Exam 100 Practice Questions And

Maine Wastewater Operator Grade I Exam 100 Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of wastewater treatment?
• To increase wastewater temperature
• To remove pollutants before discharge
• To add nutrients to water
• To increase water hardness

Answer: B

Rationale: Wastewater treatment focuses on removing contaminants to

protect public health and the environment.

• What is the main function of a bar screen? 1 / 4

• Remove dissolved solids
• Remove large debris
• Aerate wastewater
• Adjust pH

Answer: B

Rationale: Bar screens trap rags, sticks, and large objects to prevent

damage to downstream equipment.

3. Grit chambers are designed to remove:

• Organic solids
• Heavy inorganic materials
• Dissolved gases
• Nutrients

Answer: B

Rationale: Grit chambers remove sand, gravel, and silt that are heavier

than organic solids.

4. Primary clarifiers mainly remove:

• Pathogens
• Dissolved chemicals
• Settable organic and inorganic solids
• Oils only

Answer: C

Rationale: Primary clarification allows heavy solids to settle and floatables

to rise. 2 / 4

5. The activated sludge process uses microorganisms to:

• Add chlorine
• Digest organic matter
• Increase sludge moisture
• Remove grit

Answer: B

Rationale: Microbes consume organic pollutants for biological treatment.

• What is DO in wastewater treatment?
• Dissolved oxygen
• Dry organic matter
• Discharge output
• Direct oxidation

Answer: A

Rationale: DO measures oxygen available for microbial respiration.

7. Low DO in aeration basins typically leads to:

• Increased nitrification
• Improved settling
• Poor microbial activity
• Reduced sludge volume

Answer: C

Rationale: Microbes require oxygen for efficient biological treatment.

• The purpose of secondary clarification is to: 3 / 4

• Remove grit
• Separate activated sludge from treated water
• Add chlorine
• Increase pH

Answer: B

Rationale: Secondary clarifiers settle out biological solids.

9. Sludge age refers to:

• Time sludge travels through pipes
• Number of days microorganisms remain in the system
• Age of grit removed
• Duration of disinfection

Answer: B

Rationale: Sludge age measures biological solids retention time.

10. Chlorination is mainly used for:

• Nutrient removal
• Disinfection
• pH control
• Odor reduction

Answer: B

Rationale: Chlorine is applied to kill or inactivate pathogens.

• What does BOD measure?
• / 4