UFC 3-280-03
23 JULY 2003
2-2.3
Common Principles of Operation. For either type of press, the filtration cy-
cle is complete when minimum filtrate flow is achieved or the cycle time is completed, or
both. Before the plates are separated to remove the sludge cake, the sludge pump is
stopped, and core blowing may be done. Core and air blowing are commonly used and
recommended options that may be required for filter press systems, except those with
smaller presses, those with limited operation, or those for non-HTRW sites. Core and air
blowing, applying compressed air to remove liquid sludge from the feed and filtrate
ports, keeps unprocessed or wet sludge from running over the plates when they are
separated and blinding filter media. A manual or automatic mechanical plate shifting
device then controls the cake removal by separating the plates one at a time. For the
fixed-volume press, the sludge cake is removed primarily by gravity onto sludge
handling facilities located below the press. Sludge cake removal from the variable-
volume press may be enhanced by a mechanical system that shifts the filter cloth
around the bottom of each plate and then back into place when the plate is separated.
After the press is opened, the cake is typically dropped from the chambers through cake
breakers to break the rigid cake into a more easily handled form. After the cake is
removed, filter media may be periodically washed to remove residual particles bound to
them by the high pressures incurred during the filter cycle. If lime is used to condition
the sludge before it is fed into the filter press, acid washing may also be periodically
necessary to remove lime scale.
2-2.4
Overview of Filter Press Dewater System. The major components of the
recessed filter plate are the frame, plates, filter cloth, plate closing mechanism, and
plate shifting mechanism. These components are discussed in detail in Paragraph 2-
4.7. In addition to the primary components listed above for the recessed plate and frame
system, the following processes and associated accessories and auxiliary equipment
are used to support its operation: liquid sludge transfer, chemical conditioning, filter
precoating, filter media washing, and sludge cake and filtrate management.
Descriptions and design considerations for these auxiliary components are presented in
Paragraph 2-4.
2-3
FILTER PRESS APPLICABILITY. This paragraph presents a concise over-
view of sludge characteristics and dewatering system options, a comparison of filter
press applications versus other dewatering processes, and typical filter press perform-
ance data.
2-3.1
Sludge Characteristics and Dewatering Systems Options. Sludge proper-
ties to be considered when selecting a sludge processing system include the origin and
type of sludge, the quantity of sludge generated, moisture content, percent solids, and
chemical composition and biological properties of the sludge, including biodegradability,
specific gravity, rheological properties, dewatering properties, and suitability for use or
disposal without further processing.
2-3.1.1 Sludge production primarily depends on the point at which it is generated and
the mechanism and treatment process used. Typical sludges generated from water
treatment processes can be categorized as primary sludge, biological sludge, and
2-9
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