CA Grade 2 Wastewater Treatment Operator Practice Exam 1 –
Comprehensive Questions and Answers 2026 for Exam Preparation
Wastewater Treatment Technology Exam – Questions & Answers 2026
1. What is the methane content in a properly operating anaerobic digester?
Answer: 65 to 70% by volume ✅
Rationale: Methane is the main product of anaerobic digestion and typically
comprises 65–70% of digester gas.
2. What will the addition of chlorine gas do to the pH of wastewater?
Answer: Decrease the pH ✅
Rationale: Chlorine is acidic when dissolved, lowering wastewater pH.
3. What is the purpose of a Parshall Flume?
Answer: Measure the flow rate ✅
Rationale: Parshall flumes are used to accurately measure flow in open channels.
4. What is the typical removal efficiency of settleable solids in a primary
clarifier?
Answer: 95 to 99% ✅
Rationale: Primary clarifiers remove most settleable solids before secondary
treatment.
,5. Which of the following is true about pumping scum from a primary
clarifier?
Answer: Scum causes more piping problems than other substances pumped at a
wastewater treatment plant ✅
Rationale: Scum is sticky and buoyant, leading to frequent clogs and pump
issues.
6. What might cause thick billows of white sudsy foam in the aeration tank?
Answer: MLSS is too low ✅
Rationale: Low mixed liquor suspended solids can reduce biological activity,
leading to foaming.
7. What does the M in F/M ratio represent?
Answer: The mixed liquor volatile suspended solids in the aeration tank ✅
Rationale: F/M ratio compares the food (BOD) to the biomass (MLVSS) in the
aeration tank.
8. In general, how will warmer temperature affect the settling rate of solids
in a clarifier?
Answer: Increase the settling rate ✅
Rationale: Warmer water reduces viscosity, allowing solids to settle faster.
9. What could happen if the digester gas is mixed with air (85–95% by
volume)?
, Answer: Cause an explosion ✅
Rationale: Methane is highly flammable and explosive within these
concentrations.
10. How will algae impact the chlorine demand in the pond effluent?
Answer: Increase the chlorine demand ✅
Rationale: Algae react with chlorine, consuming more disinfectant.
11. Which of the following is true about a positive displacement pump?
Answer: It must never be started with the discharge valve closed ✅
Rationale: Starting a closed discharge can damage the pump due to overpressure.
12. What is true about the F/M ratio?
Answer: The volume of the secondary clarifier is not needed to determine the
F/M ratio ✅
Rationale: F/M ratio depends on influent BOD and biomass in the aeration tank,
not clarifier volume.
13. Which of the following is one of the basic rules of lab work?
Answer: Never pipet hazardous material with your mouth, even if the pipet has
been sterilized ✅
Rationale: Ensures lab safety and prevents accidental ingestion.
14. What is the recirculation ratio for a trickling filter?
Comprehensive Questions and Answers 2026 for Exam Preparation
Wastewater Treatment Technology Exam – Questions & Answers 2026
1. What is the methane content in a properly operating anaerobic digester?
Answer: 65 to 70% by volume ✅
Rationale: Methane is the main product of anaerobic digestion and typically
comprises 65–70% of digester gas.
2. What will the addition of chlorine gas do to the pH of wastewater?
Answer: Decrease the pH ✅
Rationale: Chlorine is acidic when dissolved, lowering wastewater pH.
3. What is the purpose of a Parshall Flume?
Answer: Measure the flow rate ✅
Rationale: Parshall flumes are used to accurately measure flow in open channels.
4. What is the typical removal efficiency of settleable solids in a primary
clarifier?
Answer: 95 to 99% ✅
Rationale: Primary clarifiers remove most settleable solids before secondary
treatment.
,5. Which of the following is true about pumping scum from a primary
clarifier?
Answer: Scum causes more piping problems than other substances pumped at a
wastewater treatment plant ✅
Rationale: Scum is sticky and buoyant, leading to frequent clogs and pump
issues.
6. What might cause thick billows of white sudsy foam in the aeration tank?
Answer: MLSS is too low ✅
Rationale: Low mixed liquor suspended solids can reduce biological activity,
leading to foaming.
7. What does the M in F/M ratio represent?
Answer: The mixed liquor volatile suspended solids in the aeration tank ✅
Rationale: F/M ratio compares the food (BOD) to the biomass (MLVSS) in the
aeration tank.
8. In general, how will warmer temperature affect the settling rate of solids
in a clarifier?
Answer: Increase the settling rate ✅
Rationale: Warmer water reduces viscosity, allowing solids to settle faster.
9. What could happen if the digester gas is mixed with air (85–95% by
volume)?
, Answer: Cause an explosion ✅
Rationale: Methane is highly flammable and explosive within these
concentrations.
10. How will algae impact the chlorine demand in the pond effluent?
Answer: Increase the chlorine demand ✅
Rationale: Algae react with chlorine, consuming more disinfectant.
11. Which of the following is true about a positive displacement pump?
Answer: It must never be started with the discharge valve closed ✅
Rationale: Starting a closed discharge can damage the pump due to overpressure.
12. What is true about the F/M ratio?
Answer: The volume of the secondary clarifier is not needed to determine the
F/M ratio ✅
Rationale: F/M ratio depends on influent BOD and biomass in the aeration tank,
not clarifier volume.
13. Which of the following is one of the basic rules of lab work?
Answer: Never pipet hazardous material with your mouth, even if the pipet has
been sterilized ✅
Rationale: Ensures lab safety and prevents accidental ingestion.
14. What is the recirculation ratio for a trickling filter?
