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Ohio Wastewater Operator Class A Practice Exam Questions And Correct Answers (Verified Answers) Plus Rationales 2025|2026 Q&A | Instant Download Pdf
- 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.
- Which process removes settleable solids from wastewater?
a) Aeration
b) Sedimentation 1 / 3
c) Filtration
d) Chlorination
Rationale: Sedimentation tanks allow heavier solids to settle by
gravity.
- 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.
- The measure of the amount of oxygen required to stabilize organic
matter is
a) COD
b) BOD
c) DO
- pH
Rationale: Biochemical Oxygen Demand (BOD) measures organic load
in wastewater.
- The device used to measure flow in an open channel is a
a) Pressure gauge
b) Flow meter
c) Parshall flume 2 / 3
d) Manometer
Rationale: Parshall flumes are common for open-channel flow
measurement.
- 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.
- 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.
- 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.
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