WASTEWATER OPERATOR C FINAL EXAM ACTUAL
QUESTIONS AND ANSWERS RATED A+
✔✔How much BOD will each person contribute to the wastewater treatment plant each
day? - ✔✔0.17
✔✔Cause of septic wastewater - ✔✔bacterial action
✔✔Classifications of solids in wastewater - ✔✔fixed/ash, suspended/dissolved,
organic/inorganic
✔✔Organic compounds in wastewater include - ✔✔carbon, hydrogen and oxygen
(animal and vegetable in nature)
✔✔Type of organic matter present in wastewater - ✔✔proteins
✔✔BOD is a measure of what? - ✔✔oxygen used up
✔✔Ways that oxygen can be depleted in streams - ✔✔untreated waste discharges,
algae masses at night, and high BOD in the effluent
✔✔A gas found in treatment systems that is NOT dangerous - ✔✔dissolved oxygen
✔✔Cycles of decay include - ✔✔carbon, nitrogen and sulfur
✔✔A flow totalizer is required when the plant design flow is more than - ✔✔0.5 MGD
✔✔Non-hazardous wastes include - ✔✔chlorides, alkalinity, color, phosphorous and
iron
✔✔Hazardous wastes include - ✔✔cyanide, sulfides, organics and gasoline
✔✔Synergistic Effect - ✔✔reaction between waste streams
✔✔How many cubic feet of screenings per million gallons of wastewater will coarse
screens remove? - ✔✔0.5 to 6.0
✔✔Preaeration benefits - ✔✔freshen wastewater, scour gases and remove grease
✔✔Main purpose of sedimentation tank - ✔✔allow scum to rise and solids to settle
under quiescent (low velocity) conditions
✔✔How much settleable solids is removed in primary settling? - ✔✔90-95%
, ✔✔How much suspended solids is removed in primary settling? - ✔✔50-70%
✔✔How much BOD is removed in primary settling? - ✔✔35%
✔✔How much total organic matter is removed in primary settling? - ✔✔20-30%
✔✔What percentage of suspended solids will settle out within 2 hours? - ✔✔70%
✔✔Required minutes of detention time for peak flow? - ✔✔54
✔✔Required minutes of detention time for design flow? - ✔✔108
✔✔Benefits of removing grit - ✔✔wear on pump impellers, line stoppages and taking up
space
✔✔Too high a velocity in a grit chamber can result in what? - ✔✔excess grit in primary
clarifier
✔✔One of the benefits of pre-aeration is - ✔✔gas and grease removal
✔✔Why does grit need to be washed? - ✔✔because organic matter clings to it
✔✔What is a flow equalization used for? - ✔✔to reduce excessive flows or organic
loads
✔✔How can grease be removed before sedimentation? - ✔✔by chlorination, aeration
and skimming
✔✔A primary clarifier should remove most of what? - ✔✔settleable solids
✔✔What conditions can influence settling of solids? - ✔✔temperature, condition of
solids and flow velocity
✔✔Sludge from a primary clarifier should have a moisture content of what? - ✔✔94-
96%
✔✔By performing Imhoff cone tests on the clarifier inlet and outlet, the operator can
determine what? - ✔✔the efficiency of the clarifier and a sludge pumping schedule
✔✔When temperature increases, water becomes... - ✔✔less dense
✔✔What problem is short-circuiting in a clarifier? - ✔✔flow problem
QUESTIONS AND ANSWERS RATED A+
✔✔How much BOD will each person contribute to the wastewater treatment plant each
day? - ✔✔0.17
✔✔Cause of septic wastewater - ✔✔bacterial action
✔✔Classifications of solids in wastewater - ✔✔fixed/ash, suspended/dissolved,
organic/inorganic
✔✔Organic compounds in wastewater include - ✔✔carbon, hydrogen and oxygen
(animal and vegetable in nature)
✔✔Type of organic matter present in wastewater - ✔✔proteins
✔✔BOD is a measure of what? - ✔✔oxygen used up
✔✔Ways that oxygen can be depleted in streams - ✔✔untreated waste discharges,
algae masses at night, and high BOD in the effluent
✔✔A gas found in treatment systems that is NOT dangerous - ✔✔dissolved oxygen
✔✔Cycles of decay include - ✔✔carbon, nitrogen and sulfur
✔✔A flow totalizer is required when the plant design flow is more than - ✔✔0.5 MGD
✔✔Non-hazardous wastes include - ✔✔chlorides, alkalinity, color, phosphorous and
iron
✔✔Hazardous wastes include - ✔✔cyanide, sulfides, organics and gasoline
✔✔Synergistic Effect - ✔✔reaction between waste streams
✔✔How many cubic feet of screenings per million gallons of wastewater will coarse
screens remove? - ✔✔0.5 to 6.0
✔✔Preaeration benefits - ✔✔freshen wastewater, scour gases and remove grease
✔✔Main purpose of sedimentation tank - ✔✔allow scum to rise and solids to settle
under quiescent (low velocity) conditions
✔✔How much settleable solids is removed in primary settling? - ✔✔90-95%
, ✔✔How much suspended solids is removed in primary settling? - ✔✔50-70%
✔✔How much BOD is removed in primary settling? - ✔✔35%
✔✔How much total organic matter is removed in primary settling? - ✔✔20-30%
✔✔What percentage of suspended solids will settle out within 2 hours? - ✔✔70%
✔✔Required minutes of detention time for peak flow? - ✔✔54
✔✔Required minutes of detention time for design flow? - ✔✔108
✔✔Benefits of removing grit - ✔✔wear on pump impellers, line stoppages and taking up
space
✔✔Too high a velocity in a grit chamber can result in what? - ✔✔excess grit in primary
clarifier
✔✔One of the benefits of pre-aeration is - ✔✔gas and grease removal
✔✔Why does grit need to be washed? - ✔✔because organic matter clings to it
✔✔What is a flow equalization used for? - ✔✔to reduce excessive flows or organic
loads
✔✔How can grease be removed before sedimentation? - ✔✔by chlorination, aeration
and skimming
✔✔A primary clarifier should remove most of what? - ✔✔settleable solids
✔✔What conditions can influence settling of solids? - ✔✔temperature, condition of
solids and flow velocity
✔✔Sludge from a primary clarifier should have a moisture content of what? - ✔✔94-
96%
✔✔By performing Imhoff cone tests on the clarifier inlet and outlet, the operator can
determine what? - ✔✔the efficiency of the clarifier and a sludge pumping schedule
✔✔When temperature increases, water becomes... - ✔✔less dense
✔✔What problem is short-circuiting in a clarifier? - ✔✔flow problem
