Ohio Wastewater Operator Class A
Practice Exam Questions And Correct
Answers (Verified Answers) Plus
Rationales 2025|2026 Q&A | Instant
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1. The main purpose of a wastewater treatment plant is to
a) Generate electricity
b) Protect public health and the environment
c) Produce drinking water
d) Store industrial waste
Rationale: Treatment removes harmful pollutants before discharge,
protecting health and the environment.
2. Which process removes settleable solids from wastewater?
a) Aeration
b) Sedimentation
, c) Filtration
d) Chlorination
Rationale: Sedimentation tanks allow heavier solids to settle by
gravity.
3. Wastewater from homes is called
a) Stormwater
b) Industrial waste
c) Domestic sewage
d) Groundwater infiltration
Rationale: Domestic sewage originates from human and household
activities.
4. The measure of the amount of oxygen required to stabilize organic
matter is
a) COD
b) BOD
c) DO
d) pH
Rationale: Biochemical Oxygen Demand (BOD) measures organic load
in wastewater.
5. The device used to measure flow in an open channel is a
a) Pressure gauge
b) Flow meter
c) Parshall flume
, d) Manometer
Rationale: Parshall flumes are common for open-channel flow
measurement.
6. The clear liquid above settled solids in a clarifier is called
a) Sludge
b) Supernatant
c) Scum
d) Effluent solids
Rationale: Supernatant is the clarified liquid layer above sludge.
7. A lift station is used when
a) The plant is on high ground
b) Wastewater must be pumped uphill
c) Flow is too fast
d) Effluent is too clean
Rationale: Lift stations pump wastewater where gravity flow isn’t
possible.
8. The proper sequence in wastewater treatment is
a) Secondary → Primary → Preliminary
b) Preliminary → Primary → Secondary
c) Tertiary → Secondary → Primary
d) Primary → Secondary → Disinfection → Preliminary
Rationale: Flow always starts with preliminary screening and grit
removal.
Practice Exam Questions And Correct
Answers (Verified Answers) Plus
Rationales 2025|2026 Q&A | Instant
Download Pdf
1. The main purpose of a wastewater treatment plant is to
a) Generate electricity
b) Protect public health and the environment
c) Produce drinking water
d) Store industrial waste
Rationale: Treatment removes harmful pollutants before discharge,
protecting health and the environment.
2. Which process removes settleable solids from wastewater?
a) Aeration
b) Sedimentation
, c) Filtration
d) Chlorination
Rationale: Sedimentation tanks allow heavier solids to settle by
gravity.
3. Wastewater from homes is called
a) Stormwater
b) Industrial waste
c) Domestic sewage
d) Groundwater infiltration
Rationale: Domestic sewage originates from human and household
activities.
4. The measure of the amount of oxygen required to stabilize organic
matter is
a) COD
b) BOD
c) DO
d) pH
Rationale: Biochemical Oxygen Demand (BOD) measures organic load
in wastewater.
5. The device used to measure flow in an open channel is a
a) Pressure gauge
b) Flow meter
c) Parshall flume
, d) Manometer
Rationale: Parshall flumes are common for open-channel flow
measurement.
6. The clear liquid above settled solids in a clarifier is called
a) Sludge
b) Supernatant
c) Scum
d) Effluent solids
Rationale: Supernatant is the clarified liquid layer above sludge.
7. A lift station is used when
a) The plant is on high ground
b) Wastewater must be pumped uphill
c) Flow is too fast
d) Effluent is too clean
Rationale: Lift stations pump wastewater where gravity flow isn’t
possible.
8. The proper sequence in wastewater treatment is
a) Secondary → Primary → Preliminary
b) Preliminary → Primary → Secondary
c) Tertiary → Secondary → Primary
d) Primary → Secondary → Disinfection → Preliminary
Rationale: Flow always starts with preliminary screening and grit
removal.
