Page 497 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

452 Fundamentals of Water Treatment Unit Processes: Physical, Chemical, and Biological

Diatom: (1) Unicellular photosynthetic microscopic organ- Filter Cel: Natural milled DE for use in filtration (Cummins,
ism characterized by its silica shell. The products 1975, No. 16, p. 10); trademark granted in 1915.
of the photosynthesis include a fatty oil, which has Filtration: The process by which particles are separated from
a fishy odor, and is a nutritious food for microscopic a fluid by passing the fluid through a permeable
marine animals (Cummins, 1975, No. 2, p. 2.]. (2) material.
Diatom populations in the ocean vary with location Flow: The rate of flow of a given fluid across a given area
2
9
and season but average perhaps 7–8 10 =m . Dia- whose surface is normal to the velocity vectors of the
toms have the capacity to extract silica, which has a flow. Also called ‘‘flow rate,’’ ‘‘rate of flow,’’ etc.
solubility of up to 40 mg=L, as silicic acid and create Flux: A flow of something; for example, a fluid, a suspen-
a silica shell. Siliceous sediments are an end result. sion, electrons, a magnetic field, etc.
(3) ‘‘Beginning with curved outlines, we find among Hyflo Super-Cel: Trademark granted in 1925 (Cummins,
them perfect circles of all sizes, others passing into 1975, No. 16, p. 10).
oval, elliptical, crescent, serpentine, sigmoid, and Kieselguhr: A term first applied in 1808 to earth from the Isle
other curved contours with variations almost beyond de France and later became a applied generally to
number.’’ (Cummins, 1975, No. 17, p. 1). (4) Dia- include paste-like materials occurring in bogs and
toms are classified in the Kingdom Protista, Division other deposits because of its supposed resemblance
Chrysophyta, which has about 6000 species to a fermenting mass, that is, kiesel (silica) and
(Prescott et al., 1993, p. 536). The various species guhrer (to ferment). At that time, while the silica
of algae are grouped into seven ‘‘divisions,’’ of nature of the materials was known, the fact that it
which five are under the Kingdom Protista, and was primarily diatom residues was unknown. Later
two are under the Kingdom Plantae. in 1836, the nature of kieselguhr as fossil diatoms
Diatomaceous earth: Same as diatomite. Suggested as a term was established. The discovery that kieselguhr was
in 1860 as a substitute for kieselguhr (Cummins, diatoms then stimulated a search for deposits. Ger-
1975, No. 16, p. 2). man deposits near Hanover (Luneburger) were the
Diatomite: (1) A light friable siliceous material resembling most important until those of Lompoc reached full-
chalk that is derived chiefly from the remains of scale operation in 1922. [Foregoing from Cummins,
diatoms and is used as a filter aid, adsorbent, filler 1975, No. 1, pp. 1–6.]
(as for paints and plastics), and abrasive, and for Leaf: A plate-and-frame type of filter element that includes
thermal insulation—also calleddiatomaceous earth. the support structure and septum.
See also kieselguhr (http:==www.merriam-webster. Lompoc: Town in California and the site of one of the major
com=). (2) Diatomites are essentially SiO 2 , that is, diatomite deposits in the United States and worldwide.
about 90% and contain minor amounts of aluminum, Discovery was in 1888 (Cummins, 1975, No. 3, p. 7);
iron, calcium, magnesium, and traces of other elem- full commercial development was achieved by 1922.
ents. Al 2 O 3 varies from 2%–5% (Cummins, 1975, Thedeposits areamixtureof >300 species and are
No. 15, p. 12). (3) Preferred term, introduced about of marine origin.
1880, for the rock composed of diatom residues Mesh: Number of openings in a lineal inch of wire cloth.
(Cummins, 1975, No. 16, p. 3). Micron: A metric unit of length; 10 6 m.
Differential pressure: Pressure differential across the filter Particle size: The distribution obtained from a particle
cake, pre-coat, septum, and filter leaf, usually count grouped by specific micron sizes. Usually,
expressed as DP. particle size is expressed as some characteristic of
Dynamite: Explosive containing nitroglycerine with a solid the distribution obtained, for example, d10 (i.e., 10%
substance as an absorbent. Powdered diatomite was finer than the size stated), d50, etc.
established in 1863 by Alfred Nobel as a substance Perlite: A mediam used in the pre-coat filtration process.
that stabilized the nitroglycerine and made it rela- Perlite ore is formed from a volcanic magma flow
tively safe for use. of pure alumina silicate glass deposited onto the
Embed: See straining. surface of the earth where the molten mass cools
Feed: A mixture of particles and fluid that is introduced into and subsequently hydrates water. When perlite ore
the filter. Terms used synonymously include influ- is heated to 16008F–24008F, it becomes molten
ent, incoming slurry, and raw water. glass, and the water of hydration within each granule
Filter aid: (1) Term introduced in 1914 referring to is released as expanded water vapor. Accomplished
DE powders when employed for filtration and rapidly and under carefully controlled conditions,
clarification of liquids. Adopted by the Celite Co. this glass liquefaction=water vaporization event
shortly after (Cummins, 1975, No. 16, p. 3). (2) results in the virtually instantaneous formation of
Diatomaceous earth, volcanic ash, or other material partially fractured, low-density, multicellular par-
that may form a filter cake. [The term ‘‘filter aid’’ is ticles. Additional milling and classification operations
also used in rapid filtration by some to indicate a result in a variety of grades with well-defined poros-
coagulant.] ity and density to meet the needs of a wide variety of