The Activated Sludge
Process has been employed for waste water
treatment for over one hundred years. Many
variations of the process have been employed
to optimize it for the specific applications.
Regardless of the specific configuration
of the process, the Activated Sludge Process
employs microorganisms to assimilate and
digest organic carbon compounds in the wastewater
. The microorganisms can range from simple
single cell bacteria to more complex life
forms such as protozoa.
Aeration is the
process by which air is circulated through,
mixed with or dissolved in a liquid or substance.
Aeration is the process by which the area
of contact between water and air is increased,
either by natural methods or by mechanical
devices. Aeration is one of the most elemental
techniques frequently employed in the improvement
of the physical and chemical characteristics
The role of aeration in the activated sludge
process is to provide oxygen to the microorganisms
as they assimilate the organic carbon compounds
and digest a portion of them to carbon dioxide
and water, Sulfate and Nitrate compounds.
The remaining waste solids are changed to
a form that can be settledand removed as
sludge by sedimentation.
Diffused Aeration:Diffused Aeration is
defined as the injection of air at bottom
of the aeration tank for transfer of oxygen
into the waste water.
be generally classified into:
Though there is no
specific industry / government standards
for differentiation between the two, but
one can generally say that a system which
delivers a bubble size of <
2mm is a fine
bubble aeration system and one which delivers
a bubble size of > 2mm
is a coarse bubble aeration
Fine bubble Diffused Aeration are listed
1. Delivers high
Oxygen Transfer Efficiencies.
2. Delivers high
Aeration Efficiencies (mass oxygen transferred
per unit power per unit time).
3. Suitable for high
4. Easily adaptable to existing
setups or for plant upgrades.
5. Flexibility of application
to various Tank Geometries (rectangular,
circular, L-shape etc).
5. Result in lower
Volatile Organic Compound Emissions than
coarse bubble diffusers or mechanical
aeration devices (surface aerators).