|
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.) |
|
|
|
|
P.E. |
The abbreviation for
"portable exchange". |
|
|
|
|
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. |
|
|
|
|
Per Capita |
Per person; generally used
in expressions of water use, gallons per capita per day (gpcd). |
|
|
|
|
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.) |
|
|
|
|
Permanganate |
Generally 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,
or alkaline. |
|
|
|
|
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.) |
|
|
|
|
Point-Of-Entry Water
Treatment |
Refers
to devices used in the home where water pipes enter to provide additional
treatment of drinking water used throughout the home. |
|
|
|
|
Point-Of-Use Water
Treatment |
Refers to devices used in
the home or office on a specific tap to provide additional drinking water
treatment. |
|
|
|
|
Pollution |
"Pollution is an
impairment of quality such that it interferes with the intended
usages." (House Report 2021.) |
|
|
|
|
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. |
|
|
|
|
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 void volume.) |
|
|
|
|
Positive Charge |
The net electrical charge
on an electrode or ion in solution due to the removal of electrons. (See
electron, cation.) |
|
|
|
|
Postchlorination |
The application of chlorine
to a water following other water treatment processes. (See prechlorination.) |
|
|
|
|
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 postchlorination.) |
|
|
|
|
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. |
|
|
|
|
Primacy State |
A State that has the
responsibility and authority to administer EPA's drinking water
regulations within its borders. The State must have rules at least as
stringent as EPA's. |
|
|
|
|
Public Notification |
An advisory that EPA
requires a water system to distribute to affected consumers when the
system has violated MCLs or other regulations. The notice advises
consumers what precautions, if any, they should take to protect their
health. |
|
|
|
|
Public Water System (Pws) |
Any water system which
provides water to at least 25 people for at least 60 days annually. There
are more than 170,000 PWSs providing water from wells, rivers and other
sources to about 250 million Americans. The others drink water from
private wells. There are differing standards for PWSs of different sizes
and types. |
