Practice Exam Questions And Correct

Louisiana Wastewater Operator Class I 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?
• Produce drinking water
• Remove pollutants from wastewater before discharge
• Generate electricity
• Supply water for irrigation

Rationale: The primary goal of a wastewater treatment plant is to

remove contaminants from sewage or industrial waste to protect public health and the environment.

• Which of the following is a common physical treatment process?
• Activated sludge 1 / 4

• Trickling filter
• Sedimentation
• Chlorination

Rationale: Sedimentation is a physical process where solids settle out

of wastewater by gravity.

3. BOD stands for:

• Biological Oxidation Demand
• Biochemical Oxygen Demand
• Biological Oxygen Deficiency
• Basic Oxygen Demand

Rationale: BOD measures the amount of oxygen microorganisms

require to decompose organic matter in water.

4. The primary clarifier in a wastewater plant is used to:

• Remove dissolved oxygen
• Add chemicals
• Settle suspended solids
• Filter pathogens

Rationale: Primary clarifiers allow heavier solids to settle out from

wastewater before secondary treatment.

• What type of organism primarily removes organic matter in secondary

treatment?

• Fish
• Bacteria 2 / 4

• Protozoa
• Algae

Rationale: Bacteria biologically degrade organic matter in processes

like activated sludge and trickling filters.

• Which of the following is considered a chemical disinfectant?
• Ultraviolet light
• Ozone
• Chlorine
• Aeration

Rationale: Chlorine is widely used to disinfect wastewater by killing

harmful microorganisms.

7. The term “sludge” refers to:

• Clear water after treatment
• Settled solids from wastewater
• Floating debris
• Chemical additives

Rationale: Sludge is the concentrated solid material that settles out

during wastewater treatment.

8. Nitrification is a process that converts:

• Ammonia to nitrogen gas
• Ammonia to nitrate
• Nitrate to ammonia
• Nitrite to organic matter 3 / 4

Rationale: Nitrification is a two-step biological process where

ammonia is converted first to nitrite and then to nitrate by bacteria.

• What is the main purpose of a grit chamber?
• Remove oils
• Reduce BOD
• Remove sand and gravel
• Clarify water

Rationale: Grit chambers prevent heavy inorganic materials from

damaging pumps and equipment.

10. The sludge age in an activated sludge process refers to:

• Age of the wastewater
• Average time solids remain in the system
• Time for water to reach the plant
• Time required for disinfection

Rationale: Sludge age, or solids retention time, helps control

bacterial populations in biological treatment.

11. TSS in wastewater stands for:

• Total Sanitation Score
• Total Sediment Strength
• Total Suspended Solids
• Total Sludge Solids

Rationale: TSS measures the concentration of suspended solids in

• / 4