IV Practice Exam Questions And Correct

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

• Which microorganism is primarily responsible for the nitrification

process in wastewater treatment?

• Nitrosomonas and Nitrobacter
• Escherichia coli
• Bacillus subtilis
• Clostridium perfringens

Rationale: Nitrosomonas oxidizes ammonia to nitrite and Nitrobacter

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

2. The primary purpose of a grit chamber is to:

• Remove organic matter 1 / 4

• Remove sand, gravel, and other heavy solids
• Reduce BOD
• Facilitate sludge digestion

Rationale: Grit chambers are designed to remove dense inorganic

materials that could damage equipment or settle in tanks.

• Which parameter is most commonly used to measure organic

pollution in wastewater?

• pH

B. TSS

C. BOD

• DO

Rationale: Biochemical Oxygen Demand (BOD) measures the oxygen

required by microorganisms to decompose organic matter.

4. In an activated sludge system, filamentous bacteria can cause:

• Increased sludge settling
• Reduced nutrient removal
• Bulking
• Nitrification

Rationale: Filamentous bacteria grow in long strands that trap

water, causing poor sludge settling known as bulking.

• The standard method for measuring suspended solids in wastewater

is:

• Titration 2 / 4

• Membrane filtration
• Gravimetric analysis
• Spectrophotometry

Rationale: Suspended solids are measured by filtering a known

volume and weighing the residue after drying.

6. Chlorination is primarily used in wastewater treatment to:

• Remove nutrients
• Reduce TSS
• Disinfect effluent
• Promote flocculation

Rationale: Chlorine is a strong oxidant used to kill pathogenic

microorganisms in treated wastewater.

7. The term “F/M ratio” in activated sludge refers to:

• Flow-to-membrane ratio
• Food-to-microorganism ratio
• Floc-to-mass ratio
• Filtration-to-mixing ratio

Rationale: F/M ratio measures the amount of organic material (food)

per mass of microorganisms, influencing treatment efficiency.

8. The main purpose of primary sedimentation is to:

• Remove dissolved nutrients
• Reduce BOD by 90%
• Remove settleable solids 3 / 4

• Disinfect wastewater

Rationale: Primary sedimentation tanks allow heavy solids to settle,

reducing solids load on secondary treatment.

• Which of the following is considered a point source of pollution?
• Agricultural runoff
• Wastewater treatment plant discharge
• Stormwater from streets
• Atmospheric deposition

Rationale: Point sources are identifiable, discrete sources such as

pipes or ditches discharging pollutants.

10. Denitrification in wastewater treatment is the process of:

• Converting ammonia to nitrate
• Converting nitrate to nitrogen gas
• Converting nitrite to ammonia
• Removing phosphorus

Rationale: Denitrification is a microbial process that reduces nitrate

to nitrogen gas, removing nitrogen from wastewater.

11. The purpose of an equalization basin is to:

• Clarify effluent
• Balance flow and load variations
• Increase sludge production
• Remove grit
• / 4