Class B Practice Exam Questions And

Pennsylvania Wastewater Operator Class B Practice Exam Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of screening in a wastewater treatment

plant?

• Reduce dissolved oxygen
• Remove large solids
• Neutralize pH
• Kill pathogens

Rationale: Screens are used to remove large debris such as sticks,

rags, and plastics to prevent damage to downstream equipment.

• The process of removing suspended solids by allowing them to settle

naturally is called: 1 / 4

• Filtration
• Aeration
• Sedimentation
• Coagulation

Rationale: Sedimentation allows suspended particles to settle by

gravity, forming sludge at the bottom of the basin.

• Which of the following is a common method for sludge stabilization?
• Filtration
• Anaerobic digestion
• Chlorination
• Coagulation

Rationale: Anaerobic digestion stabilizes sludge by breaking down

organic material in the absence of oxygen, reducing odor and volume.

4. The term BOD stands for:

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

Rationale: BOD measures the amount of oxygen microorganisms

require to decompose organic matter in water.

• What is the typical detention time in a primary clarifier?
• 1–2 minutes 2 / 4

• 1–2 hours
• 6–12 hours
• 24 hours

Rationale: Primary clarifiers are designed to allow sufficient time (1–

• hours) for heavier solids to settle.
• Which chemical is commonly used for phosphorus removal in

wastewater?

• Chlorine
• Sodium hypochlorite
• Alum (Aluminum sulfate)
• Sodium hydroxide

Rationale: Alum binds with phosphate ions to form insoluble

aluminum phosphate, which can then be removed by sedimentation.

• In an activated sludge system, what is the purpose of the aeration

tank?

• Settle solids
• Disinfect effluent
• Promote microbial decomposition of organic matter
• Remove grit

Rationale: Aeration tanks provide oxygen to support microorganisms

that break down organic pollutants in wastewater.

• Which microorganism type is most active in the aerobic digestion

process? 3 / 4

• Anaerobic bacteria
• Fungi
• Aerobic bacteria
• Protozoa

Rationale: Aerobic bacteria require oxygen to metabolize organic

matter and are the main agents in aerobic digestion.

9. The main purpose of chlorination in wastewater treatment is:

• Remove nutrients
• Remove solids
• Disinfect the effluent
• Enhance sedimentation

Rationale: Chlorine kills or inactivates pathogenic microorganisms to

prevent disease transmission.

• What is the main function of a grit chamber?
• Reduce BOD
• Remove fine suspended solids
• Remove sand, gravel, and other heavy inorganic solids
• Promote sludge digestion

Rationale: Grit chambers settle out heavy inorganic particles that

could cause wear and tear on equipment.

• Which of the following parameters is commonly used to control

aeration in an activated sludge system?

• pH
• / 4