II Practice Exam Questions And Correct

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

• Which of the following microorganisms is primarily responsible for

nitrification in wastewater treatment?

• Escherichia coli
• Nitrosomonas and Nitrobacter
• Clostridium
• Streptococcus

Rationale: Nitrosomonas oxidizes ammonia to nitrite and Nitrobacter

oxidizes nitrite to nitrate, which are the key steps in nitrification.

2. The pH of most municipal wastewater is typically:

A. 3–5 1 / 4

B. 6.5–8.5

C. 9–11

D. 12–14

Rationale: Wastewater is generally near neutral, which allows

biological treatment processes to function optimally.

• What is the main purpose of primary clarifiers?
• Remove dissolved nutrients
• Remove settleable solids
• Disinfect effluent
• Aerate wastewater

Rationale: Primary clarifiers allow solids to settle out of the

wastewater by gravity, reducing the load on secondary treatment.

• Which of the following is a common coagulant used in wastewater

treatment?

• Sodium hypochlorite
• Aluminum sulfate (alum)
• Sodium hydroxide
• Calcium carbonate

Rationale: Alum is widely used to aggregate fine particles into larger

flocs for easier settling.

5. Sludge digestion is primarily used to:

• Increase oxygen content
• Reduce organic matter and pathogens 2 / 4

• Remove nitrogen
• Remove phosphorus

Rationale: Anaerobic or aerobic digestion stabilizes sludge by

reducing volatile solids and pathogen levels.

6. The primary purpose of aeration in secondary treatment is to:

• Remove heavy metals
• Provide oxygen for microorganisms
• Increase pH
• Disinfect the effluent

Rationale: Oxygen is needed to sustain aerobic bacteria that break

down organic matter.

• What is the main function of a trickling filter?
• Remove grit
• Remove oil and grease
• Promote biological treatment
• Dechlorinate effluent

Rationale: Wastewater passes over a media surface where

microorganisms metabolize organic pollutants.

• Which of the following is an advantage of extended aeration over

conventional activated sludge?

• Requires less energy
• Produces more stable sludge
• Lower aeration requirements 3 / 4

• Faster treatment time

Rationale: Extended aeration stabilizes sludge more completely due

to longer retention times.

9. The most common method for disinfection of wastewater is:

• Ozone
• Ultraviolet light
• Chlorination
• Filtration

Rationale: Chlorine is widely used because it is effective and cost-

efficient for pathogen removal.

10. The purpose of a grit chamber is to:

• Remove floating debris
• Remove sand, gravel, and heavy solids
• Reduce BOD
• Aerate wastewater

Rationale: Grit chambers slow flow to allow heavy particles to settle,

preventing damage to equipment.

• What does BOD stand for?
• Biological Oxygen Demand
• Basic Oxidation Density
• Biochemical Oxidation Data
• Biochemical Oxygen Demand
• / 4