23 JULY 2003
typically consists of an additional layer of media, impregnation with a coating, or
insertion of a different material. However, if reinforcement is used, the thickness at all
locations should be uniform to alleviate the potential of plate deflection or blowouts.
e. The attachment of the cloth to the plates is also an important aspect of filter
media construction. The non-gasketed type of filter media are placed on the faces of the
plate and fastened through grommets located around the perimeter with ties to the filter
media on the opposite side of the plate. A sewn loop is typically attached to the top
edge of the filter media through which a rod is inserted to provide uniform support of the
filter media across the press.
f. Filter media can also be attached to the plates using a gasket at the perime-
ter of the recessed area. The advantage of the gasketed filter media plate is less leak-
age than the non-gasketed plate because of the seal created around the recessed
chamber and filtration ports.
2-8.1.2 Filter Press Accessories and Auxiliary Systems. The following
subparagraphs provide an overview of construction materials for filter press accessories
and auxiliary systems. Additional information is presented in WEF (1992).
2-18.104.22.168 Chemical Feed Systems. Chemical feed systems associated with filter
presses primarily are those related to sludge conditioning, such as lime, ferric chloride,
and polymers. Scaling and corrosion are the primary design concerns for construction
materials for facilities handling conditioning chemicals, such as lime and ferric chloride.
a. Although not corrosive, lime slurry tends to cake and line piping systems
with calcium carbonate scale. To reduce maintenance of the facilities, the distance from
the lime slurry day tank to the sludge conditioning tank should be minimized and flexible
hose with quick disconnects should be utilized for piping. Most materials that are
standard for industry, such as carbon steel, are suitable for tanks and piping handling
b. Because the ferric chloride solution may range in pH from 3 to 5, appropri-
ate materials should be considered. For storage tanks, suitable materials of construction
include most plastics, fiberglass with vinyl or polyester resin material, titanium, and
rubber-lined steel. For piping and equipment, suitable materials include chlorinated
polyvinyl chloride (CPVC), polyvinyl chloride (PVC), polypropylene, hypalon, and neo-
c. Polymers are not corrosive, therefore, suitable construction materials
include PVC, fiberglass reinforced plastic (FRP), and stainless steel.
2-22.214.171.124 Other Auxiliary Systems. Other auxiliary equipment with specific material
construction considerations includes sludge storage, sludge conditioning, precoat, and
filter media wash systems.