Level II Practice Exam Questions And

Saskatchewan Wastewater Operator Level II Practice Exam Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• Which of the following is the primary purpose of a grit chamber in

wastewater treatment?

• Remove organic solids
• Remove inorganic solids
• Reduce biological oxygen demand
• 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. 1 / 4

2. In wastewater treatment, BOD stands for:

• Biological Oxidation Demand
• Biochemical Oxygen Demand
• Basic Oxygen Determination
• 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.

• Which of the following is a common source of nitrogen in municipal

wastewater?

• Detergents
• Human waste
• Heavy metals
• 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:

• Remove pathogens
• Settle suspended solids
• Aerate the wastewater
• Remove nutrients 2 / 4

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:

• Wasted sludge sent to disposal
• Sludge returned to the aeration tank
• Sludge discharged to the river
• 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:

• High dissolved oxygen
• Low dissolved oxygen and high BOD
• Completely pathogen-free
• 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.

• What is the most common method to disinfect treated wastewater

before discharge?

• Filtration
• Sedimentation 3 / 4

• Chlorination
• Nitrification

Answer: C. Chlorination

Rationale: Chlorination is widely used to kill pathogens before wastewater is

released to receiving waters.

• Which microorganism is primarily responsible for nitrification?
• Escherichia coli
• Nitrosomonas and Nitrobacter
• Clostridium
• 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:

• Sedimentation
• Filtration
• Biological decomposition
• Coagulation

Answer: C. Biological decomposition

Rationale: Anaerobic or aerobic digestion breaks down organic matter in

sludge, reducing solids and volume.

• Which parameter indicates the strength of wastewater?
• Turbidity
• / 4