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