Page 278 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

Coagulation 233

Lyophilic colloid: The attraction between the colloid and the Nonionic polymer: A polymer without ionizable groups and
dispersing medium (e.g., water) is large (Black, thus zero charge.
1948, p. 143). Orthokinetic flocculation: (1) Langelier and Ludwig (1949,
Lyophobic colloid: The attraction between the colloid and p. 165) introduced the terms perikinetic flocculation
the dispersing medium (e.g., water) is small (Black, and orthokinetic flocculation, taken from the field
1948, p. 143). of soil chemistry, to mean, respectively, aggregation
Masking agent: Ligand that reduces the concentration of the of flocs as permitted by neutralization of zeta
hydrated metal ion to a point at which the metal ion potential of colloids and aggregation of flocs as
does not significantly participate in a metal ion reac- caused by enmeshment with other flocs and colloids.
tion because a stable complex has been formed (2) Argaman and Kaufman (1968) gave definitions
(Freiser, 1996). based on the type of energy associated with the
Micelle: Molecular aggregates (Myers, 1991, p. 301), which reaction: (a) perikinetic coagulation is by contacts
is brief definition. between reactants being due to Brownian motion,
Microfloc: The term ‘‘microfloc’’ seems to have originated and (b) orthokinetic coagulation is due to turbulence.
with A.P. Black (1948, p. 143), who stated: ‘‘When Particle: Defined here as any contiguous matter that may
the positively charged aluminum or ferric ions have range in size from a few angstroms, such as macro-
neutralized a considerable portion, perhaps most of molecules or viruses to perhaps 1000 mm. Examples
the negatively charged colloidal particles of color or include viruses, bacteria, protozoan cysts, alga cells,
turbidity, the resulting particles may be called micro- rotifers, and mineral particles such as colloids and
flocs for the purpose of this discussion since they are grains of sand.
beyond the limits of visibility and are far too small Particle count: The results of a particle count instrument,
to settle under the influence of gravity. If subject to which may be by total count and counts by particle
flocculation the microflocs will grow in size to form size ranges. The instrument may be batch or online.
settleable flocs.’’ Pilipovich et al. (1958, p. 1468) Online instruments have become increasingly com-
adopted this term and its definition by Black as did mon since about 1990.
Moffet (1968, p. 1263), among others. Particle destabilization: The process of reducing the repul-
Microscopic particulate analysis (MPA): Microscopic sive forces between colloidal particles such that
examination of particles retained by a cartridge filter, when contacts occur the particles will attach to
which may include counting the species present. each other.
(Hibler, 1988; Hancock et al. 1996). The examin- Particulate organic carbon (POC): Organic carbon passing
ation does not include bacteria or viruses. See cart- retained by a 0.45 mm filter. Usually, POC is a small
ridge filter. fraction of the TOC compared to DOC (Edzwald,
Molecular weight: The sum of atomic masses of all atoms 1993, p. 24).
comprising a molecule. Permittivity: When electric charges are immersed in a dielec-
Mono-disperse: All particles in a colloidal system are tric medium (like water) the strength of the electric
approximately the same size, that is, they have a field is significantly reduced because the molecular
narrow size distribution (Myers, 1991, p. 192). dipoles tend to align themselves in such a way as to
Monomer: The individual repeating units that make up a cancel part of the field. The capacity of a substance
polymer are called monomers (Singley et al., 1971). to affect the electric field strength is measured by its
Montmorillonite: A type of clay noted by interlayer swelling permittivity. The reference is the permittivity of a
with a CEC 80–150 meq=100 g. The external spe- vacuum, e o . The dielectric constant, D, is the correc-
2
cific surface area 50–120 m =g and the secondary tion for the medium. Thus, e(water) ¼ e o D(water)
2
specific surface area 840 m =g; the latter is (Hunter, 1981, p. 349).
exposed by an expanded lattice (Mitchell, 1993, Perikinetic coagulation: (1) The first phase of coagulation in
p. 31). See also clay. which the zeta potential of the colloid is reversed,
Natural organic matter: Organic molecules that occur in neutralized, or reduced to a point where the London-
ambient waters as a result of natural processes. A van der Waals forces become predominant and pri-
portion of NOMis FA and HA. See also Chapter 2. mary coagulation takes place (Black and Willems,
Neat solution: Without dilution. For example, liquid alum as 1961, p. 599). (2) The process of contacting between
provided by the manufacturer is a ‘‘neat’’ solution. particles caused by Brownian diffusion. [peri is from
The same is true for a liquid polymer. the Greek, meaning around, near; kinetic is from
Nephelometeric turbidity unit (NTU): A unit of turbidity the Greek kinein, to move.] See also orthokinetic
based on the light scattering principle as calibrated coagulation.
by a standard. A formazin suspension is a common Physicochemical treatment: Term referring to chemical
standard, made up in accordance with prescribed precipitation and settling, activated carbon adsorp-
protocol. tion, filtration, etc. (Weber et al., 1970; Burns
Nernst potential: The potential at the surface of a colloid. and Shell, 1971). The term came to use, c.1967,