MIL-HDBK-1005/16
EPA 625/1/79/001. The relative advantages and disadvantages of
each pump type are presented below.
Table 17
Pump Selection
Type of Solids
Applicable Pump
Raw or digested primary
Centrifugal pump (torque-flow or
solids
screw feed type)
Plunger pump
Progressing cavity pump
Diaphragm pump (air operated)
Trickling filter biosolids
Centrifugal pump (torque-flow or
nonclog type)
Plunger pump
Progressing cavity pump
Raw or digested waste
Centrifugal pump (nonclog type)
activated sludge
Thickened waste activated
Progressing cavity pump
sludge
Scum
Progressing cavity pump
Centrifugal pump (cutter
or torque-flow type)
Peristaltic (hose) pump
Rotary lobe pump
Diaphragm pump
Plunger pump
10.4.1
Centrifugal Pumps. Standard centrifugal pumps are
generally not suitable for pumping solids streams because the
impellers are prone to clogging. In the torque-flow centrifugal
pump design, the impeller is recessed and imparts a vortex into
the fluid, which propels the flow without the impeller directly
contacting the solids stream. As a result, the pump is able to
pass solids as large as the suction and discharge piping,
although an upstream grinder is still recommended. Abrasive wear
is also not a significant problem with torque-flow pumps.
Torque-flow pumps are relatively inefficient, but they are
170
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