Wastewater Treatment Certification
Practice Questions Set 1 QUESTIONS
AND CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2025
1. What is the main purpose of primary treatment in a wastewater
treatment plant?
A. Remove pathogens
B. Remove settleable solids
C. Remove dissolved oxygen
D. Remove nutrients
Primary treatment is designed to remove large particles and settleable
solids before secondary treatment begins.
2. Which of the following best describes a trickling filter?
A. A device that filters sand from water
B. A pressurized membrane system
C. A bed of media over which wastewater is distributed
,D. A rapid sand filter
Trickling filters use a bed of media (like rocks or plastic) to promote biofilm
growth that breaks down organic matter as wastewater flows over it.
3. What is BOD a measure of?
A. Bacteria content
B. Chlorine demand
C. Organic matter in the water
D. Nitrogen content
Biochemical Oxygen Demand (BOD) measures the amount of oxygen
microorganisms need to break down organic material.
4. What is the purpose of aeration in the activated sludge process?
A. To remove nitrogen
B. To disinfect water
C. To provide oxygen for microorganisms
D. To coagulate solids
Aeration supplies oxygen, which is essential for aerobic microorganisms to
digest organic pollutants.
5. What term refers to the solid material that settles during primary
treatment?
A. Scum
B. Sludge
C. Effluent
,D. Grit
Sludge is the semi-solid material that settles during primary clarification.
6. Which gas is commonly produced in anaerobic digestion?
A. Carbon monoxide
B. Oxygen
C. Methane
D. Nitrogen
Methane is a primary byproduct of anaerobic digestion and can be used for
energy.
7. What is the typical detention time for primary clarifiers?
A. 10–15 minutes
B. 1–2 hours
C. 2–3 hours
D. 6–8 hours
A 2–3 hour detention time allows for efficient settling of solids in primary
clarification.
8. What does TSS stand for?
A. Total Sulfide Solids
B. Total Sewer Suspensions
C. Total Suspended Solids
D. Treatment System Solids
TSS measures the suspended solids in water that can be trapped by a filter.
, 9. What is the main function of a grit chamber?
A. Remove organic solids
B. Add chlorine
C. Remove heavy inorganic particles
D. Mix chemicals
Grit chambers remove sand, gravel, and other heavy inorganic matter to
protect downstream equipment.
10. Which of the following is used to measure flow in wastewater
treatment plants?
A. Hydrometer
B. Parshall flume
C. Conductivity meter
D. Turbidity sensor
Parshall flumes are commonly used to measure flow in open channels
accurately.
11. What does F/M ratio represent in activated sludge systems?
A. Flow/Mass ratio
B. Filtration/Mixing ratio
C. Food to microorganism ratio
D. Flow to mixing time
The F/M ratio is the amount of food (BOD) available to microorganisms
and is crucial in maintaining treatment efficiency.
Practice Questions Set 1 QUESTIONS
AND CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2025
1. What is the main purpose of primary treatment in a wastewater
treatment plant?
A. Remove pathogens
B. Remove settleable solids
C. Remove dissolved oxygen
D. Remove nutrients
Primary treatment is designed to remove large particles and settleable
solids before secondary treatment begins.
2. Which of the following best describes a trickling filter?
A. A device that filters sand from water
B. A pressurized membrane system
C. A bed of media over which wastewater is distributed
,D. A rapid sand filter
Trickling filters use a bed of media (like rocks or plastic) to promote biofilm
growth that breaks down organic matter as wastewater flows over it.
3. What is BOD a measure of?
A. Bacteria content
B. Chlorine demand
C. Organic matter in the water
D. Nitrogen content
Biochemical Oxygen Demand (BOD) measures the amount of oxygen
microorganisms need to break down organic material.
4. What is the purpose of aeration in the activated sludge process?
A. To remove nitrogen
B. To disinfect water
C. To provide oxygen for microorganisms
D. To coagulate solids
Aeration supplies oxygen, which is essential for aerobic microorganisms to
digest organic pollutants.
5. What term refers to the solid material that settles during primary
treatment?
A. Scum
B. Sludge
C. Effluent
,D. Grit
Sludge is the semi-solid material that settles during primary clarification.
6. Which gas is commonly produced in anaerobic digestion?
A. Carbon monoxide
B. Oxygen
C. Methane
D. Nitrogen
Methane is a primary byproduct of anaerobic digestion and can be used for
energy.
7. What is the typical detention time for primary clarifiers?
A. 10–15 minutes
B. 1–2 hours
C. 2–3 hours
D. 6–8 hours
A 2–3 hour detention time allows for efficient settling of solids in primary
clarification.
8. What does TSS stand for?
A. Total Sulfide Solids
B. Total Sewer Suspensions
C. Total Suspended Solids
D. Treatment System Solids
TSS measures the suspended solids in water that can be trapped by a filter.
, 9. What is the main function of a grit chamber?
A. Remove organic solids
B. Add chlorine
C. Remove heavy inorganic particles
D. Mix chemicals
Grit chambers remove sand, gravel, and other heavy inorganic matter to
protect downstream equipment.
10. Which of the following is used to measure flow in wastewater
treatment plants?
A. Hydrometer
B. Parshall flume
C. Conductivity meter
D. Turbidity sensor
Parshall flumes are commonly used to measure flow in open channels
accurately.
11. What does F/M ratio represent in activated sludge systems?
A. Flow/Mass ratio
B. Filtration/Mixing ratio
C. Food to microorganism ratio
D. Flow to mixing time
The F/M ratio is the amount of food (BOD) available to microorganisms
and is crucial in maintaining treatment efficiency.
