Environmental Engineering Reference
In-Depth Information
Aeration tank
Settling tank
Air
Activated sludge
figure 8.1 The activated sludge process.
8.1 aCTivaTed sludge TerMinology
To better understand the discussion of the activated sludge process
presented in the following sections, it is necessary to understand the
terms associated with the process. Some of these terms have been used
and defined earlier in the text, but we include them here again to refresh
your memory. Review these terms and remember them, as they are used
throughout the discussion.
absorption—
Taking in or reception of one substance into the body of
another by molecular or chemical actions and distribution through-
out the absorber.
activated—
Refers to speeding up a reaction. When applied to sludge,
it means that many aerobic bacteria and other microorganisms are
in the sludge particles.
activated sludge—
A floc or solid formed by the microorganisms. It
includes organisms, accumulated food materials, and waste prod-
ucts from the aerobic decomposition process.
activated sludge process—
A biological wastewater treatment process
in which a mixture or influent and activated sludge are agitated and
aerated. The activated sludge is subsequently separated from the
treated mixed liquor by sedimentation and is returned to the pro-
cess as needed. The treated wastewater overflows the weir of the
settling tank in which separation from the sludge takes place.
adsorption—
The adherence of dissolved, colloidal, or finely divided
solids to the surface of solid bodies when they are brought into
contact.
aeration—
Mixing air and a liquid by one of the following methods:
spraying the liquid in the air, diffusing air into the liquid, or agitat-
ing the liquid to promote surface adsorption of air.
aerobic—
A condition in which free or dissolved oxygen is present in
the aquatic environment. Aerobic organisms must be in the pres-
ence of dissolved oxygen to be active.
Bacteria—
Single-cell plants that play a vital role in the stabilization
of organic waste.
