II Practice Exam Questions And Correct

Mississippi 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 grit chamber in wastewater

treatment?

• Remove dissolved organics
• Remove pathogens
• Remove sand, gravel, and heavy solids
• Reduce biochemical oxygen demand (BOD)

Rationale:

Grit chambers are designed to remove heavy inorganic particles like sand and gravel, which can damage downstream equipment. 1 / 4

• What is the typical detention time for primary sedimentation in a

municipal wastewater plant?

• 10-20 minutes
• 30-60 minutes
• 1.5-3 hours
• 5-6 hours

Rationale:

Primary sedimentation typically requires 1.5–3 hours to allow solids to settle adequately.

• Which type of bacteria is primarily responsible for nitrification in

wastewater treatment?

• Denitrifying bacteria
• Nitrifying bacteria (Nitrosomonas & Nitrobacter)
• Sulfate-reducing bacteria
• Coliform bacteria

Rationale:

Nitrifying bacteria convert ammonia to nitrite and nitrate during biological treatment.

4. The main function of a clarifier in wastewater treatment is to:

• Aerate the water
• Settle suspended solids
• Remove dissolved nutrients
• Reduce odors 2 / 4

Rationale:

Clarifiers allow solids to settle from wastewater, separating sludge from the clarified effluent.

5. In wastewater terminology, BOD stands for:

• Biological Oxidation Demand
• Biochemical Oxygen Demand
• Bacterial Oxidation Demand
• Biological Oxygen Deficiency

Rationale:

BOD measures the amount of oxygen required by microorganisms to break down organic matter.

• Which chemical is commonly used for disinfection in wastewater

treatment?

• Sodium hydroxide
• Chlorine
• Ammonia
• Calcium carbonate

Rationale:

Chlorine is widely used for disinfecting wastewater to kill pathogens.

• What is the primary purpose of an aeration tank in activated sludge

treatment?

• Remove grit 3 / 4

• Sediment solids
• Provide oxygen for microbial decomposition
• Filter wastewater

Rationale:

Aeration tanks supply oxygen, promoting microbial growth to degrade organic matter.

• What is the main concern with hydrogen sulfide in sewer systems?
• Causes foaming
• Corrodes pipes and poses a health hazard
• Increases BOD
• Reduces chlorine efficiency

Rationale:

Hydrogen sulfide is toxic, foul-smelling, and can corrode concrete and metal pipes.

• Which of the following is a common method for sludge thickening?
• Aeration
• Gravity thickening
• Disinfection
• Filtration

Rationale:

Gravity thickening allows sludge solids to settle, reducing water content before further treatment.

• / 4