Glossary Of Water Treatment Industry Terms . . ."P"
P alkalinity - Phenolphthalein
alkalinity of a water as determined by titration with standard acid solution
to the phenolphthalein endpoint (pH approx. 8.3). Includes carbonate and
hydroxide alkalinity. (See total alkalinity.)
particle size - As used
in industry standards, the size of a particle suspended in water as determined
by its smallest dimension, usually expressed in micrometers.
parts per million (ppm) -
A common basis for reporting the results of water and waste water
analyses, indicating the number of parts by weight of a dissolved or suspended
constituent, per million parts by weight of water or other solvent. In
dilute water solutions, one part per million is practically equal to one
milligram per liter, which is the preferred unit. 17.12 ppm equals one
grain per U.S. gallon.
pathogen - An organism which
may cause disease.
P.E.- The abbreviation for "portable
percentage values - These
are needed to calculate specific resin capacities for this water supply.
They are also to calculate DI water quality.
permanent hardness - Water
hardness due to the presence of the chlorides and sulfates of calcium
and magnesium, which will not precipitate by boiling. This term is largely
replaced by "noncarbonate hardness". (See noncarbonate hardness.)
refers to potassium permanganate, a chemical compound used in water treatment.
(See potassium permanganate.)
pH - The negative logarithm
of the hydrogen ion concentration. The pH scale ranges from zero to 14
with 7 as the neutral point, indicating the presence of equal concentrations
of free hydrogen and hydroxide ions. pH values below 7.0 indicate acidity,
with 0 most acid; pH values above 7 indicate basicity, with 14 most basic,
phreatophyte- A plant which
takes its water from the zone of saturation or the capillary fringe of
ground water. Excessive growths of phreatophytes are undesirable in some
areas since they may consume large quantities of scarce water.
physical stability - A measure of the ability of an ion exchanger or filter medium to resist breakdown by physical forces such as friction, high temperatures and crushing to which it may be subjected in use.
pK - The reciprocal of the logarithm
of the ionization constant of a chemical compound.
pOH - The negative logarithm
of the hydroxyl ion concentration. The pOH is related to pH by the expression:
pH + pOH = 14. (See pH.)
population equivalent - A
unit of measure used to express the strength of waste water from any source
by comparison to the strength and volume of normal household waste water.
The figure of 0.17 pound of BOD per capita per day is often used as a
base figure for calculations.
pollution - "Pollution
is an impairment of quality such that it interferes with the intended
usages." (House Report 2021.)
porosity- A measure of the
volume of internal pores, or voids, in ion exchangers and filter media;
sometimes expressed as a ratio to the total volume of the medium. (See
portable exchange A term
applied to water softeners, filters and deionizers which are designed
for connection to a water system with special fittings, and disconnection
and transport to a central station or plant for regeneration or servicing.
positive charge - The net
electrical charge on an electrode or ion in solution due to the removal
of electrons. (See electron, cation.)
application of chlorine to a water following other water treatment processes.
potable water- Water
which is suitable for human consumption.
potassium permanganate- An
oxidizing chemical commonly used in processes for removing iron, hydrogen
sulfide and manganese.
ppm - The abbreviation for
"parts per million".
prechlorination- The application
of chlorine to a water prior to other water treatment processes. (See
precipitate - To cause a
dissolved substance to form a solid particle which can be removed by settling
or filtering, such as in the removal of dissolved iron by oxidation, precipitation
and filtration. The term is also used to refer to the solid formed, and
to the condensation of water in the atmosphere to form rain or snow.
precoat - The application
of a granular filter medium, such as diatomaceous earth or powdered activated
carbon to a membrane or screen or other filtration surface, prior to the
service cycle of a filter.
pressure differential - A
difference or change in pressure detected between two points in a system
due to differences in elevation and/or pressure drop due to flow.
pressure drop - A decrease in water pressure during flow due to internal friction between molecules of water, and external friction due to irregularities or roughness in surfaces past which the water flows.