1|Page
Wastewater Treatment Operator Certification Test (NEW UPDATED VERSION)
LATEST ACTUAL EXAM QUESTIONS AND CORRECT ANSWERS (VERIFIED QUESTIONS
AND ANSWERS) | GUARANTEED PASS A+ UPDATED THIS YEAR
1. Multiple Choice:
Which parameter is most commonly used to measure organic pollution in wastewater?
A. pH
B. BOD (Biochemical Oxygen Demand)
C. TSS (Total Suspended Solids)
D. Ammonia
Answer: B
Rationale: BOD measures the amount of oxygen required by microorganisms to decompose
organic matter, indicating organic pollution levels.
2. Scenario:
A wastewater treatment plant operator notices high BOD levels in the influent.
What is the most likely cause?
A. High industrial discharge
B. Low temperature
C. Excessive chlorination
D. High dissolved oxygen
Answer: A
Rationale: High BOD typically indicates increased organic load, often due to industrial or
domestic wastewater inputs.
3. Code/Regulation:
Which federal agency regulates discharge permits for wastewater treatment plants in the United
States?
A. OSHA
B. EPA
C. FDA
D. USDA
Answer: B
Rationale: The EPA enforces the Clean Water Act and issues NPDES permits for wastewater
discharges.
2026 2027 GRADED A+
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4. Calculation:
A wastewater treatment plant receives 2 MGD (million gallons per day) of wastewater. If the
influent BOD is 200 mg/L, calculate the daily BOD load in pounds. (1 MGD = 8.34 × 10⁵
lbs/day per mg/L)
A. 334,000 lbs/day
B. 334,000 lbs/day
C. 334 lbs/day
D. 334,000,000 lbs/day
Answer: B
Rationale: BOD load (lbs/day) = 2 MGD × 200 mg/L × 8.34 = 3,336 lbs/day → round to 3,336
lbs/day. (Note: careful with unit conversions.)
5. Multiple Choice:
Which treatment process is considered primary treatment?
A. Activated sludge
B. Sedimentation
C. Trickling filter
D. Chlorination
Answer: B
Rationale: Primary treatment removes settleable solids by sedimentation. Biological processes
(activated sludge, trickling filters) are secondary treatment.
6. Scenario:
A clarifier is experiencing sludge bulking, causing poor settling.
Which action is most appropriate?
A. Increase chemical dosing
B. Adjust aeration in the aeration tank
C. Reduce sludge age and monitor filamentous bacteria
D. Add chlorine to sludge
Answer: C
Rationale: Sludge bulking is often caused by filamentous bacteria. Reducing sludge age and
controlling aeration helps improve settling.
2026 2027 GRADED A+
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7. Multiple Choice:
What is the normal pH range for biological wastewater treatment processes?
A. 3–5
B. 6–9
C. 10–12
D. 4–6
Answer: B
Rationale: Biological treatment processes function optimally within pH 6–9.
8. Calculation:
If a flow meter reads 1.5 MGD and the plant operates 24 hours/day, what is the flow rate in gpm
(gallons per minute)?
A. 1042 gpm
B. 1041 gpm
C. 1500 gpm
D. 2000 gpm
Answer: B
Rationale: 1.5 MGD × 1,000,000 ÷ 24 ÷ 60 ≈ 1041 gpm.
9. Multiple Choice:
Which chemical is commonly used for disinfection of treated wastewater?
A. Alum
B. Chlorine
C. Lime
D. Ferric chloride
Answer: B
Rationale: Chlorine is widely used for wastewater disinfection, either as gas, liquid, or tablets.
10. Scenario:
During a safety inspection, the operator notices a leak in the chlorine feed system.
2026 2027 GRADED A+
Wastewater Treatment Operator Certification Test (NEW UPDATED VERSION)
LATEST ACTUAL EXAM QUESTIONS AND CORRECT ANSWERS (VERIFIED QUESTIONS
AND ANSWERS) | GUARANTEED PASS A+ UPDATED THIS YEAR
1. Multiple Choice:
Which parameter is most commonly used to measure organic pollution in wastewater?
A. pH
B. BOD (Biochemical Oxygen Demand)
C. TSS (Total Suspended Solids)
D. Ammonia
Answer: B
Rationale: BOD measures the amount of oxygen required by microorganisms to decompose
organic matter, indicating organic pollution levels.
2. Scenario:
A wastewater treatment plant operator notices high BOD levels in the influent.
What is the most likely cause?
A. High industrial discharge
B. Low temperature
C. Excessive chlorination
D. High dissolved oxygen
Answer: A
Rationale: High BOD typically indicates increased organic load, often due to industrial or
domestic wastewater inputs.
3. Code/Regulation:
Which federal agency regulates discharge permits for wastewater treatment plants in the United
States?
A. OSHA
B. EPA
C. FDA
D. USDA
Answer: B
Rationale: The EPA enforces the Clean Water Act and issues NPDES permits for wastewater
discharges.
2026 2027 GRADED A+
,2|Page
4. Calculation:
A wastewater treatment plant receives 2 MGD (million gallons per day) of wastewater. If the
influent BOD is 200 mg/L, calculate the daily BOD load in pounds. (1 MGD = 8.34 × 10⁵
lbs/day per mg/L)
A. 334,000 lbs/day
B. 334,000 lbs/day
C. 334 lbs/day
D. 334,000,000 lbs/day
Answer: B
Rationale: BOD load (lbs/day) = 2 MGD × 200 mg/L × 8.34 = 3,336 lbs/day → round to 3,336
lbs/day. (Note: careful with unit conversions.)
5. Multiple Choice:
Which treatment process is considered primary treatment?
A. Activated sludge
B. Sedimentation
C. Trickling filter
D. Chlorination
Answer: B
Rationale: Primary treatment removes settleable solids by sedimentation. Biological processes
(activated sludge, trickling filters) are secondary treatment.
6. Scenario:
A clarifier is experiencing sludge bulking, causing poor settling.
Which action is most appropriate?
A. Increase chemical dosing
B. Adjust aeration in the aeration tank
C. Reduce sludge age and monitor filamentous bacteria
D. Add chlorine to sludge
Answer: C
Rationale: Sludge bulking is often caused by filamentous bacteria. Reducing sludge age and
controlling aeration helps improve settling.
2026 2027 GRADED A+
, 3|Page
7. Multiple Choice:
What is the normal pH range for biological wastewater treatment processes?
A. 3–5
B. 6–9
C. 10–12
D. 4–6
Answer: B
Rationale: Biological treatment processes function optimally within pH 6–9.
8. Calculation:
If a flow meter reads 1.5 MGD and the plant operates 24 hours/day, what is the flow rate in gpm
(gallons per minute)?
A. 1042 gpm
B. 1041 gpm
C. 1500 gpm
D. 2000 gpm
Answer: B
Rationale: 1.5 MGD × 1,000,000 ÷ 24 ÷ 60 ≈ 1041 gpm.
9. Multiple Choice:
Which chemical is commonly used for disinfection of treated wastewater?
A. Alum
B. Chlorine
C. Lime
D. Ferric chloride
Answer: B
Rationale: Chlorine is widely used for wastewater disinfection, either as gas, liquid, or tablets.
10. Scenario:
During a safety inspection, the operator notices a leak in the chlorine feed system.
2026 2027 GRADED A+
