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Illinois Wastewater 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 wastewater treatment?
- Produce drinking water
- Remove pollutants before discharge
- Increase water temperature
- Reduce industrial production
Answer: b
Rationale: Treatment is designed to remove contaminants to protect
receiving waters.
2. BOD measures: 1 / 4
- Nitrogen concentration
- Carbon dioxide content
- Biodegradable organic matter
- Solids settling rate
Answer: c
Rationale: BOD quantifies oxygen used by microorganisms to break down
organics.
- What does TKN represent?
- Total potassium nitrate
- Total Kjeldahl Nitrogen
- Total kinetic nitrogen
- Total kernel nitrogen
Answer: b
Rationale: TKN includes organic nitrogen and ammonia.
4. The activated sludge process relies primarily on:
- Chemical precipitation
- Biological oxidation
- Filtration alone
- Sedimentation only
Answer: b
Rationale: Microorganisms oxidize organic pollutants.
5. A clarifier’s main function is: 2 / 4
- Mixing influent
- Separating solids from liquid
- Heating sludge
- Filtering gases
Answer: b
Rationale: Clarifiers allow solids to settle or float for removal.
6. The F/M ratio compares:
- Flow to mass
- Fuel to microorganisms
- Food to microorganisms
- Filtration to mixing
Answer: c
Rationale: F/M quantifies organics applied relative to biomass.
7. The purpose of aeration is to:
- Remove grit
- Increase solids loading
- Provide oxygen for biomass
- Reduce alkalinity
Answer: c
Rationale: Microbial respiration requires oxygen.
- Which lab test measures settleability of activated sludge? 3 / 4
- BOD test
- COD test
- SVI
- Chlorine residual
Answer: c
Rationale: Sludge Volume Index evaluates settling characteristics.
9. Nitrification converts ammonia to:
- Hydrocarbons
- Nitrite and nitrate
- Carbon dioxide
- Sulfates
Answer: b
Rationale: Nitrifying bacteria oxidize ammonia to nitrite then nitrate.
10. Alum is used in wastewater primarily for:
- Disinfection
- Neutralization
- Chemical coagulation
- Dechlorination
Answer: c
Rationale: Alum causes fine particles to clump for settling.
- What does MLSS stand for?
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