Practice Exam Questions And Correct

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

• What is the primary purpose of a wastewater treatment plant?
• To increase water temperature
• To remove solids, organics, and pathogens from wastewater
• To add minerals to water
• To increase water color
• To remove solids, organics, and pathogens from wastewater

Rationale: The main goal of a wastewater treatment plant is to reduce

pollutants to levels that meet regulatory standards before discharge.

• Which of the following is a common method for primary treatment?
• Filtration 1 / 4

• Sedimentation
• Chlorination
• Activated sludge
• Sedimentation

Rationale: Sedimentation allows solids to settle out of wastewater, which

is the principal mechanism in primary treatment.

• What is the typical range of BOD5 in domestic wastewater?
• 10–50 mg/L
• 100–300 mg/L
• 400–600 mg/L
• 800–1000 mg/L
• 100–300 mg/L

Rationale: Domestic wastewater usually has a BOD5 concentration within

this range, reflecting the biodegradable organic load.

4. In wastewater, TSS stands for:

• Total Suspended Solids
• Total Soluble Substances
• Total Sedimentation Solids
• Total Sulfate Solids
• Total Suspended Solids

Rationale: TSS measures the solids suspended in water that can be trapped

by a filter, indicating water clarity and treatment efficiency. 2 / 4

• Which microorganism is primarily responsible for nitrification in

wastewater?

• Escherichia coli
• Nitrosomonas and Nitrobacter
• Clostridium
• Staphylococcus
• Nitrosomonas and Nitrobacter

Rationale: Nitrosomonas converts ammonia to nitrite, and Nitrobacter

converts nitrite to nitrate in the nitrification process.

• What is the main function of an aeration tank?
• To settle solids
• To add chlorine
• To provide oxygen for microbial decomposition
• To remove fats and oils
• To provide oxygen for microbial decomposition

Rationale: Aeration tanks supply oxygen to microorganisms that degrade

organic matter in activated sludge systems.

• Which of the following is a potential problem if sludge is not properly

handled?

• Reduced BOD removal
• Foul odors
• Increased pathogens
• All of the above 3 / 4

• All of the above

Rationale: Improper sludge handling can decrease treatment efficiency,

create odors, and pose health risks.

• What is the main chemical used in chlorination?
• Calcium hydroxide
• Sodium hypochlorite
• Ferric chloride
• Sodium bisulfate
• Sodium hypochlorite

Rationale: Sodium hypochlorite is commonly used for disinfecting

wastewater before discharge.

• Which of the following is a secondary treatment process?
• Screening
• Grit removal
• Trickling filter
• Primary sedimentation
• Trickling filter

Rationale: Trickling filters are a biological process where microorganisms

break down organic matter, characteristic of secondary treatment.

• What is the primary purpose of grit removal?
• Remove dissolved organics
• Remove heavy inorganic solids like sand and gravel
• / 4