North Dakota Wastewater Treatment Operator Class II Practice Exam Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf
- Which of the following is the primary purpose of preliminary
- Remove dissolved organic matter
- Remove large solids and debris
- Remove nutrients
- Disinfect the wastewater
treatment in a wastewater treatment plant?
Rationale: Preliminary treatment removes large solids, grit, and debris to
protect downstream equipment and processes.
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- What is the main function of a grit chamber?
- Remove grease
- Remove sand, gravel, and other heavy inorganic solids
- Promote biological treatment
- Remove pathogens
Rationale: Grit chambers allow heavy inorganic solids to settle while
preventing them from damaging pumps and other equipment.
- Which microorganism is primarily responsible for breaking down
- Viruses
- Bacteria
- Protozoa
- Algae
organic matter in an activated sludge system?
Rationale: Bacteria metabolize organic matter, converting it into simpler
compounds and biomass.
- What is the purpose of aeration in secondary treatment?
- To remove heavy metals
- To clarify effluent
- To provide oxygen for microorganisms
- To disinfect wastewater 2 / 4
Rationale: Aeration supplies oxygen that bacteria need for the aerobic
digestion of organic matter.
- The process of removing nitrogen from wastewater using nitrification
and denitrification is called:
- Phosphorus removal
- Biological nutrient removal (BNR)
- Chlorination
- Sedimentation
Rationale: BNR processes remove nitrogen and sometimes phosphorus
through microbial conversions.
- Which chemical is commonly used for disinfection in wastewater
- Ammonia
- Chlorine
- Lime
- Sulfate
treatment?
Rationale: Chlorine is widely used to kill pathogenic microorganisms in
treated effluent.
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- What is the main goal of tertiary treatment?
- Remove grit
- Polish effluent by removing nutrients and residual solids
- Remove coarse debris
- Aerate wastewater
Rationale: Tertiary treatment improves effluent quality by targeting residual
solids, nutrients, and sometimes pathogens.
- What does BOD stand for?
- Biological Oxidation Demand
- Base Oxygen Dilution
- Biochemical Oxygen Demand
- Bacterial Oxidation Detection
Rationale: BOD measures the oxygen required by microorganisms to break
down organic matter in water.
9. A high BOD in influent indicates:
- Low organic content
- High organic content
- Low nutrient concentration
- High pH
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