Operator Class II Practice Exam

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

• What is the primary purpose of secondary treatment in wastewater

plants?

• Removal of grit
• Disinfection
• Removal of dissolved and colloidal organics
• Sludge thickening

Rationale: Secondary treatment uses biological processes to reduce

dissolved and colloidal organic matter.

• Which process is most commonly used for secondary treatment?
• Screening
• Chlorination 1 / 4

• Activated sludge
• Sand filtration

Rationale: The activated sludge process is the most widely used biological

secondary treatment.

3. In wastewater, BOD measures:

• Nutrient loading
• Amount of biodegradable organic matter
• Total solids
• pH variation

Rationale: BOD indicates how much oxygen microorganisms require to

degrade organic matter.

4. Typical dissolved oxygen (DO) range in an aeration basin is:

• 0.1–0.5 mg/L
• 5–9 mg/L
• 1–3 mg/L
• 10–15 mg/L

Rationale: A DO of 1–3 mg/L supports aerobic microbial activity without

excessive energy use.

5. High sludge age in activated sludge systems tends to:

• Increase filamentous bacteria
• Reduce nitrification
• Lower settleability 2 / 4

• Support nitrification

Rationale: Nitrifiers require longer sludge retention times to thrive.

6. A common cause of foaming in aeration basins is:

• Low MLSS
• Nocardia filamentous bacteria
• High pH
• Low F/M ratio

Rationale: Nocardia species often cause brown, stable foam on aeration

basins.

7. Clarifier short-circuiting typically results from:

• High MLSS
• Excessive sludge age
• Poor hydraulic flow patterns
• Excessive alkalinity

Rationale: Short-circuiting is caused by uneven flow, reducing detention

time and efficiency.

• What is the purpose of an equalization basin?
• Sludge digestion
• Odor control
• Flow and load equalization
• Disinfection 3 / 4

Rationale: Equalization basins smooth out variations in flow and organic

loading.

9. Chlorine demand is defined as:

• Chlorine remaining after disinfection
• Chlorine consumed before a residual appears
• Total chlorine added
• Free chlorine residual

Rationale: In wastewater, certain compounds consume chlorine before a

residual can be measured.

• What is the MOST common cause of high effluent TSS?
• High pH
• Sludge washout
• High alkalinity
• Low temperature

Rationale: Excess flow or poor settling can cause solids to wash out of the

clarifier.

11. Nitrification is carried out by:

• Protozoa
• Fungi
• Autotrophic bacteria
• Viruses
• / 4