Practice Exam Questions And Correct

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

• What is the primary purpose of preliminary treatment in a wastewater

treatment plant?

• To remove dissolved nutrients
• To reduce biological oxygen demand (BOD)
• To remove large solids and debris
• To disinfect wastewater

Rationale: Preliminary treatment removes large solids and debris to

protect downstream equipment and processes.

• Which process is used to remove suspended solids from wastewater

after preliminary treatment? 1 / 4

• Chlorination
• Trickling filter
• Aeration
• Primary sedimentation

Rationale: Primary sedimentation allows suspended solids to settle out by

gravity, reducing solids load on secondary treatment.

3. Biological treatment in an activated sludge process primarily removes:

• Heavy metals
• Organic matter (BOD)
• Phosphates
• Pathogens

Rationale: Activated sludge uses microorganisms to consume organic

matter, effectively reducing BOD.

4. In wastewater treatment, the term “BOD” stands for:

• Biological Oxidation Demand
• Biochemical Oxygen Demand
• Basic Oxygen Difference
• Biological Organic Deposition

Rationale: BOD measures the amount of oxygen microorganisms consume

while decomposing organic matter in wastewater.

• What is the typical purpose of chlorination in wastewater treatment?
• Remove nutrients
• Remove solids 2 / 4

• Disinfect wastewater
• Reduce pH

Rationale: Chlorination kills pathogenic microorganisms, ensuring

wastewater is safe before discharge.

6. Nitrification is the biological oxidation of:

• Ammonia to nitrate
• Nitrate to ammonia
• Nitrite to ammonia
• Ammonia to nitrite and then nitrate

Rationale: Nitrification occurs in two steps: ammonia is first oxidized to nitrite, then to nitrate by nitrifying bacteria.

7. Denitrification converts nitrate into:

• Ammonia
• Nitrogen gas (N₂)
• Nitrite
• Nitrous oxide

Rationale: Denitrifying bacteria convert nitrate to nitrogen gas under

anoxic conditions, removing nitrogen from wastewater.

• Which microorganism is primarily responsible for nitrification?
• Escherichia coli
• Saccharomyces
• Nitrosomonas
• Clostridium 3 / 4

Rationale: Nitrosomonas bacteria oxidize ammonia to nitrite, a key step in

nitrification.

• Which of the following methods is used to remove phosphorus from

wastewater?

• Aeration
• Chemical precipitation with alum or ferric chloride
• Chlorination
• Filtration

Rationale: Chemical precipitation binds phosphate into insoluble forms,

which can then settle out in primary or secondary treatment.

10. In trickling filter systems, microorganisms grow on:

• Suspended flocs
• Media surfaces (biofilm)
• Sand beds
• Activated sludge

Rationale: Trickling filters rely on a biofilm on media surfaces to degrade

organic matter as wastewater flows over them.

• The main advantage of extended aeration over conventional activated

sludge is:

• Lower oxygen requirement
• Reduced sludge production
• Higher nutrient removal
• Faster treatment
• / 4