Class 1 Exam Practice Questions And

Québec Wastewater Treatment Operator Class 1 Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of a wastewater treatment plant?
• Generate electricity
• Provide drinking water
• Remove contaminants from wastewater
• Irrigate crops

Rationale: The main function of a wastewater treatment plant is to

treat sewage to remove physical, chemical, and biological contaminants before releasing it into the environment.

• Which of the following is considered a physical treatment process?
• Chlorination
• Screening 1 / 4

• Activated sludge
• Nitrification

Rationale: Screening is a physical process that removes large solids

from wastewater.

• Which process primarily removes dissolved organic matter from

wastewater?

• Screening
• Sedimentation
• Biological treatment
• Coagulation

Rationale: Biological treatment uses microorganisms to break down

dissolved organic compounds.

• What is the typical first step in wastewater treatment?
• Screening
• Chlorination
• Aeration
• Filtration

Rationale: Screening removes large debris from raw wastewater

before it enters further treatment stages.

• What is the function of grit chambers?
• Remove bacteria
• Remove dissolved chemicals
• Remove sand and heavy particles 2 / 4

• Remove oils

Rationale: Grit chambers slow down flow to allow sand, gravel, and

other heavy particles to settle.

• What is primary clarification in wastewater treatment?
• Filtration
• Biological oxidation
• Sedimentation of suspended solids
• Disinfection

Rationale: Primary clarification allows heavy solids to settle, forming

primary sludge.

• What is the main purpose of aeration in secondary treatment?
• Increase sludge density
• Provide oxygen for microbial growth
• Remove sand and grit
• Add chlorine

Rationale: Aeration supplies oxygen to microorganisms for the

breakdown of organic matter in secondary treatment.

• Which microorganisms are commonly used in activated sludge

processes?

• Protozoa only
• Algae only
• Bacteria and protozoa
• Viruses 3 / 4

Rationale: Bacteria are the primary decomposers, and protozoa help

control bacterial populations.

• What is the typical range for dissolved oxygen in an aeration tank?
• 0–1 mg/L
• 2–4 mg/L
• 10–12 mg/L
• 15–20 mg/L

Rationale: Dissolved oxygen must be maintained at 2–4 mg/L to

support microbial activity.

• What is sludge thickening?
• Burning sludge
• Adding chemicals to wastewater
• Reducing water content in sludge
• Chlorinating sludge

Rationale: Thickening concentrates sludge by removing water,

reducing volume for further treatment.

• What is the purpose of disinfection in wastewater treatment?
• Remove solids
• Remove nutrients
• Kill pathogens
• Remove grease

Rationale: Disinfection reduces the number of disease-causing

microorganisms before effluent is discharged.

• / 4