor
D. It affects microbial activity and chemical reactions
pH influences biological processes and chemical precipitation
effectiveness.
8. The sludge age (SRT) influences:
A. Chlorine demand
B. Microbial population dynamics
C. Grit removal
D. Screen efficiency
Solids retention time affects which microorganisms dominate in the
activated sludge process.
, 9. Which nutrient is often limiting in wastewater biological treatment?
A. Sodium
B. Potassium
C. Nitrogen or phosphorus
D. Chlorine
Excessive nutrient removal is required to prevent eutrophication in
receiving waters.
10. Total Suspended Solids (TSS) in effluent must be controlled
because high TSS can:
A. Improve water taste
B. Increase turbidity and harm aquatic life
C. Raise pH
D. Eliminate bacteria
Suspended solids reduce light penetration and can carry pollutants
downstream.
11. Chlorination is used primarily for:
A. Nutrient removal
B. Disinfection
C. Sludge digestion
D. Sedimentation
Chlorine inactivates pathogens before discharge.
12. Chemical oxygen demand (COD) differs from BOD by measuring:
A. Only oxygen
B. Total oxidizable material by chemical means
C. Burning water
D. Color intensity
COD uses strong oxidant to measure organic matter irrespective of
biodegradability.
13. The purpose of a grease trap is to:
A. Increase dissolved oxygen
B. Remove fats, oils and grease
C. Add nutrients
D. Remove heavy metals
Grease traps intercept and collect fats that can clog downstream
equipment.
Operator Level 2 Exam Practice
Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. Which of the following best describes the primary purpose of
wastewater treatment?
A. Increase solids concentration
B. Produce potable water
C. Protect public health and the environment
D. Generate energy
Primary treatment processes remove pollutants to protect
downstream receptors and comply with regulations.
2. The Biochemical Oxygen Demand (BOD) test measures:
A. pH change over time
B. Total suspended solids
C. Oxygen consumed by microorganisms
D. Chemical contaminants present
BOD quantifies organic matter by measuring oxygen consumption
during microbial decomposition.
3. Primary treatment primarily removes which type of material?
A. Dissolved nutrients
B. Pathogens
C. Settleable solids
D. Gases
Primary clarifiers settle heavy particles out of the wastewater.
,4. Activated sludge treatment is classified as:
A. Chemical settling
B. Trickling filtration
C. Biological treatment
D. Disinfection
Activated sludge uses microbes in aerated conditions to degrade
organic matter.
5. The Mixed Liquor Suspended Solids (MLSS) refers to:
A. Settled sludge only
B. Clarified effluent
C. Biomass concentration in aeration basin
D. Sludge in digesters
MLSS measures the suspended solids that include microorganisms in
the aeration tank.
6. Aeration basins are primarily used to:
A. Remove grit
B. Supply oxygen to microorganisms
C. Clarify treated water
D. Disinfect effluent
Aeration introduces oxygen to sustain the biological oxidation of
pollutants.
7. pH control in wastewater treatment is important because:
A. Higher pH kills pathogens only
B. It improves color
C. It increases odor
D. It affects microbial activity and chemical reactions
pH influences biological processes and chemical precipitation
effectiveness.
8. The sludge age (SRT) influences:
A. Chlorine demand
B. Microbial population dynamics
C. Grit removal
D. Screen efficiency
Solids retention time affects which microorganisms dominate in the
activated sludge process.
, 9. Which nutrient is often limiting in wastewater biological treatment?
A. Sodium
B. Potassium
C. Nitrogen or phosphorus
D. Chlorine
Excessive nutrient removal is required to prevent eutrophication in
receiving waters.
10. Total Suspended Solids (TSS) in effluent must be controlled
because high TSS can:
A. Improve water taste
B. Increase turbidity and harm aquatic life
C. Raise pH
D. Eliminate bacteria
Suspended solids reduce light penetration and can carry pollutants
downstream.
11. Chlorination is used primarily for:
A. Nutrient removal
B. Disinfection
C. Sludge digestion
D. Sedimentation
Chlorine inactivates pathogens before discharge.
12. Chemical oxygen demand (COD) differs from BOD by measuring:
A. Only oxygen
B. Total oxidizable material by chemical means
C. Burning water
D. Color intensity
COD uses strong oxidant to measure organic matter irrespective of
biodegradability.
13. The purpose of a grease trap is to:
A. Increase dissolved oxygen
B. Remove fats, oils and grease
C. Add nutrients
D. Remove heavy metals
Grease traps intercept and collect fats that can clog downstream
equipment.
