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Water Pollution Control Operator Class III Practice Exam 100 Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf
- What is the primary purpose of a grit chamber in a wastewater
- Remove dissolved solids
- Remove organic materials
- Remove heavy inorganic particles
- Remove pathogens
treatment plant?
Rationale: Grit chambers remove sand, gravel, and other heavy inorganic
particles to protect downstream equipment.
- Which process is mainly responsible for converting ammonia to nitrate?
- Denitrification
- Nitrification 1 / 3
- Coagulation
- Flocculation
Rationale: Nitrification is the aerobic biological process that oxidizes
ammonia to nitrate.
3. The typical pH range for effective chlorination is:
A. 4–5
B. 5–6
C. 6–7
D. 9–10
Rationale: Chlorination works most efficiently near neutral pH where
hypochlorous acid predominates.
4. Sludge bulking in activated sludge is commonly caused by:
- High DO
- Excessive chlorination
- Filamentous bacteria overgrowth
- High alkalinity
Rationale: Filamentous organisms cause poor settling, leading to bulking.
5. A clarifier short-circuiting issue is most likely caused by:
- Low influent TSS
- High chlorine dose
- Uneven flow distribution
- High alkalinity 2 / 3
Rationale: Uneven flow allows water to bypass settling zones, reducing
performance.
- Which device measures wastewater flow using head pressure?
- Turbine meter
- Magnetic meter
- Parshall flume
- Venturi pump
Rationale: Parshall flumes calculate flow based on water depth at a
specific point.
7. The process that stabilizes sludge under anaerobic conditions is:
- Nitrification
- Aerobic digestion
- Anaerobic digestion
- Coagulation
Rationale: Anaerobic digestion reduces volatile solids and produces
methane in oxygen-free conditions.
8. Dissolved oxygen in aeration basins should generally be maintained at:
- 0.1 mg/L
- 0.5 mg/L
- 2.0 mg/L
- 8.0 mg/L
- / 3
Rationale: Around 2 mg/L DO supports healthy aerobic biological activity.
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