Wastewater Treatment Practice Exam
Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A
Instant Download Pdf
1. What is the primary purpose of preliminary treatment in wastewater
systems?
A. Remove dissolved nutrients
B. Remove large debris and grit
C. Disinfect pathogens
D. Remove organic matter
Correct Answer: Remove large debris and grit
Rationale: Preliminary treatment removes large solids, grit, and debris to
protect downstream equipment from damage.
2. Which process is used for biological treatment of wastewater?
A. Filtration
B. Activated sludge
C. Sedimentation
D. Screening
Correct Answer: Activated sludge
Rationale: Activated sludge uses microorganisms to break down organic
matter in wastewater.
,3. What does BOD measure?
A. Oxygen in water
B. Organic pollution strength
C. Chlorine demand
D. Nitrogen levels
Correct Answer: Organic pollution strength
Rationale: Biochemical Oxygen Demand (BOD) indicates the amount of
oxygen required to decompose organic matter.
4. Which unit removes fine particles from wastewater?
A. Grit chamber
B. Clarifier
C. Bar screen
D. Aeration tank
Correct Answer: Clarifier
Rationale: Clarifiers allow suspended solids to settle out of wastewater by
gravity.
5. What is the main function of aeration in wastewater treatment?
A. Add chlorine
B. Increase oxygen levels
C. Remove solids
D. Reduce flow rate
Correct Answer: Increase oxygen levels
Rationale: Aeration supplies oxygen to microorganisms to break down
organic matter.
6. Which microorganism is most responsible for breaking down organic waste?
A. Algae
B. Protozoa
, C. Bacteria
D. Fungi
Correct Answer: Bacteria
Rationale: Bacteria are the primary decomposers in wastewater
treatment systems.
7. What is the purpose of a primary clarifier?
A. Disinfect water
B. Remove sludge
C. Settle suspended solids
D. Add oxygen
Correct Answer: Settle suspended solids
Rationale: Primary clarifiers remove settleable solids from influent
wastewater.
8. Which process follows primary treatment?
A. Disinfection
B. Preliminary treatment
C. Secondary treatment
D. Sludge disposal
Correct Answer: Secondary treatment
Rationale: Secondary treatment biologically removes dissolved and
suspended organic matter.
9. What is the typical disinfectant used in wastewater treatment?
A. Oxygen
B. Chlorine
C. Nitrogen
D. Carbon dioxide
Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A
Instant Download Pdf
1. What is the primary purpose of preliminary treatment in wastewater
systems?
A. Remove dissolved nutrients
B. Remove large debris and grit
C. Disinfect pathogens
D. Remove organic matter
Correct Answer: Remove large debris and grit
Rationale: Preliminary treatment removes large solids, grit, and debris to
protect downstream equipment from damage.
2. Which process is used for biological treatment of wastewater?
A. Filtration
B. Activated sludge
C. Sedimentation
D. Screening
Correct Answer: Activated sludge
Rationale: Activated sludge uses microorganisms to break down organic
matter in wastewater.
,3. What does BOD measure?
A. Oxygen in water
B. Organic pollution strength
C. Chlorine demand
D. Nitrogen levels
Correct Answer: Organic pollution strength
Rationale: Biochemical Oxygen Demand (BOD) indicates the amount of
oxygen required to decompose organic matter.
4. Which unit removes fine particles from wastewater?
A. Grit chamber
B. Clarifier
C. Bar screen
D. Aeration tank
Correct Answer: Clarifier
Rationale: Clarifiers allow suspended solids to settle out of wastewater by
gravity.
5. What is the main function of aeration in wastewater treatment?
A. Add chlorine
B. Increase oxygen levels
C. Remove solids
D. Reduce flow rate
Correct Answer: Increase oxygen levels
Rationale: Aeration supplies oxygen to microorganisms to break down
organic matter.
6. Which microorganism is most responsible for breaking down organic waste?
A. Algae
B. Protozoa
, C. Bacteria
D. Fungi
Correct Answer: Bacteria
Rationale: Bacteria are the primary decomposers in wastewater
treatment systems.
7. What is the purpose of a primary clarifier?
A. Disinfect water
B. Remove sludge
C. Settle suspended solids
D. Add oxygen
Correct Answer: Settle suspended solids
Rationale: Primary clarifiers remove settleable solids from influent
wastewater.
8. Which process follows primary treatment?
A. Disinfection
B. Preliminary treatment
C. Secondary treatment
D. Sludge disposal
Correct Answer: Secondary treatment
Rationale: Secondary treatment biologically removes dissolved and
suspended organic matter.
9. What is the typical disinfectant used in wastewater treatment?
A. Oxygen
B. Chlorine
C. Nitrogen
D. Carbon dioxide
