Saskatchewan Wastewater Operator
Level II Practice Exam Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
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1. Which of the following is the primary purpose of a grit chamber in
wastewater treatment?
A. Remove organic solids
B. Remove inorganic solids
C. Reduce biological oxygen demand
D. Clarify effluent
Answer: B. Remove inorganic solids
Rationale: Grit chambers are designed to remove heavy, inorganic particles
like sand, gravel, and grit to prevent wear on equipment.
,2. In wastewater treatment, BOD stands for:
A. Biological Oxidation Demand
B. Biochemical Oxygen Demand
C. Basic Oxygen Determination
D. Biochemical Oxidation Density
Answer: B. Biochemical Oxygen Demand
Rationale: BOD measures the amount of dissolved oxygen needed by
microorganisms to decompose organic matter over a specified time,
indicating wastewater strength.
3. Which of the following is a common source of nitrogen in municipal
wastewater?
A. Detergents
B. Human waste
C. Heavy metals
D. Sand
Answer: B. Human waste
Rationale: Nitrogen primarily comes from urea in urine and proteins in feces,
which convert to ammonia during treatment.
4. The main purpose of a primary clarifier is to:
A. Remove pathogens
B. Settle suspended solids
C. Aerate the wastewater
D. Remove nutrients
,Answer: B. Settle suspended solids
Rationale: Primary clarifiers allow heavier solids to settle out, reducing the
load on secondary treatment processes.
5. In activated sludge systems, return activated sludge (RAS) is:
A. Wasted sludge sent to disposal
B. Sludge returned to the aeration tank
C. Sludge discharged to the river
D. Settled solids in primary clarifier
Answer: B. Sludge returned to the aeration tank
Rationale: RAS maintains a high concentration of microorganisms in the
aeration tank to efficiently treat incoming wastewater.
6. A characteristic of septic tank effluent is:
A. High dissolved oxygen
B. Low dissolved oxygen and high BOD
C. Completely pathogen-free
D. High nutrient removal
Answer: B. Low dissolved oxygen and high BOD
Rationale: Septic tank effluent is partially treated, with organic matter
remaining, resulting in low oxygen content.
7. What is the most common method to disinfect treated wastewater
before discharge?
A. Filtration
B. Sedimentation
, C. Chlorination
D. Nitrification
Answer: C. Chlorination
Rationale: Chlorination is widely used to kill pathogens before wastewater is
released to receiving waters.
8. Which microorganism is primarily responsible for nitrification?
A. Escherichia coli
B. Nitrosomonas and Nitrobacter
C. Clostridium
D. Pseudomonas
Answer: B. Nitrosomonas and Nitrobacter
Rationale: Nitrosomonas oxidizes ammonia to nitrite, and Nitrobacter
oxidizes nitrite to nitrate in nitrification.
9. Sludge digestion reduces volume primarily through:
A. Sedimentation
B. Filtration
C. Biological decomposition
D. Coagulation
Answer: C. Biological decomposition
Rationale: Anaerobic or aerobic digestion breaks down organic matter in
sludge, reducing solids and volume.
10. Which parameter indicates the strength of wastewater?
A. Turbidity
Level II Practice Exam Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
1. Which of the following is the primary purpose of a grit chamber in
wastewater treatment?
A. Remove organic solids
B. Remove inorganic solids
C. Reduce biological oxygen demand
D. Clarify effluent
Answer: B. Remove inorganic solids
Rationale: Grit chambers are designed to remove heavy, inorganic particles
like sand, gravel, and grit to prevent wear on equipment.
,2. In wastewater treatment, BOD stands for:
A. Biological Oxidation Demand
B. Biochemical Oxygen Demand
C. Basic Oxygen Determination
D. Biochemical Oxidation Density
Answer: B. Biochemical Oxygen Demand
Rationale: BOD measures the amount of dissolved oxygen needed by
microorganisms to decompose organic matter over a specified time,
indicating wastewater strength.
3. Which of the following is a common source of nitrogen in municipal
wastewater?
A. Detergents
B. Human waste
C. Heavy metals
D. Sand
Answer: B. Human waste
Rationale: Nitrogen primarily comes from urea in urine and proteins in feces,
which convert to ammonia during treatment.
4. The main purpose of a primary clarifier is to:
A. Remove pathogens
B. Settle suspended solids
C. Aerate the wastewater
D. Remove nutrients
,Answer: B. Settle suspended solids
Rationale: Primary clarifiers allow heavier solids to settle out, reducing the
load on secondary treatment processes.
5. In activated sludge systems, return activated sludge (RAS) is:
A. Wasted sludge sent to disposal
B. Sludge returned to the aeration tank
C. Sludge discharged to the river
D. Settled solids in primary clarifier
Answer: B. Sludge returned to the aeration tank
Rationale: RAS maintains a high concentration of microorganisms in the
aeration tank to efficiently treat incoming wastewater.
6. A characteristic of septic tank effluent is:
A. High dissolved oxygen
B. Low dissolved oxygen and high BOD
C. Completely pathogen-free
D. High nutrient removal
Answer: B. Low dissolved oxygen and high BOD
Rationale: Septic tank effluent is partially treated, with organic matter
remaining, resulting in low oxygen content.
7. What is the most common method to disinfect treated wastewater
before discharge?
A. Filtration
B. Sedimentation
, C. Chlorination
D. Nitrification
Answer: C. Chlorination
Rationale: Chlorination is widely used to kill pathogens before wastewater is
released to receiving waters.
8. Which microorganism is primarily responsible for nitrification?
A. Escherichia coli
B. Nitrosomonas and Nitrobacter
C. Clostridium
D. Pseudomonas
Answer: B. Nitrosomonas and Nitrobacter
Rationale: Nitrosomonas oxidizes ammonia to nitrite, and Nitrobacter
oxidizes nitrite to nitrate in nitrification.
9. Sludge digestion reduces volume primarily through:
A. Sedimentation
B. Filtration
C. Biological decomposition
D. Coagulation
Answer: C. Biological decomposition
Rationale: Anaerobic or aerobic digestion breaks down organic matter in
sludge, reducing solids and volume.
10. Which parameter indicates the strength of wastewater?
A. Turbidity
