Class III Practice Exam Questions And

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

• The primary purpose of primary clarifiers in wastewater treatment is

to:

• Remove dissolved nutrients
• Remove pathogens
• Remove settleable solids
• Increase dissolved oxygen

Rationale: Primary clarifiers are designed to remove settleable solids and

floating material, reducing the load on secondary treatment.

2. The primary source of nitrogen in wastewater is:

• Detergents 1 / 4

• Human and animal waste
• Industrial chemicals
• Stormwater

Rationale: Nitrogen mainly comes from urea and proteins in human and

animal waste, which is transformed into ammonia and other nitrogen compounds in treatment.

• What is the function of an aeration basin in activated sludge

treatment?

• To settle solids
• To disinfect wastewater
• To supply oxygen for microbial degradation
• To remove fats and oils

Rationale: Aeration basins supply oxygen, allowing microorganisms to

biologically degrade organic matter.

4. The term "BOD" stands for:

• Biological Oxygen Demand
• Biochemical Oxidation Density
• Biochemical Oxygen Demand
• Basic Oxidation Demand

Rationale: BOD measures the amount of oxygen microorganisms need to

decompose organic matter in water. 2 / 4

• What is the typical retention time for secondary clarifiers?
• 1–2 minutes
• 30–60 minutes
• 2–4 hours
• 24 hours

Rationale: Secondary clarifiers usually operate with a retention time of 2–4

hours to allow solids to settle.

6. Nitrification is the process of converting:

• Nitrogen gas to ammonia
• Ammonia to nitrate
• Nitrate to nitrogen gas
• Organic nitrogen to protein

Rationale: Nitrification is a two-step aerobic process: ammonia is converted first to nitrite and then to nitrate.

• Which microorganism is primarily responsible for nitrification?
• E. coli
• Nitrosomonas and Nitrobacter
• Pseudomonas
• Clostridium

Rationale: Nitrosomonas oxidizes ammonia to nitrite, and Nitrobacter

oxidizes nitrite to nitrate. 3 / 4

8. The purpose of disinfection in wastewater treatment is to:

• Remove solids
• Remove nitrogen
• Reduce pathogens
• Adjust pH

Rationale: Disinfection targets pathogens to protect public health before

discharge or reuse.

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

treatment?

• Alum
• Lime
• Chlorine
• Sand

Rationale: Chlorine is widely used to inactivate microorganisms in effluent

water.

10. Sludge digestion primarily reduces:

• Dissolved oxygen
• Organic solids
• pH
• Temperature

Rationale: Anaerobic or aerobic digestion breaks down organic solids,

reducing sludge volume and stabilizing material.

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