Summary of solids handling and disposal
Table 7-3.
Preliminary
Major Equipment
App lication
Treatment Steps
Purpose
Required
Unit Processes
All plant sizes and sludge
None.
A. Thickening
Gravity or flotation equip-
Reduce volume handled in
types. Usually not used for
ment, tanks, usually covers
subsequent steps by re-
military plants since trick-
for flotation.
moval of water.
ling filter sludges predomi-
nate which are returned
to the primary.
9. Anaerobic Digestion
All plant sizes. Is particu-
Sometimes
thickening.
Tanks, covers, gas collec-
Biologically stabilizes
larlydesirable for military
tion equipment, heat ex-
and transforms sludge into
installation.
changers, and mixing
a material suitable for
equipment.
disposal on the land.
Sometimes
thickening.
Usually plants under 15 to
c.
Aerobic Digest< on
Tanks and aeration
Biologically stabilizes
20 mgd.
equipment.
and transforms sludge into
a material suitable for
disposal on the land.
Usually economical for
Must have a thickened
Thermal reactor, steam
Thermal Condit ioning/
D.
Thermally conditions sludge
plants larger than
sludge for economical
generating equipment, heat
for dewatering without
Stabilization
10 mgd.
operation.
exchangers, sludge, grinder,
chemicals and-stabilizes
pumps and piping, and
the material by heat dis-
decant tanks.
infection for subsequent
land disposal.
Usually plants under 1 mgd.
Must have digestion to
Land, sand and gravel beds,
E. Sludge Drying Beds
Reduces the sludge moisture
Limited to areas which have
avoid odors.
and underdrain system.
content for easier handling
sufficient land.
in final disposal, changes
sludge from a liquid to a
semi-solid.
May be used for raw or
Digestion, thermal con-
Filter units, pumps,
Mechanical Dewatering
Reduces the sludge moisture
F.
digested sludges. Equip-
ditioning or chemical
piping, conveyor equipment,
content for easier handling
ment selection dependent
conditioning, usually
chemical conditioning facili-
in final disposal, changes-
thickening.
on means of disposal
ties, and building.
sludge from a liquid to a
semi-solid.
Mainly for very large plants
Furnaces, feed and air
Dewatering.
Reduces hauling and final
G. Sludge Incineration
(over 10mgd) in metropoli-
blower equipment, ash
disposal land requirements.
ton areas where land is ex-
handling equipment, and
Provides acceptable material
tremely scarce and costly.
air pollution control
for disposal.
All plant sizes.
Stabilization and de-
Land and landfill equip-
H. Landfill
Dispose of sludge solids
watering
under soil cover in an
ment.
envirornmentally acceptable
manner.
Land Spreading
I.
Disposes of sludge solids
Land, pumping, piping,
Stabilization.
storage ponds, mixers,
on the land in an environ-
and spray equipment for
mentally acceptable manner.
liquid sludge; or tractors,
and solids storage and
spreading equipment for
dewatered sludge.
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