Level 4 Practice Exam 100 Questions And

Alberta Wastewater Treatment Operator Level 4 Practice Exam 100 Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of step-feed activated sludge in high-flow

conditions?

• Improve sludge settleability
• Increase DO levels
• Reduce peak loading to aeration zones
• Improve nitrification rates

Rationale: Step-feed distributes influent across multiple aeration zones,

reducing peak organic loading and preventing washout.

• What is the expected result of increasing RAS flow excessively? 1 / 4

• Increased MLSS in aeration
• Overloading of secondary clarifier
• Improved nitrification
• Reduced sludge production

Rationale: Excessive RAS can hydraulically and solids-overload the clarifier,

reducing settling efficiency.

• Which microorganism group dominates in a well-nitrifying system?
• Protozoa
• Nitrifying bacteria
• Yeasts
• Fungi

Rationale: Nitrifiers oxidize ammonia and dominate when stable

nitrification occurs.

• A drop in ORP to -200 mV in a reactor indicates what condition?
• Aerobic
• Anoxic
• Anaerobic
• Oxic

Rationale: Strongly negative ORP values indicate anaerobic conditions

with no nitrate or oxygen present.

• The sludge age required for complete nitrification in Alberta cold-

weather systems is typically: 2 / 4

• 3–5 days
• 5–8 days
• 8–10 days
• 12–20 days

Rationale: Nitrifiers grow slowly, especially in cold climates, requiring long

SRT values.

• Which parameter most strongly influences filamentous bulking?
• Temperature
• pH
• F/M ratio

D. ORP

Rationale: Low F/M conditions favor filamentous bacteria, causing bulking.

• What happens when aeration is reduced too much in extended

aeration?

• Improved BOD removal
• Reduced sludge age
• Onset of septic conditions
• Faster settling

Rationale: Low oxygen allows septic conditions, generating odor and poor

settling sludge.

• Which chemical is most effective for alkalinity restoration during

nitrification? 3 / 4

• Alum
• Polymer
• Sodium bicarbonate
• Ferric chloride

Rationale: Sodium bicarbonate directly raises alkalinity consumed during

nitrification.

9. The primary purpose of tertiary filtration is:

• Remove oil and grease
• Remove suspended solids and residual BOD
• Remove nitrogen
• Reduce pathogens only

Rationale: Filtration polishes effluent by removing fine solids and

remaining organics.

• Which process is most sensitive to toxic shock loading?
• Primary clarification
• Grit removal
• Biological nutrient removal
• Disinfection

Rationale: BNR microbial populations are easily inhibited by toxic

chemicals.

• What is the typical range for MLSS in conventional activated sludge?
• / 4