UFC 3-280-03
23 JULY 2003
and it does not require any special storage conditions. However, it is more expensive
and less available than quick lime.
c. Lime handling systems typically include storage and processing equipment,
lime slurry and day tanks equipped with mechanical mixers, and feed pumps to transfer
the slurry from the day tank to the conditioning system. The feed pumps used for
transferring the lime slurry should be capable of handling concentrations ranging from 5
to 25% solids (WPCF 1983). Diaphragm-type and plunger-type meter pumps and
progressive cavity pumps are typically used. Potential scaling in transfer lines and
equipment should be prevented.
2-4.6.1.2 Ferric Chloride Feed Systems. Ferric chloride handling equipment typically
consists of a bulk storage tank, a dilution tank, and feed pumps to transfer the dilute
ferric chloride solution to the sludge conditioning system. Ferric chloride can be stored
for long periods without deterioration. It is typically stored in aboveground tanks con-
structed of resistant plastic or in lined steel tanks. At temperatures lower than 0
degrees C (32 degrees F), ferric chloride solutions can crystallize. Therefore, tanks
must be stored indoors or heated. Because of the corrosive nature of ferric chloride,
only components made of special materials must be used, including epoxy, rubber,
ceramic, PVC, and vinyl. Provisions should also be taken to avoid direct skin contact
with ferric chloride.
Ferric chloride is usually fed to filter press conditioning systems in a solution
ranging between 10 and 20%. Although ferric chloride is typically available in
commercial strengths between 38 and 42%, direct addition of commercial strength ferric
chloride to sludge may liberate heat and cause splatter. In addition, the costs would be
high. The feed pumps need to be capable of handling ferric chloride solution
concentrations ranging from 10 to 42% (WPCF 1983). For this application, diaphragm-
type metering pumps, chemical gear-type pumps, and progressive cavity pumps are
typically used.
2-4.6.1.3 Polymer Feed Systems. As described in Subparagraph 2-4.4.5, the poly-
mers typically used in filter presses are dry and liquid polymers. A brief discussion of
feed systems for these types of polymers will be presented in the subparagraphs that
follow. Typically, the dry polymer systems are used because they are more economical
than the liquid polymer systems, although some facilities are built with both types to add
versatility. More detailed information on polymer feed and preparation systems, in addi-
tion to feed systems for other polymer types (i.e., emulsion, gel, Mannich polymers), is
presented in the publication Design of Municipal Wastewater Treatment Plants--Manual
of Practice No. 8 (WEF 1992).
a. Dry Polymer Feed Systems. Dry polymers are typically available in 22-kg
(50-lb) double-walled paper bags or polyethylene bags. Dry polymers can also be sup-
plied in 820-kg (1800-lb) bags or in bulk shipments. However, this is not usually
desirable because dry polymers should be stored in a dry, cool, low-humidity area and
usually have a shelf life of only 15 to 30 days. Because dust may develop when the
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