Exam Practice Questions And Correct

Maine Wastewater Operator Grade I Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of a wastewater treatment plant?
• Generate electricity
• Remove pollutants from wastewater
• Supply drinking water
• Irrigate crops

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

remove pollutants to protect public health and the environment.

• Which of the following is a typical characteristic of domestic

wastewater?

• High industrial metals 1 / 4

• High organic content
• High pH (>10)
• Oil and grease from manufacturing

Rationale: Domestic wastewater typically contains high levels of organic

matter such as food waste, human waste, and detergents.

• What is BOD (Biochemical Oxygen Demand) a measure of?
• pH of water
• Total solids
• Amount of oxygen required by microorganisms to decompose organic

matter

• Chlorine concentration

Rationale: BOD measures the oxygen needed by bacteria to biologically

degrade organic material in wastewater.

• Which stage of wastewater treatment is designed to remove settleable

solids?

• Primary treatment
• Secondary treatment
• Tertiary treatment
• Disinfection

Rationale: Primary treatment involves physical processes like

sedimentation to remove settleable solids.

• What is the primary method for disinfection of treated wastewater?
• Filtration 2 / 4

• Chlorination
• Coagulation
• Sedimentation

Rationale: Chlorination is the most common method for disinfecting

wastewater to kill pathogenic organisms.

• What is the main purpose of aeration in secondary treatment?
• Remove oil and grease
• Supply oxygen to microorganisms for decomposition of organic matter
• Reduce solids
• Increase pH

Rationale: Aeration provides oxygen for aerobic microorganisms to digest

organic matter.

• Activated sludge is a process used in which treatment stage?
• Preliminary
• Primary
• Secondary
• Tertiary

Rationale: Activated sludge is a biological treatment method used in

secondary treatment.

• What is the ideal pH range for biological wastewater treatment?

A. 3.0–5.0

B. 6.5–8.5

C. 9.0–11.0 3 / 4

D. 11.5–13.0

Rationale: Most microorganisms function optimally at near-neutral pH,

typically 6.5–8.5.

• What type of solids are removed during primary sedimentation?
• Dissolved solids
• Suspended solids
• Volatile solids
• Heavy metals

Rationale: Primary sedimentation targets suspended solids, allowing them

to settle out.

10. Sludge thickening reduces:

• Pathogens
• Water content of sludge
• Organic matter
• pH

Rationale: Thickening reduces water content, making sludge easier to

handle and treat.

• Which test is used to measure the concentration of suspended solids in

wastewater?

• BOD test
• Total Suspended Solids (TSS) test
• COD test
• pH test
• / 4