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Delaware Wastewater Operator Class II ACTUAL EXAM
COMPLETE QUESTIONS AND CORRECT ANSWERS LATEST
UPDATE THIS YEAR
SUMMARIZED EXAM COVERAGE (point form)
• Regulatory Framework: Clean Water Act (EPA), Delaware Administrative Code Title 7 (DNREC),
NPDES permits, effluent limits, 7 DE Admin. Code 7204 (Operator Licensing regulations)
• Treatment Processes: Preliminary (screening, grit removal), Primary (sedimentation, primary
clarifiers), Secondary (activated sludge – aeration, MLSS, SVI, F/M ratio; trickling filters; RBCs),
Tertiary (filtration, nutrient removal), Disinfection (chlorine, UV, ozone, dechlorination)
• Key Parameters: BOD (Biochemical Oxygen Demand), COD, TSS (Total Suspended Solids), DO
(Dissolved Oxygen), pH, Alkalinity, Ammonia, Nitrate/Nitrite, Total Phosphorus, FOG
(Fats/Oils/Grease), Settleable Solids, Sludge Volume Index (SVI), Mixed Liquor Suspended Solids
(MLSS)
• Biological Nutrient Removal (BNR): Nitrification (ammonia → nitrate), Denitrification (nitrate →
N₂ gas under anoxic conditions), Phosphorus removal (chemical with alum or biological)
• Process Control & Monitoring: Aeration control (DO), sludge wasting, sludge age/MCRT, return
activated sludge (RAS), waste activated sludge (WAS), microscopic examination (filamentous
organisms, bulking), settleometer test
• Safety: Confined space entry (gas testing, ventilation, PPE, permit), lockout/tagout (LOTO), H₂S
toxicity, chlorine safety, PPE for biosolids handling, emergency response planning
• Laboratory & Sampling: Grab vs. composite samples, sample preservation, BOD incubation (5
days, 20°C), DO measurement (meter or Winkler titration), pH meter calibration, turbidity, chain
of custody
• Equipment Operation & Maintenance: Pumps (centrifugal, submersible, positive displacement),
valves, blowers, mixers, screens, grit chambers, clarifiers, belt filter presses, centrifuges, drying
beds, flow measurement (Parshall flume, Venturi, mag meter)
• Solids Handling: Sludge thickening (gravity, drum), digestion (aerobic, anaerobic), dewatering
(belt press, centrifuge, drying beds), biosolids disposal/land application regulations
• Collection Systems: Sewer line velocities (minimum 2 fps to prevent sedimentation), lift
stations, FOG control, infiltration/inflow (I/I)
• Odor Control: Chemical scrubbers, biofilters, covered tanks, aeration
250 RANDOM SCENARIO-BASED MCQs
QUESTION 1: A Class II operator notices that the activated sludge mixed liquor has a dark brown color
and a "musty" odor. Microscopic examination shows numerous stalked ciliates and rotifers. What does
this indicate?
A) Young sludge with poor settling
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B) Old, well-stabilized sludge with a healthy microorganism population
C) Toxic upset requiring immediate wasting
D) Anaerobic conditions in the aeration basin
Answer: B – Stalked ciliates and rotifers are associated with older, stable sludge and indicate good
treatment.
QUESTION 2: Which Delaware regulation governs the licensing of wastewater operators?
A) 7 DE Admin. Code 7204
B) 7 DE Admin. Code 7405
C) Delaware Clean Water Act Title 5
D) 7 DE Admin. Code 1122
Answer: A – 7 DE Admin. Code 7204 is the Regulations for Licensing Operators of Wastewater Facilities.
QUESTION 3: An operator needs to collect a sample for BOD analysis. How should the sample be
preserved if it cannot be analyzed within 2 hours?
A) Freeze immediately
B) Add sulfuric acid to pH <2 and cool to 4°C
C) Add chlorine to prevent biological activity
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D) Store at room temperature in a clear glass bottle
Answer: B – BOD samples must be preserved at 4°C and analyzed within 48 hours; acidification to pH <2
is not correct for BOD (that is for nutrient samples). [Correction: BOD samples are cooled to 4°C without
acid; acidification would kill microorganisms needed for BOD test.]
QUESTION 4: A wastewater treatment plant’s secondary clarifier has floating sludge on the surface.
What is the most likely cause?
A) Over-aeration – denitrification in the clarifier producing nitrogen gas bubbles
B) Under-aeration – anaerobic conditions in the aeration basin
C) Low influent BOD
D) Excessive waste activated sludge removal
Answer: A – Denitrification in the clarifier produces nitrogen gas bubbles that lift sludge to the surface.
QUESTION 5: What is the minimum years of acceptable operating experience required for a Delaware
Class II Wastewater Operator license?
A) 1 year
B) 2 years
C) 3 years
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D) 4 years
Answer: C – Class II requires a high school diploma and three years of acceptable operating experience
in facilities of Class I or higher .
QUESTION 6: An operator reading a flow meter sees 1.2 MGD. How many gallons per day is this?
A) 120,000 GPD
B) 1,200,000 GPD
C) 12,000,000 GPD
D) 120,000,000 GPD
Answer: B – 1.2 MGD = 1.2 × 1,000,000 = 1,200,000 gallons per day.
QUESTION 7: During a confined space entry into a wet well, which gas is the most immediate concern
for an operator entering first?
A) Methane (explosive risk)
B) Carbon dioxide (displaces oxygen)
C) Oxygen deficiency (below 19.5%)
D) Carbon monoxide (toxic)
Delaware Wastewater Operator Class II ACTUAL EXAM
COMPLETE QUESTIONS AND CORRECT ANSWERS LATEST
UPDATE THIS YEAR
SUMMARIZED EXAM COVERAGE (point form)
• Regulatory Framework: Clean Water Act (EPA), Delaware Administrative Code Title 7 (DNREC),
NPDES permits, effluent limits, 7 DE Admin. Code 7204 (Operator Licensing regulations)
• Treatment Processes: Preliminary (screening, grit removal), Primary (sedimentation, primary
clarifiers), Secondary (activated sludge – aeration, MLSS, SVI, F/M ratio; trickling filters; RBCs),
Tertiary (filtration, nutrient removal), Disinfection (chlorine, UV, ozone, dechlorination)
• Key Parameters: BOD (Biochemical Oxygen Demand), COD, TSS (Total Suspended Solids), DO
(Dissolved Oxygen), pH, Alkalinity, Ammonia, Nitrate/Nitrite, Total Phosphorus, FOG
(Fats/Oils/Grease), Settleable Solids, Sludge Volume Index (SVI), Mixed Liquor Suspended Solids
(MLSS)
• Biological Nutrient Removal (BNR): Nitrification (ammonia → nitrate), Denitrification (nitrate →
N₂ gas under anoxic conditions), Phosphorus removal (chemical with alum or biological)
• Process Control & Monitoring: Aeration control (DO), sludge wasting, sludge age/MCRT, return
activated sludge (RAS), waste activated sludge (WAS), microscopic examination (filamentous
organisms, bulking), settleometer test
• Safety: Confined space entry (gas testing, ventilation, PPE, permit), lockout/tagout (LOTO), H₂S
toxicity, chlorine safety, PPE for biosolids handling, emergency response planning
• Laboratory & Sampling: Grab vs. composite samples, sample preservation, BOD incubation (5
days, 20°C), DO measurement (meter or Winkler titration), pH meter calibration, turbidity, chain
of custody
• Equipment Operation & Maintenance: Pumps (centrifugal, submersible, positive displacement),
valves, blowers, mixers, screens, grit chambers, clarifiers, belt filter presses, centrifuges, drying
beds, flow measurement (Parshall flume, Venturi, mag meter)
• Solids Handling: Sludge thickening (gravity, drum), digestion (aerobic, anaerobic), dewatering
(belt press, centrifuge, drying beds), biosolids disposal/land application regulations
• Collection Systems: Sewer line velocities (minimum 2 fps to prevent sedimentation), lift
stations, FOG control, infiltration/inflow (I/I)
• Odor Control: Chemical scrubbers, biofilters, covered tanks, aeration
250 RANDOM SCENARIO-BASED MCQs
QUESTION 1: A Class II operator notices that the activated sludge mixed liquor has a dark brown color
and a "musty" odor. Microscopic examination shows numerous stalked ciliates and rotifers. What does
this indicate?
A) Young sludge with poor settling
, Page 2 of 114
B) Old, well-stabilized sludge with a healthy microorganism population
C) Toxic upset requiring immediate wasting
D) Anaerobic conditions in the aeration basin
Answer: B – Stalked ciliates and rotifers are associated with older, stable sludge and indicate good
treatment.
QUESTION 2: Which Delaware regulation governs the licensing of wastewater operators?
A) 7 DE Admin. Code 7204
B) 7 DE Admin. Code 7405
C) Delaware Clean Water Act Title 5
D) 7 DE Admin. Code 1122
Answer: A – 7 DE Admin. Code 7204 is the Regulations for Licensing Operators of Wastewater Facilities.
QUESTION 3: An operator needs to collect a sample for BOD analysis. How should the sample be
preserved if it cannot be analyzed within 2 hours?
A) Freeze immediately
B) Add sulfuric acid to pH <2 and cool to 4°C
C) Add chlorine to prevent biological activity
, Page 3 of 114
D) Store at room temperature in a clear glass bottle
Answer: B – BOD samples must be preserved at 4°C and analyzed within 48 hours; acidification to pH <2
is not correct for BOD (that is for nutrient samples). [Correction: BOD samples are cooled to 4°C without
acid; acidification would kill microorganisms needed for BOD test.]
QUESTION 4: A wastewater treatment plant’s secondary clarifier has floating sludge on the surface.
What is the most likely cause?
A) Over-aeration – denitrification in the clarifier producing nitrogen gas bubbles
B) Under-aeration – anaerobic conditions in the aeration basin
C) Low influent BOD
D) Excessive waste activated sludge removal
Answer: A – Denitrification in the clarifier produces nitrogen gas bubbles that lift sludge to the surface.
QUESTION 5: What is the minimum years of acceptable operating experience required for a Delaware
Class II Wastewater Operator license?
A) 1 year
B) 2 years
C) 3 years
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D) 4 years
Answer: C – Class II requires a high school diploma and three years of acceptable operating experience
in facilities of Class I or higher .
QUESTION 6: An operator reading a flow meter sees 1.2 MGD. How many gallons per day is this?
A) 120,000 GPD
B) 1,200,000 GPD
C) 12,000,000 GPD
D) 120,000,000 GPD
Answer: B – 1.2 MGD = 1.2 × 1,000,000 = 1,200,000 gallons per day.
QUESTION 7: During a confined space entry into a wet well, which gas is the most immediate concern
for an operator entering first?
A) Methane (explosive risk)
B) Carbon dioxide (displaces oxygen)
C) Oxygen deficiency (below 19.5%)
D) Carbon monoxide (toxic)
