III Exam Practice Questions And Correct

Nebraska Wastewater Operator Grade III Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• Which of the following is the primary function of a grit chamber in

wastewater treatment?

• Remove sand, gravel, and heavy solids
• Remove dissolved nutrients
• Aerate the wastewater
• Settle biological solids

Rationale: Grit chambers are designed to remove heavy, inorganic

materials like sand and gravel that could damage downstream equipment or accumulate in tanks. 1 / 4

2. The primary purpose of primary sedimentation is to:

• Remove dissolved organics
• Remove settleable solids
• Kill pathogens
• Increase dissolved oxygen

Rationale: Primary sedimentation removes settleable solids through

gravity, reducing the load on secondary treatment processes.

• Which type of bacteria predominates in the activated sludge process

for organic matter removal?

• Nitrifying bacteria
• Sulfate-reducing bacteria
• Heterotrophic bacteria
• Methanogenic bacteria

Rationale: Heterotrophic bacteria consume organic carbon and are

responsible for most of the BOD removal in activated sludge systems.

4. Chlorination of treated wastewater is primarily used for:

• Removing suspended solids
• Disinfection
• Nutrient removal
• Odor control

Rationale: Chlorine effectively kills pathogenic microorganisms, reducing

health risks from wastewater effluent. 2 / 4

• Which of the following is a sign of excessive sludge in an aeration

basin?

• Clear effluent
• Bulking sludge
• High DO
• Low mixed liquor suspended solids

Rationale: Bulking occurs when filamentous bacteria dominate, preventing

proper settling of sludge.

6. The purpose of a flow equalization basin is to:

• Remove phosphorus
• Reduce hydraulic shock loads
• Promote nitrification
• Aerate wastewater

Rationale: Equalization basins buffer large variations in flow and strength,

preventing overloading downstream processes.

• Which parameter is most commonly used to measure organic

pollution in wastewater?

A. TSS

• pH

C. BOD

• Conductivity 3 / 4

Rationale: BOD (Biochemical Oxygen Demand) indicates the amount of

oxygen required by microorganisms to decompose organic matter.

• What is the ideal pH range for biological treatment processes in

wastewater?

A. 4.0–5.0

B. 9.0–10.0

C. 6.5–8.5

D. 3.0–4.5

Rationale: Most microorganisms in activated sludge function optimally

between 6.5 and 8.5.

9. The main cause of septic sludge in an aeration tank is:

• High DO
• Low DO
• Excessive aeration
• High pH

Rationale: Low dissolved oxygen levels create anaerobic conditions,

leading to septic or sour sludge formation.

• What is the primary mechanism of nitrogen removal in a

conventional activated sludge system with nitrification and denitrification?

• Filtration
• Microbial conversion to nitrogen gas
• / 4