Michigan Wastewater Treatment Operator
Level II Exam Practice Test Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant Download Pdf
1. What is the primary purpose of secondary treatment in a
wastewater plant?
A. Remove grit
B. Disinfect pathogens
C. Oxidize dissolved and colloidal organics
D. Remove heavy metals
Answer: C
Secondary treatment biologically oxidizes organic matter remaining
after primary settling.
2. Which parameter is most commonly used to measure organic
strength entering a plant?
A. TSS
B. Alkalinity
C. pH
D. BOD
Answer: D
BOD indicates oxygen-demanding organic load.
3. The typical DO concentration maintained in an aeration tank is:
,A. 0.5 mg/L
B. 1.0 mg/L
C. 2.0 mg/L
D. 10 mg/L
Answer: C
Most activated sludge systems maintain around 2 mg/L DO for stable
treatment.
4. What does MLSS stand for?
A. Mixed Liquor Suspended Solids
B. Mixed Lime Sludge Solids
C. Main Line Settling Solids
D. Mixed Liquid Solids Sample
Answer: A
MLSS measures solids concentration in aeration basins.
5. Nitrification converts:
A. Ammonia to nitrate
B. Nitrate to nitrogen gas
C. Nitrogen gas to ammonia
D. Nitrite to ammonia
Answer: A
Autotrophic bacteria like Nitrosomonas and Nitrobacter oxidize
ammonia to nitrate.
6. A low F/M ratio generally results in:
A. Sludge bulking
B. Over-aeration
C. Long sludge age
,D. Ammonia breakthrough
Answer: C
Low food relative to microorganisms results in older, more endogenous
biomass.
7. What is the primary cause of filamentous bulking?
A. High DO
B. Low SRT
C. Low F/M
D. Excess chlorine
Answer: C
Filamentous organisms thrive in low nutrient (low F/M) conditions.
8. What is the main purpose of primary clarification?
A. Remove dissolved organics
B. Reduce suspended solids
C. Add DO
D. Remove nitrogen
Answer: B
Primary clarifiers remove settleable and floatable solids before
biological treatment.
9. A chlorine residual of 0.5 mg/L after 30 minutes contact is typically:
A. Free chlorine
B. Total chlorine
C. Combined chlorine
D. Breakpoint chlorine
Answer: A
Free chlorine residual is commonly maintained after proper disinfection.
, 10. Sludge age in activated sludge systems is also known as:
A. F/M ratio
B. MCRT
C. RAS
D. MLSS
Answer: B
MCRT and sludge age both describe solids retention time.
11. Which process removes phosphorus biologically?
A. Conventional activated sludge
B. Trickling filters
C. EBPR
D. Imhoff tanks
Answer: C
Enhanced Biological Phosphorus Removal uses PAOs to remove
phosphorus.
12. Alum addition for chemical phosphorus removal works by:
A. Oxidation
B. Adsorption and precipitation
C. Filtration
D. Disinfection
Answer: B
Aluminum salts precipitate phosphorus for removal.
13. A common indicator of anaerobic digester upset is:
Level II Exam Practice Test Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant Download Pdf
1. What is the primary purpose of secondary treatment in a
wastewater plant?
A. Remove grit
B. Disinfect pathogens
C. Oxidize dissolved and colloidal organics
D. Remove heavy metals
Answer: C
Secondary treatment biologically oxidizes organic matter remaining
after primary settling.
2. Which parameter is most commonly used to measure organic
strength entering a plant?
A. TSS
B. Alkalinity
C. pH
D. BOD
Answer: D
BOD indicates oxygen-demanding organic load.
3. The typical DO concentration maintained in an aeration tank is:
,A. 0.5 mg/L
B. 1.0 mg/L
C. 2.0 mg/L
D. 10 mg/L
Answer: C
Most activated sludge systems maintain around 2 mg/L DO for stable
treatment.
4. What does MLSS stand for?
A. Mixed Liquor Suspended Solids
B. Mixed Lime Sludge Solids
C. Main Line Settling Solids
D. Mixed Liquid Solids Sample
Answer: A
MLSS measures solids concentration in aeration basins.
5. Nitrification converts:
A. Ammonia to nitrate
B. Nitrate to nitrogen gas
C. Nitrogen gas to ammonia
D. Nitrite to ammonia
Answer: A
Autotrophic bacteria like Nitrosomonas and Nitrobacter oxidize
ammonia to nitrate.
6. A low F/M ratio generally results in:
A. Sludge bulking
B. Over-aeration
C. Long sludge age
,D. Ammonia breakthrough
Answer: C
Low food relative to microorganisms results in older, more endogenous
biomass.
7. What is the primary cause of filamentous bulking?
A. High DO
B. Low SRT
C. Low F/M
D. Excess chlorine
Answer: C
Filamentous organisms thrive in low nutrient (low F/M) conditions.
8. What is the main purpose of primary clarification?
A. Remove dissolved organics
B. Reduce suspended solids
C. Add DO
D. Remove nitrogen
Answer: B
Primary clarifiers remove settleable and floatable solids before
biological treatment.
9. A chlorine residual of 0.5 mg/L after 30 minutes contact is typically:
A. Free chlorine
B. Total chlorine
C. Combined chlorine
D. Breakpoint chlorine
Answer: A
Free chlorine residual is commonly maintained after proper disinfection.
, 10. Sludge age in activated sludge systems is also known as:
A. F/M ratio
B. MCRT
C. RAS
D. MLSS
Answer: B
MCRT and sludge age both describe solids retention time.
11. Which process removes phosphorus biologically?
A. Conventional activated sludge
B. Trickling filters
C. EBPR
D. Imhoff tanks
Answer: C
Enhanced Biological Phosphorus Removal uses PAOs to remove
phosphorus.
12. Alum addition for chemical phosphorus removal works by:
A. Oxidation
B. Adsorption and precipitation
C. Filtration
D. Disinfection
Answer: B
Aluminum salts precipitate phosphorus for removal.
13. A common indicator of anaerobic digester upset is:
