Manitoba Wastewater Treatment Operator
Level II Practice Exam Questions And Correct
Answers (Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. What is the primary purpose of preliminary treatment in a
wastewater facility?
A. Remove dissolved nutrients
B. Remove grit and large solids
C. Adjust pH
D. Disinfect efluent
B
Preliminary treatment focuses on removing large solids and grit to
prevent damage to downstream equipment.
2. Which microorganism is most commonly responsible for biological
oxygen demand (BOD) removal in activated sludge systems?
A. Viruses
B. Protozoa
C. Bacteria
D. Algae
C
Bacteria metabolize organic matter, reducing BOD in wastewater.
3. In a facultative lagoon, what process occurs in the upper layers of
the pond?
A. Anaerobic digestion
, B. Aerobic treatment
C. Sludge thickening
D. Chemical precipitation
B
The upper layers are oxygenated, allowing aerobic bacteria to
break down organic material.
4. What is the typical range for dissolved oxygen in a healthy
activated sludge aeration tank?
A. 0-1 mg/L
B. 2-4 mg/L
C. 4-6 mg/L
D. 8-10 mg/L
C
Dissolved oxygen must be sufficient to support aerobic bacteria
without causing energy waste.
5. What is the main function of a grit chamber?
A. Remove fats, oils, and grease
B. Remove sand and gravel
C. Remove organic solids
D. Increase hydraulic retention time
B
Grit chambers slow flow so heavy inorganic particles settle out,
protecting equipment.
6. Which of the following best describes sludge age in an activated
sludge system?
A. Average time solids remain in the system
B. Time wastewater spends in primary clarifier
, C. Duration of chlorination
D. Time sludge spends in a digester only
A
Sludge age is the average retention time of microorganisms in the
aeration tank, influencing system performance.
7. Which chemical is commonly used for disinfection in wastewater
treatment?
A. Sodium hydroxide
B. Chlorine
C. Ferric chloride
D. Alum
B
Chlorine is widely used to disinfect treated wastewater before
discharge.
8. Nitrification in a wastewater treatment plant converts:
A. Ammonia to nitrate
B. Nitrate to ammonia
C. Organic matter to methane
D. Phosphate to phosphate salts
A
Nitrifying bacteria oxidize ammonia to nitrite and then nitrate.
9. What does the term “F/M ratio” represent?
A. Flow per meter of tank
B. Food to microorganism ratio
C. Filtration multiplier
D. Fat to moisture ratio
B
, The F/M ratio measures the amount of organic material relative to
the microbial population in the aeration tank.
10. Which of the following is a common problem caused by
filamentous bacteria?
A. Low BOD removal
B. Sludge bulking
C. Excess nitrification
D. Chlorine demand increase
B
Filamentous bacteria can cause poor sludge settling and bulking in
clarifiers.
11. What is the purpose of a secondary clarifier?
A. Remove grit
B. Remove suspended solids after biological treatment
C. Adjust pH
D. Remove heavy metals
B
Secondary clarifiers separate biomass from treated water after
aeration.
12. What does MLSS stand for in activated sludge systems?
A. Maximum liquid suspended solids
B. Mixed liquor suspended solids
C. Microbial liquid sediment solids
D. Minimum lagoon solids standard
B
MLSS measures the concentration of suspended solids, primarily
microorganisms, in the aeration tank.
Level II Practice Exam Questions And Correct
Answers (Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. What is the primary purpose of preliminary treatment in a
wastewater facility?
A. Remove dissolved nutrients
B. Remove grit and large solids
C. Adjust pH
D. Disinfect efluent
B
Preliminary treatment focuses on removing large solids and grit to
prevent damage to downstream equipment.
2. Which microorganism is most commonly responsible for biological
oxygen demand (BOD) removal in activated sludge systems?
A. Viruses
B. Protozoa
C. Bacteria
D. Algae
C
Bacteria metabolize organic matter, reducing BOD in wastewater.
3. In a facultative lagoon, what process occurs in the upper layers of
the pond?
A. Anaerobic digestion
, B. Aerobic treatment
C. Sludge thickening
D. Chemical precipitation
B
The upper layers are oxygenated, allowing aerobic bacteria to
break down organic material.
4. What is the typical range for dissolved oxygen in a healthy
activated sludge aeration tank?
A. 0-1 mg/L
B. 2-4 mg/L
C. 4-6 mg/L
D. 8-10 mg/L
C
Dissolved oxygen must be sufficient to support aerobic bacteria
without causing energy waste.
5. What is the main function of a grit chamber?
A. Remove fats, oils, and grease
B. Remove sand and gravel
C. Remove organic solids
D. Increase hydraulic retention time
B
Grit chambers slow flow so heavy inorganic particles settle out,
protecting equipment.
6. Which of the following best describes sludge age in an activated
sludge system?
A. Average time solids remain in the system
B. Time wastewater spends in primary clarifier
, C. Duration of chlorination
D. Time sludge spends in a digester only
A
Sludge age is the average retention time of microorganisms in the
aeration tank, influencing system performance.
7. Which chemical is commonly used for disinfection in wastewater
treatment?
A. Sodium hydroxide
B. Chlorine
C. Ferric chloride
D. Alum
B
Chlorine is widely used to disinfect treated wastewater before
discharge.
8. Nitrification in a wastewater treatment plant converts:
A. Ammonia to nitrate
B. Nitrate to ammonia
C. Organic matter to methane
D. Phosphate to phosphate salts
A
Nitrifying bacteria oxidize ammonia to nitrite and then nitrate.
9. What does the term “F/M ratio” represent?
A. Flow per meter of tank
B. Food to microorganism ratio
C. Filtration multiplier
D. Fat to moisture ratio
B
, The F/M ratio measures the amount of organic material relative to
the microbial population in the aeration tank.
10. Which of the following is a common problem caused by
filamentous bacteria?
A. Low BOD removal
B. Sludge bulking
C. Excess nitrification
D. Chlorine demand increase
B
Filamentous bacteria can cause poor sludge settling and bulking in
clarifiers.
11. What is the purpose of a secondary clarifier?
A. Remove grit
B. Remove suspended solids after biological treatment
C. Adjust pH
D. Remove heavy metals
B
Secondary clarifiers separate biomass from treated water after
aeration.
12. What does MLSS stand for in activated sludge systems?
A. Maximum liquid suspended solids
B. Mixed liquor suspended solids
C. Microbial liquid sediment solids
D. Minimum lagoon solids standard
B
MLSS measures the concentration of suspended solids, primarily
microorganisms, in the aeration tank.
