Wastewater Operator Exam TN 2024 Set
With complete solution | Updated
2024/25
What is the purpose of wastewater treatment? - Prevention of pollution and protect public
II II II II II II II II II II II II II II II
health
II
What is inflow? - Direct discharge into the sewer from sources other than regular
II II II II II II II II II II II II II II II II
connections
II
What is infiltration? - Seepage of groundwater into the sewer system through cracks,
II II II II II II II II II II II II II II II
manholes, pipes, and connections
II II II II
How many feet apart should manholes be placed to provide access for inspections and
II II II II II II II II II II II II II II
cleaning? - 300-500
II II II II II
Manholes must be installed - At the ends of any line 8" in diameter or larger line
II II II II II II II II II II II II II II II II II II II II
Changes in grade, size of pipe or alignment II II II II II II II II
At intersections
II II
Not greater than 400ft on a 15" diameter and smaller sewers or 500ft on 18-30" sewers
II II II II II II II II II II II II II II II
Hydrogen sulfide is made in the collection system and can cause what problems? -
II II II II II II II II II II II II II II II II
Make waste more difficult to treat
II II II II II II II
Damage concrete structures II II II
Cause odor problems II II
Biological activity in long, flat sewer lines will likely cause: - Hydrogen sulfide production
II II II II II II II II II II II II II II II II II
Oxygen deficiency in sewers, manholes, or wet wells
II II II II II II II II
Metal and concrete corrosion
II II II
What is an indicator that a toxic load has entered an activated sludge plant? - Increase in
II II II II II II II II II II II II II II II II II II II
oxygen concentration in the aeration basin
II II II II II II
What two factors can influence the amount of dissolved oxygen present? - Water
II II II II II II II II II II II II II II II
temperature and organic matter
II II II II
How does water temperature affect dissolved oxygen? - Greater temperature means
II II II II II II II II II II II II II
less D.O.
II II
Lower temperature means more D.O. II II II II
How does organic matter affect dissolved oxygen? - More organic material requires
II II II II II II II II II II II II II II
more D.O.
II II
,What are problems associated with excess nutrients? - An increase in productivity of
II II II II II II II II II II II II II II II
aquatic plants thus depleting D.O. Level
II II II II II II II
Odor problems II II
Extra vegetation near surface may inhibit light
II II II II II II
II What is your best defense against infections and disease? - Good personal hygiene
II II II II II II II II II II II II II II
What may a solids build up in a receiving stream cause? - May cause oxygen depletion
II II II II II II II II II II II II II II II II II II
and be a source of odors
II II II II II II
What problems do solids cause in the system? - Fill storage areas, clog ditches and
II II II II II II II II II II II II II II II II II
channels
II II
Interfere with mechanical systems II II II II
Associated with taste/color/clarity problems in drinking water II II II II II II
What types of solids are in wastewater? - Total solids
II II II II II II II II II II II II
Dissolved solids II
Suspended solids II II
Organic solids II
Inorganic solids II
Floatable solids II
II Fresh domestic wastewater is usually what color - Grey/dishwater color
II II II II II II II II II II II
II What color is septic wastewater typically? - Black
II II II II II II II II II
II How does fresh domestic wastewater smell? - Musty early odor
II II II II II II II II II II II
In the state of TN flow measuring devices must be calibrated and maintained to ensure
II II II II II II II II II II II II II II II
_____________ of the true flow - +/- 10%
II II II II II II II II II II
What is the parshall flume best for? - Flow with solids or debris
II II II II II II II II II II II II II II II
Large flows II II
Variable flows II
II What is the usual detention time in a primary clarifier? - 1.5-2.0 hours
II II II II II II II II II II II II II II
II What does velocity drop to in a primary clarifier? - < 1fps
II II II II II II II II II II II II II
For wastewater to be considered "disinfected" what is the qualifications? - 200 CFU/100
II II II II II II II II II II II II II II II
ml for fecal colioforms
II II II II II
126cfu/100ml for E. Coli II II II
Preliminary treatment commonly consists of: - Screening
II II II II II II II II II
Shredding
Grit removal II
,Pre aeration
II
What do coarse screens remove? - Large solids, trash, wood, tree limbs, rocks, and
II II II II II II II II II II II II II II II II
other large debris
II II II
What are three coarse screens? - Bar rack
II II II II II II II II II II II
Manually cleaned bar screen II II II II
Mechanically cleaned bar screen II II II
What are three fine screens? - Wedge wire
II II II II II II II II II II II
Rotary drum screens II II II
Escalating step screen II II
II How much spacing is between bar racks? - 3-4 inches
II II II II II II II II II II II
II How much spacing is between bar screens? - ~3/8 in to 2 inches
II II II II II II II II II II II II II II
II Where are bar racks found? - In bypass channels for when flows get diverted
II II II II II II II II II II II II II II II
If manually cleaned bar screens are not attended to frequently this could cause: - Debris
II II II II II II II II II II II II II II II II II
collecting and cause head loss
II II II II II II
Flow backs up ->Organic wastes settle out-> depletes DO -> leads to septic
II II II II II II II II II II II II II
Sudden rush of septic can lead to "shock load" II II II II II II II II
The allowable head loss behind a bar screen should be ___________ - A max of 3
II II II II II II II II II II II II II II II II II II
inches
II
On a mechanically cleaned bar screen list some maintenance items: - Drive units:
II II II II II II II II II II II II II II II
adjustments must be made if cables dont wind up evenly on drums of cable machines
II II II II II II II II II II II II II II II II
Frayed or excessively worn chain must be replaced
II II II II II II II II
Bent or broken bars must be replaced
II II II II II II
If the motor on a mechanical cleaned bar screen runs but the rack doesnt operate what
II II II II II II II II II II II II II II II II
may be the problem? - Broken chain, cable or shear pin
II II II II II II II II II II II II II
What do fine screens typically consists of: - Wedge wire
II II II II II II II II II II II II II
Closely spaced bars/screening cloth II II II II
Perforated plate II
II What are the openings of fine screens - 0.06-0.25 inch
II II II II II II II II II II II
What are the three steps of maintenance to monitor with fine screens? - Visual
II II II II II II II II II II II II II II II II II
Auditory
Proper lubrication II
II What is the opening for wedge wire screens? - 0.010-0.100 in opening
II II II II II II II II II II II II II
, What wastewater is wedgewire screen not recommended for? - Wastewater that
II II II II II II II II II II II II II
contains grease
II II
How are screenings removed from internally fed rotary drum screens? - Auger/conveyor
II II II II II II II II II II II II II II
and squeezed to drain
II II II II
How are screenings removed from an externally fed rotary drum screen - Screenings
II II II II II II II II II II II II II II II
collected in the hopper
II II II II
II What are the openings on an escalating step screen? - 0.125-0.250 inch
II II II II II II II II II II II II II
What are comminutors? - Devices with cutters and screens that shred solids and return
II II II II II II II II II II II II II II II II
them to wastewater stream
II II II II
What are three disadvantages of comminutors? - Shredded rags affect operation of
II II II II II II II II II II II II II II
downstream units
II II II
Increased load on downstream units II II II II II
Head loss downstream if not checked or maintained properly
II II II II II II II II
What are four maintenance items for comminutors and barminutors? - Check for debris
II II II II II II II II II II II II II II II
in the cutting drums and bars
II II II II II II II
Sharpen and adjust the cutting blades II II II II II
Exercise inlet/outlet gates II II
Inspect travel and rotation of cutting blades
II II II II II II
If stringing parts of rags are hanging from slotted drum or U shaped bars of the
II II II II II II II II II II II II II II II II
comminutor what would that indicate? - The cutter is worn or out of adjustment
II II II II II II II II II II II II II II II II
II What is the conventional bar screen capture rate? - 6 cubic ft/ MG
II II II II II II II II II II II II II II
How do you calculate screenings removed in cubic feet of screenings per MG of flow? -
II II II II II II II II II II II II II II II II II II
Screenings removed cu ft/day
II II II II II
——————————————————
Flow MGD
II II
II What does the paint filter test measure? - Leaching effect of your screenings
II II II II II II II II II II II II II II
What benefit does grit removal have on the treatment system? - Reduce the clogging of
II II II II II II II II II II II II II II II II II
pipes and protects moving mechanical equipment/pumps from abrasion and
II II II II II II II II II
accompanying wear
II II
What does a grit channel do? - Allow grit to settle out while keeping the lighter organic
II II II II II II II II II II II II II II II II II II II
solids moving to the next treatment unit
II II II II II II II
II What is the best velocity for a grit channel? - 1ft/sec
II II II II II II II II II II II II
With complete solution | Updated
2024/25
What is the purpose of wastewater treatment? - Prevention of pollution and protect public
II II II II II II II II II II II II II II II
health
II
What is inflow? - Direct discharge into the sewer from sources other than regular
II II II II II II II II II II II II II II II II
connections
II
What is infiltration? - Seepage of groundwater into the sewer system through cracks,
II II II II II II II II II II II II II II II
manholes, pipes, and connections
II II II II
How many feet apart should manholes be placed to provide access for inspections and
II II II II II II II II II II II II II II
cleaning? - 300-500
II II II II II
Manholes must be installed - At the ends of any line 8" in diameter or larger line
II II II II II II II II II II II II II II II II II II II II
Changes in grade, size of pipe or alignment II II II II II II II II
At intersections
II II
Not greater than 400ft on a 15" diameter and smaller sewers or 500ft on 18-30" sewers
II II II II II II II II II II II II II II II
Hydrogen sulfide is made in the collection system and can cause what problems? -
II II II II II II II II II II II II II II II II
Make waste more difficult to treat
II II II II II II II
Damage concrete structures II II II
Cause odor problems II II
Biological activity in long, flat sewer lines will likely cause: - Hydrogen sulfide production
II II II II II II II II II II II II II II II II II
Oxygen deficiency in sewers, manholes, or wet wells
II II II II II II II II
Metal and concrete corrosion
II II II
What is an indicator that a toxic load has entered an activated sludge plant? - Increase in
II II II II II II II II II II II II II II II II II II II
oxygen concentration in the aeration basin
II II II II II II
What two factors can influence the amount of dissolved oxygen present? - Water
II II II II II II II II II II II II II II II
temperature and organic matter
II II II II
How does water temperature affect dissolved oxygen? - Greater temperature means
II II II II II II II II II II II II II
less D.O.
II II
Lower temperature means more D.O. II II II II
How does organic matter affect dissolved oxygen? - More organic material requires
II II II II II II II II II II II II II II
more D.O.
II II
,What are problems associated with excess nutrients? - An increase in productivity of
II II II II II II II II II II II II II II II
aquatic plants thus depleting D.O. Level
II II II II II II II
Odor problems II II
Extra vegetation near surface may inhibit light
II II II II II II
II What is your best defense against infections and disease? - Good personal hygiene
II II II II II II II II II II II II II II
What may a solids build up in a receiving stream cause? - May cause oxygen depletion
II II II II II II II II II II II II II II II II II II
and be a source of odors
II II II II II II
What problems do solids cause in the system? - Fill storage areas, clog ditches and
II II II II II II II II II II II II II II II II II
channels
II II
Interfere with mechanical systems II II II II
Associated with taste/color/clarity problems in drinking water II II II II II II
What types of solids are in wastewater? - Total solids
II II II II II II II II II II II II
Dissolved solids II
Suspended solids II II
Organic solids II
Inorganic solids II
Floatable solids II
II Fresh domestic wastewater is usually what color - Grey/dishwater color
II II II II II II II II II II II
II What color is septic wastewater typically? - Black
II II II II II II II II II
II How does fresh domestic wastewater smell? - Musty early odor
II II II II II II II II II II II
In the state of TN flow measuring devices must be calibrated and maintained to ensure
II II II II II II II II II II II II II II II
_____________ of the true flow - +/- 10%
II II II II II II II II II II
What is the parshall flume best for? - Flow with solids or debris
II II II II II II II II II II II II II II II
Large flows II II
Variable flows II
II What is the usual detention time in a primary clarifier? - 1.5-2.0 hours
II II II II II II II II II II II II II II
II What does velocity drop to in a primary clarifier? - < 1fps
II II II II II II II II II II II II II
For wastewater to be considered "disinfected" what is the qualifications? - 200 CFU/100
II II II II II II II II II II II II II II II
ml for fecal colioforms
II II II II II
126cfu/100ml for E. Coli II II II
Preliminary treatment commonly consists of: - Screening
II II II II II II II II II
Shredding
Grit removal II
,Pre aeration
II
What do coarse screens remove? - Large solids, trash, wood, tree limbs, rocks, and
II II II II II II II II II II II II II II II II
other large debris
II II II
What are three coarse screens? - Bar rack
II II II II II II II II II II II
Manually cleaned bar screen II II II II
Mechanically cleaned bar screen II II II
What are three fine screens? - Wedge wire
II II II II II II II II II II II
Rotary drum screens II II II
Escalating step screen II II
II How much spacing is between bar racks? - 3-4 inches
II II II II II II II II II II II
II How much spacing is between bar screens? - ~3/8 in to 2 inches
II II II II II II II II II II II II II II
II Where are bar racks found? - In bypass channels for when flows get diverted
II II II II II II II II II II II II II II II
If manually cleaned bar screens are not attended to frequently this could cause: - Debris
II II II II II II II II II II II II II II II II II
collecting and cause head loss
II II II II II II
Flow backs up ->Organic wastes settle out-> depletes DO -> leads to septic
II II II II II II II II II II II II II
Sudden rush of septic can lead to "shock load" II II II II II II II II
The allowable head loss behind a bar screen should be ___________ - A max of 3
II II II II II II II II II II II II II II II II II II
inches
II
On a mechanically cleaned bar screen list some maintenance items: - Drive units:
II II II II II II II II II II II II II II II
adjustments must be made if cables dont wind up evenly on drums of cable machines
II II II II II II II II II II II II II II II II
Frayed or excessively worn chain must be replaced
II II II II II II II II
Bent or broken bars must be replaced
II II II II II II
If the motor on a mechanical cleaned bar screen runs but the rack doesnt operate what
II II II II II II II II II II II II II II II II
may be the problem? - Broken chain, cable or shear pin
II II II II II II II II II II II II II
What do fine screens typically consists of: - Wedge wire
II II II II II II II II II II II II II
Closely spaced bars/screening cloth II II II II
Perforated plate II
II What are the openings of fine screens - 0.06-0.25 inch
II II II II II II II II II II II
What are the three steps of maintenance to monitor with fine screens? - Visual
II II II II II II II II II II II II II II II II II
Auditory
Proper lubrication II
II What is the opening for wedge wire screens? - 0.010-0.100 in opening
II II II II II II II II II II II II II
, What wastewater is wedgewire screen not recommended for? - Wastewater that
II II II II II II II II II II II II II
contains grease
II II
How are screenings removed from internally fed rotary drum screens? - Auger/conveyor
II II II II II II II II II II II II II II
and squeezed to drain
II II II II
How are screenings removed from an externally fed rotary drum screen - Screenings
II II II II II II II II II II II II II II II
collected in the hopper
II II II II
II What are the openings on an escalating step screen? - 0.125-0.250 inch
II II II II II II II II II II II II II
What are comminutors? - Devices with cutters and screens that shred solids and return
II II II II II II II II II II II II II II II II
them to wastewater stream
II II II II
What are three disadvantages of comminutors? - Shredded rags affect operation of
II II II II II II II II II II II II II II
downstream units
II II II
Increased load on downstream units II II II II II
Head loss downstream if not checked or maintained properly
II II II II II II II II
What are four maintenance items for comminutors and barminutors? - Check for debris
II II II II II II II II II II II II II II II
in the cutting drums and bars
II II II II II II II
Sharpen and adjust the cutting blades II II II II II
Exercise inlet/outlet gates II II
Inspect travel and rotation of cutting blades
II II II II II II
If stringing parts of rags are hanging from slotted drum or U shaped bars of the
II II II II II II II II II II II II II II II II
comminutor what would that indicate? - The cutter is worn or out of adjustment
II II II II II II II II II II II II II II II II
II What is the conventional bar screen capture rate? - 6 cubic ft/ MG
II II II II II II II II II II II II II II
How do you calculate screenings removed in cubic feet of screenings per MG of flow? -
II II II II II II II II II II II II II II II II II II
Screenings removed cu ft/day
II II II II II
——————————————————
Flow MGD
II II
II What does the paint filter test measure? - Leaching effect of your screenings
II II II II II II II II II II II II II II
What benefit does grit removal have on the treatment system? - Reduce the clogging of
II II II II II II II II II II II II II II II II II
pipes and protects moving mechanical equipment/pumps from abrasion and
II II II II II II II II II
accompanying wear
II II
What does a grit channel do? - Allow grit to settle out while keeping the lighter organic
II II II II II II II II II II II II II II II II II II II
solids moving to the next treatment unit
II II II II II II II
II What is the best velocity for a grit channel? - 1ft/sec
II II II II II II II II II II II II
