Page 496 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

Cake Filtration 451

and involved a pilot plant study as well as the survey; the convert to a powder or to a friable state by heating,
three reports for the city are listed in references. Todd Rogers, (b) to heat in order to drive off volatile matter (as
PE, then with Nolte, obtained the data from operating plants; carbon dioxide from limestone, ores, or concentrates,
see also an interim report by Rogers (1997). or chemically combined water from clay) (http:==
Walter Pavlakovich, technical services and marketing www.unabridged.merriam-webster). (2) The process
manager, Celite Corp=World Minerals Inc. (a division of used in manufacturing diatomaceous earth by melt-
Imerys Corp.), Lompoc, California, provided photographs ing and fusing particles.
and data that were used as cited. Pavlakovich reviewed the Celite: Registered trademark, 1915. In 1917, the corporate
manuscript and made several corrections, which improved name was changed from Kieselguhr of America to
accuracy, and provided material on cellulose and perlite, the Celite Products Co. The term Celite was applied
which was added to the Glossary. George Christoferson not only to the company but was used as a name for
(retired from Celite Corp=World Minerals Inc.) provided the the DE of the Lompoc deposit; this latter usage was
photographs of the mining operations (Figure 14.4 used in the abandoned, however, as it was recognized as being
2006 edition and in this revision). restrictive (Cummins, 1975, No. 16, p. 10).
O. Alan Wirsig, formerly with Johns-Manville and later Cellulose: (1) Fibrous material of vegetable origin (Celite=
principal of Alan Wirsig Engineering, gave permission to use World Minerals Brochure FA-84A, 2010). (2) Cel-
correspondence material from his work with communities in lulose fibers bridge rapidly on coarse septum to form
Colorado and to use his image in Box 14.2. The late Ray a firmer pre-coat. Additionally, cellulose forms
McIndoe, formerly with Johns-Manville, gave permission, stronger cakes less likely to be disturbed by pressure
c. 2002, to use his image in Box 14.2 and to summarize his changes. Filtration fibers are made from both hard-
career in diatomite filtration. wood and softwood pulp in both bleached and
Ascension Industries (Durco Filters by Ascension), North unbleached grades.
Tonawanda, New York, gave permission to use a photograph Table 14.G.1 lists important properties of Fiber-
of one of their units, downloaded from their website, www. Celt Cellulose (Manufactured by International Fiber
asmfab.com, and material from one of their catalogs as cited Corp, Tonawanda, New York and sold by Celite=
in Table 14.4. Bruce Hindle, director of filtration services, World Minerals Inc.) in descending order of particle
provided updated references for Durco filter products. size, which corresponds to decreasing permeability.

GLOSSARY
TABLE 14.G.1
Adsorption: As related to filtration, the particles to be Typical Properties of Fiber-Cel Cellulose Filter Aid
removed become attached to the media grains (see
Fiber Length Permeability Bulk Density Through 200
Section 12.3.3.4).
3
Grade (mm) (Darcy’s) (lb=ft ) Mesh (%)
Air bump: A pulse of air pressure to dislodge the filter cake
from the septum at the end of the filtration cycle. SW5 120 20 7 15
Asbestiform fibers: A term for an asbestos fiber found in L. SW10 120 16 8 20
Superior near Diluth at levels to 17 million fibers=L BH 100 9 9 35
for total fibers. Other kinds of fibers include amphi- BH 65 6.5 12 40
bole and chrysotile. BH 40 3.5 16 70
Blinding: Particle concentration at a surface causing inordin- BH 35 2.5 18 75
BH 30 2 18 85
ate increase in headloss.
Bridging: Joining of two or more particles by arching over
Source: Courtesy of Walter Pavlakovich, Celite Corp=World Minerals Inc.
individual openings in the filter septum or between (a division of Imerys Corp.), Lompoc, CA.
the individual filter elements.
Body feed: Continuous flux of DE into the raw-water flow
that results in particles to be removed becoming
embedded in the filter cake and a linear rate of head- Cycle: Filtration interval, length of time filter operates before
loss increase. cleaning.
Cake: A layer of filter media on the septum that develops due Darcy: A permeability of 1 darcy permits a flow of 1 mL of
2
to body feed, after the pre-coat but the pre-coat and liquid of 1 centipoise viscosity through 1 cm of
the body-feed cake are referred to collectively as the porous solid 1 cm thick under a differential pressure
‘‘cake’’ or the ‘‘filter cake.’’ of 1 atm in 1 s (Bell, 1962, p. 1247). Darcy ¼ 0.987
2
Cake filtration: Filtration through the layer of filter media, 10 12 m . See also Equation E.5 and Appendix E—
that is, filter cake, that has developed on the septum. Glossary.
Calcined: (1) To heat (as inorganic materials) to a high Detection limit: The minimum concentration of an organism
temperature but without fusing in order to effect or chemical that can be detected by the given sampling
useful physical and chemical changes such as (a) to protocol and particular analysis procedure.