Texas Wastewater Class A | Questions with
100% Correct Answers | Verified | Latest
Update 2025
1. What is the purpose of primary treatment in a wastewater treatment plant?
A. Remove dissolved organics
B. Remove settleable solids
C. Disinfect pathogens
D. Aerate the influent
Primary treatment focuses on removing large and settleable solids
through sedimentation.
2. What is the typical range for biochemical oxygen demand (BOD) removal in a
primary clarifier?
A. 10–20%
B. 20–30%
C. 25–40%
D. 50–70%
Primary clarifiers typically remove 25–40% of BOD by settling heavier
organic material.
,3. What is the main function of an activated sludge process?
A. Remove biodegradable organic matter
B. Remove grit and large debris
C. Kill bacteria
D. Reduce nitrates
The activated sludge process uses microorganisms to degrade and
remove organic material.
4. What is the F/M ratio used to monitor in wastewater treatment?
A. Filter media usage
B. Food to microorganism ratio
C. Flow to membrane ratio
D. Fermentation measurement
The F/M ratio determines the balance between organic load and
microbial population in aeration.
5. Which gas is primarily produced in anaerobic digesters?
A. Oxygen
B. Carbon dioxide
C. Methane
D. Nitrogen
Methane is produced during the anaerobic digestion of organic
materials.
6. A high sludge volume index (SVI) indicates what condition in the aeration
tank?
A. Good settling
,B. Bulking sludge
C. High chlorine residual
D. Septic sludge
A high SVI suggests poor settling characteristics, often due to
filamentous bacteria growth.
7. Which of the following is a common method for dewatering sludge?
A. Sand filtration
B. Belt filter press
C. Trickling filter
D. Flotation
Belt filter presses are widely used for sludge dewatering by mechanical
compression.
8. What is the primary concern with excessive filamentous bacteria?
A. Sludge bulking
B. Odor generation
C. pH fluctuations
D. Ammonia toxicity
Filamentous bacteria cause bulking, preventing proper settling in
clarifiers.
9. What is the ideal range for dissolved oxygen (DO) in activated sludge
systems?
A. 0.5–1.0 mg/L
B. 1.5–2.5 mg/L
C. 3.5–5.5 mg/L
, D. 6.0–8.0 mg/L
Maintaining DO between 1.5–2.5 mg/L supports microbial activity while
conserving energy.
10. What laboratory test determines the amount of organic matter in a sample?
A. TSS
B. VSS
C. BOD
D. pH
BOD measures the oxygen required to biologically decompose organic
matter in water.
11. What is the purpose of secondary clarification?
A. Disinfect effluent
B. Settle out biological solids
C. Remove heavy metals
D. Adjust pH
Secondary clarifiers allow biological floc from the activated sludge
process to settle.
12. Which nutrient must be controlled to prevent eutrophication in receiving
waters?
A. Phosphorus
B. Sodium
C. Chloride
100% Correct Answers | Verified | Latest
Update 2025
1. What is the purpose of primary treatment in a wastewater treatment plant?
A. Remove dissolved organics
B. Remove settleable solids
C. Disinfect pathogens
D. Aerate the influent
Primary treatment focuses on removing large and settleable solids
through sedimentation.
2. What is the typical range for biochemical oxygen demand (BOD) removal in a
primary clarifier?
A. 10–20%
B. 20–30%
C. 25–40%
D. 50–70%
Primary clarifiers typically remove 25–40% of BOD by settling heavier
organic material.
,3. What is the main function of an activated sludge process?
A. Remove biodegradable organic matter
B. Remove grit and large debris
C. Kill bacteria
D. Reduce nitrates
The activated sludge process uses microorganisms to degrade and
remove organic material.
4. What is the F/M ratio used to monitor in wastewater treatment?
A. Filter media usage
B. Food to microorganism ratio
C. Flow to membrane ratio
D. Fermentation measurement
The F/M ratio determines the balance between organic load and
microbial population in aeration.
5. Which gas is primarily produced in anaerobic digesters?
A. Oxygen
B. Carbon dioxide
C. Methane
D. Nitrogen
Methane is produced during the anaerobic digestion of organic
materials.
6. A high sludge volume index (SVI) indicates what condition in the aeration
tank?
A. Good settling
,B. Bulking sludge
C. High chlorine residual
D. Septic sludge
A high SVI suggests poor settling characteristics, often due to
filamentous bacteria growth.
7. Which of the following is a common method for dewatering sludge?
A. Sand filtration
B. Belt filter press
C. Trickling filter
D. Flotation
Belt filter presses are widely used for sludge dewatering by mechanical
compression.
8. What is the primary concern with excessive filamentous bacteria?
A. Sludge bulking
B. Odor generation
C. pH fluctuations
D. Ammonia toxicity
Filamentous bacteria cause bulking, preventing proper settling in
clarifiers.
9. What is the ideal range for dissolved oxygen (DO) in activated sludge
systems?
A. 0.5–1.0 mg/L
B. 1.5–2.5 mg/L
C. 3.5–5.5 mg/L
, D. 6.0–8.0 mg/L
Maintaining DO between 1.5–2.5 mg/L supports microbial activity while
conserving energy.
10. What laboratory test determines the amount of organic matter in a sample?
A. TSS
B. VSS
C. BOD
D. pH
BOD measures the oxygen required to biologically decompose organic
matter in water.
11. What is the purpose of secondary clarification?
A. Disinfect effluent
B. Settle out biological solids
C. Remove heavy metals
D. Adjust pH
Secondary clarifiers allow biological floc from the activated sludge
process to settle.
12. Which nutrient must be controlled to prevent eutrophication in receiving
waters?
A. Phosphorus
B. Sodium
C. Chloride
