MIL-HDBK-1005/16
6.7.1
Garbage Grinders. Garbage grinders are commonly used to
dispose of large portions of solid waste created by food service
facilities. Such facilities have created problems in the
wastewater collection and treatment systems serving military
housing areas. Garbage grinders that discharge into public
wastewater collection and treatment facilities generally present
few problems. However, when discharge is to a relatively small
package wastewater treatment plant, a lagoon system, or especially
to septic tank and soil absorption/leach field systems, problems
can occur. These problems include overloading of the treatment
system, clogging of sewer lines or leach field distribution lines,
and grease ball formation in the collection and treatment systems.
Designers should discourage the use of garbage grinders for users
discharging into small flow treatment systems.
6.7.2
Grinder Pumps. Grinder pumps are appropriate for use
where small flows (less than 200 gpm) are encountered and where a
high degree of solids is discharged into a package-type activated
sludge wastewater treatment plant. Typically a grinder would be
used to serve one or two facilities or residences and to pump the
wastewater into a larger force main or into a gravity system
feeding a package plant system. Grinder pumps are not
recommended for systems that discharge to septic tank and other
small flow treatment systems since they may suffer from the same
problems that garbage grinders can cause.
For larger systems, the grinder pump station should be
equipped with all the features of a larger pump station. It
should be a duplex system with alternating pumps for reliability
operating on a float control system. The control panel should be
protected against lightning strikes, have remote alarm capability
and an emergency generator connect capability. Grinder pumps
shall be manufactured with all metal components and have high-
strength, reversible cutter rings. Grinder pumps should be
equipped with a quick-disconnect, lift-out assembly so pumps can
be removed without the need for disconnecting the discharge
piping or for entering the wet well.
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