WASTEWATER OPERATOR C COMPREHENSIVE EXAM
QUESTIONS AND ANSWERS RATED A+
✔✔Backflow - ✔✔Non-potable water that flows into the potable water supply due to
back pressure
✔✔Backsiphonage - ✔✔Water flowing into the potable water supply due to negative
pressure
✔✔FOG - ✔✔Fats, Oil, and Grease. Congeal in system and cause blockages
✔✔Hydrogen Sulfide - ✔✔Sewer gas that smells like rotten eggs and:
is heavier than air
is explosive when mixed with air
is corrosive
✔✔Methane - ✔✔Sewer gas that is
Colorless
Odorless
Extremely flammable
Forms explosive mixture with air
Displaces oxygen
✔✔Septic Condition - ✔✔A condition in sewers resulting from gases produced by
anaerobic bacteria when sewage sits for too long
Characteristics
Foul odor
Black appearance
Little or no D.O.
High oxygen demand
✔✔Parshall Flume - ✔✔An open channel flow meter common in wastewater plants that
has a narrow throat
✔✔V-Notch Weirs - ✔✔An open channel flow meter used in wastewater plants to
measure small flows that is a "V" shape cut out of a weir
✔✔Perimeter - ✔✔The distance around an object, expressed in linear inches, feet,
yards, etc.
✔✔Area - ✔✔The amount of space enclosed by a boundary usually expressed in
square inches, square feet, etc.
✔✔Volume - ✔✔The amount of space enclosed by a three-dimensional object
expressed in cubic inches, cubic feet, cubic yards, etc
,✔✔Flow - ✔✔Volume per unit of time
✔✔Velocity (definition) - ✔✔the distance traveled per unit of time
✔✔Preliminary Treatment - ✔✔Prepares wastewater for downstream plant processes.
The main preliminary process are:
-Screening
-Shredding
-Grit Removal
-Preaeration
✔✔Screening - ✔✔Purpose is to remove large items from the wastestream
-Rags
-Sticks
✔✔Bar Rack - ✔✔AKA Trash Racks. Bars are 3-6 inches apart and angled back from
30-45 degrees
✔✔Bar Screen - ✔✔Bars are 3/4 - 2 inches apart and are angled back 15-30 degrees.
Channel width is 2-14 feet. There are two types: Manual and Mechanical
✔✔Head Loss - ✔✔The difference in height between the water level on the upstream
side of a bar screen and the downstream side of the bar screen.
✔✔Screenings - ✔✔Material removed from a bar screen or bar rack
✔✔Shredding - ✔✔Shred, grinding, or chop solids in the wastestream that could
interfere with downstream processes
✔✔Communitor - ✔✔Horizontal cutting "torpedo" drum with slots that the water must
pass through.
Vertical or horizontal cutting drums with teeth that pass through stationary or rotating
bars
✔✔Barminutor - ✔✔Similar to a mechanical bar screen
The "rakes" are rotating drums
✔✔Preaeration - ✔✔The addition of air before primary sedimentation
Common process to use during grit removal
✔✔Mechanical Aerator - ✔✔A mechanical device that splashes water into the air where
it absorbs oxygen
, ✔✔Diffused Aerator - ✔✔Blowers force air through a pipe into the wastestream
Pipes have a sock or plate at the end with tiny holes acting as the diffuser, breaking
apart the airstream into tiny bubbles
✔✔Cascade Aerator - ✔✔Series of steps water travels over causing it to splash so it
gets oxygen from the air
✔✔Grit - ✔✔Heavy, inorganic, particulate matter that does not readily decompose
(Sand, eggshells, cinders, coffee grounds)
✔✔Purpose of Grit Removal - ✔✔Remove the heavy, inorganic, particulate matter that
does not readily decompose from the wastestream
✔✔Hand-cleaned Grit Collector - ✔✔Typically used at very small plants, <1 MGD
Two elongated channels
Shovel out grit
✔✔Mechanically-cleaned Collector - ✔✔All are gravity-type, velocity controlled, cleaning
mechanism, grit removal system
Some are grit classifier, grit washer, aerators
✔✔Aerated Vortex - ✔✔Augments gravitational forces
Comprised of aerated vortex unit, may also go to either a grit classifier or grit washer
✔✔Grit Washing - ✔✔Washes organics from grit
-Reduce odor
-Improve removal efficiency
-Dispose of more easily
✔✔Grit Classifying - ✔✔Process used to dry grit
✔✔Primary Treatment - ✔✔Main Primary Process
-Settling tanks/clarifiers
-Fine screen
-Dissolved air floatation thickeners
✔✔Purpose of Primary Treatment - ✔✔Separate and remove the readily settleable and
floatable solids from the wastewater
✔✔Types of Primary Clarifiers - ✔✔-Circular
-Rectangular
✔✔Circular Clarifier - ✔✔-Inlet baffle
-Outlet baffle
QUESTIONS AND ANSWERS RATED A+
✔✔Backflow - ✔✔Non-potable water that flows into the potable water supply due to
back pressure
✔✔Backsiphonage - ✔✔Water flowing into the potable water supply due to negative
pressure
✔✔FOG - ✔✔Fats, Oil, and Grease. Congeal in system and cause blockages
✔✔Hydrogen Sulfide - ✔✔Sewer gas that smells like rotten eggs and:
is heavier than air
is explosive when mixed with air
is corrosive
✔✔Methane - ✔✔Sewer gas that is
Colorless
Odorless
Extremely flammable
Forms explosive mixture with air
Displaces oxygen
✔✔Septic Condition - ✔✔A condition in sewers resulting from gases produced by
anaerobic bacteria when sewage sits for too long
Characteristics
Foul odor
Black appearance
Little or no D.O.
High oxygen demand
✔✔Parshall Flume - ✔✔An open channel flow meter common in wastewater plants that
has a narrow throat
✔✔V-Notch Weirs - ✔✔An open channel flow meter used in wastewater plants to
measure small flows that is a "V" shape cut out of a weir
✔✔Perimeter - ✔✔The distance around an object, expressed in linear inches, feet,
yards, etc.
✔✔Area - ✔✔The amount of space enclosed by a boundary usually expressed in
square inches, square feet, etc.
✔✔Volume - ✔✔The amount of space enclosed by a three-dimensional object
expressed in cubic inches, cubic feet, cubic yards, etc
,✔✔Flow - ✔✔Volume per unit of time
✔✔Velocity (definition) - ✔✔the distance traveled per unit of time
✔✔Preliminary Treatment - ✔✔Prepares wastewater for downstream plant processes.
The main preliminary process are:
-Screening
-Shredding
-Grit Removal
-Preaeration
✔✔Screening - ✔✔Purpose is to remove large items from the wastestream
-Rags
-Sticks
✔✔Bar Rack - ✔✔AKA Trash Racks. Bars are 3-6 inches apart and angled back from
30-45 degrees
✔✔Bar Screen - ✔✔Bars are 3/4 - 2 inches apart and are angled back 15-30 degrees.
Channel width is 2-14 feet. There are two types: Manual and Mechanical
✔✔Head Loss - ✔✔The difference in height between the water level on the upstream
side of a bar screen and the downstream side of the bar screen.
✔✔Screenings - ✔✔Material removed from a bar screen or bar rack
✔✔Shredding - ✔✔Shred, grinding, or chop solids in the wastestream that could
interfere with downstream processes
✔✔Communitor - ✔✔Horizontal cutting "torpedo" drum with slots that the water must
pass through.
Vertical or horizontal cutting drums with teeth that pass through stationary or rotating
bars
✔✔Barminutor - ✔✔Similar to a mechanical bar screen
The "rakes" are rotating drums
✔✔Preaeration - ✔✔The addition of air before primary sedimentation
Common process to use during grit removal
✔✔Mechanical Aerator - ✔✔A mechanical device that splashes water into the air where
it absorbs oxygen
, ✔✔Diffused Aerator - ✔✔Blowers force air through a pipe into the wastestream
Pipes have a sock or plate at the end with tiny holes acting as the diffuser, breaking
apart the airstream into tiny bubbles
✔✔Cascade Aerator - ✔✔Series of steps water travels over causing it to splash so it
gets oxygen from the air
✔✔Grit - ✔✔Heavy, inorganic, particulate matter that does not readily decompose
(Sand, eggshells, cinders, coffee grounds)
✔✔Purpose of Grit Removal - ✔✔Remove the heavy, inorganic, particulate matter that
does not readily decompose from the wastestream
✔✔Hand-cleaned Grit Collector - ✔✔Typically used at very small plants, <1 MGD
Two elongated channels
Shovel out grit
✔✔Mechanically-cleaned Collector - ✔✔All are gravity-type, velocity controlled, cleaning
mechanism, grit removal system
Some are grit classifier, grit washer, aerators
✔✔Aerated Vortex - ✔✔Augments gravitational forces
Comprised of aerated vortex unit, may also go to either a grit classifier or grit washer
✔✔Grit Washing - ✔✔Washes organics from grit
-Reduce odor
-Improve removal efficiency
-Dispose of more easily
✔✔Grit Classifying - ✔✔Process used to dry grit
✔✔Primary Treatment - ✔✔Main Primary Process
-Settling tanks/clarifiers
-Fine screen
-Dissolved air floatation thickeners
✔✔Purpose of Primary Treatment - ✔✔Separate and remove the readily settleable and
floatable solids from the wastewater
✔✔Types of Primary Clarifiers - ✔✔-Circular
-Rectangular
✔✔Circular Clarifier - ✔✔-Inlet baffle
-Outlet baffle
