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:
ff ff ff ff ff ff ff ff ff
A. F/M ratio f
B. MCRT
C. RAS
D. MLSS
Answer: B ff
MCRT and sludge age both describe solids retention time.
ff ff ff ff ff ff ff ff
11. Which process removes phosphorus biologically?
ff ff ff ff
A. Conventional activated sludge ff ff
B. Trickling filters ff
C. EBPR
D. Imhoff tanks f
Answer: C ff
Enhanced Biological Phosphorus Removal uses PAOs to remove
ff ff ff ff ff ff ff
phosphorus.
ff
12. Alum addition for chemical phosphorus removal works by:
ff ff ff ff ff ff ff
A. Oxidation
B. Adsorption and precipitation ff ff
C. Filtration
D. Disinfection
Answer: B ff
Aluminum salts precipitate phosphorus for removal.
ff ff ff ff ff
13. A common indicator of anaerobic digester upset is:
ff ff ff ff ff ff ff
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:
ff ff ff ff ff ff ff ff ff
A. F/M ratio f
B. MCRT
C. RAS
D. MLSS
Answer: B ff
MCRT and sludge age both describe solids retention time.
ff ff ff ff ff ff ff ff
11. Which process removes phosphorus biologically?
ff ff ff ff
A. Conventional activated sludge ff ff
B. Trickling filters ff
C. EBPR
D. Imhoff tanks f
Answer: C ff
Enhanced Biological Phosphorus Removal uses PAOs to remove
ff ff ff ff ff ff ff
phosphorus.
ff
12. Alum addition for chemical phosphorus removal works by:
ff ff ff ff ff ff ff
A. Oxidation
B. Adsorption and precipitation ff ff
C. Filtration
D. Disinfection
Answer: B ff
Aluminum salts precipitate phosphorus for removal.
ff ff ff ff ff
13. A common indicator of anaerobic digester upset is:
ff ff ff ff ff ff ff
