Course TEN-702
Industrial waste management
unit-2
• Lecture -10
Pretreatment – Grit Removal
• Grit is typically removed during pretreatment at larger plants
– Grit can cause premature wear of equipment
– Becomes cleaning issue if not removed
• Aerated grit tanks and vortex systems are
common grit removal processes
• Grit removal systems typically employ a
classifier/washer
Pretreatment – Grit Removal
• Vortex grit unit
• Unit rotates to
suspend light
organics
• Heavy, dense grit
settles to bottom
Pretreatment – Grit Removal
• Grit removal requires “hardened” pump
• Classifier and washer
• Washed material into dumpster
Pretreatment – Grit Removal
• Aerated grit
tank
• Diffused air
suspends light
weight
organics
• Heavy, dense
grit settles to
bottom of tank
• Submersible
pump in tank
Pretreatment – Grit Removal
• Aerated grit
tank also has
classifier and
washer
• Note that
washed grit is
deposited to
screw
conveyor
Pretreatment - Equalization
• Some sanitary collection systems have
high levels of infiltration and inflow (I/I)
that result in excessive peak flows
– I/I is storm water and ground water that
enters sanitary system
– Present in all systems, but can be excessive
• Removing I/I is difficult, and best solution
may be to build Equalization tank
Pretreatment - Equalization
• Influent
EQ
Basin
Pretreatment – Odor Control
• Raw wastewater is often odorous,
usually due to the lack of dissolved
oxygen
• Covered channels and tanks often
control odor sufficiently
• Pretreatment Buildings are ventilated
and can be source of odor.
• Odor control equipment is used to limit
odors from the Pretreatment Building,
and from tanks
Pretreatment – Odor Control
• Activated carbon systems are common
• Biofilters can be used
• Chemical addition sometimes used
reduce odor potential from downstream
additions
Pretreatment – Odor Control
• Activated
carbon odor
control
equipment
• Odorous
compounds
adsorb to the
activated
carbon
Pretreatment – Chem. Addition
• Chemical addition for pH control
• Nutrient addition for industrial
wastewaters
Assignment-3
• Why is equilization necessary in a
wastewater treatment plant.? With
appropriate diagrams describe the
difference between on-line and off-line
equilization.
On line/off line equalization
QU
QU
Equilization
Tank
QS
QS
Equilization Tank
On-Line Equalization:
Variable flow, QU is influent to the
equalization tank.? However, a steady
flow QS is effluent from this tank.?
When QU>QS, excess wastewater is
stored in the tank.? When QU<QS, the
deficit is made up from the wastewater
stored in the tank.
Off-line Equalization
When QU > QS, the difference, i.e.,
QU-QS is stored in the
equalization tank.? When QU <
QS, the difference, i.e., QS-QU is
supplied from the equalization
tank.
In next lecture we will primary clarifier in detail
thanks!