WASTEWATER OPERATOR CLASS C
COMPREHENSIVE SCRIPT 2026 QUESTIONS
AND ANSWERS GUARANTEED TO PASS
◉ Ways that oxygen can be depleted in streams. Answer: untreated
waste discharges, algae masses at night, and high BOD in the effluent
◉ A gas found in treatment systems that is NOT dangerous. Answer:
dissolved oxygen
◉ Cycles of decay include. Answer: carbon, nitrogen and sulfur
◉ A flow totalizer is required when the plant design flow is more
than Answer: 0.5 MGD
◉ Non-hazardous wastes include Answer: chlorides, alkalinity, color,
phosphorous and iron
◉ Hazardous wastes include Answer: cyanide, sulfides, organics and
gasoline
◉ Synergistic Effect Answer: reaction between waste streams
,◉ How many cubic feet of screenings per million gallons of
wastewater will coarse screens remove? Answer: 0.5 to 6.0
◉ Preaeration benefits Answer: freshen wastewater, scour gases and
remove grease
◉ Main purpose of sedimentation tank Answer: allow scum to rise
and solids to settle under quiescent (low velocity) conditions
◉ How much settleable solids is removed in primary settling?
Answer: 90-95%
◉ How much suspended solids is removed in primary settling?
Answer: 50-70%
◉ How much BOD is removed in primary settling? Answer: 35%
◉ How much total organic matter is removed in primary settling?
Answer: 20-30%
◉ What percentage of suspended solids will settle out within 2
hours? Answer: 70%
, ◉ Required minutes of detention time for peak flow? Answer: 54
◉ Required minutes of detention time for design flow? Answer: 108
◉ Benefits of removing grit Answer: wear on pump impellers, line
stoppages and taking up space
◉ Too high a velocity in a grit chamber can result in what? Answer:
excess grit in primary clarifier
◉ One of the benefits of pre-aeration is Answer: gas and grease
removal
◉ Why does grit need to be washed? Answer: because organic
matter clings to it
◉ What is a flow equalization used for? Answer: to reduce excessive
flows or organic loads
◉ How can grease be removed before sedimentation? Answer: by
chlorination, aeration and skimming
◉ A primary clarifier should remove most of what? Answer:
settleable solids
COMPREHENSIVE SCRIPT 2026 QUESTIONS
AND ANSWERS GUARANTEED TO PASS
◉ Ways that oxygen can be depleted in streams. Answer: untreated
waste discharges, algae masses at night, and high BOD in the effluent
◉ A gas found in treatment systems that is NOT dangerous. Answer:
dissolved oxygen
◉ Cycles of decay include. Answer: carbon, nitrogen and sulfur
◉ A flow totalizer is required when the plant design flow is more
than Answer: 0.5 MGD
◉ Non-hazardous wastes include Answer: chlorides, alkalinity, color,
phosphorous and iron
◉ Hazardous wastes include Answer: cyanide, sulfides, organics and
gasoline
◉ Synergistic Effect Answer: reaction between waste streams
,◉ How many cubic feet of screenings per million gallons of
wastewater will coarse screens remove? Answer: 0.5 to 6.0
◉ Preaeration benefits Answer: freshen wastewater, scour gases and
remove grease
◉ Main purpose of sedimentation tank Answer: allow scum to rise
and solids to settle under quiescent (low velocity) conditions
◉ How much settleable solids is removed in primary settling?
Answer: 90-95%
◉ How much suspended solids is removed in primary settling?
Answer: 50-70%
◉ How much BOD is removed in primary settling? Answer: 35%
◉ How much total organic matter is removed in primary settling?
Answer: 20-30%
◉ What percentage of suspended solids will settle out within 2
hours? Answer: 70%
, ◉ Required minutes of detention time for peak flow? Answer: 54
◉ Required minutes of detention time for design flow? Answer: 108
◉ Benefits of removing grit Answer: wear on pump impellers, line
stoppages and taking up space
◉ Too high a velocity in a grit chamber can result in what? Answer:
excess grit in primary clarifier
◉ One of the benefits of pre-aeration is Answer: gas and grease
removal
◉ Why does grit need to be washed? Answer: because organic
matter clings to it
◉ What is a flow equalization used for? Answer: to reduce excessive
flows or organic loads
◉ How can grease be removed before sedimentation? Answer: by
chlorination, aeration and skimming
◉ A primary clarifier should remove most of what? Answer:
settleable solids
