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Wastewater Operator Class III Licensing Practice Exam Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf
(Multiple Subjects — Regulations, Safety, Treatment Processes, Math, Sampling, Laboratory, Equipment, Collections, Solids Management, Disinfection)
1. The primary purpose of a wastewater treatment plant is to:
- Produce potable water
- Protect public health and the environment
- Create fertilizer
- Remove only solids
Rationale: Protecting public health and the environment is the core
regulatory purpose of treatment plants.
2. The term BOD stands for:
- Biological Oxygen Demand 1 / 3
- Bacterial Oxygen Dissolution
- Biochemical Oxygen Demand
- Biodegradable Oxide Deposition
Rationale: BOD measures the oxygen used by microorganisms to
break down organic matter.
3. Grit removal protects downstream equipment by removing:
- Oils
- Inorganic abrasive materials like sand and gravel
- Fats and grease
- Biological solids
Rationale: Grit is abrasive and can damage pumps and clarifiers.
- Which device measures pressure in pumps and pipes?
- Barometer
- Thermometer
- Pressure gauge
- Flow meter
Rationale: Pressure gauges monitor system pressure for operational
safety and performance.
5. A confined space can be deadly due to:
- Noise levels
- Oxygen deficiency or toxic gases
- Bright lighting
- Cold temperatures 2 / 3
Rationale: Biological and chemical gases displace oxygen and create
hazardous atmospheres.
- What is the typical pH range for biological treatment?
A. 2–4
B. 5–6
C. 6.5–8.5
D. 9–12
Rationale: Most treatment microorganisms thrive in a neutral pH
range.
- Which is most commonly used for disinfection in WWTPs?
- Fluoride
- Chlorine
- Potassium permanganate
- Alum
Rationale: Chlorine is widely used due to effectiveness and
availability.
- F:M ratio compares food (BOD) to:
- Flow rate
- Bacteria age
- Microorganism mass
- Nitrogen load
- / 3
Rationale: F:M ensures proper biomass balance for treatment performance.
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