Table 7-3 (Cont'd).
Summary of solids handling and disposal
Aesthetic
Resource
Problems
Side Streams
Performance
Consumption
Operation
Economics
Potential odors if
Increases solid content Flotation is usually lower
Flotation requires closer Supernatant or sub-
Lower power use; flota-
A.
natant return must be
improperly operated.
tion is higher than
to the 4 to 6 percent in capital but higher in
operator attention,
gravity.
range
particularly if chemicals considered in design.
operating.
are used.
Produces combustible
Digested sludge readily Relatively high capital
B.
Improperly operated
Requires close operator
Supernatant return must
dewaters and is
units will produce
attention; subject to
be considered in design.
costs.
gas for the process and
stabilized for sub-
other uses; also produces
odors.
upsets with wide varia-
sequent disposal.
a soil conditioner.
tions In load.
c.
Digested sludge some-
Higher energy use than
Lower capital costs
Relatively free of upsets Surpernatant return must
Improperly operated
times difficult to de-
anaerobic digestion.
than anaerobic digestion,
Poor operation in cold
be considered in design.
units will produce
but operating costs are
water. Stabilized
climates. Simpler opera-
odors
higher.
sludge for subsequent
tion than anaerobic
disposals.
digestion.
D. Eliminates use of
High capital and operating
Large fuel use.
Odors may result
Skilled labor required
A major portion of
chemicals for con-
costs.
the sludge is resolubil-
with improper opera-
ditioning. Stabilizes
ized and is returned as
tion.
sludge for land dis-
a supernatant. This load
posal. Improved
must be considered in the
cake moisture.
liquid treatment faci-
lities design loading.
E. Proper dewatering can
Potential odors.
Underdrainage must be
Minimal power or
Normally poor winter
Usually lower costs than
returned to the plant.
be accomplished, but
chemical use. Large land
operation.
mechanical dewatering
is usually difficult
usage.
until large areas are
required.
to control since it
is weather dependent.
Power use high. Small
Filtrate return must be
High capital and
Odors for personnel
F. Sludge cake solids
Nearly continuous
be considered in design.
working in building
land area used.
operating costs.
operator attention
content: vacuum filter
with equipment.
required.
15 to 25 percent;
belt press 20 to
30 percent; filter
press 25 to 40
percent.
G. Renders a sterile ash
High capital and
Large fuel use. Dis-
Air emissions must be
Potential odor and
Skilled operators
regards other bene-
which can be readily
operating costs.
controlled, scrubber
particulates from
required.
ficial uses of the
disposed of on the
water return
exhaust gases If not
land. Air pollution
waste solids.
properly operated.
must be considered
control can be a
problem.
H. Suitable disposal tech-
Minimal fuel and land
None unless material
Potential odors If
Moderate costs. De-
Mixing with refuse is
nique with proper
use.
is improperly stabi-
improperly operated.
pendent on land values
desirable for efficient
facility siting and
lized or landfill is
in the specific area.
operation.
operation.
not properly located
or operated.
Suitable disposal tech- Moderate costs. Oe-
I.
Minimal fuel use.
Winter storage facil-
None unless material
Potential odors if
niques with proper
Moderate power use with
pendent on land values
ities are needed in
is Improperly stabil-
improperly operated.
facility siting and
in the specific area.
liquid spreading. High
cold climates. Applica-
ized or applied.
Use of large land
operation. Careful
land use, but solids
tion to the land is
areas for sludge
control of applica-
used beneficially as a
quite dependent on
disposal may be
tion rates and other
soil conditioner.
crops, soils, and
a problem in some
factors are particu-
weather.
areas.
larly important for
liquid sludge.
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