Manitoba Wastewater Treatment Operator Class III Practice Exam 100 Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf
- What is the primary purpose of secondary treatment in wastewater
- Removal of grit
- Removal of heavy metals
- Removal of dissolved and colloidal organics
- Disinfection
plants?
Rationale: Secondary treatment uses biological processes to remove
organic material not removed in primary treatment.
- In activated sludge, the term MCRT refers to: 1 / 4
- Mixed Cell Retention Time
- Mean Cell Residence Time
- Maximum Clarifier Return Time
- Mean Clarifier Retention Time
Rationale: MCRT is the average time microorganisms remain in the
treatment system.
3. A typical range for DO in an aeration basin is:
- 0.1–0.5 mg/L
- 5–8 mg/L
- 1–3 mg/L
- 8–10 mg/L
Rationale: Most activated sludge systems are optimized at 1–3 mg/L DO.
4. Nitrification is carried out primarily by:
- Algae
- Autotrophic bacteria
- Protozoa
- Fungi
Rationale: Nitrosomonas and Nitrobacter are autotrophic nitrifiers.
- What is the main operational indicator of clarifier sludge settling
- pH
- Alkalinity 2 / 4
quality?
C. ORP
D. SVI
Rationale: Sludge Volume Index (SVI) measures settling characteristics of
activated sludge.
- Which parameter indicates the oxygen demand of organic matter?
A. TSS
B. BOD
C. VSS
- Alkalinity
Rationale: BOD measures how much oxygen microorganisms require to
degrade organics.
7. A sudden drop in pH in a nitrifying system usually indicates:
- Excess alkalinity
- Increased nitrification
- Decreased nitrogen load
- Increased sludge age
Rationale: Nitrification consumes alkalinity and lowers pH.
8. In a primary clarifier, typical removal of TSS is:
A. 5–10%
B. 90–95%
C. 50–70%
D. 80–90% 3 / 4
Rationale: Primary settling removes roughly half to two-thirds of
suspended solids.
9. RAS stands for:
- Raw Activated Sludge
- Return Activated Sludge
- Residual Aeration Solids
- Recycled Aerobic Solids
Rationale: RAS is sludge pumped from clarifier underflow back to aeration.
10. The primary purpose of waste activated sludge (WAS) removal is to:
- Improve clarifier scum removal
- Control sludge age
- Increase DO
- Reduce alkalinity
Rationale: Sludge wasting regulates MCRT and microbial population.
- Trickling filters primarily use which microbial growth type?
- Suspended growth
- Attached growth
- Floating growth
- Anaerobic growth
Rationale: Trickling filters use biofilm attached to media.
- What is the main consequence of too low MCRT?
- / 4