Grade 1 Exam Practice Questions And

Massachusetts Wastewater Operator Grade 1 Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of wastewater treatment?
• Increase water turbidity
• Produce sludge
• Protect public health and the environment
• Reduce operating costs

Rationale: Wastewater treatment removes harmful contaminants to

protect the environment and human health.

• Which treatment process is typically the first step in a wastewater

plant? 1 / 4

• Secondary clarification
• Disinfection
• Preliminary treatment
• Activated sludge

Rationale: Preliminary treatment removes large debris before other

processes.

3. Bar screens are used to remove:

• Dissolved solids
• Large rags and debris
• Pathogens
• Nutrients

Rationale: Bar screens capture large materials to protect downstream

equipment.

4. Grit chambers remove:

• Fats, oils, and grease
• Pathogens
• Heavy inorganic particles like sand
• Organic solids

Rationale: Grit removal prevents abrasion and wear on equipment.

5. Primary clarifiers mainly remove:

• Dissolved oxygen
• Nitrogen 2 / 4

• Settleable solids
• Chlorine

Rationale: Primary clarification settles heavier solids by gravity.

6. The activated sludge process relies on:

• Chemical oxidation
• Microorganisms consuming organic matter
• UV radiation
• Filtration

Rationale: Biological treatment depends on microorganisms degrading

waste.

7. Dissolved oxygen (DO) in aeration tanks is typically maintained around:

• 0 mg/L
• 0.5 mg/L
• 10 mg/L
• 2 mg/L

Rationale: Most activated sludge systems operate efficiently at ~2 mg/L

DO.

8. Sludge age refers to:

• Age of equipment
• Average time microorganisms stay in the system
• Dewatered sludge storage time 3 / 4

• Time wastewater stays in the plant

Rationale: Sludge age reflects microbial population stability.

9. High sludge age usually results in:

• Young, fast-growing organisms
• More bulking
• Older, slower-growing microorganisms
• Less nitrification

Rationale: A high sludge age promotes slow-growing nitrifiers and stable

biomass.

10. A common sign of filamentous bulking is:

• Clear sludge blanket
• Rapid settling
• Poor settling and fluffy biomass
• High DO

Rationale: Filamentous organisms interfere with settling, causing bulking.

11–20

11. Disinfection in wastewater treatment is used to:

• Remove BOD
• Remove nutrients
• Destroy pathogens
• Remove solids
• / 4