Class IV Practice Exam Questions And

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

• Which of the following is the primary purpose of a wastewater

treatment plant?

• Generate electricity
• Remove pollutants to protect public health and the environment
• Produce drinking water
• Increase river flow

Rationale: The main goal of wastewater treatment is to reduce

pollutants so that water released into the environment is safe.

• What is the typical BOD5 concentration of domestic wastewater

influent?

• 50–100 mg/L 1 / 4

• 100–150 mg/L
• 200–300 mg/L
• 400–500 mg/L

Rationale: Typical municipal wastewater has a 5-day BOD (BOD5) of

200–300 mg/L, representing biodegradable organic matter.

• Which process is primarily responsible for removing suspended solids?
• Chlorination
• Primary sedimentation
• Nitrification
• Trickling filter

Rationale: Primary sedimentation tanks settle out heavier solids

from wastewater before biological treatment.

4. Nitrification is the biological conversion of:

• Nitrite to nitrate
• Ammonia to nitrite and nitrate
• Nitrate to ammonia
• Organic nitrogen to ammonia

Rationale: Nitrification is an aerobic process where ammonia is first

oxidized to nitrite by Nitrosomonas and then to nitrate by Nitrobacter.

5. Denitrification converts nitrate to:

• Nitrite
• Ammonia 2 / 4

• Nitrogen gas
• Organic nitrogen

Rationale: Denitrification is an anoxic process where nitrate is

converted to nitrogen gas, reducing nitrogen levels in effluent.

• What is the primary purpose of chlorination?
• Remove solids
• Disinfect wastewater
• Remove nitrogen
• Adjust pH

Rationale: Chlorination kills pathogenic microorganisms to protect

public health before discharge.

7. The standard method for measuring suspended solids is:

• pH meter
• Gravimetric filtration and drying
• Turbidity meter
• Spectrophotometer

Rationale: Suspended solids are measured by filtering a known

volume of wastewater, drying the residue, and weighing it.

8. Sludge age in an activated sludge system refers to:

• Hydraulic retention time
• Flow rate
• Mean cell residence time (MCRT)
• Sludge settling velocity 3 / 4

Rationale: Sludge age or MCRT indicates the average time

microorganisms remain in the system, influencing biological treatment efficiency.

• What is the primary cause of bulking in activated sludge?
• Low DO
• Filamentous bacteria overgrowth
• High alkalinity
• Excess nutrients

Rationale: Filamentous bacteria can dominate and prevent proper

settling, leading to bulking sludge.

• What is the primary role of a trickling filter?
• Settle solids
• Remove nitrogen
• Provide a medium for microbial growth to degrade organic matter
• Disinfect wastewater

Rationale: Trickling filters allow wastewater to flow over a microbial

biofilm that consumes organic matter.

11. The term “MLSS” refers to:

• Mixed liquid soluble solids
• Mixed liquor suspended solids
• Maximum load suspended solids
• Minimal level soluble solids
• / 4