TM 5-814-8
ment plan may be dictated by the need to expand
conditioning methods include:
--Polymer addition.
the solids processing facilities.
--Inorganic chemical addition.
c. Solids disposal alternatives. The two most
feasible methods for disposing of sewage solids
--Heat treatment.
Ash addition.
from military installations include sanitary land-
fill and land spreading.
(a) Chemical conditioning requirements. Ta-
ble 8-3 lists the common types of chemicals used
(1) Landfill. Disposing of dewatered sewage
for conditioning sludge and enumerates a range of
sludge with refuse in a sanitary landfill is nor-
dosages common for various types of sludge.
mally an economical operation. Sewage solids
tend to sift among the voids in compacted refuse,
Table 8-3. Chemical conditioning requirements for
and nominal land savings are achieved. Combin-
various sludge types (167)
ing the two waste materials at one facility is also
FeCl3
Ca(OH) z
Polymers
desirable from a management standpoint.
lb/ton
lb/ton
lb/ton
Sludge Type
dry solids dry solids dry solids
(2) Landfarm. Land spreading dewatered sew-
age sludge is currently used by several military
Raw Primary
20-60
0-100
3-5
Primary & Activated
operations and is a cost-effective alternative to
Sludge
80-160
0-300
6-15
sanitary landfill. The land spreading technique
Activated Sludge
100-300
120-200
8-25
can be utilized for either liquid or dewatered
Digested Primary
40-60
60-160
3-8
sludge, but the sludge must be stabilized; raw
Digested Primary &
sludge application is unacceptable. This disposal
Activated Sludge
100-300
120-200
6-20
method effectively utilizes the soil conditioning
(b) Heat treatment. Heat treatment of
characteristics of the sewage solids. Proper moni-
sludge uses a combination of temperature, time
toring and close attention to procedures employed
and pressure to condition a sludge without the
during spreading are required to avoid potential
use of chemicals. The process significantly
environmental difficulties. Land requirements for
changes the characteristics of the sludge by
spreading are greater than landfill; consequently,
breaking down the cellular matter and releasing a
this method is feasible only where sufficient land
major portion of the water in the cell mass. The
area is available.
dewaterability is improved by reducing the spe-
d. System performance.
cific resistance to the sludge for filtering. Temper-
(1) Introduction. The performance of solids
atures in the range of 350 to 450 degrees F and
handling systems is dependent upon many vari-
pressures in the range of 200 to 500 psig are
ables including: solids loading, operation, chemical
generally required. Additional information con-
addition, equipment maintenance and waste char-
cerning the design of a heat treatment system
acteristics. These variables will greatly affect the
can be found in the literature (10)(11) (167).
output of the unit and should be considered when
(c) Ash addition. Ash is primarily used as a
designing the system and when comparing perfor-
filler to reduce chemical addition requirements
mance data from similar type units. The perfor-
and improve the dewatering characteristics of the
mance and general design criteria discussed below
sludge. Generally, ash is used to improve the cake
are recorded average values and should be used
release from belt or filter presses and improve the
as guidelines in preparation of design documents
dewatering of sludge in a vacuum filter. Depend-
or in reviewing the performance of an existing
ing on the type of ash available, a hydrolysis
facility. Bench scale testing or jar tests are
between free water in the sludge and ash will
recommended to determine the optimum operat-
result in a dryer cake. Bench scale tests are
ing point or quantity of chemical required. For
recommended to determine the optimum dosage
additional information, refer to the U.S. EPA
of ash because excess quantities may only result
Process Design Manual, "Sludge Treatment and
in an increased volume of sludge without any
Disposal". For additional description of the types
additional improvement in the dewaterability.
of solids handling systems available, refer to
(3) Thickening. Sludge thickening can be ac-
chapter 7.
complished by a variety of methods. These meth-
(2) Conditioning and stabilization. Sludge
ods have been discussed in Chapter 7 and include:
conditioning is generally described as a pretreat-
gravity, air flotation and centrification. Table 8-4
ment of sludge to improve water removal by a
summarizes typical performance data for these
method of thickening or dewatering. Common
processes for different types of sludges.
8-12
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