MIL-HDBK-1005/16
Section 10:
SOLIDS CONVEYANCE AND SOLIDS PRETREATMENT
10.
10.1
Introduction. Topics involved with solids handling and
disposal include characterization of the solids, pumping, piping,
pretreatment, conditioning, thickening, stabilization,
dewatering, storage, transport, and disposal. The WEF design
guidance set provides design information on all of these aspects
of solids handling and disposal. However, supplementary design
information was considered necessary for piping, pump selection
and design, and pretreatment (which includes grinding, screening,
degritting, blending, and storage). These topics are covered in
this section.
10.2
Data Requirements for Design of Solids Conveyance and
Pretreatment Systems. The following data are typically required
for designing solids conveyance and pretreatment systems:
a)
Solids production maximum, average, and minimum
rates and associated solids concentration ranges
b)
Characteristics of the solids with respect to
grit, abrasive materials, rags, plastics, and stringy material
content
10.3
Piping Design
10.3.1
Pipe Sizing. To minimize plugging problems, gravity
solids withdrawal lines should not be less than 8 inches (200 mm)
in diameter. Pressurized piping should be designed to provide
average flow velocities between 3 and 8 fps (0.9 and 2.4 m/s) but
should be no smaller than 4 inches (100 mm) in diameter to
minimize plugging. Some state regulations may require a minimum
of 6-inch (150-mm) diameter pipe (refer to Great Lakes-Upper
Mississippi River Board of State Public Health and Environmental
Managers, 1990). Note that for installations using positive
displacement pumps and producing pulsating flow rates, velocities
during the discharge stroke may range up to 15 fps (4.6 m/s).
10.3.2
Material Selection. Glass-lined ductile iron pipe is
the material of choice for pressurized pipe used for conveying
primary solids or scum. It is able to withstand high pressures
and is much smoother than unlined pipe. The glass is also more
resistant than plastic to abrasive material. Teflon-type
coatings may also be considered. In addition, plastic-lined
steel, iron, or Schedule 80 CPVC pipe can be used. For
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