Sewage Treatment Operator Class I Licensi f f f f f
ng Exam Practice Test Questions And Correc
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t Answers (Verified Answers) Plus Rational
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es 2026\2027 Q&A | Instant Download Pdf
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1. What is the primary purpose of preliminary treatment in a sewage tr
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eatment plant? f
A. Remove dissolved solids f f
B. Remove pathogens f
C. Remove large debris and grit f f f f
D. Remove nutrients f
Rationale: Preliminary treatment focuses on screening and grit removal to pr
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otect downstream equipment.
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2. What is the typical pH range for biological wastewater treatment?
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,A. 4–5
B. 5–6
C. 6.5–8.5
D. 8.5–10
Rationale: Most microorganisms in activated sludge processes thrive in a neutra
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l to slightly alkaline pH.
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3. In primary clarification, most of the solids removed are:
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A. Colloidal solids f
B. Settleable solids f
C. Dissolved solids f
D. Nutrient solids f
Rationale: Primary clarifiers mainly remove solids that can settle by gravity.
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4. The activated sludge process relies primarily on which biological group?
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A. Viruses
B. Algae
C. Bacteria
D. Protozoa
Rationale: Bacteria perform the majority of organic matter breakdown in acti
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vated sludge.
f
,5. Sludge age is defined as: f f f f
A. The time sludge spends in the digester
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B. The average time microorganisms remain in the system
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C. The age of solids removed daily
f f f f f
D. The time between wasting events
f f f f
Rationale: Sludge age (SRT) measures how long biomass stays in the system, c
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ontrolling treatment efficiency. f f
6. What does BOD measure?
f f f
A. Nitrogen concentration f
B. Organic strength of wastewater f f f
C. Suspended solids f
D. Pathogen concentration f
Rationale: BOD indicates how much oxygen microorganisms need to break do
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wn organics.
f
7. A high F/M ratio typically causes:
f f f f f
A. Bulking sludge f
B. Low DO f
C. Young sludge with rapid bacterial growth
f f f f f
D. Old sludge with nitrification
f f f
, Rationale: High food-to-microorganism ratio results in fast-
f f f f f f
growing, young biomass.
f f
8. What is the purpose of an aeration basin?
f f f f f f f
A. Reduce pH f
B. Remove grit f
C. Provide oxygen for biological treatment
f f f f
D. Remove heavy metals f f
Rationale: Aeration supplies oxygen needed to support aerobic microorganis
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ms.
9. Chlorination is primarily used to: f f f f
A. Remove BOD f
B. Remove solids f
C. Disinfect treated water f f
D. Reduce nutrients
f
Rationale: Chlorine disinfects effluent by killing pathogens.
f f f f f f
10. A sludge that settles too slowly in the secondary clarifier is called:
f f f f f f f f f f f
A. Flocculent sludge f
B. Bulking sludge f
ng Exam Practice Test Questions And Correc
f f f f f f
t Answers (Verified Answers) Plus Rational
f f f f f
es 2026\2027 Q&A | Instant Download Pdf
f f f f f f
1. What is the primary purpose of preliminary treatment in a sewage tr
f f f f f f f f f f f f
eatment plant? f
A. Remove dissolved solids f f
B. Remove pathogens f
C. Remove large debris and grit f f f f
D. Remove nutrients f
Rationale: Preliminary treatment focuses on screening and grit removal to pr
f f f f f f f f f f
otect downstream equipment.
f f
2. What is the typical pH range for biological wastewater treatment?
f f f f f f f f f
,A. 4–5
B. 5–6
C. 6.5–8.5
D. 8.5–10
Rationale: Most microorganisms in activated sludge processes thrive in a neutra
f f f f f f f f f f
l to slightly alkaline pH.
f f f f
3. In primary clarification, most of the solids removed are:
f f f f f f f f
A. Colloidal solids f
B. Settleable solids f
C. Dissolved solids f
D. Nutrient solids f
Rationale: Primary clarifiers mainly remove solids that can settle by gravity.
f f f f f f f f f f
4. The activated sludge process relies primarily on which biological group?
f f f f f f f f f
A. Viruses
B. Algae
C. Bacteria
D. Protozoa
Rationale: Bacteria perform the majority of organic matter breakdown in acti
f f f f f f f f f f
vated sludge.
f
,5. Sludge age is defined as: f f f f
A. The time sludge spends in the digester
f f f f f f
B. The average time microorganisms remain in the system
f f f f f f f
C. The age of solids removed daily
f f f f f
D. The time between wasting events
f f f f
Rationale: Sludge age (SRT) measures how long biomass stays in the system, c
f f f f f f f f f f f f
ontrolling treatment efficiency. f f
6. What does BOD measure?
f f f
A. Nitrogen concentration f
B. Organic strength of wastewater f f f
C. Suspended solids f
D. Pathogen concentration f
Rationale: BOD indicates how much oxygen microorganisms need to break do
f f f f f f f f f f
wn organics.
f
7. A high F/M ratio typically causes:
f f f f f
A. Bulking sludge f
B. Low DO f
C. Young sludge with rapid bacterial growth
f f f f f
D. Old sludge with nitrification
f f f
, Rationale: High food-to-microorganism ratio results in fast-
f f f f f f
growing, young biomass.
f f
8. What is the purpose of an aeration basin?
f f f f f f f
A. Reduce pH f
B. Remove grit f
C. Provide oxygen for biological treatment
f f f f
D. Remove heavy metals f f
Rationale: Aeration supplies oxygen needed to support aerobic microorganis
f f f f f f f f
ms.
9. Chlorination is primarily used to: f f f f
A. Remove BOD f
B. Remove solids f
C. Disinfect treated water f f
D. Reduce nutrients
f
Rationale: Chlorine disinfects effluent by killing pathogens.
f f f f f f
10. A sludge that settles too slowly in the secondary clarifier is called:
f f f f f f f f f f f
A. Flocculent sludge f
B. Bulking sludge f
