TEXAS WASTEWATER D FINAL EXAM ACTUAL QUESTIONS
AND SOLUTIONS RATED A+
✔✔Dissolved Oxygen Determination - ✔✔Dissolved oxygen can be determined by the
Azide modification of the Winkler titration method.
✔✔Sample Preservation for Dissolved Oxygen - ✔✔When preserved with sulfuric acid,
a sample collected for dissolved oxygen can wait up to 8 hour(s) before analysis when
using the Winkler method.
✔✔BOD Sample Preservation - ✔✔Samples collected for BOD analysis can be
preserved by refrigerating between 0 and 4 degrees Celsius.
✔✔Preserved BOD Sample Holding Time - ✔✔Preserved BOD samples can be held for
2 days.
✔✔BOD Samples for Process Control - ✔✔BOD samples are generally not used for
process control since the test takes 5 days to complete.
✔✔Suspended Solids Sample Holding Time - ✔✔Samples collected for suspended
solids can be preserved and held for 7 days before analysis.
✔✔Beaker - ✔✔A beaker is used in the laboratory for measuring approximate volumes
and mixing chemicals.
✔✔Graduated Cylinder - ✔✔A graduated cylinder can be used to quickly measure and
pour various liquid volumes.
✔✔Chlorine Residual Analysis - ✔✔Chlorine residual should be analyzed immediately
after sample collection.
✔✔Pipette - ✔✔A pipette is used to accurately measure small volumes of liquid in a
laboratory.
✔✔Comminution - ✔✔A mechanical treatment process which cuts large pieces of
wastes into smaller pieces so they won't plug pipes or damage equipment.
✔✔Detritus - ✔✔The heavy, coarse mixture of grit and organic material carried by
wastewater. Also called grit.
✔✔Grit - ✔✔The heavy material present in wastewater, such as sand, coffee grounds,
eggshells, gravel and cinders.
,✔✔Grit Classifier - ✔✔A grit classifier separates and removes organic waste from the
grit that has been removed from the grit channel.
✔✔Hydrogen Sulfide Gas (H2S) - ✔✔Hydrogen sulfide is a gas with a rotten egg odor,
produced under anaerobic conditions, dangerous because it dulls the sense of smell, is
very poisonous to the respiratory system, explosive, flammable, colorless and heavier
than air.
✔✔Inorganic Waste - ✔✔Waste material such as sand, salt, iron, calcium, and other
mineral materials which are only slightly affected by the action of organisms.
✔✔Organic Waste - ✔✔Waste material which comes mainly from animal or plant
sources and can generally be consumed by bacteria and other small organisms.
✔✔Rack - ✔✔Evenly spaced parallel metal bars or rods spaced 2 to 6 inches apart
located in the influent channel to remove rags, rocks, and cans from wastewater.
✔✔Screen - ✔✔A device used to retain or remove suspended or floating objects in
wastewater. The screen has openings that are generally uniform in size, ranging from
0.75 to 2 inches.
✔✔Parshall Flume - ✔✔A flow measuring device that is made of an open channel that
narrows and widens. Flow is measured by water depth in the narrow portion of the
channel.
✔✔Grit - ✔✔Composed of primarily inorganic material that does not decompose during
the biological treatment process.
✔✔Grit removal - ✔✔Grit is removed since it will not breakdown in the anaerobic
digester and to prevent equipment damage in downstream processes.
✔✔Comminutor - ✔✔A device that shreds solids from the wastewater and passes them
to the next process.
✔✔Screens installation - ✔✔Screens are installed to remove large debris at the plant
headworks.
✔✔Organic waste settling - ✔✔If wastewater is allowed to "back up" behind a screen,
organic waste can settle out and cause odor problems.
✔✔Grit classifier - ✔✔A device that separates and removes organic waste from the grit
that has been removed from the grit channel.
, ✔✔Flow velocity in grit channel - ✔✔Organic waste mixed with the grit indicates that
flow velocities are too low in the grit channel.
✔✔Grit disposal - ✔✔Grit is typically disposed of by burial in a landfill.
✔✔Hydrogen sulfide - ✔✔A gas that smells like rotten eggs, is heavier than air, dulls the
sense of smell, is extremely toxic, and is explosive at certain concentrations in air.
✔✔Heavy rainfall impact - ✔✔Periods of heavy rainfall will deliver wastewater with high
levels of grit in systems that experience infiltration and inflow in the collection system.
✔✔Grit removal timing - ✔✔Grit is removed early in the treatment process since it can
damage pumps, and cause problems in pipes and digesters.
✔✔Trash Racks (Bar Racks) - ✔✔Constructed of steel bars spaced 2 to 6 inches apart,
placed in a flow channel at an angle ranging from 30 degrees to 45 degrees from
vertical.
✔✔Bar screens - ✔✔Similar to bar racks except the spacing between the bars is
smaller, ranging from 0.75 to 2 inches.
✔✔Grit channel flow rate - ✔✔Flow through the grit channel should be approximately 1
ft/sec.
✔✔Normal grit channel flow range - ✔✔The normal range of grit channel flow is 0.7 fps
to 1.4 fps to keep organic material suspended while allowing the grit to settle.
✔✔Grit classifier purpose - ✔✔The purpose of a grit classifier is to remove organic
material from the grit.
✔✔Screening press - ✔✔Reduces the volume and weight of screening waste sent to
the landfill since it dewaters and compacts screening waste.
✔✔Fine screens - ✔✔Collect more organic waste than larger, more coarse screens,
which can cause odor problems.
✔✔Coagulants - ✔✔Chemicals that cause very fine particles to clump (flock) together
into larger particles, making it easier to separate the solids from the water.
✔✔Flocculation - ✔✔The gathering together of fine particles after coagulation to form
larger particles by a process of gentle mixing.
✔✔Colloids - ✔✔Very small, finely divided solids that remain dispersed in a liquid for a
long time due to their small size and electrical charge.
AND SOLUTIONS RATED A+
✔✔Dissolved Oxygen Determination - ✔✔Dissolved oxygen can be determined by the
Azide modification of the Winkler titration method.
✔✔Sample Preservation for Dissolved Oxygen - ✔✔When preserved with sulfuric acid,
a sample collected for dissolved oxygen can wait up to 8 hour(s) before analysis when
using the Winkler method.
✔✔BOD Sample Preservation - ✔✔Samples collected for BOD analysis can be
preserved by refrigerating between 0 and 4 degrees Celsius.
✔✔Preserved BOD Sample Holding Time - ✔✔Preserved BOD samples can be held for
2 days.
✔✔BOD Samples for Process Control - ✔✔BOD samples are generally not used for
process control since the test takes 5 days to complete.
✔✔Suspended Solids Sample Holding Time - ✔✔Samples collected for suspended
solids can be preserved and held for 7 days before analysis.
✔✔Beaker - ✔✔A beaker is used in the laboratory for measuring approximate volumes
and mixing chemicals.
✔✔Graduated Cylinder - ✔✔A graduated cylinder can be used to quickly measure and
pour various liquid volumes.
✔✔Chlorine Residual Analysis - ✔✔Chlorine residual should be analyzed immediately
after sample collection.
✔✔Pipette - ✔✔A pipette is used to accurately measure small volumes of liquid in a
laboratory.
✔✔Comminution - ✔✔A mechanical treatment process which cuts large pieces of
wastes into smaller pieces so they won't plug pipes or damage equipment.
✔✔Detritus - ✔✔The heavy, coarse mixture of grit and organic material carried by
wastewater. Also called grit.
✔✔Grit - ✔✔The heavy material present in wastewater, such as sand, coffee grounds,
eggshells, gravel and cinders.
,✔✔Grit Classifier - ✔✔A grit classifier separates and removes organic waste from the
grit that has been removed from the grit channel.
✔✔Hydrogen Sulfide Gas (H2S) - ✔✔Hydrogen sulfide is a gas with a rotten egg odor,
produced under anaerobic conditions, dangerous because it dulls the sense of smell, is
very poisonous to the respiratory system, explosive, flammable, colorless and heavier
than air.
✔✔Inorganic Waste - ✔✔Waste material such as sand, salt, iron, calcium, and other
mineral materials which are only slightly affected by the action of organisms.
✔✔Organic Waste - ✔✔Waste material which comes mainly from animal or plant
sources and can generally be consumed by bacteria and other small organisms.
✔✔Rack - ✔✔Evenly spaced parallel metal bars or rods spaced 2 to 6 inches apart
located in the influent channel to remove rags, rocks, and cans from wastewater.
✔✔Screen - ✔✔A device used to retain or remove suspended or floating objects in
wastewater. The screen has openings that are generally uniform in size, ranging from
0.75 to 2 inches.
✔✔Parshall Flume - ✔✔A flow measuring device that is made of an open channel that
narrows and widens. Flow is measured by water depth in the narrow portion of the
channel.
✔✔Grit - ✔✔Composed of primarily inorganic material that does not decompose during
the biological treatment process.
✔✔Grit removal - ✔✔Grit is removed since it will not breakdown in the anaerobic
digester and to prevent equipment damage in downstream processes.
✔✔Comminutor - ✔✔A device that shreds solids from the wastewater and passes them
to the next process.
✔✔Screens installation - ✔✔Screens are installed to remove large debris at the plant
headworks.
✔✔Organic waste settling - ✔✔If wastewater is allowed to "back up" behind a screen,
organic waste can settle out and cause odor problems.
✔✔Grit classifier - ✔✔A device that separates and removes organic waste from the grit
that has been removed from the grit channel.
, ✔✔Flow velocity in grit channel - ✔✔Organic waste mixed with the grit indicates that
flow velocities are too low in the grit channel.
✔✔Grit disposal - ✔✔Grit is typically disposed of by burial in a landfill.
✔✔Hydrogen sulfide - ✔✔A gas that smells like rotten eggs, is heavier than air, dulls the
sense of smell, is extremely toxic, and is explosive at certain concentrations in air.
✔✔Heavy rainfall impact - ✔✔Periods of heavy rainfall will deliver wastewater with high
levels of grit in systems that experience infiltration and inflow in the collection system.
✔✔Grit removal timing - ✔✔Grit is removed early in the treatment process since it can
damage pumps, and cause problems in pipes and digesters.
✔✔Trash Racks (Bar Racks) - ✔✔Constructed of steel bars spaced 2 to 6 inches apart,
placed in a flow channel at an angle ranging from 30 degrees to 45 degrees from
vertical.
✔✔Bar screens - ✔✔Similar to bar racks except the spacing between the bars is
smaller, ranging from 0.75 to 2 inches.
✔✔Grit channel flow rate - ✔✔Flow through the grit channel should be approximately 1
ft/sec.
✔✔Normal grit channel flow range - ✔✔The normal range of grit channel flow is 0.7 fps
to 1.4 fps to keep organic material suspended while allowing the grit to settle.
✔✔Grit classifier purpose - ✔✔The purpose of a grit classifier is to remove organic
material from the grit.
✔✔Screening press - ✔✔Reduces the volume and weight of screening waste sent to
the landfill since it dewaters and compacts screening waste.
✔✔Fine screens - ✔✔Collect more organic waste than larger, more coarse screens,
which can cause odor problems.
✔✔Coagulants - ✔✔Chemicals that cause very fine particles to clump (flock) together
into larger particles, making it easier to separate the solids from the water.
✔✔Flocculation - ✔✔The gathering together of fine particles after coagulation to form
larger particles by a process of gentle mixing.
✔✔Colloids - ✔✔Very small, finely divided solids that remain dispersed in a liquid for a
long time due to their small size and electrical charge.
