Illinois Wastewater Operator Class 1
Exam Practice Questions And Correct
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1. What is the primary purpose of wastewater treatment?
a. Produce drinking water
b. Remove pollutants before discharge
c. Increase water temperature
d. Reduce industrial production
Answer: b
Rationale: Treatment is designed to remove contaminants to protect
receiving waters.
2. BOD measures:
,a. Nitrogen concentration
b. Carbon dioxide content
c. Biodegradable organic matter
d. Solids settling rate
Answer: c
Rationale: BOD quantifies oxygen used by microorganisms to break down
organics.
3. What does TKN represent?
a. Total potassium nitrate
b. Total Kjeldahl Nitrogen
c. Total kinetic nitrogen
d. Total kernel nitrogen
Answer: b
Rationale: TKN includes organic nitrogen and ammonia.
4. The activated sludge process relies primarily on:
a. Chemical precipitation
b. Biological oxidation
c. Filtration alone
d. Sedimentation only
Answer: b
Rationale: Microorganisms oxidize organic pollutants.
5. A clarifier’s main function is:
,a. Mixing influent
b. Separating solids from liquid
c. Heating sludge
d. Filtering gases
Answer: b
Rationale: Clarifiers allow solids to settle or float for removal.
6. The F/M ratio compares:
a. Flow to mass
b. Fuel to microorganisms
c. Food to microorganisms
d. Filtration to mixing
Answer: c
Rationale: F/M quantifies organics applied relative to biomass.
7. The purpose of aeration is to:
a. Remove grit
b. Increase solids loading
c. Provide oxygen for biomass
d. Reduce alkalinity
Answer: c
Rationale: Microbial respiration requires oxygen.
8. Which lab test measures settleability of activated sludge?
, a. BOD test
b. COD test
c. SVI
d. Chlorine residual
Answer: c
Rationale: Sludge Volume Index evaluates settling characteristics.
9. Nitrification converts ammonia to:
a. Hydrocarbons
b. Nitrite and nitrate
c. Carbon dioxide
d. Sulfates
Answer: b
Rationale: Nitrifying bacteria oxidize ammonia to nitrite then nitrate.
10. Alum is used in wastewater primarily for:
a. Disinfection
b. Neutralization
c. Chemical coagulation
d. Dechlorination
Answer: c
Rationale: Alum causes fine particles to clump for settling.
11. What does MLSS stand for?
Exam Practice Questions And Correct
Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
1. What is the primary purpose of wastewater treatment?
a. Produce drinking water
b. Remove pollutants before discharge
c. Increase water temperature
d. Reduce industrial production
Answer: b
Rationale: Treatment is designed to remove contaminants to protect
receiving waters.
2. BOD measures:
,a. Nitrogen concentration
b. Carbon dioxide content
c. Biodegradable organic matter
d. Solids settling rate
Answer: c
Rationale: BOD quantifies oxygen used by microorganisms to break down
organics.
3. What does TKN represent?
a. Total potassium nitrate
b. Total Kjeldahl Nitrogen
c. Total kinetic nitrogen
d. Total kernel nitrogen
Answer: b
Rationale: TKN includes organic nitrogen and ammonia.
4. The activated sludge process relies primarily on:
a. Chemical precipitation
b. Biological oxidation
c. Filtration alone
d. Sedimentation only
Answer: b
Rationale: Microorganisms oxidize organic pollutants.
5. A clarifier’s main function is:
,a. Mixing influent
b. Separating solids from liquid
c. Heating sludge
d. Filtering gases
Answer: b
Rationale: Clarifiers allow solids to settle or float for removal.
6. The F/M ratio compares:
a. Flow to mass
b. Fuel to microorganisms
c. Food to microorganisms
d. Filtration to mixing
Answer: c
Rationale: F/M quantifies organics applied relative to biomass.
7. The purpose of aeration is to:
a. Remove grit
b. Increase solids loading
c. Provide oxygen for biomass
d. Reduce alkalinity
Answer: c
Rationale: Microbial respiration requires oxygen.
8. Which lab test measures settleability of activated sludge?
, a. BOD test
b. COD test
c. SVI
d. Chlorine residual
Answer: c
Rationale: Sludge Volume Index evaluates settling characteristics.
9. Nitrification converts ammonia to:
a. Hydrocarbons
b. Nitrite and nitrate
c. Carbon dioxide
d. Sulfates
Answer: b
Rationale: Nitrifying bacteria oxidize ammonia to nitrite then nitrate.
10. Alum is used in wastewater primarily for:
a. Disinfection
b. Neutralization
c. Chemical coagulation
d. Dechlorination
Answer: c
Rationale: Alum causes fine particles to clump for settling.
11. What does MLSS stand for?
