Treatment Operator Level 3 Exam Practice

Newfoundland and Labrador Wastewater Treatment Operator Level 3 Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• Which of the following best describes the primary purpose of a grit

chamber?

• Remove organic matter
• Reduce nitrogen levels
• Remove heavy inorganic solids
• Promote microbial growth

Rationale: Grit chambers are designed to remove heavy inorganic

solids like sand and gravel to prevent damage to downstream equipment.

• The process of breaking down organic matter in the absence of oxygen

is called: 1 / 4

• Nitrification
• Anaerobic digestion
• Aeration
• Flocculation

Rationale: Anaerobic digestion occurs without oxygen, using

microorganisms to decompose organic matter, producing biogas.

• What is the main function of a primary clarifier?
• Remove dissolved nutrients
• Settle suspended solids
• Neutralize pH
• Oxidize ammonia

Rationale: Primary clarifiers allow solids to settle out from

wastewater, reducing the load on secondary treatment.

• Which parameter is most critical for controlling a biological nutrient

removal process?

• pH
• Dissolved oxygen
• Turbidity
• Temperature

Rationale: Dissolved oxygen levels directly affect microbial activity in

biological nutrient removal processes.

5. In activated sludge systems, the term "sludge age" refers to:

• Time solids remain in the primary clarifier 2 / 4

• Time sludge spends in storage
• Average time microorganisms spend in the aeration tank
• Time required for sludge digestion

Rationale: Sludge age or mean cell residence time measures how

long microorganisms are maintained in the system.

6. The main purpose of chlorination in wastewater treatment is:

• Remove nutrients
• Disinfect effluent
• Remove grit
• Increase BOD

Rationale: Chlorination is primarily used to kill pathogenic organisms

before discharge.

• Which of the following is an example of a tertiary treatment process?
• Primary settling
• Filtration
• Aeration
• Grit removal

Rationale: Tertiary treatment includes advanced processes like

filtration, nutrient removal, or chemical treatment.

8. The term BOD5 refers to:

• Biochemical oxygen demand over 1 day
• Biochemical oxygen demand over 5 days
• Total organic carbon 3 / 4

• Chemical oxygen demand

Rationale: BOD5 is a standard measure of the amount of oxygen

microorganisms consume over five days.

9. Nitrification is carried out by:

• Heterotrophic bacteria
• Autotrophic bacteria
• Fungi
• Protozoa

Rationale: Autotrophic bacteria, like Nitrosomonas and Nitrobacter,

oxidize ammonia to nitrate.

10. Denitrification requires:

• Oxygen
• High pH
• Anoxic conditions
• UV light

Rationale: Denitrification occurs in the absence of oxygen, converting

nitrate to nitrogen gas.

11. The sludge volume index (SVI) is used to assess:

• Sludge digestion rate
• Settling characteristics of activated sludge
• Filtration efficiency
• Chlorine demand
• / 4