Practice Exam Questions And Correct

Maine Wastewater Operator Grade III 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?

• To produce drinking water
• To reduce environmental pollution
• To generate electricity
• To desalinate water
• To reduce environmental pollution

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

remove pollutants from wastewater before it is discharged into the environment, protecting public health and ecosystems. 1 / 4

• What is the most common method of primary treatment in a

wastewater plant?

• Filtration
• Sedimentation
• Chlorination
• Aeration
• Sedimentation

Rationale: Sedimentation allows solids to settle out of wastewater

by gravity, which is the primary method used in primary treatment.

• Which microorganism is primarily responsible for the biological

treatment of wastewater?

• Algae
• Protozoa
• Bacteria
• Fungi
• Bacteria

Rationale: Bacteria are responsible for breaking down organic

matter in activated sludge and other biological treatment processes.

• What is the function of a clarifier in wastewater treatment?
• To add chemicals to remove nutrients
• To separate solids from liquids
• To disinfect wastewater
• To aerate water 2 / 4

• To separate solids from liquids

Rationale: Clarifiers are used to settle solids out of the wastewater

after primary or secondary treatment.

• Which parameter is used to measure the organic strength of

wastewater?

• pH
• Total Suspended Solids (TSS)
• Biochemical Oxygen Demand (BOD)
• Chlorine residual
• Biochemical Oxygen Demand (BOD)

Rationale: BOD measures the amount of oxygen required by

microorganisms to decompose organic matter in wastewater, indicating its organic load.

• Which process is used to remove nitrogen from wastewater?
• Coagulation
• Nitrification and Denitrification
• Sedimentation
• Chlorination
• Nitrification and Denitrification

Rationale: Nitrogen removal is accomplished biologically through

nitrification (ammonia to nitrate) and denitrification (nitrate to nitrogen gas). 3 / 4

• What is the purpose of an aeration tank?
• To settle solids
• To disinfect wastewater
• To supply oxygen for microbial activity
• To remove grit
• To supply oxygen for microbial activity

Rationale: Aeration tanks provide oxygen to bacteria, which helps in

breaking down organic pollutants in the wastewater.

• Which of the following is a typical method for sludge thickening?
• Chlorination
• Gravity thickening
• Reverse osmosis
• Filtration
• Gravity thickening

Rationale: Gravity thickening allows sludge to consolidate by

settling, reducing water content before further processing.

• What is the purpose of chlorination in wastewater treatment?
• To settle solids
• To remove nutrients
• To disinfect wastewater
• To reduce BOD
• To disinfect wastewater
• / 4