Texas Wastewater Class C | Questions with
100% Correct Answers | Verified | Latest
Update 2025
1. What is the main purpose of a bar screen in a wastewater treatment plant?
A. Remove large debris such as rags and sticks
B. Aerate the wastewater
C. Remove nitrogen
D. Disinfect the effluent
Bar screens are used in preliminary treatment to remove large solids that
could damage equipment.
2. What is the typical detention time in a primary clarifier?
A. 15 minutes
B. 2 hours
C. 6 hours
D. 1 day
Primary clarifiers generally have a detention time of around 2 hours to
allow solids to settle.
3. What gas is commonly produced in anaerobic digesters?
A. Oxygen
, B. Methane
C. Carbon monoxide
D. Ammonia
Methane is produced during the anaerobic digestion of organic matter.
4. What laboratory test is commonly used to measure the strength of organic
pollutants in wastewater?
A. BOD (Biochemical Oxygen Demand)
B. DO (Dissolved Oxygen)
C. pH
D. TSS
BOD measures how much oxygen is needed by bacteria to break down
organic material.
5. What is the ideal pH range for biological activity in activated sludge?
A. 4.5–5.5
B. 5.0–6.0
C. 6.5–8.5
D. 8.5–10.5
Bacteria in the activated sludge process perform best in a neutral to
slightly basic pH range.
6. The term “MLSS” stands for:
A. Mixed Liquor Sludge Solids
, B. Main Line Suspended Solids
C. Mixed Liquor Suspended Solids
D. Minimum Level Sludge Settling
MLSS is the concentration of suspended solids in the mixed liquor of the
aeration tank.
7. What is the function of a trickling filter in a treatment process?
A. Biological treatment using attached growth media
B. Chemical disinfection
C. Solids settling
D. Odor control
Trickling filters provide a surface for microorganisms to attach and treat
wastewater biologically.
8. What is the best method for calibrating a flow meter?
A. Using a stopwatch
B. Guessing based on pump capacity
C. Using a known volume and time method
D. Comparing to a pressure gauge
Flow meters should be calibrated against a known volume over a known
time period for accuracy.
9. What is the purpose of chlorination in wastewater treatment?
A. Increase BOD
, B. Kill pathogenic organisms
C. Add nutrients
D. Remove solids
Chlorine is used to disinfect treated wastewater before discharge.
10.What is the function of a digester in sludge treatment?
A. Aerate the sludge
B. Stabilize organic material through microbial activity
C. Increase water content
D. Chemically treat sludge
Digesters reduce pathogens and odors while stabilizing sludge.
11. What is the purpose of a grit chamber in preliminary treatment?
A. To remove grease and oil
B. To remove sand and heavy inorganic solids
C. To neutralize pH
D. To settle organic matter
Grit chambers remove heavy, inorganic particles like sand and gravel to protect
downstream equipment.
12. What is the typical DO (Dissolved Oxygen) level maintained in the aeration
tank?
A. 0.5 mg/L
B. 2.0 mg/L
100% Correct Answers | Verified | Latest
Update 2025
1. What is the main purpose of a bar screen in a wastewater treatment plant?
A. Remove large debris such as rags and sticks
B. Aerate the wastewater
C. Remove nitrogen
D. Disinfect the effluent
Bar screens are used in preliminary treatment to remove large solids that
could damage equipment.
2. What is the typical detention time in a primary clarifier?
A. 15 minutes
B. 2 hours
C. 6 hours
D. 1 day
Primary clarifiers generally have a detention time of around 2 hours to
allow solids to settle.
3. What gas is commonly produced in anaerobic digesters?
A. Oxygen
, B. Methane
C. Carbon monoxide
D. Ammonia
Methane is produced during the anaerobic digestion of organic matter.
4. What laboratory test is commonly used to measure the strength of organic
pollutants in wastewater?
A. BOD (Biochemical Oxygen Demand)
B. DO (Dissolved Oxygen)
C. pH
D. TSS
BOD measures how much oxygen is needed by bacteria to break down
organic material.
5. What is the ideal pH range for biological activity in activated sludge?
A. 4.5–5.5
B. 5.0–6.0
C. 6.5–8.5
D. 8.5–10.5
Bacteria in the activated sludge process perform best in a neutral to
slightly basic pH range.
6. The term “MLSS” stands for:
A. Mixed Liquor Sludge Solids
, B. Main Line Suspended Solids
C. Mixed Liquor Suspended Solids
D. Minimum Level Sludge Settling
MLSS is the concentration of suspended solids in the mixed liquor of the
aeration tank.
7. What is the function of a trickling filter in a treatment process?
A. Biological treatment using attached growth media
B. Chemical disinfection
C. Solids settling
D. Odor control
Trickling filters provide a surface for microorganisms to attach and treat
wastewater biologically.
8. What is the best method for calibrating a flow meter?
A. Using a stopwatch
B. Guessing based on pump capacity
C. Using a known volume and time method
D. Comparing to a pressure gauge
Flow meters should be calibrated against a known volume over a known
time period for accuracy.
9. What is the purpose of chlorination in wastewater treatment?
A. Increase BOD
, B. Kill pathogenic organisms
C. Add nutrients
D. Remove solids
Chlorine is used to disinfect treated wastewater before discharge.
10.What is the function of a digester in sludge treatment?
A. Aerate the sludge
B. Stabilize organic material through microbial activity
C. Increase water content
D. Chemically treat sludge
Digesters reduce pathogens and odors while stabilizing sludge.
11. What is the purpose of a grit chamber in preliminary treatment?
A. To remove grease and oil
B. To remove sand and heavy inorganic solids
C. To neutralize pH
D. To settle organic matter
Grit chambers remove heavy, inorganic particles like sand and gravel to protect
downstream equipment.
12. What is the typical DO (Dissolved Oxygen) level maintained in the aeration
tank?
A. 0.5 mg/L
B. 2.0 mg/L
